specification for rcc construction

8/2/2019 Specification for Rcc Construction

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Construction specification for hydraulic roller compacted concrete

Issued on Nov. 03, 2000 Implement from Jan. 1, 2001Issued by State Economic and Trade Commission of the People'sRepublic of ChinaConstruction specification for hydraulic roller compacted concrete

Chief Development OrganizationChina National Water Resources and

Hydropower Engineering CorporationApproval Department: State Economic and Trade Commission of thePeople's Republic of ChinaApproval Document No: State Economic and Trade Power [2000] 1048

China Electric Power Press


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2000 BeijingDL/T5112-2000

Contents

Preface1 Scope2 Cited standard3 General rules..4 Vocabulary of terms..5 Materials..

5.1 Cement5.2 Flyash or other additive blend.5.3 Concrete admixture5.4 Aggregate5.5 Water for concrete mixing and curing..

6 Mix design..7 Construction7.1 Preparation before placing7.2 Mixing.7.3 Transportation.7.4 Dumping and block leveling..7.5 Rolling...7.6 Joint forming..

7.7 Treatment of layer and joint face.

7.8 Casting ofdissimilar concrete ..

7.9 Casting of abnormal concrete.7.10 Curing and protecting.7.11 Construction of embedded parts7.12 Construction under special meteorologic condition

8 Quality management and assessment..8.1 Testing and controlling of raw materials.8.2 Testing and controlling of newly mixed RCC.8.3 On-site quality testing of RCC..8.4 Quality control and assessment..Annex A (standard annex) Conversion factor of compression strength

between specimen of different height-diameter ratio & cylinder and cubicspecimen.Explanation of clauses..


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1 Scope

This specification mainly includes the following contents: material, mixdesign, construction, quality management and assessment.This specification is applicable for the RCC construction of grade I, II III

hydraulic structure in large and medium-scale hydropower stationsand

RCC construction in other project can refer to this.

2 Cited standardsThe clauses of the following standards comprise the clauses of thisspecification through being cited in this specification. While thisspecification is published, all the editions showed here are effective. The

parties using this specification should discuss the possibility to use thenewest editions of the following standards since all the standards may berevised.GB 175-1999 Portland cement and ordinary Portland cementGB 200-1989 Moderate-heat Portland cement and low-heat slag Portland

cementGB 1344-1999 Slag Portland cement, pozzolanic Portland cement and

flyash Portland cementGB 8076-1997 Concrete admixtureGB/T 1596-1991 Flyash used in cement and concreteGBJ 119-1988 Application technical standard for concrete admixtureDL/T 5055-1996 Technical specification of flyash mixing in hydraulic

concreteDL/T 5100-1999 Technical code of hydraulic concrete additive blend


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DL/T 5123-2000 Acceptance code for basic construction project ofhydropower station

SD 105-1982 Test code for hydraulic concreteSDJ 207-1982 Construction specification for hydraulic concrete

SL 48-1994 Test code for hydraulic RCCSL 176-1996 Construction quality assessment code for water resources

and hydropower project

3 General rules3.0.1 Besides complying with this specification, the construction of

Hydraulic RCC should also carry out the current relevant specificationsand industry standards of the nation where this specification does notcover.3.0.2 Field test should be carried out before RCC construction to verify

the mix design, process flow of construction, adaptability of constructionsystem and construction equipment, and determine the constructiontechnology and parameters.3.0.3 The performance of RCC should satisfy the indices such as unit

weight, Physical and Mechanical properties impermeability and frost

resistance required by design.3.0.4 The temperature should be controlled in the RCC construction.3.0.5 The new technique, new technology, new materials and new

equipments verified and demonstrated by practice can be applied in RCC

construction after passing through the technical results approval.


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4 Vocabulary of terms4.0.1 blend

Means the active and inactive mineral substances mixed in the cementwhen it leaves the factory.

4.0.2 additive blendMeans the mineral substances mixed into the concrete on construction

site.4.0.3 construction jointThe joint set up according to construction requirement.4.0.4 spreading thicknessMeans the concrete thickness of each working layer before being

compacted.4.0.5 compacted thicknessMeans the thickness of each working layer being compacted to the

designed compactness or unit weight.4.0.6 relative densityMeans the ratio between the real tested unit weight in construction block

and the average basic unit weight acquired from the RCC indoor test.

4.0.7 basic unit weightAverage value of RCC with selected mix proportion acquired from

indoor test.4.0.8 intermittent time between layersMeans the period starting from adding water to the lower layer concrete

mixture till finishing the compaction of upper layer concrete.4.0.9 permissible time interval between placing layersThe maximum time interval between layers for placing the upper layer

RCC to satisfy the combining quality requirement between layers directlywithout any layer surface treatment.4.0.10 permissible time interval between placing layers while using

bending mixThe maximum time interval between layers in which the combining

quality requirement can be satisfied by placing RCC after spreadingbending mix on the layer surface.

4.0.11 cold jointThe compacting layer of which the intermittent time between layers has

exceeded the permissible time interval between placing layers whileusing bending mix.

4.0.12 abnormal concreteThe vibrated and compacted concrete by mixing a certain proportion of


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mortar into the spread RCC.4.0.13 bending mix

The plaster, mortar or small aggregate concrete adaptable tocorresponding RCC placing on the cast layer or foundation rock surface.

5 Materials5.1 Cement

5.1.1 The cement quality should be in conformity with the relevantregulations of the current national standards.5.1.2 Special requirements of mineral components and alkali content can

be proposed for the cement used in hydraulic RCC according to specificcondition. The cement should be produced by fixed manufacturer andadopt bulk cement in priority.5.1.3 It is better to choose Portland cement, ordinary Portland cement

and moderate-heat Portland cement for the variety of the cement. Thecement grade should be no lower than No.4255.1.4 There should be factory inspection report for each batch of cement.

It should be rechecked according to table 8.1.1 after being transported tothe site and chemical analysis should be carried out for it if necessary.The inspection of cement quality should be executed according to thecurrent national standards.5.1.5 The cement should be transported and stored respectively

according to different variety, grade and factory number.

5.1.6 There should be rainproof and damp-proof facilities for the placeof cement transportation and storage. The cement stored for more than 3months must be rechecked before use and be used according to therechecked results. Caked concrete is strictly forbidden to use.

5.2 Flyash or other additive blend5.2.1 Appropriate amount of excellent flyash or other active additive

blend should be mixed into the RCC in priority, and inactive additiveblend can also be mixed into after test demonstration.

5.2.2 The flyash mixed in the RCC should be in conformity with therequirement of DL/T 5055, and be checked according to table 8.1.1 after

being transported to the site.5.2.3 The mixing quantity of flyash or other additive blend in the RCC

should be determined by test.5.3 Concrete admixture

5.3.1 Admixture should be mixed into the RCC, and its variety andmixing quantity should be determined by test.5.3.2 Compound admixtures should be mixed into the RCC. Mainly

select the slow-setting and water-reducing admixtures for construction insummer. Select air-entraining admixtures for the concrete with frost-

resistant requirement.5.3.3 The mobilized admixtures should have product instruction book


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and material certificate, and should comply with the regulations in DL/T5100. Quality inspection must be carried out before it is used.

5.4 Aggregate5.4.1 Quality, technical and economic demonstration should be carried

out for the used coarse and fine aggregate.5.4.2 Aggregate test should be carried out following the relevant

regulations in SD 105.5.4.3 The reserve of aggregate should be enough, and sun-shading,

rainproof and dewatering facilities should be set up for the aggregate. Thewater content of sand should not exceed 6% while mixing.5.4.4 Control the screening quality while flushing and screening the

aggregate, make sure that all grades of produced aggregate comply withrequirements, and pay attention to the loss of rock powder in the fine sandand artificial sand.5.4.5 The artificial sand should be produced by crushing machine with

high productive efficiency and can produce good-sized grain.5.4.6 While producing aggregate with dry method, measures should be

taken to prevent the aggregate grain being adhered to and wrapped bylarge amount of rock powder.5.4.7 While transporting and piling the aggregate, prevent to mix with

clay and mix up different graduations.5.4.8 The sand should be hard and the gradation should be well. The

modulus of fineness of artificial sand should be within 2.2-2.9, and that of

natural sand should be within 2.0-3.0. The content of oversized grainshould be strictly controlled. The natural sand with the modulus offineness less than 2.0 should be demonstrated by test.5.4.9 The content of rock powder (grain with d 0.16mm) in artificial

sand should be controlled within 10%-20%, and the best rock powdercontent should be determined by test.5.4.10 The sediment percentage ((grain with d 0.08mm) of natural

sand should not be over 5%.5.4.11 The quality index of fine aggregate (sand) and coarse aggregate

should be in conformity with 5.4.8, 5.4.9 and 5.4.10, besides, otherquality indices of them should be in conformity with the requirements ofSDJ207.

