optimization of the technology for recycling concrete ... · the usage of recycled concrete as an...

1 INTRODUCTION

Some differences should be realised from reconsiderating modes of usage for secondary materials and natural raw materials. Secondary raw materials generally provide worse quality parameters than natural materials, which is why the utilisation of secondary raw materials is limited. One of the possibilities as to how to decrease environmental loads is to improve the recycling of building and demolition waste. This results in an economical resource of natural raw materials. The recycling of building materials has a positive impact on the environment, productivity and decreasing new building costs.Developments in the recycling of building materials, especially in concrete constructions, has in recent years been closely linked to the development of new demolition technologies and technical progress in grinding, separation of armature etc. The usage of recycled concrete as an aggregate for construction concrete has brought about new knowledge as well as problems. It is

necessary to deal with the worst of properties aggregates in recycled concrete, e.g. the heterogeneity of the recycled the quality compared with natural aggregates, which results in a higher dispersion of the parameters (e. g., according to research on recycled aggregate concrete, concretes with recycled aggregates have o 25% lower compressive strength than concretes with natural aggregates)Despite all the political, economic and environmental pressures, the application of alternative materials in civil engineering is still low. This is a consequence of confidence of civil engineers in the technical parameters achieved, the cost of modifying the lack of materials and transport and also the negative impact upon the environment.

2 STATE OF THE ART

An ealuation of waste and the minimisation of its negative impact on the environment have been included in the strategic

M. LEDEREROVÁ, K. GRÜNNER

OPTIMIZATION OF THE TECHNOLOGY FOR RECYCLING CONCRETE MATERIALS

KEY WORDS

• Waste• Recycling• Aggregates• End use• Recycling conveyer• Economic comparison

ABSTRACT

Consideration of the appropriate usage of recycled aggregates from crushed concrete into new constructions and the optimal application of recycling plants from ecological and economic aspects.

Miriam LEDEREROVÁ, Ing., PhD., Senior Assistant

Department of Material EngineeringFaculty of Civil EngineeringSlovak University of TechnologyRadlinského 11, 813 68 Bratislava, Slovakiae-mail: [email protected]

Karol GRÜNNER, Assoc. Prof., Ing., PhD.

Road Scientific and Research Laboratory – Department of Transport Construction and Traffic Engineering Faculty of Civil Engineering Slovak University of Technology Technická 3, 821 04 Bratislava, SlovakiaResearch field: Road pavements, Construction technology, Properties of road materialse-mail: [email protected]

2005/4 PAGES 29 – 40 RECEIVED 3. 4. 2006 ACCEPTED 4. 5. 2006

2005 SLOVAK UNIVERSITY OF TECHNOLOGY 29

ledererova.indd 29 28. 6. 2006 9:24:13

30 OPTIMIZATION OF THE TECHNOLOGY FOR RECYCLING CONCRETE MATERIALS

2005/4 PAGES 29 — 40

tasks of Slovakia’s politics. Civil engineering and the building materials industry provide a large arena for different waste evaluations. The tendency is to create better conditions for a broader use of wastes whose storage poses a very high load on the environment.The notion of ”charging waste” means waste pooling, transporting, assessing and liquidation. Act No.223/2001 Coll. states that waste assessment is a process for improving the physical, chemical or biological properties of waste. Two basic methods of valuation are distinguished – energy and material methods. The energy valuation method utilises waste to obtain energy from the transformation process, while the material valuation method sees waste as a secondary material for manufacturing useable products (including regressive resumption and recycling).Waste created in civil engineering is characteristic by the heterogeneousness of the material. This is related mostly to unhomogeneous materials from different sources and compositions. In its shape, chemical and technological froms the material is heterogeneous and lacks certain properties concentrated in a specific location, because of uncoordinated manipulation and unorganised storage.Table 1 shows the quantity of waste in the Slovak and Czech Republics from 1996 - 2003. It also shows a comparison between the volume of solid mineral waste and building as well as demolition waste. The quantity of estimated waste is also shown in Figure 1. (SOD) (RISO and ISOH sources). [14]The following items belong to the tasks of recycling building materials: building debris, concrete, road materials, etc. Recycling in civil engineering represents the restoration of waste the to production cycle for the primary raw materials targeted.

Concrete recyclate - it is possible to use concrete recyclates as aggregates in new concrete. The utilisation of recycled concrete requires observing specific principles:• consistent extraction and separation of particular building

materials, metal, plastics, wood and sorting out glass;• consistent quality control of building waste, i. e., verification of

the physical and mechanical properties such as strength, bulk density, absorbability, pollution, etc.;

• investigation of the physical and mechanical properties of the materials obtained such as properties of shapes, particle density, voids, absorbability, strength, etc.