5.5 Water for concrete mixing and curing5.5.1 All drinking water in conformity with national standard can be

used to mix and cure various concrete.5.5.2 The substance content of the concrete mixing water should be in

line with the requirements of SDJ 207.6 Mix design

6.0.1 The mix Design of RCC should satisfy all technical indices of

engineer design and requirements of construction technology.6.0.2 Selection of parameter of mix design:


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1 mixing quantity of additive blend: it should be determined by test,and special test demonstration should be done when the mix quantity hasexceeded 65%.

2 water-binder ratio: should be determined according to concrete

strength, tensile strain, heat insulating temperature rise and frostresistance proposed by design, and its value should be less than 0.70.

3 sand rate: the best sand rate value should be selected by test. Whileusing the natural aggregate, the sand rate of graduation III RCC is 28%-32%, and 32%-37% while it is graduation II; the sand rate should add3%-6% while using artificial aggregate.

4 unit water consumption: can be selected according to theconstruction workability of RCC (VC value), variety of aggregate andmaximum grain diameter, sand rate as well as admixture.6.0.3 The designed workability (VC value) of RCC mixtures can adopt

5s-12s, the VC value at the outlet of the machine should be selected andcontrolled dynamically according to the variation of climate condition onconstruction site. And the value at the outlet of the machine should bewithin 5s-12s.6.0.4 The cementing material consumption of RCC of mass permanent

structure should not be less than 130kg/m3.6.0.5 If it is required to change the variety or source of raw materials in

construction, the mix proportion should be adjusted by test in advance.

7 Construction7.1 Preparation before placing

7.1.1 Before placing the RCC, check the production and storage systemof aggregate, raw materials supply, the capability of equipments ofconcrete making, transporting, placing, compacting and testing, workcondition and construction measures combining with the on sitecompacting test. The construction can only be started when therequirements of relevant technical documents are satisfied.7.1.2 Before placing the RCC, technical training should be carried out to

the construction personnel.7.1.3 Before placing in each block, there should be detailed plan for

construction, and be fulfilled to specific construction operator.7.1.4 Before placing RCC on foundation block, place mortar on the

foundation rock surface first, and then place a layer of cushion concreteor abnormal concrete. Its thickness should take convenience for

compaction after being leveled as principle except there is specialrequirement.


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7.1.5 The formwork for RCC construction should be adaptable for fastand continuous construction and should satisfy the requirement to let thevibrating roller to get close. The formwork used should be designedspecifically if necessary, including: vertical formwork, inclined

formwork, concrete pre-cast formwork, and waterstop, formwork passingin and out of the blocks and holes.

7.2 Mixing7.2.1 The forced mixing equipment should be selected in priority for

RCC mixing, other types of mixing equipments such as free-fall.7.2.2 The weighing system of the mixing equipment should be sensitive,

accurate and reliable, and should be checked regularly to ensure that theaccuracy requirement of weighing will be satisfied in the process ofconcrete production.7.2.3 The mixing time, feeding order, mixing quantity of RCC should all

be determined by test of concrete mixing homogeneity on site.7.2.4 The mixing equipment should be installed quick testing device of

water content of fine aggregate, and should have the automatic adjustingfunction of corresponding mixing water quantity.7.2.5 The fall free from the outlet of the dump skip to the transportation

tool should not exceed 5m.7.2.6 The requirements of proportioning accuracy and mixing quality of

mortar and plaster are as the same as those of mixing quality of concrete.The plaster should be mixed by machine. Collective mixing plant should

be set up for large-scale project, and device to keep the plasterhomogenous should be allocated.

7.3 Transportation7.3.1 It is better to transport RCC with dumper, belt conveyor, negative

pressure chute (pipe), special vertical chute. Overall examination andclearance of transportation machines should be carried out before they are

being used. Cable machinegantry crane and tower crane etc. can be

adopted while necessary.7.3.2 The road for dumpers carrying concrete must be even; the dumpertyres must be flushed clean to prevent bringing clay and water into the

block; the operations such as sudden break and sharp turn which maydamage the quality of concrete layer should be avoided while running inthe block.7.3.3 While transporting concrete with belt conveyor, measures should be

taken to reduce aggregate separationplaster loss rate. And there should

be sun-shading and rainproof facilities.7.3.4 While transporting concrete with negative pressure chute (pipe),

elbow heading down vertically should be made at the outlet of thenegative pressure chute (pipe); the partly broken part of the cover tape of


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negative pressure chute (pipe) should be repaired in time, and the covertape should be changed timely while it has broke to a certain degree. Thegrade of slope and the anti-separation measures should be determined byfield test.

7.3.5 The special vertical chute should have the function of anti-separation. Control device for preventing blockage can be set up ifnecessary.7.3.6 while all kinds of transportation tools are running or dumping, thefall free of concrete at the outlet should not exceed 1.5m. While it

exceeds, special vertical chute or transferring hopperwhile continuous

transporting tools and batch transporting tools are used jointly, storagehopper with enough capacity should be set up at the transferring position;there should be measures to solve concrete camber while usingtransferring hopper; outlet of waste residue and cleaning waste watershould be set up on the continuously closed transportation line form themixing equipment to the block.7.3.7 There should be measures to prevent slurry sediment and bleedingwhile transporting plaster, and ensure that the slurry transported to thesite is homogeneous. The mortar can be transported by concretetransporting tools, or by special mortar transporting tools.

7.4 Dumping and block leveling7.4.1 RCC should be placed continuously in thin layer in big block or

placed intermittently, and the placing method should be level course fulllength placement, or inclined-layer placing method, step method. The

placing size should be adaptable to the placing strength and permissibleintermittent time between layers of RCC.7.4.2 While adopting inclined-layer placing method, it should be placedfrom the downstream to the upstream to make the layer surface trend tothe upstream, and the grade of slope should not be more steeper than1:10, and avoid to form thin-layer sharp angle at the foot of the slope. Thesecondary contaminant on the construction joint should be strictly clearedaway before placing the mortar, and the RCC should be coveredimmediately after placing mortar.7.4.3 The RCC layer should be placed belt by belt in the same direction;in the scope of 3m-5m of the upstream face, the block leveling directionshould be in parallel with the dam axis.7.4.4 While dumping concrete with dumper directly in the block, theheight of concrete pile should be controlled. The separated aggregate onthe side of the concrete pile should be distributed into the concrete evenlyduring the leveling process.7.4.5 The unqualified concrete mixture is strictly forbidden to enter the

block; the already entered should be treated.7.4.6 While the compacted thickness is about 30cm, it can be levelly


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placed once; in order to improve the separate condition or the compactedthickness is greater, it can be placed twice or three times.7.4.7 The concrete surface should be flat and smooth after leveling, andthe compacted thickness should be even.

7.5 Rolling7.5.1 The selection of model of vibratory roller should take account ofrolling efficiency, exciting force, dimension of rolling drum, vibratingfrequency, amplitude of vibration, walking speed, maintenancerequirement and running reliability.7.5.2 The surrounding parts of the structure should be rolled closing tothe formwork by the same type of vibratory roller as the same as theinside. The part can not get close to should be compacted by small-sizedvibratory roller. The permissible compacted thickness and passingnumber should be determined by test.7.5.3 The walking speed of vibratory roller should be controlled within1.0km/h-1.5km/h.7.5.4 The compacted thickness and passing number in constructionshould be determined by test, and take account of the factors such ascomprehensive production capability of placement. Different compactingthickness can be selected according to climate, placement method etc.The compacted thickness should not less than three times of themaximum aggregate grain diameter.7.5.5 In the scope of 3m-5m of the upstream face, the rolling direction

should be vertical to the flow direction. The rolling work should adoptoverlapping method. The overlapping width of rolling belt should be10cm-20cm; and the overlapping width at the ends should be about100cm.7.5.6 After finishing the rolling work of each belt, lay out the testing

points in mesh timely to test the compacted density of concrete. If thetested density is lower than the regulated index, retest at once, find outthe reason and take treatment measures. The parts where spring soiloccurs, there is no need to treat if the tested compact density meets therequirements.7.5.7 The bedding surface or cold joint that should be stopped ashorizontal construction joint should be rolled 1-2 times without vibrationafter reached the regulated passing number and compacted density.7.5.8 While walking on the compacted concrete bedding surface, theequipments should avoid damaging the formed bedding surface. The partwhere is damaged should be repaired in time.7.5.9 After entering the block, the RCC should be leveled and rolled assoon as possible. The permissible longest period from mixing tocompacting finish should be determined by test or make analogy with

other projects according to different season, weather conditions andvariation law of RCC workability, and should not exceed 2h.


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Preserve 20cm-30 cm to compact with the next belt at the same time atthe brim placing belt in the compacted layer, brim of slope foot with theinclined-layer placing method, and brim of step with the step method.The final complete time for these parts should be controlled in

permissible time interval between placing layers.7.6 Joint forming

7.6.1 Transverse joint can be formed by cutting with grooving machine,setting up induce hole or partition. The location, structure form of jointand the filled materials in the joint should meet the design requirements.7.6.2 Cutting by grooving machine should adopt cutting first, rollinglater or rolling first, cutting later according to the specific condition of

project.7.6.3 The setting-up of induce hole should be finished in the intermittenttime between layers. Fill dry sand in the hole timely after the hole isformed.7.6.4 The spacing length at the partition joint should not be larger than10cm, the height of partition should be 3cm-5cm lower than thecompacted thickness.7.6.5 The making and installing of transverse with re-groutingrequirement should meet the design requirements.

7.7 Treatment of layer and joint face7.7.1 For the placed RCC rising continuously, the intermittent time

between layers should be controlled in permissible time interval between

placing layers. For the layer surface exceeding permissible time intervalbetween placing layers, bedding mix should be placed on it first, and thenplacing a layer of RCC. The layer surface exceeding permissible timeinterval between placing layers while using bending mix is cold joint.7.7.2 Permissible time interval between placing layers and permissibletime interval between placing layers while using bending mix should bedetermined by test according to the layer shear capacity and bindingquality required by project structure, comprehensively taking account ofmixture property, season, weather, construction method and differentareas upstream and downstream.7.7.3 Joint treatment must be done to the construction joint and cold joint,to clean the laitance and loose aggregate on the surface of the concretewith the roughening method of brushing and flushing. After treatment andclean, and being accepted qualified, place bedding mix first, and then

place a layer of concrete to continue the construction.7.7.4 The roughening time of flushing and brushing should be determined

by field test according to construction season, concrete strength,equipment performance etc. Roughening too early is prohibited.7.7.5 The bedding mix can adopt plaster, mortar or small aggregate

concrete adaptable to RCC. The water-binder ratio should as the same asRCC, the strength grade of mortar and small aggregate concrete should


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enhance one grade. The bedding mix should be spread belt by belt justlike the RCC. In which, the spread thickness of mortar is 1.0cm-1.5cm,and spread RCC on it immediately, and complete the rolling before theinitial setting of mortar.

7.7.6 While the construction is interrupted by construction schedulechange, rainfall or other reasons, the spread concrete should be rolled intime. The concrete face at where the placing stops should be rolled intoinclined slope not more than 1:4, and ekscind the part with thickness lessthan 15cm. While the construction condition resumed, continueconstruction after treating the layer and joint surface according to theinterrupted time.

7.8 Casting ofdissimilar concrete7.8.1 The conventional concrete should be placed with the RCC of main

body synchoronously.7.8.2 The binding part of conventional concrete and RCC should betreated seriously as shown in graph 7.8.2. The two kinds of concreteshould be placed alternately, and the conventional concrete is required tocompacted before initial setting; the rolling of RCC should be finished inthe permissible intermittent time between layers.

Vibrating scope of vibratorConventional concrete\ RCC

(a)Vibrating scope of vibrator

Conventional concrete\ RCC(b)

(a) first placing conventional concrete and then RCC;(b) first placing RCC and then conventional concrete

Graph 7.8.2 Treatment of binding part ofdissimilar concrete7.9 Casting of abnormal concrete

7.9.1 The abnormal concrete should be constructed layer by layeraccompanying the RCC casting, and the plaster should be sprayed at the

bottom and middle part of the newly compacted concrete. The placinglayer thickness of abnormal concrete should be as the same as the blockleveling thickness, and the plaster consumption should be determined bytest.7.9.2 The used mortar plaster in abnormal concrete is made of cement,flyash and admixture. Its water-binder ratio should be no larger than thatof the same type RCC.7.9.3 The plaster should be used strictly following the regulated quantity,and spread in the abnormal scope or 30cm-50cm near the rock face orformwork. The plaster consumption deviation per unit volume of concreteshould be controlled in the allowed range.

7.9.4 The homogeneity and binding between layers of abnormal concreteshould be ensured by forced vibration. The overlapping width between


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abnormal zone and adjacent zone should exceed 20cm while compacting.7.9.5 The layer and joint surface treatment of abnormal concrete should

be carried out as per the regulations in 7.7 of this standard.7.10 Curing and protecting

7.10.1 The RCC block should be kept wet during construction.7.10.2 Prevent out-coming water running into the block underconstruction or just finished rolling.7.10.3 During construction interval, water curing should start after thefinal setting of RCC. For the horizontal construction joint and cold joint,the water curing should sustain till the placement of the upper layer ofRCC; for the permanent exposed surface, the curing time should not lessthan 28d; the curing of edge angle of step-like surface should bestrengthened.7.10.4 Corresponding curing measures should be taken for the RCC withtemperature control requirement according to temperature control design;and special protective measures should be made for low-temperatureseason and cold spell.

7.11 Construction of embedded parts7.11.1 Later-embedding should be taken for the embedding of monitorequipments and cable in RCC. A backfill protective layer larger than20cm should be ensured at the top of the pit depth for the instruments andcables without direction requirement. A backfill protective layer at least50cm should be made at the upper part for the instruments without

direction requirement. The backfill material should be flesh concreteremoving the aggregate larger than 40mm from the original concrete mixdesign.7.11.2 Measures must be taken for the backfill concrete in the pit toensure good binding with the surrounded concrete. Artificial backfill inlayers should be adopted except for cable, and compact with woodhammer to ensure the compactness of backfilled concrete. For cable or

bunch of cables, mortar should be backfilled into the pit to avoid formingleakage passage.7.11.3 Reasonably arrange the construction schedule according to theelevation of embedded equipments, try to make the horizontalconstruction joint during construction interval become the excavationlayer of pit, and guarantee the good cooperation and coordination

between embedding and concrete placing.7.11. 4 The embedded equipments should be maintained and protected.While the initial setting of backfilled concrete at the embedded area hasnot finished or the upper layer of concrete has not been placed, allequipments are forbidden to walking on.7.11.5 Monitor should be strengthened in the instrument installation,

embedding, and concrete backfilling. If the equipment is found unusual orbroken, take remedy measures in time. After the instruments and cables


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mobilizing date, and the storage place should be ventilated and dry. Theadmixture being tested qualified should be retested before use if it has

been stored over 6 months. The admixture must be made into solutionand mixed evenly while being used, and be stored in the indoor vessel to

avoid contamination.Table 8.1.1 Test item and test frequency of raw material

Name Item Specimenlocation

Frequency

Aim

Cement Fast test thegrade

Cementstorageof mixing

plant

If it isnecessary

To verifythe cementactivity

Fineness,stability,waterconsumption ofstandardconsistency,settingtime, grade

Cementstorage

Twiceper 200t-400t 1)

To test thecementqualityleaving thefactory

Flyash Density,fineness,waterdemandratio,ignitionloss

Warehouse

Twiceper 200t-400t 1)

Assessqualitystability

Strengthratio

Ifnecessary

Testactivtity

Fine aggregate Modulus offineness

Mixingplant,screening

plant

Once perday

Thescreening

plantcontrols

productionand adjustthe mix

proportion

Graduation If necessary

Water

content

Mixing

plant

Once per

2h or if

Adjust

water


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necessary

consumption of concrete

Sediment

percentage,unit weight

Mixing

plant,screening

plant

If

necessary

Coarseaggregate

Large-sizedstone

Exceedingand inferiordiameter


plant

Once pershift

screeningplantcontrols

productionand adjustthe mix

proportionMedium-sized stone

Watercontent

Mixingplant

Once pershift or ifnecessary

Adjustwaterconsumption of concrete

Small-sizedstone

Content ofclay, silt,and fines


plant

Ifnecessary

Admixture Solutionconcentration

Mixingplant

Once pershift

Adjust themixingquantity ofadmixture

1) it should be tested once while less than 200t per batch8.2 Testing and controlling of newly mixed RCC

8.2.1 The weighing apparatus for batch weighing of RCC should bechecked once a month, and the allowable deviation of batch weighingfollows the regulations in table 8.2.1.