Asphalt recyclate – is one possibility for particularly or completely retrieving natural aggregates using repeated technology of road materials (aggregates, bitumen binder) from old roads. Recycled aggregates are obtained from the milling or demolishing of separate layers, perhaps from a whole road construction, and the subsequent

Tab. 1 Quantity of building and demolition waste

YearWaste quantity in the Slovak

Republic (mil. t)

Waste quantity in the Czech

Republic (mil. t)

Solid mineral of quantity waste

(t)

Building and demolition of

quantity waste (t)

Rate of solid mineral waste to overall of

quantity waste (%)

Rate of BDW to overall of

quantity waste (%)

1996 20.2 51.2 149 188 1 272 600 0.74 6.31997 19.8 65.2 127 790 1 782 000 0.65 9.01998 10.1 43.9 123 085 1 643 564 1.2 16.61999 19.6 35.6 197 166 1 051 020 1.0 20.62000 16.1 40.6 420 229 3 622 500 2.6 22.52001 16.4 38.7 377 918 1 335 366 2.3 21.92002 13.6 35.9 134 225 795 276 9.8 5.882003 19.9 - 208 154 1 494 812 1.05 7.48

Additional text : BDW – Building and demolition waste

Legend:Overall of quantity waste in the Slovak RepublicBDW quantity

Fig. 1. Comparison of quantities of building waste and demolition waste

ledererova.indd 30 28. 6. 2006 9:24:15

2005/4 PAGES 29 — 40

31OPTIMIZATION OF THE TECHNOLOGY FOR RECYCLING CONCRETE MATERIALS

modification of the materials obtained. Recycling aggregates as a result of milling bitumen layers includes aggregate conglomerates covered with bitumen.

Brick recyclate – is aggregate from brick brash. Such aggregates are obtained from brick fragments or grinding brick debris. Its bulk density is from 1,400 to 2,000 kg.m-3. It is necessary to observe the separation of each debris material.

Each type of building and demolition waste could be recycled and repeatedly used. Table 2 shows examples of the option of repeated usage of concrete and brick building waste. Recycling material used as sharp of natural materials requires the achievement of technical parameters (established according to the standard STN EN) and should be economically available.

3 VERIFICATION OF THE PROPERTIES OF CONCRETE RECYCLATE

In order to obtain a consistently valuation of the usae of recycled aggregates and a comparison of the different kinds of recycled concrete, it was necessary to perform basic tests of the properties of concrete recyclate and compare them with the properties of natural aggregates. The concrete recyclate, which was used for verification of the Road Scientific and Research Laboratory (CVVL) and for comparison of properties with natural aggregates, was taken from:• an old brick factory in the Bratislava, suburb of Devínska Nová

Ves – company: Špeciálne činnosti, a.s. – separated storage rooms; material overcrushed from demolished concrete roads and concrete constructions in the HARTL jawed granulator after crushing particles over 63 mm, mould and reinforcements were removed - (sample 1),

• the central storage of building waste in the port of Bratislava– company: Gaukum a.s. – building waste from building demolition; material overcrushed in the Resta reflected granulator, max. particle size 150 mm; mould and reinforcement were removed - (sample 2),

• waste storage in Bratislava`s Old Town – company: Gaukum a.s. – building waste from the demolition of private buildings; material crushed in the Resta reflected granulator, particles under 63 mm and over 63 mm selected, mould and reinforcement were removed - (sample 3),

• natural aggregates (mined) from gravelly sand location in Bernolákovo; grain size of 32 mm - (sample 4).

3.1 Sampling

The sampling and laboratory treatment of concrete recyclate samples and natural aggregates were realised due to the established STN norm:• sampling according to STN EN 932-1,• reducing of laboratory samples according to STN EN 932-2.

Sample 1 of approximately 800 kg and samples 2, 3 and 4 of approximately 4 500 kg were stored at the Road Scientific and Research Laboratory of the Department of Transport Construction and Traffic Engineering of the Faculty of Civil Engineering. Laboratory samples were made from these samples for the appropriate tests.

Estimate of physical and mechanical propertiesAfter gathering representative samples from the bulk samples 1, 2, 3 and 4, a laboratory sample (sample minimised from the coarse sample assigned for the laboratory testing) was prepared, and test portions and test specimens were made from these laboratory samples. Then, according to the established STN EN, following physical properties of concrete recyclate and natural aggregates were determined:• particle size distribution; sieve analysis according to STN EN

933-1,• particle shape; shape index according to STN EN 933-4 [38] and

flakiness index according to STN EN 933-3,• resistance to wear (micro-Deval) according to STN EN 1097-1,• resistance to LA fragmentation according to STN EN 1097-2,

Tab. 2 Ability to use concrete and brick waste material

No. Primary material used for Recycling Utilisation

1Concrete roads, bridges, airports, piping, buildings (foundations, decking, walls etc.)

Crushed demolished concrete, bricks, masonry

Materials for concrete, backgrounds for constructions

2 Cable backfill aggregates Packing material3 Playgrounds, courts etc. Crushed concrete, asphalt mixture Mixture material4 Pavements, temporary roads Crushed concrete Replacement of natural aggregates5 Roadways, parking lots, other fields Crushed concrete, asphalt mixture Background layers of roads

ledererova.indd 31 28. 6. 2006 9:24:16


2005/4 PAGES 29 — 40

• determination of loose bulk density and voids according to STN EN 1097-3,

• particle density and water absorption according to STN EN 1097-6,• coefficient of polishing of aggregates accelerated according to

STN 72 1182,• resistance to freezing and thawing according to STN EN 1367-1.

All the tests conducted permormed were on the test portions and test specimens with the determined weight according to the new STN EN; only the coefficients of the accelerated polishing equipment listed in STN were used, because new equipment was hot available. The results are shown in Tables 3a – 3d.The fineness content (f) (passed a 0,063 mm sieve) of sample 1 was 1.7 %, that of sample 2 was 0.4 % thatof sample 3 was 0.7 % and that of sample 4 was 2.3%.The rate of fine aggregates (under 4 mm) of sample 1 was 44.5 % that of sample 2 was 9.4 % that of sample 3 was 27.6 % and that of sample 4 was 41.6 %.Sample 2 contained a high rate of extraneous particles, mostly from crushed asphalt mixture and bricks, the majority of which ranged between 63 and 250 mm, but a large portion was also between 16

Tab. 3a Results of sieve analysis – sample 1 Test specimen 12 950 g

Sieve (mm)

Average sieve residue Sieve passed(g) (%) (%)

63 – – 100.0045 605 4.67 95.3332 1 754 13.55 81.7822 541 4.18 77.6016 837 6.46 71.1411 815 6.29 64.85 8 1 030 7.95 56.90 4 1 596 12.32 44.58 2 1 701 13.14 31.44 1 1 523 11.76 19.68 05 1 072 8.28 11.40 025 742 5.73 5.67

0125 350 2.70 2.97 009 101 0.78 2.19 0063 62 0.48 1.71

bottom 221 1.71

Tab. 3b Results of sieve analysis – sample 2 Test specimen 462 050 g

Sieve (mm)Sieve residue Sieve passed

Extraneous particlesSieve residue Rate

(g) (%) (%) (g) (%) (%) 250 100.00 125 40 520 8.77 91.23 3 460 0.75 8.54 63 175 480 37.98 53.25 16 480 3.57 9.39 45 81 370 17.61 35.64 1 430 0.31 1.76 32 24 130 5.22 30.42 360 0.08 1.49 22 24 150 5.23 25.19 820 0.18 3.40 16 17 100 3.70 21.49 490 0.11 2.87 11 15 010 3.25 18.24 – – – 8 19 590 4.24 14.00 – – – 4 21 270 4.60 9.40 – – – 2 10 220 2.21 7.19 – – – 1 10 310 2.23 4.96 – – – 05 7 290 1.58 3.38 – – – 025 7 110 1.54 1.84 – – – 125 3 650 0.79 1.05 – – – 009 1 750 0.38 0.67 – – – 0063 1 150 0.25 0.42 – – –bottom 1 950 0.42 – – – –

ledererova.indd 32 28. 6. 2006 9:24:18

2005/4 PAGES 29 — 40


and 63 mm. The rate of extraneous particles from the recycled material over 16 mm was up to 6.3 %. The rate of extraneous particles from the recycled material fewer than 16 mm could not be determined, but there were also extraneous particles in addition to the concrete grains.

a) Results of the sieving analysis considered as an average of three determinations (Table 3 a - d).Sample 3 contained a smaller portion of extraneous particles, but there were no asphalt particles. The rate of extraneous particles over 11 mm was 4.6 %.The sieve analysis presented showed distinct differences between each material, but this method showed the possibility of recycling material utilised for different construction purposes. b) Particle shape – shape index (SI) and flakiness index (FI) – determined on 8/16 mm fraction (Table 4).