Table 8.2.1 Test standard for batch weighing

Materialname

Water Cement andflyash

Coarse andfineaggregate

Admixture

Allowabledeviation

1% 1% 2% 1%

8.2.2 After determined the model of mixer, test the mixture homogeneityof RCC through test so as to determine the mixing time and feeding order.The testing results of mixture homogeneity of RCC must comply with thefollowing regulations:

1 While testing the coarse aggregate content with washing-analysis


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method, the D-value between the two samples should be lower than 10%;2 While testing the unit weight with mortar unit weight analysis method,the D-value between the two samples should be not larger than 30kg/m3.After the batching plant is put into operation, it should be tested regularly.

8.2.3 The test of RCC quality can be done by sampling from the outlet ofthe mixer.Test item and frequency follows the regulations in table 8.2.3

Table 8.2.3 Test item and frequency of RCC

Item Frequency AimVC value Once per 2h 1) Test the compactability

of RCC and control theviability of workability

Air content 1-2 times per shiftwhile using air entraining agent

Adjust the quantity ofadmixture

Temperature Once per 2h-4h Temperature controlrequirement

Compression strength Once per 300-500m3,specimen at least oncefor each shift whileless than 300m3

Test the RCC qualityand constructionquality

1) the testing times should be added appropriately while the climatechange greatly (strong wind, rain, high-temperature)

8.2.4 After the VC value of RCC value is chosen, if the allowabledeviation at the outlet of the machine exceeds the 3s controlling limit, thereason should be found out. Modify the mixing water consumption ofRCC and keep the water-binder ratio unchanged.8.2.5 Strictly control the air content of RCC mixed with air entrainingagent, and the allowable deviation is 1%.

8.3 On-site quality testing of RCC8.3.1 While placing RCC, it should be tested according to regulations intable 8.3.1, and should be recorded.

Table 8.3.1 On-site testing item and standard of RCC placingItem Frequency Control standard

VC value Once per 2h The allowabledeviation of VC valueon site is 5s

Compression strength Amount to 5%-10% ofthe sampled quantity atthe outlet of the mixer

Compacted density Refer to 8.3.2 The tested unit weightof each placing layer

should reach the


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relative compactnessindex regulated in8.3.4

Aggregate separation Whole-process control Aggregate

concentration is notallowed

Intermittent time between two rollinglayers

Whole-process control The permissibleintermittent time

between layers underdifferent temperatureshould be determined

by test, and judgeaccording to it

The period fromadding water to mixthe concrete to therolling finished

Whole-process control Less than 2h

Entering block temperature

Once per 2-4h

8.3.2 The compacted density shall be tested by nuclear moisture-densitygauge or compaction densitometer. There should be at least on testing

point for per 100m2-200m2 RCC placed, and more than 3 testing pointsshould be arranged for each placing layer in the block. Take the result

tested by the nuclear moisture-density gauge after 10min of rolling as thejudge criteria of compacted density.8.3.3 The nuclear moisture-density gauge should be calibrated by RCCmade of actual raw materials before it is used.8.3.4 The relative compactness is the index to assess the compactionquality of RCC. For the external concrete of structure, the relativecompactness should not less than 98%; while for the internal concrete, itshould not less than 97%.

8.4 Quality control and assessment8.4.1 The specimen of RCC should be formed by sampling from theoutlet of the mixer. The production quality control of RCC should be

based on the 15cm standard cubic specimen and compression strengthstandardly cured 28d.8.4.2 The percent of pass of concrete anti-frost and impervious test

should not lower than 80%.8.4.3 Refer to table 8.4.3 for the control standard of production quality ofRCC. The mean square deviation and coefficient of variation ofcompression strength should be evaluated from a batch of (at least 30groups) tested value of samples continuously sampled from the outlet of

the mixer.


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Table 8.4.3 Management level criteria of production quality of RCC(age 28d)

Qualitymanagementlevel

Assessment

standard

Assessment item

Excellent Good Ordinary Bad

Coefficient of variation Cv

0.15 0.15-0.18 0.18-0.22 0.22

Mean squaredeviation S(Mpa)

3.5 3.5-4.0 4.0-4.8 4.8

Note: mean compression strength: , adopt S standard of mean square deviation to assess;

, adopt Cv standard of coefficient of variation to assess

8.4.4 The quality assessment of RCC should be based on the compressionstrength with designed age, and assess in big specimen and smallspecimen according to specimen numbers.1 Big sample. While the continuous sampling of concrete is more than 30groups, adopt big specimen to assess, and calculate the assessmentfunction according to the following formula:

Or

Where, F(X)-assessment function;

--mean value of test compression strength of N times, Mpa;

Smean square deviation of test compression of N times, Mpa;;Rconcrete strength grade (design grade), Mpa;

tcoefficient of ensuring rate of strength, relevant to test times Nand ensuring rate P(X). Refer to table 8.4.4-1 while N 30.

Xmin the lowest compression strength in N times of tests, MPa;K and Bcoefficient relevant to ensuring rate of strength andproduction control level, refer to table 8.4.4-1.

While F(X) R or Xmin KR or R+BS, the RCC is qualified. Table 8.4.4-1 Coefficient of quality assessment formula of RCC

coefficient of


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ensuring rate ofstrength t

K B(while S isgiven)

BS (S=4.3Mpa)

0.84 0.73 -1.16 -4.982 Small sample. While the test group of concrete specimen is less than

6, refer to 8.4.4-2 the assessment standard.

3 When , the quality of RCC is qualified.

Table 8.4.4-2 Allowable lowest mean strength of small specimen(Xmin)

Continuoussampling groupfor evaluatingmean strength

Cv=0.19 S is given When S=4.3Mpa

1 0.73R R-1.16s R-4.982 0.87R R-0.57S R-2.463 0.92R R-0.31S R-1.354 0.96R R-1.16s R-0.68

5 0.98R R-0.05S R-0.236 R R-0.02s R-0.18.4.5 Boring specimen is the comprehensive method to assess the RCCquality. Boring specimen can be carried out after the RCC reached thedesigned age. The boring position and quantity should be determinedaccording to elevation.

The assessment contents of boring specimen are as follows:

1. percentage recovery of core sample to assess the homogeneity of

RCC;2. water-pressure test: to assess the impermeability of RCC;3. physical and mechanical property test of core sample: to assess the

homogeneity and mechanical property of RCC;4. appearance description of core sample: to assess the homogeneity and

compactness of RCC, see table 8.4.5 for the assessment standard.

Table 8.4.5 Assessment standard of core specimen appearance of RCCGrade Smooth degreeof surface

Density of surface

Evenness of aggregatedistribution

Excellent Smooth Dense EvenOrdinary Basically

smoothWith small holes Basically even

Bad Not smooth With part of holes

Uneven

Note: this table is applicable for the core specimen drilled by drill bit

8.4.6 The diameter of core specimen for compression strength testing is


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better to be 15cm-20cm. For large-scale project or the project withmaximum aggregate grain larger than 80mm of concrete, it is better touse core specimen with diameter 20cm or even larger.8.4.7 Take the core specimen with height-diameter ration 2.0 as the

standard specimen. Refer to Annex A for the ratio of compressionstrength between specimens of different height-diameter ratio andstandard specimen with the height-diameter ratio 2.0. The specimen ofcore sample with the height-diameter ratio less than 1.5 is not allowed to

be used in compression strength test. Refer to Annex A for the

compression conversion relationship between standard

specimen and 15cm cubic specimen.

Annex A (standard annex)Conversion factor of compression strength between specimen of differentheight-diameter ratio & cylinder and cubic specimen

Table A1 Conversion factor of compression strength

Strength gradeMpa

Conversion factor of compressionstrength of specimen with differentheight-diameter ratio

compressionstrength/compressionstrength of 15cmcube

height-diameter ratio1.5 2.0

10-20 1.166 1.0 0.77520-30 1.066 1.0 0.82130-40 1.039 1.0 0.86740-50 1.013 1.0 0.910

Note:

1 the height-diameter ratios of test specimen of elastic modulus, axial


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tensile strength and tensile strain are within 2.0-3.0.2 the conversion factor with the height-diameter ratio within 1.5-2.0 can

be evaluated with interpolation method.3 Conversion factor of compression strength of specimen with different

height-diameter ratio = compression strength of specimen with differentheight-diameter ratio/compression strength of specimen with height-diameter ratio 2.0

Construction specification for hydraulic roller compacted concreteExplanation of clauses

Chief Development OrganizationChina National Water Resources and

Hydropower Engineering CorporationApproval Department: State Economic and Trade Commission of thePeople's Republic of China


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China Electric Power Press2001 Beijing

Contents3 General rules..5 Materials..

5.1 Cement5.2 Flyash or other additive blend.5.3 Concrete admixture5.4 Aggregate

6 Mix design..7 Construction7.1 Preparation before placing7.2 Mixing.7.3 Transportation.7.4 Dumping and block leveling..7.5 Rolling...7.6 Joint forming..7.7 Treatment of layer and joint face.7.8 Casting ofdissimilar concrete

7.9 Casting of abnormal concrete..7.10 Curing and protecting.7.11 Construction of embedded parts7.12 Construction under special meteorologic condition

8 Quality management and assessment..8.1 Testing and controlling of raw materials.8.2 Testing and controlling of newly mixed RCC.8.3 On-site quality testing of RCC..8.4 Quality control and assessment..


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3 General rules3.0.1 This clause illustrates the relationship between this Specificationand the current relevant specifications and professional standards of thestate. These standards mainly includes: SDJ207, SL48, DL/T5100,SL176, DL/T5123 and national standard relevant to materials and so on.3.0.2 This clause stresses the importance of field test for RCC throughwhich the rationality of concrete mix design can be verified; test theoperating reliability and overcoatability of raw material productionsystem, concrete preparation system, transporting system and machinetools of leveling and rolling during construction. Determine thereasonable construction technology and parameter through test, such asspreading way, leveling thickness, rolling thickness and passing numberetc. In addition, it will have technical training effect on the personnel lackof construction practice experience.3.0.3 This clause illustrates that the RCC should meet the technicalrequirements proposed by design. Accompanying with the more maturetechnique of RCC dam day after day, using RCC as the external concrete

of hydraulic structure has become true. So besides satisfying the strengthrequirement, the RCC should also satisfy the requirement such asimpermeability and frost resistance of external concrete.3.0.4 This clause stresses the importance of temperature control in RCCconstruction. In the construction of RCC, the actual block-enteringtemperature will take great effect on the project quality. In theconstruction, take measures of temperature control, temperature-keepingand maintenance economically and reasonably according to the propertyof RCC to prevent cracking.3.0.5 This clause is made with the purpose to favor the creation andapplication of new technique, new technology, new material and newequipment in the RCC construction and to guarantee the project quality.The technical achievement should be justified by the governingdepartment of the project.

5 Materials5.1 Cement

5.1.1 The cement quality should be in conformity with the currentrelevant specifications, such as requirements of GB175, GB200, andGB1344.

5.1.2 The performance of the cement being used should be ensured stable.5.1.3 While selecting variety of cement, better to select the low-heat


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cement in priority.5.2 Flyash or other additive blend

5.2.1 The quality of flyash should be in accordance with the relevantregulations such as GBJ146, DL/T5055, GB/T1596 and GB/2847.

Flyash or other additive blend is indispensable component materialsof RCC. In recent years, RCC has commonly adopt great mixing quantityof flyash in RCC at home and abroad, the flyash mixing quantity ofconstructed RCC dam is within 50%-70% at home. The mixing quantityof flyash should be determined by test according to quality grade, designrequirement. If there is no flyash resource, other active or inactiveadditive blend with comparatively reasonable technical and economic

indices can be chosen nearby, such as tuff, phosphate slagblast-furnace

slagtailing slag and rock powder etc. All of them could be mixed after

grinding, and their mixing quantity should be selected be testdemonstration.Concrete admixture5.3.1-5.3.3 The admixture mixing in the RCC is indispensable important

material for preparing high-quality RCC. According to the design indexof RCC, requirements of project and construction reason, mixingadmixture in concrete can not only improve the RCC property and makeconvenience for construction, but also can save engineering costs. In

order to ensure the RCC quality, choose the admixture with goodperformance. The quality standard of admixture mixing in the RCCshould comply with the requirements of GB8076, GBJ119 and DL/T5100.

5.4 Aggregate5.4.6 The rock powder produced in the artificial aggregate productionwith dry method will adhere to the surface of aggregate grain after beingwetted, which will influence the RCC quality. The productive technologyshould be improved to prevent the aggregate being adhered to by rock

powder, and wash the severely polluted aggregate.5.4.8 The content of grain larger than 5mm in the sand has sensitiveinfluence on the modulus of fineness, which should be controlled. It iscontrolled in 5% in some projects.5.4.9 Several projects and repeated tests prove that proper rock powder inartificial sand will obviously improve the workability and water retentionof mortar and concrete and promote the homogeneity, compactness,impermeability, mechanical index and fracture toughness property ofconcrete; rock powder can replace part of the flyash as additive blend ofcement; properly increasing the content of rock powder can also promote

the output of artificial sand, reduce the costs and increase the technicaland economic benefits. Therefore, reasonable control of content of


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artificial sand is in one of the most important measures to promote theconcrete quality. While adopting artificial sand made of lime rock and thecontent of rock powder is 17.6%, each property of concrete is excellent;artificial sand made of granite has good property while the content of

rock powder is 15%, artificial sand made of dolomite has good propertywhile the content of rock powder is 20%. This shows that although thereis difference between better content of rock powder in artificial sandmade of different rock character, their better contents are all higher thanthe contents of rock powder regulated in the original Construction

specification for hydraulic concrete. Seeing from the versatility, thecontent of rock power should be better controlled within 10%-22%.Production with dry method can promote the output of artificial sand andincrease the contents of fine grain in rock powder so as to improve theworkability of concrete and save equipment costs at the same time.5.4.10 The sediment in sand means the silt and clay with diameter lessthan 0.08mm. The comparative tests at home and abroad relevant to theinfluence of sediment in sand on concrete strength prove that while thecontent of fine grain (less than 0.08mm) is within 3%-7% in the leanconcrete, it can improve the workability, viscidity and compactness ofconcrete, promote the compression strength and impermeability ofconcrete. Accordingly, the sediment content in sand is promote from 3%to 5% in the JBJ52-1992 Sand quality standard and test method ofordinary concrete issued by Ministry of Construction

6 Mix design6.0.1 The mix design of RCC should satisfy all technical indices ofengineering design and construction technology, including:

1 the concrete should be homogeneous, and separation of coarseaggregate will not happen easily in construction;

2 the workability is appropriate, the mixture is relatively easy to becompacted, and the unit weight of concrete is relatively great;

3 the initial setting time of mixture is long, and easy to ensure good bonding between construction layers of RCC, and the physical andmechanical properties of layers are good;

4 the mechanical strength and impermeability of concrete meet thedesign requirements, and the concrete has high capacity of tensile strain.

The RCC out of the structures should have durability adapting to theenvironment of the structure.6.0.2 The mixing quantity of additive blend in permanent and importantstructures at home has reached 60%-65% (e.g. the mixing quantity ofadditive blend in dam RCC of hydropower station of TianshengqiaoSecond Grade and Yantan are 60.7% and 65.4% respectively. The mixingquantity of additive blend in Shangjing Dam of America has exceeded

70%. The research results of Wuhan University of Hydraulic andElectrical Engineering indicates that it is feasible to use RCC with


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excellent flyash and mixing quantity larger than 70% as the internalconcrete of mass hydraulic structure. The concrete strength has a certainincrease during 8-9 years, the internal structure of concrete iscontinuously improving and the impermeability and anti-erosion of

concrete are strong. The research result of Yangtze River ScientificResearch Institute on clinker covering 16.5% of low-clinker RCCindicates: the hydration and sclerous reaction of this kind of concrete are

basically consist with conventional concrete, its major hydrationproductions are stable, and the internal structure of concrete is dense. So65% is feasible for the maximum mixing quantity of additive blend.

The water-binder ratio of RCC should be different according to thematerials of each project and technical requirement, and should bedetermined by test. Generally, the water-binder ratio of each project athome is within 0.50-0.70.