Tab. 3c Results of sieve analysis – sample 3 Test specimen 211 460 g

Sieve (mm)Sieve residue Sieve passed

Extraneous particlesSieve residue Rate

(g) (%) (%) (g) (%) (%) 125 100.00 63 11 430 5.41 94.59 260 0.12 2.28 45 30 160 14.27 80.32 2 570 1.22 8.52 32 27 150 12.84 67.48 1 210 0.57 4.46 22 22 680 10.73 56.75 860 0.41 3.79 16 19 410 9.18 47.57 450 0.21 2.32 11 17 170 8.12 39.45 590 0.28 3.44 8 7 430 3.51 35.94 – – – 4 17 560 8.30 27.64 – – – 2 9 820 4.64 23.00 – – – 1 11 160 5.28 17.72 – – – 05 9 190 4.35 13.37 – – – 025 10 160 4.80 8.57 – – – 0125 8 570 4.05 4.52 – – – 009 2 630 1.24 3.28 – – – 0063 1 970 0.93 2.35 – – – bottom 4 970 2.35 – – – –

Tab. 3d Results of sieve analysis – sample 4 Test specimen 10 252 g

Sieve (mm)

Average sieve residue Sieve passed

(g) (%) (%) 63 100.00 45 97 0.95 99.05 32 398 3.89 95.16 22 778 7.59 87.57 16 973 9.49 78.08 11 1 066 10.40 67.68 8 987 9.63 58.05 4 1 686 16.44 41.61 2 806 7.86 33.75 1 462 4.51 29.24 05 429 4.18 25.06 025 1 670 16.29 8.77 0125 726 7.08 1.69 009 70 0.68 1.01 0063 31 0.30 0.71 bottom 73 0.71 –

Tab. 4 Results of particle shape estimate

Sample No. Shape index (SI) Flakiness index (FI)1 3.86 31.72 2.74 33.43 3.12 34.14 2.35 28.6

ledererova.indd 33 28. 6. 2006 9:24:20


2005/4 PAGES 29 — 40

c) Resistance to wear – wet microDeval (MDE), through 1.6 mm sieve – determined on 10/14 mm fraction (Table 5).

d) Resistance to fragmentation – Los Angeles (LA), through 1.6 mm sieve – determined on 10/14 mm fraction (Table 5).

e) Loose bulk density (ρb) and void (ν) – determined on 8/16 mm fraction (Table 6).

f) Particle density (ρrd) and absorbability (WA) – determined on fraction 8/16 mm (Table 7).

g) Coefficient of accelerated polishing of aggregates fOK – determined on 8/11 mm fraction (Table 8).

h) Freezing and thawing resistance F – determined on fraction 8/16 mm (Table 8).

3.2 Result of recycling material test

Recycling aggregates, which will be used for different building structures have to meet the same demands as natural or artificial aggregates. No European standards have been published for to evaluate applicability Based on the results achieved, a testing sample could be recommended for an end purpose from the following constructions:a) Sample 1 could be used for concrete constructions, where a high

coefficient of freezing and thawing is not required (cement-concrete road pavement, concrete flats exposed to frost), a high coefficient of polishing (floors, pavements, wearing courses of roads) and a high value of shape characteristics. It could mostly be used for hydraulically bounded and unbounded layers of base constructions used in civil engineering, roads. After another separation, only small a portion of these materials could be used for mortar production.

b) Sample 2 could only be use for hydraulically unbounded base courses.

c) Sample 3 could be used for bounded and unbounded hydraulic materials and for water constructions.

d) Sample 4, as comparative aggregates (mined), could be used in all kinds of cement concretes and for the base courses of roads. It could be not used for areas where high polishing resistance is needed.

4 METHODOLOGICAL MODE FOR RECYCLING OPTIMAL SOLUTION

With regard to the expected, a technical solution for recycling was verified and an optimum solution for recycling equipment variants was detected for treating building waste from an economic point of view. The solution was divided into three sections:• Preliminary phase. • Design treatment – analyze the state of the art, input statements

Tab. 5 Results of resistance to wear (MDE) and resistance to fragmentation (LA) tests

Sample No.microDeval (MDE)

(%)Los Angeles (LA)

(%)1 20.2 31.22 24.3 33.43 22.8 29.54 4.6 24.6

Tab. 6 Results of loose bulk density (ρb) and voids (ν) tests

Sample No.Loose bulk density (ρb)

(Mg.m-3 )Voids (ν)

(%)1 1.615 21.152 1.437 23.103 1.535 20.934 1.836 18.63

Tab. 7 Results of grain bulk density (ρrd) and water absorption (WA) tests

Sample No.

Particle density (ρrd) (Mg.m-3)

Water absorption (WA) (%)

1 2.591 4.532 2.483 5.823 2.560 4.964 2.677 0.79

Tab. 8 Results of coefficient of accelerated polishing of aggregates fOK and freezing and thawing resistance F estimate

Sample No.

Coefficient accelerated polishing of aggregates (fOK)

(–)

Freezing and thawing resistance

(F) (%)1 0.46 3.632 0.47 4.273 0.45 4.114 0.41 0.72

ledererova.indd 34 28. 6. 2006 9:24:21

2005/4 PAGES 29 — 40


and the treatment of various solutions. Analyzing the state of the art and the input statements is basis of comparison for a final valuation of the progress and efficiency of the design solution.