The sand rate directly influences the construction performance,strength and duration of concrete. While determining the mix proportionof RCC, the best sand rate should be selected through test, i.e. the sandrate which can get good anti-separation after concrete mixing, reach theVC value required in construction and use the least cementing materials.The scope of sand rate listed in this clause is the general scope for

projects at home.The selection of water consumption per unit does not only connect

with the rollability but also relevant to economical efficiency. So while

the rollability is satisfied, the smallest water consumption per unit isusually adopted to save cement and additive blend. For the graduation IIIRCC, the water consumption is within 70kg/m3-110kg/m3.6.0.3 According to the project construction experience at home, in orderto guarantee the rollability of RCC, easily bleeding and bonding quality

between layers, the proper on-site VC value of mixture should be within5s-15s. Taking account of the influences of transportation, differenttemperature condition and water absorption on the VC value of mixture,the VC value 5s-12s at the outlet of mixer recommended by this clauseshould only be taken as the VC value of mix design. Because all kinds offactors may influence the on-site VC value in actual construction,therefore, the VC value at the outlet of mixer can be less than 5s while thenormal compaction on site is satisfied.6.0.4 The construction practices indicate: while the cementing materialconsumption is less than 120kg in per cubic meter of RCC, theimpermeability of the hardened concrete will be poor. In order toguarantee that the prepared RCC satisfy the impermeability requirementof mass hydraulic concrete, the cementing material consumption per unitrequired by this clause should not be less than 130kg. This limitation is

not applicable for small-scaled projects and temporary projects.


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7 Construction7.1 Preparation before placing

7.1.1 The characteristics of RCC construction are quick, continuous and

high-mechanized construction. Failure, incoordination or unsuitabilityoccurring to any link of the whole production system will impact the

project progress and the exertion of RCC construction characteristics.Thats why this clause is formulated.7.1.2 The operation qualification of construction personnel has greatinfluence on the construction quality especially on the earlier constructionquality. So the training should be strengthened after the construction

begins.7.1.3 The detailed plan arrangement of block is the embodiment ofconstruction technology in the block, which can avoid arbitrariness ofconstruction, ensure the strictly execution of construction technology, and

be helpful to promote the construction efficiency, and be taken as thebasis of field inspection.7.1.4 It is not convenient for RCC concrete placing on the accidentedrock foundation, so a certain thickness of bending concrete or abnormalconcrete to make the surface level. The construction practices in therecent years indicate that the quality and property of RCC can completelyreach those of conventional concrete. So the leveling course should not betoo thick in order to turn to RCC construction quickly, which will be

helpful to temperature control and construction progress.7.1.5 Formwork is the important equipment for RCC dam construction,and has great influences on appearance, quality, construction progress andcosts of RCC. So the selection of formwork has the same importance withallocation of mechanical equipment. The design of formwork should meetthe requirement of quick and continuous construction of RCC. For theconvenience of surrounded placement, no inclined stay should be set up.Waterstop, entrance and exit of block, and part of hole structure are the

position where has high requirement or problems come out, and theyshould be stressed in the design. Step mode may be taken for thedownstream surface, but the height of step should not be too small.

7.2 Mixing7.2.1 Forced mixer is applicable to mixing dry and hard concrete.According to the construction experience abroad, and construction

practice of guide wall of Shuikou Hydropower station, dam of Guanyingereservoir and dam of Jiangwan Hydropower station, RCC mixed withforced mixer does not only have good quality, but also has short mixingtime. According to the construction practice abroad, the mixers such asfall-free type can also mix RCC with good quality. Additionally, the

continuous mixer is also commonly used abroad.7.2.2 Except checking the accuracy of the weighing devices themselves,


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the actual batching result should also be checked while inspecting theweighing system.7.2.3 Practices indicate that the required time for even concrete mixing isinfluenced by concrete mix design, type of mixing equipment, feeding

order and mixing quantity. Therefore, the feeding order and mixing timeshould be determined by mixing test.7.2.4 The water content variation of fine aggregate will obviouslyinfluence the workability and water-binder ratio of concrete mixture.Generally, the modern batching plants are usually installed with quicktesting devices of water content in sand, and have the adjusting andcomplementing function of corresponding mixing water.7.2.5 For RCC, the larger fall it has while being dropped, the moreserious aggregate separation will come out. So this clause limits theheight of free fall of concrete mixture.7.2.6 The consumption of mortar and plaster are great in RCC dam, andshould be stressed as the same as concrete. In order to guarantee thequantity, the mortar and plaster must be fresh while being used. Mixing

plaster with machine is for the purpose to keep its homogeneity. Theplaster consumption of large-scaled project is great, and concentratedmixing station should be set up to supply plaster.

7.3 Transportation7.3.1 According to construction practices at home and abroad, dumper,

belt conveyor, negative pressure chute (pipe), special vertical straight

chute are relatively mature. Cable crane, gantry crane and tower cranecan also be used as auxiliary transportation tools.7.3.2 While transporting concrete with dumper, the number of entrance tothe block, structure and construction method of block sealing have greatinfluence on the quality and speed of construction; the filth and soil beingcarried by the wheel will influence the bonding quality of concrete layers.The water being carried in will change the workability and water-binderratio of the concrete and influence the concrete quality; sudden brake andsharp turning will damage the strength of concrete surface not highenough and influence the bonding between layers; the passing gap left onthe structure can be filled in the consequent construction.7.3.3 The sun-shading and rainproofing measures can reduce the

influence of external environment on the concrete consistency

aggregate separation may easily happen while the aggregate is transferredbetween belt conveyors, so anti-separating devices should be installed atthe discharge end; larger groove angle is favorable to slow down theseparation on the belt; practices indicate that proper scraper and cleaningdevice will control the loss of plaster.

7.3.4 In the usage of negative pressure chute (pipe), accompanying withthe increase of the damage of cover tape, the speed of concrete at the


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outlet may reach 10m/s-15m/s, and the concrete will be dischargeddirectly on the dumper, which will cause great impact and aggregateseparation. Install elbow downward at the outlet will greatly slow downthe speed and mix the concrete, which will prevent impact and separation

effectively. A section of circumferential split of cover tape can be added,and repair in the way of imbricate connection. The radial slit can be partlyreplaced after cutting the slit part. The whole cover tape should bereplaced while the mean distance of circumferential split of cover tape isless than 3m-5m or the negative pressure reduce rapidly and the speedand separation at the outlet are out of control owing to broken of covertape.7.3.5 Adopting purpose-made rubber hose and other chute with specialstructure will effectively prevent aggregate separation. Clogging-controlis for the purpose to ensure the equipment safety.7.3.6 In order to guarantee the continuous running of continuousequipment, the volume of storage hopper should be enough; the camberof transferring funnel has great impact on the capacity of transportingsystem.

7.4 Dumping and block leveling7.4.1 Level course full-length placement is the most popular adopted wayat home and abroad. The aim of adopting inclined-layer placing methodand step method is mainly to reduce the placing area and shorten theintermittent time between layers. According to the construction practices,

inclined-layer method can cast lager-sized block with small castingcapacity to realize the aim of reducing input, promote work efficiency,reducing costs and improving quality of layer bonding. The effect of thiskind of construction method is in evidence in higher temperature season.7.4.2 According to the practice of Jiangya project, the construction can becarried out normally while the slope of inclined layer is 1:10, and its hardto ensure the even thickness of spreading if the slope is too steep.Avoiding forming thin layer sharp angle at the foot of the slope andstrictly cleaning the secondary contamination are the two main problemsto ensure the construction quality of inclined-layer placing method.7.4.3 Placing belt by belt in the fixed direction makes the constructionlayer clear, the intermittent time between layers easily controlled, and theconstruction in order. The leveling direction in parallel with the dam axisin the scope of 3m-5m upstream is for the purpose to avoid forming

potential weak zone in the direction of flow at important parts.7.4.5 The unqualified concrete mentioned in this clause means: the VCvalue of concrete mixture exceeds the scope determined on site; thecontent error of each group exceeds the regulated scope; the mixedconcrete quantity is damaged due to human factors.

7.4.6 According to construction practices, level the concrete from thedumped position with bulldozer when the compacted thickness is 30cm


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and the leveling thickness is 34cm, the better effect of improvingseparation can be gain.7.4.7 In order to guarantee the rolling quantity, the leveling quantity must

be also guaranteed. Make the thickness of rolling layer even.

7.5 Rolling7.5.1 According to project practices of our country, BW-200, BW-201ADand BW-202AD made by former West Germany are more applicable. The

products with similar performance abroad and vibrating roller made athome can also be adopted if their vibrating force and vibrating frequencymet the technical requirements after tests.7.5.2 Project practices show that rolling the part near the formworkdirectly with large-sized vibrating roller can get high constructionefficiency and good quality.7.5.3 The walking speed of vibrating roller directly influences the rollingefficiency and compaction quality. The compaction effect is bad if thewalking speed is too fast according to construction practices at home. Thespeed can increase to 1.5km/h while the passing number is properlyadded.7.5.4 The compaction thickness of different vibrating roller is different,and the required passing numbers for mixture with the same mixing

proportion is also different for different vibrating rollers. The rollingthickness and passing number can be determined through site testcombining with the comprehensive production capacity of production

system. Adopting different rolling thickness according to conditions inconstruction will be helpful to meet the requirement of intermittent time

between layers. If the rolling thickness is less than 3 times of themaximum grain diameter of aggregate, the compaction effect will beinfluenced by the maximum grain diameter aggregate or the aggregatewill be crushed.7.5.5 Leakage passage owing to bad contact between rolling belts can beavoided if the rolling direction is perpendicular to the flow direction.Therefore, the rolling direction in the scope of 3m-5m upstream must be

perpendicular to the flow direction. Feasible measures must be takenwhile inclined-layer placing method is adopted. The overlapping ofrolling belts is mainly for the purpose to guarantee the compaction qualityof the overlapping parts.The overlapping length at the ends should ensure that both the front and

back wheel of the vibrating roller can enter the overlapping scope. Theoverlapping length can be determined by the axle base of the selectedvibrating roller.7.5.6 The value of compacted density is the major mark to judge whetherthe RCC is compacted, so it should be tested following the rolling in

construction. When the tested unit weight is lower than the regulatedindex, add the passing number, test again, if still could not reach the


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regulated index, analyze the reason and take corresponding measures.The spring soil occurred in rolling process can be ignored if thecompacted density can meet the requirement.7.5.7 Rolling without vibration can heal the slight surface crack.

7.5.9 In order to avoid concrete quality problems owing to long standingtime of mixture, the time from mixing of mixture to the finished time of

rolling should be limitedand it should be determined according to VC

value variation under different weather and influence on compacteddensity. The rolling work should be finished in 2h after the concretemixing begins according to the tests on retaining wall of switch station ofShaxikou hydropower station and cofferdam project of Yantan, the fasterthe better. The situation of Jiangya project is similar to this. The timeshould be shorten while the temperature is high and be prolonged whilethe temperature is low or in rainy days.The finished rolling time of the part being rolled with the next belt at thesame time should be strictly controlled in the maximum intermittent time

between layers that can satisfy the bonding quality between layers.7.6 Joint forming

7.6.1 According to the project practices, the joint can be successfullyformed by cutting with grooving machine, setting up induce hole or

presetting joint partition.7.6.2 There are two ways to form joints with grooving machine: cutting

first, rolling later or rolling first, cutting later. In order to guarantee theformation of joint, the regulated joint-forming size of each layer shouldmeet the requirements, and the left part should wait for the natural tensionfracture of the concrete. Galvanized sheet iron can be used as thematerials filling in the joint. Some projects adopted chemical fiber clothor dry sand to fill in the joint.7.6.3 While placing continuously in thin layers, the induce hole can beformed by hitting poker bar by man or boring with air drill. Fill dry sandinto the hole after it is formed to avoid the induce hole being filled byconcrete while the upper-layer is constructed, which could not realize theaim of forming induce joint. While intermittent-type construction isadopted, the induce hole can be formed by air drill during the intermittenttime between layers.The drilling of induce hole of Tianshengqiao II Grade was done after theconcrete had a certain strength (about 7d age), hole diameter 90mm,distance between holes 1m, hole depth for each time 3m. The jointforming was controlled accurately and the effect was good.7.6.4 The aim of limiting the distance between partitions is to guaranteethe area of formed joint; the height of partition is regulated in order not to

influence the concrete compactness and damage the partition.7.7 Treatment of layer and joint face


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7.7.1 In order to ensure good bonding between concrete layers, theintermittent time between layers must be controlled. The control standardof intermittent time between layers directly influences the boding quality

between layers. The control standard and specific measure of each project

are different at home and abroad. But actually, they are all about thelimitation of time. In fact, many projects at home and abroad take doublestandard: one is used to control direct placement, viz. permissible timeinterval between placing layers; the other is used to control placementwhile using bending mix, viz. permissible time interval between placinglayers while using bending mix. The construction practices show thatonce choose the proper time standard, this course of action cancompletely meet the requirement of bonding quality and shear index

between layers. Since the direct placement has simple procedure, highefficiency and good bonding quality between layers, it should be adoptedin priority in construction arrangement.7.7.2 Considering importance and complexity of the problem, permissibletime interval between placing layers and permissible time interval

between placing layers while using bending mix should be determinedcomprehensively taking account of all kinds of factors. The time ofmedium-small scale projects can be determined by comparing with thesimilar type projects. Different dams have different standards. Even forthe same dam, the standard should also be discriminating for differentconditions and different parts. Generally, the permissible time interval

between placing layers can adopt the initial setting time or time a littleless than that under normal weather condition. The two periods of Jiangya

project are 6h and 24h respectively. The actual permissible time intervalbetween placing layers adopts the initial setting time, and actually testedlongest permissible time interval between placing layers while using

bending mix is 22h, usually it is within 18h-22h.7.7.3 The construction joint and cold joint in RCC dam are weak links.Leakage passage is usually formed, which will influence the stability ofanti-sliding, and should be seriously treated.7.7.4 The purpose of brushing and greencutting is to clean the laitance,filth and loose aggregate on concrete surface, increase the roughness ofthe surface and enhance the bonding capacity between layers. Placing

bending mix on the treated layer will guarantee good bonding betweenupper and lower layers. Brushing and greecutting vary accompanyingwith difference of concrete mix proportion, construction season andmechanical performance. Usually, they should be done after initial settingand before final setting. Greecutting too early not only causes concreteloss, but also damages the concrete quality. So this clause regulates thatgreencutting in advance is not allowed.

7.7.5 According to construction practices at home and abroad, there aresuccessful experiences for bending mix adopting plaster and mortar.


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While adopting mortar, special mix design should be made according tousing part, and should be one grade higher than RCC strength. The jointsurfaces of construction joint and cold joint are rougher after rougheningtreatment and flushing clean. In order to guarantee sufficient filling and

great , mortar with the thickness of 1.0cm-1.5cm should be used.

Spread the concrete closely after the spreading of mortar layer to preventwater loss or initial setting of the spread concrete.7.7.6 While the RCC placement is stopped due to change of constructionschedule, rainfall or other reasons, the slope where the placement stopsshould not be steeper than the steepest slope (1:4) for vibrating rollerworking. The concrete on the slope should be compacted. The sharp anglewith thickness less than 10cm-15cm is hard to compacted and should beeliminated.

According to construction practices, while the construction conditionresumes where the construction suspended, its bonding quality can bereliably guaranteed as long as the layer surface is treated according to theregulation of intermittent time between layers. The bonding quality

between layers can also be guaranteed as long as the damaged surface istreated according to 7.5.8. Generally, the strength of RCC increasesslowly, and the effect of waiting for its increase is not evident. So in orderto enhance the construction efficiency, the construction can be resumedimmediately after the condition is available.

7.8 Casting ofdissimilar concrete()

7.8.1 The aim of synchronous casting is to guarantee the bonding qualityof interface between two kinds of concretes. The conventional concrete ofmiddle outlet, bottom outlet, overflow surface and pier and so on whererequires high smoothness of surface or with greater thickness or volumeand the RCC of dam body are hard to guarantee their appearance andquality, and the rising speed will be influenced. At the same time, they arehard to cast alternately and synchronously. So it is better to cast in twostages, but good bonding between stage I and II must be ensured.

7.9 Casting of abnormal concrete7.9.1 Abnormal concrete is the RCC with rich mortar by spreading mortarduring the placement of RCC. It can be compacted by vibrating methodlevel by level accompanying with RCC construction. The abnormalconcrete is popularly used in many projects at home, and the effect iswell. According to construction practices, the spreading thickness of RCCwith mortar can be as the same as block-leveling thickness, so as toreduce the artificial work quantity and enhance the constructionefficiency. The added mortar quantity should be determined by test

according to specific requirements.7.9.3 In order to guarantee the quality, the measurement of tools


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spreading mortar and the corresponding spread size must be calibratedaccurately, and the construction should be organized abrasively.7.9.4 The construction of abnormal concrete should be carried out beforerolling, and a certain width should be overlapped while rolling to

guarantee good transitional bonding between abnormal zone and rollingzone. Strong vibration is the necessary measure to guarantee thehomogeneity of abnormal concrete, bonding between upper and lowerlayers and bonding quality of rolling zone. The abnormal concrete can bereplaced by the low-slump non-plastic concrete with same mix proportionmixed by mixer.