• Optimisation phase – selection of an optimum solution. The definitive option of some processing variants preceded the technical-economical comparison of the variants. This is an analytical investigation of the technically comparable variants which is oriented towards choosing the optimum variant. The technically comparable variants are those that satisfy the basic conditions implicated in the building process at the same rate, but the mode of implementation is different as well as the economic effect.

4.1 Preliminary phase – input statements

Input statements represent the basic infobases for research. First, there has to be a definite kind of recycling. At the same time, quality requirements for the end product – recyclate are known.

Transport pathA high quality ordering of the work is organisation is needed because of the specific conditions of production – the mobility of production and the stability of building premises, the large amount to be transfer red, high degree of mechanisation of some processes.

Time characteristics The time analysis is based on an assumption of the work effect. The following data have to be known for an evaluation of the recycling technology. These data are also the basis for an efficiency evaluation:• Readiness of the onset.• Sequence of each particular process of the recycling cycle and the

need for readiness of individual the building machines.• Influences on the theoretical time are unplanned, and they result

in non-productive times. The ideal solution is to estimate the exact values of the duration of any stoppages and the designation of any pauses. Respected building machines companies claim service work must be permormed every 24 hours. The duration of one service call is 30 minutes. The stoppage of technological processes has been established in one at feasibility project.

Environment protectionThe building process participates in the degradation of our environment. The effect of harmful pollutants created by the building process can not be fully eliminated, but the task is to minimise them along with increasing costs of construction. It is necessary to eliminate:

• Dustiness – primary and secondary.• Air pollution from gas pollutants.• The sound of building machines.• Vibrations.

The work environmentThe culture of work environments refers to the material and thought arrangements forming the optimal conditions for technological processes. A systematic approach to resolving this condition can be supported by the development of all the other elements participating in the process. Finally, it will influence the final effect of the process.An increase in work productivity by about 10 – 30 % could be achieved with a suitable solution to problems of the work environment, especially better lighting, lower noise and optimum work comfort.

Machine parametersAn evaluation of a recycling design is affected, to a large extent by the recycling machine itself. A machine as a main part of the recycling process has to be seen as a complex with the following characteristics:• technical,• economic.

Technical parameters such as the comporents of the machine, its tonnage, the weight moment, the weight of the machine, its work rhythm, theoretical efficiency, work radius, kind of gear, relocability, accessories and the machine is facilities are necessary characteristics that are indicated by the manufacturer, althougt they are unchangeable.Economic parameters, such as the of acquisitiont price, the leasing cost price, leasing terms, general costs per work unit, assembly costs and the machine is age can be changed.

Quality requirements of end productThe selection of an optimal process for recycling places emphasis on the qualitative properties of the recyclate. The basic comparative criteria are requirements in the following STN EN:• STN EN 12620 Aggregates for concrete,• STN EN 206-1 Concrete. Part 1: Specification, properties,

production,• STN EN 13242 Aggregates for unbound and hydraulically

bound materials for use in civil engineering work and road construction,

• STN EN 13450 Aggregates for railway ballastThese days recycling lines are employed that are suitable for the above-mentioned STN EN.

ledererova.indd 35 28. 6. 2006 9:24:22


2005/4 PAGES 29 — 40

Economic criteriaAn important factor in recycling consists of the economic criteria. A technical machine for recycling involves primary costs for its use. The service costs of a machine are also high. The consumption of recycling material will be secured only in the case where the price of the recycled material will be lower than natural material, but recycled materials have to have required parameters. For the achievement of the above-mentioned target, it is necessary to ensure:• A sufficient source of recyclable waste.• The selection of suitable technical equipment for recycling. • A mode of recycling the material in the building process.• Consistent qualitative properties of the recycling materials.• Availability of a site for locating the recycling machines.It can be seen from the above-mentioned criteria that building companies have a limited ability to realise the recycling of building or demolition waste. The extension of recycling technologies with regard to efficient processing needs:• The development of companies’ capacities in their basic activities

for the recycling process.• Resolution of financial requests for building waste storage at

community dumps and at closed mines.• Construction of local storage for building and demolition waste

and its separation.• Extension of the recycling use of materials in the building

process. • Upgrading equipment facilities, especially in the phase of

preparing material to be crushed and its separation.

4.2 Processing recycling applications

a) Analysis of recycling technology according to the following technical parameters – the selection of useful machines and compiling equipment, list of technically applicable machines.

b) Analytic system for rating recycling technology.c) Analysis of selected recycling technology following economic

parameters.A definitive selection precedes a technical-economic comparison of variants. The optimal economic variant is selected according to adequate technical variants, which have to be looked at thoroughly. For the sake of completeness, it is necessary to say, that the optimal variant is not always that one which achieves a maximal commercial effect, minimal unit cost products. The choice of a recycling mode has to be adapted to certain conditions.

a) Analysis of recycling technology according to the technical parametersFollowing the analyses of the input data and capacity calculations it is advisable to work out a technical list of the applicable machines.