7.10 Curing and protecting7.10.1 RCC is non-plastic concrete which will be greatly influenced bythe external environment, so the concrete in the block is required to keepwet.7.10.3 The water consumption of RCC per unit is small, and the earlierstrength is low. In order to avoid crack, the curing time should be longerthan that the conventional concrete. The edge angle is easy to crack, andthe curing of it should be strength.

7.11 Construction of embedded parts7.11.1 In order not to obstruct the rolling construction and not to damagethe embedded parts, later-embedding method should be adopted for theinternal monitor instruments and cable. In order to guarantee the rate ofinstrument in good condition and working accuracy, sufficient backfilling

protection layer must be ensured on the top according to different types ofinstrument.7.11.2 While the protection layer is filled back, if the RCC had exceededthe permissible time interval between placing layers, bending mix should

be used at the connecting part to guarantee good bonding betweenbackfilling concrete and rolled concrete when the concrete is filled back.While it is filled back by man in layers, removing the big aggregate is theimportant measure to guarantee the rate of instrument in good condition.The cable may cause concentrated leakage passage, so the compactnessof backfilled mortar must be ensured.7.11.3 It is quite beneficial to the rate of instrument in good condition ifthe instrument embedding is being done on the horizontal construction

joints. Good cooperation and coordination between placing andembedding is one of the most important factors to guarantee the rate ofinstrument in good condition.7.11.4 According to construction practices, roll the surface of backfilledconcrete directly with mechanical equipments may still damage theinstrument before its initial setting, thats why this clause is formulated.For the continuous rising rolling layers, a layer of concrete should be

placed on the instrument embedding part before the normal placing workgoes on.


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7.11.6 Preserve a certain surplus length near the embedding part ofmonitor cable to guarantee the connection between instrument and cablein rolling construction.

7.12 Construction under special meteorologic condition

7.12.2 The rainfall intensity should be controlled in construction as perthe equivalent value of rainfall measured in 5min-10min.7.12.4 The moisture on the surface of the concrete loses quickly in strongwind. In order to guarantee the rolling compactness and good bonding

between layers, spraying measures should be taken to complementmoisture and keep the block humid.7.12.5 The principal way to guarantee construction quality in high-temperature weather is to greatly reduce the intermittent time betweenlayers, meanwhile, take measures to control and complement theevaporation and loss of surface moisture.

8 Quality management and assessment8.1 Testing and controlling of raw materials

8.1.1 Table 8.1.1 is made according to project construction experience athome and referring to foreign data. The aim for testing raw material:check whether the quality of cement, additive blending, aggregate andadmixture can meet the quality standard, and adjust the mix proportion ofRCC and improve the construction technology, as well as assess the

production control level of raw materials.8.1.2 The production of fine aggregate should be mainly controlled in

terms of graduation and water content of sand.The variation of fineness modulus of sand will cause the workability

variation of RCC. Therefore, it is necessary to control the finenessmodulus of sand in the variation range for stable RCC production. Whilethe D-value between the tested results of fineness modulus of sand andthe given value has exceeded 0.2 of the allowable deviation, the mix

proportion of RCC should be adjusted.The water content of the sand in RCC construction should be more

strictly controlled than the conventional concrete. Because when theallowable deviation of water content exceeds 0.5%, it will arouse unstableworkability of RCC. In principle, the water content should be testedcontinuously, and should be checked according to regulations withtraditional oven dry method.8.1.3 For the coarse aggregate produced on site, mainly control itsexceeding and inferior grain and the water content in each grade of stone.

The exceeding and inferior grain inspection should be done with

or exceeding and inferior grain screen.Mainly test the water content of small-sized stone (5mm-20mm) for

coarse aggregate. The tested results of water content of small-sized stone,RCC workability (VC) and compression strength show that the


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fluctuation of water content of small-sized stone will cause fluctuation ofRCC workability (VC) and compression strength or vice versa.

8.2 Testing and controlling of newly mixed RCC8.2.1 The weighing accuracy of each ingredient of each pan of RCC is

one important factor influencing RCC production quality. So theweighing apparatus should be check regularly.8.2.2 The ingredients of RCC should be mixed evenly. The proper mixingtime differs according to RCC workability, volume of mixer, type andfeeding order, and should be determined by mixing test.8.2.3 The emphasis of RCC quality test and control is the newly mixedconcrete not setting after came out of the mixer. The aim is to find thefactors out of control in construction and adjust accordingly to avoidcausing quality accident in structure. Make a certain amount ofcompression strength specimen to assess whether the design requirementsare satisfied by RCC quality.8.2.4 According to construction experiences of projects like Yantan,Tongjiezi, Tianshengqiao II Grade, Shaxikou and Kengkou, the allowabledeviation of VC value at the outlet of the mixer is determined as 3s.8.2.5 The test results of RCC mixed with air entraining agent points outthat: the mixing of air entraining agent will reduce the water consumptionwhile keeping the same workability, if the water-binder ratio does notchange, the cement can be saved. The greater the air content is, the morecement is saved. But the compression strength reduces accompanying

with the increase of air content. The air content of RCC mixing with airentraining agent should be strictly controlled. Otherwise, the compressionstrength will reduce excessively owing to too much air content, whichmay cause quality accident of project. The variation range of air contentshould be controlled within 1%.

8.3 On-site quality testing of RCC8.3.1 This clause is formulated based on the construction experiences of

projects such as Tongjiezi, Shaxikou, Kengkou and Jiangya. Theallowable deviation of VC value 5s refers to the tested value on cast field.The proposing of permissible intermittent time between layers is toguarantee good bonding between layers and make layers satisfy therequirements of strength and impermeability. Therefore, it is proposedthat the permissible intermittent time between layers under differenttemperature should be determined by test.8.3.2 Some experiences have been accumulated for testing compactedapparent density with surface nuclear moisture-density gauge. And someof the products at home have reached the requirements of performanceand quality. So it is regulated that the compacted apparent density should

be tested with surface nuclear moisture-density gauge. Since there is a

releasing period of energy after rolling compaction, so it should be tested10min later.


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8.3.4 The apparent density of RCC must reach higher than 97% of thetheoretical unit weight of mix design to meet the basic requirements ofgravity stabilization and compactness of RCC dam.

8.4 Quality control and assessment

8.4.1 The compression strength of 28d specimens molded by samplingfrom the outlet of the mixer is mainly used to judge the qualitymanagement level of RCC mixture production.8.4.3 The criteria listed in table 8.4.3 is formulated based on ordinaryconcrete referring to American ACI-214.8.4.4 Whether the RCC quality can meet the design requirement or not,assess it in big sample and small sample according to sample times. Takethe Cubic compressive strength with designed age as the basis.For the big sample, assess the quality of RCC with the same gradeaccording to week, ten days or month. The small sample reflects fast, it isto assess the RCC quality of one placing layer or one placing day.According to mathematical theory of statistics, the larger the sample size

N is, the closer the value of mean square deviation S will close to thetruth value. Most scholars believe that N 30 is proper, so the continuous sampling times is regulated more than 30 times. Considering one placinglayer or placing day of RCC, the sampling times should not be more than6, so the continuous sampling times for small sample is regulated lessthan 6. In table 8.4.4-1, the t value is the coefficient of strength ensuringrate while the strength ensuring rate of concrete is 80%.

8.4.5 The standard cubic specimen molded by sampling from the mixerconcrete could not reflect the quality difference aroused by a series ofconstruction operation, including transportation, block leveling, rollingand curing. Core-boring is the most popular method to comprehensivelyassess the RCC quality on site at present.8.4.6 According to the general regulation, the diameter of core sampleshould be (2.5-3.0 times) larger than the maximum aggregate diameter ofconcrete. If the maximum aggregate diameter of RCC is 80mm, thediameter of core sample should be 200mm-240mm. Taking account ofdriller performance in our country at present, this clause regulates that thediameter of core sample should better be 15cm-20cm. For the large-scaled project or project with the maximum aggregate diameter ofconcrete larger than 80mm, core samples with diameter 20cm or largercan be adopted.8.4.7 While the height of specimen is 1.7times larger than the diameter,the constraint of end surface has reduced out of account. As a result, thespecimen of core sample with the height-diameter ratio 2.0 is taken as thestandard specimen. This is also formulated according to test data of ourcountry and referring to specifications of ASTMC42-77 of America and

BS1881.4 of UK. Considering the maximum aggregate diameter is 80mmfor projects and the constraint problem of end surface, it is regulated that


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the core sample with height-diameter ratio less than 1.5 is forbidden to beused in compression strength test.

specification for rcc construction

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