For the recycling, of secondary material single mobile, semi-mobile and stationary links are mostly used.

b) Analysis of a rating system for recycling technology Systems of environmental management, as a tool of control of a higher quality system in a company. Some of these represent production support and product consumption, which could be seen as environmentally convenient. For an evaluation of the control system in companies, the methods of LCA, EVV and value analysis are especially used.

c) Analysis of the selection of recycling technology according to economic parametersBased on the research of CWMEM (Centre of Waste Economy and Environmental Management), approximately 20 organisations in Slovakia treat recycling waste in buildings. The most efficient modes of recycling, which are on-site companies, surpass the recycling off-situ (recycling at a recycling factory). An alternative solution is also the recycling of building works and building waste in place (recycling in situ), where mobile recycling links are used. For a complete solution of the given issue, it is also necessary to reflect a variant of recycling with a semi-mobile recycling line. These recycling modes are possible only if the following conditions are in place: • economically stabile environs,• a sufficient quantity of input materials (waste),• transportation paths and the costs related to them, • an optimum combination of machines.

High transportation costs have a negative effect on recycling technology and recycling costs. Too high transporting paths, transport of recycling links to the workplace directly increases the final costs of producing recyclate. An evaluation of the availability of recycling technology is necessary to observe all the environmental requirements and to ensure the continuity of the supply of input materials, to ensure the quality of the product and to ensure safety at work with the building machine. The analytic model then suggests equivalent economic environs, the admission of material at the workplace (stoppages are minimised), a comparative set-up of the recycling links (the individual parameters of links are different, but for simplicity`s sake are considered as identical). A set-up the combination of machines is formed from compatible construction machines – a granulator, a sorting machine, a feeder, rolling stock or towing vehicle, as the case may be. Then the economic comparison restis on the choice of an economically optimum variant, a variant that shows the maximum economic features, i.e., a minimum production unit cost.

ledererova.indd 36 28. 6. 2006 9:24:24

2005/4 PAGES 29 — 40


4.3 Economic comparison selection of technology recycling

When selecting of individual variants, technical parameters provide insufficient results of possible implication. These analyses support the thesis that the optimum partial and final results are accomplished with lowest invested equipment.The principle of recycling with a mobile line is the recycling of building waste in situ. Preference of it is mobility, a small built-up area, simplicity, decreasing of primary costs, and variability of input materials and processing of a relatively small quantity of secondary material. The disadvantage is the lower quality of the recyclate. Figures 2 and 3 show examples of mobile crushing machines.

Composition of machine compilation:1. Mobile recycling line.2. Loader.

At the economical comparison we issue from following charges:

Costs of machine formation N:

N = NNL + NOS [1]

NNL cost of recycling lineNOS cost of service machines

NNL = NZN + NPN + NPČ [2]

NZN cost related to recycling line investment (writing off Od), insurance (P) and payment (Mz)

NPN cost of recycling line transportation (Pr ),NPČ cost related to line service (Ph- fuelling and grease costs,

Op – deterioration of chassis, Ud – recovery and servicing costs)

and NOS = N1 + N2 [3]

N1 cost of product unit group 1 – constant,N2 cost of product unit group 2 – variable,

This part presents an example of an account of two alternatives of economically compared recycling machinery that was used in the framework of the dissertation thesis.

1. Variant Recycling line RESTA 1120 x 1000 + Loader UNC 200

Cost price line RESTA NC = 7 020 000.00 SKK Cost price loader UNC 200 NC = 3 200 000.00 SKKCapacity Q = 60 tons/hrTime Fčr = [(250-2) x 10] x 0,9 = 2 232 hr/yearTime yearly Q = 133 920 tons/year

NNL –costs of recycling line

NNL = NZN + NPN + NPČ

NZN – costs associated with investment in recycling line Od = 0.134 x 7 020 000.00 = 940 680.00 SKK/yearP = 0.03 x 7 020 000.00 = 210 600.00 SKK/yearMz = 180 x 2 232 x 2 = 803 520.00 SKK/year

NZN = 1 954 800.00 SKK/year ⇒ 15.34 SKK/tons

NPN – costs of transit of recycling line NPN:Pr = 200.00 + 200.00 + 25 x 65.00 = 2 025.00 SKK50 x = 2 025 x 50 = 101 250.00 SKK/year ⇒ 0.75 SKK/tons

NPČ – costs associated with operations recycling line PHM = 1.075 x 7.2 l/hr x 2,232 x 37 = 594 605.00 SKK/yearOP = 2 300 000.00 x 1/7 = 85 714.00 SKK/yearUd = 0.22 x 7 020 000.00 SKK = SKK/year

NPČ = 2 224 719.00 SKK/year ⇒ 16.61 SKK/tonsNNL =15.34 +0.75 +16.61 ⇒ 32.70 SKK/tons

Figure 2 mobile crushing machines with 900 x 600stripe chassis

Figure 3 Mobile crushing machine 1120/1000

ledererova.indd 37 28. 6. 2006 9:24:26


2005/4 PAGES 29 — 40

Price calculation for loader UNC 200 ⇒ 43 x UNC, Q = 60 tons/hr (determination power of production facilities)

NOS – cost waiting NOS = N1 + N2

N1 – costs on product unit group 1 – constantOd = 0.134 x 3 200 000.00 = 428 800 SKK/year x 3 = 1 286 400.00 SKK/yearP = 0.015 x 3 200 000.00 = 48 000.00 SKK/year x 3 = 144 000.00 SKK/yearMz = 180 x 2 232 x 3= 1 205 280.00 SKK/year

N1 = 2 635 680.00 SKK/year ⇒ 19.68 SKK/tons

N2 – costs on product unit group 2 – variablePHM = 1.075 x 6.4 l/hr x 2 232 x 37 x 3) = 1 704 534.00 SKK/yearOP = (4 x 50 000 x 1/2 250 x 2 232) x 3 = 595 200.00 SKK/yearUd = (0.22 x 3 200 000.00 SKK) x 3 =2 112 000.00 SKK/yearPr = (50 x 6.4 x 37) x 3 = 35 520.00 SKKN2 = 4 447 254.00 SKK/ year ⇒ 33.20 SKK/tons

N – travelling expensesN = NNL + NOS = 32.70 + 52.88 = 85.58 SKK/tons

2. Variant Recycling line RESTA RESTA 800 x 1000 + Loader UNC 200

Cost price line RESTA NC = 7 420 000.00 SKK Cost price loader UNC 200 NC = 3 200 000.00 SKKCapacity Q = 90 tons/hrTime fund Fčr = [(250-2) x 10] x 0.9 = 2 232 hr/yearTime yearly Q = 200 800 tons/year

Od = 0.134 x 7 420 000.00 = 994 280.00 SKK/ yearP = 0.03 x 7 420 000.00 = 148 400.00 SKK/ yearMz = 4 x 180 x 2 232 = 1 607 040.00 SKK/ year

NZN = 2 749 720.00 SKK/year ⇒ 13.69 SKK/tons

NPN: costs of transit of recycling line NPN:NPN = (500 + 25 x 65) x 40 = 85 000.00 SKK/year

NPN = 85 000.00 SKK/year ⇒ 0.42 SKK/tons

NPČ: costs associated with operations recycling line PHM = 1.075 x 7.2 l/hr x 2 232 x 37 = 594 605.00 SKK/yearUd = 0.22 x 7 420 000.00 SKK = 1 632 400.00 SKK/year

NPČ = 2 227 005.00 SKK/ year ⇒ 11.09 SKK/tons

NNL =13.69 +0.42 +11.09 ⇒ 25.20 SKK/tons

Price calculation for loaderUNC 200 ⇒ 4 x UNC, Q = 90 tons/hr (determination power of production facilities)

NOS – cost waiting NOS = N1 + N2

Od = 0.134 x 3 200 000.00 = 428 800 SKK/year x 4 = 1 715 200.00 SKK/yearP = 0.015 x 3 200 000.00 = 48 000.00 SKK/year x 4 = 192 000.00 SKK/yearMz = 180 x 2 232 x 4 = 1 607 040.00 SKK/year

N1 = 3 514 240.00 SKK/year ⇒ 17.49 SKK/tons

PHM = 1.075 x 6.4 l/hr x 2 232 x 37 x 4) = 2 272 712 SKK/yearOP = 200 000 x 2 232/2 250 x 4 = 793 600 SKK/yearUD = (0.2 x 3 200 000.00 SKK) x 4 =2 816 000.00 SKK/year

N2 = 5 882 312 SKK/year ⇒ 29.28 SKK/tons

N – travelling expensesN = NNL + NOS = 25.20 + 46.77 = 71.97 SKK/tons

4.4 The results of recycling line

The basic solution to recycling demolished concrete consists in an analysis of the efficiency of the appropriate recycling process. In a technically sufficient version, inputs of optimum economic variant into the account selection.The operating costs of a recycling machine depend on the quantity of waste and on the machine`s use. Figures 4 and 5 show the effect of the amount of waste depending on the time and costs.It follows from Figure 5 that an increasing quantity of processed material costs for 1 t of recyclate is decreasing. Figures 4 and 5 shows that with this technology, it is better to process more than 5000 t of waste, because it needs a higher primary investment, and it is designated for a larger quantity.An optimum selection of recycling technology applications is by economic analyses, which means the selection of recycling links (mobile, semi-mobile, stationary), the selection of a crushing system (jawcrusher crusher, impact crusher, separator), etc.There would be an adequate area for operating and service on definitive material. Stationary links would be equipped with dust equipment or, as the case may be, individual machines would be

ledererova.indd 38 28. 6. 2006 9:24:28

2005/4 PAGES 29 — 40


attached with an anti-acoustic wall. From an economic aspect, the selection of a stationary line would be better for quantity material and periodical supplies of material from 5000 t (Figure 5).A semi-mobile line is equipment where the ambient area of the line has limits because of the need to assemble several machines and respectively disassemble them for transport. A greater amount of machines increases the cost of assembly work, transportation as well as they also increase time pressure.A mobile line is in practice considered as the most flexible, but it has the smallest area for use and location of the machine. Mobile links are used in one place for a short time period and they are economically interesting for a lower quantity of material. Mobile links donot have any dust-removing equipment, which is a negative factor for use in

some locations (urban areas, habitable locations etc).At a specific project, the application and selection of a recycling line also has to be implemented with additional parameters, while the design must also be considered from these points of view. These side effects could be:• power seriousness, • noise and dust barrier,• environment protection. An example is a project, which could be realised in built-up areas, where the allowable noise level is precisely defined. If the project run over this limit, the responsibility of the manufacturer is to resolve this problem and suggest a solution. These changes automatically activate changes in other parameters and including cost values. The solution can be machines with a lower consumption, which is automatically significant in the value of efficiency and costs.

Tab. 9 Costs of equipment combination on a product unit under ideal conditions depending on the amount of material

Material amount (t) 1 000 5 000 10 000 15 000 20 000 Costs (SKK) 11 363.70 2 272.74 1 136.37 757.58 568.18Costs (SKK) 14 458.27 2 891.65 1 445.82 963.88 772.91Costs (SKK) 28 800.21 5 760.04 2 880.02 1 920.01 1 440.01

Tab. 10 Costs of equipment combination on a product unit under actual conditions depending on the amount of material

Material amount (t) 1,000 5,000 10,000 20,000 Costs – stationary line (SKK) 91.52 87.58 85.3 85.2

Costs – semi-mobile line (SKK) 96.86 74.42 74.4 73.0Costs – mobile line (SKK) 129.9 69.75 64.5 40.98

Stationary lineSemimobile lineMobile line

Fig. 4 Costs of equipment combination on a product unit under ideal conditions depending on

Fig. 5 Costs of equipment combination on a product unit under actual conditions depending on the amount of material

ledererova.indd 39 28. 6. 2006 9:24:29


2005/4 PAGES 29 — 40

5 CONCLUSION

The results obtained in this PhD thesis indicate a new range of knowledge that could be used in different building branches and that has never been published in such a scope in research projects. By means of tests, the state of waste treatments in Slovakia was verified, the state of waste storage of demolished materials of different kinds from building constructions, and the state of concrete recyclate usage. There was also designed a concept of economic evaluation for optimised applications of recycling building materials.The state of the art regarding waste treatment in the Slovak Republic urges us to recycling. The state has supported dynamic progress with legislative measures, but this issue has no been applied in building practice so far. Improvement could be implemented with a suitable environmental of the existing technologies and thread providing for orderly progress in treatment of waste recycling lines. Recycling equipment could be applied mostly by waste treatment of concrete and asphalt mixtures (road layers, demolition of concrete

and precast structures). Universal materials could find use in the construction of road layers as an additional material in cement concrete, concrete for less demanding structures, foundations, etc. Waste obtained from a building demolition is considered from the perspective of the processing of the waste, because it requires the separation of individual kinds of materials, which afterwards have to be processed separately (concrete, masonry, mortar, reinforcement). It is also important to exclude materials that are contaminated and thus unsuitable for use. The whole process of treating building materials is directed to wards reach the best quality end product with the minimum respective comparative economic coefficing.The quality of the end product distinctly affects its price and also its future use. Waste obtained from demolitions is mostly heterogeneous, while it requires its separation right on the a spot, depending on the kind the material of separated. The control systems priority is to achieve high quality of the end product and material classification for its end use. In selecting a recycling line, should be considered the kind and amount of material, the transport distance and the location of the recycling line.

REFERENCES

1 Ledererová, M.: Optimalizácia technológie recyklácie betónových silikátových materiá-lov. (Optimisation of Technology for Recycling Silicate Materials.) In: Dissertation work, Faculty of Civil Engineering, STU Bratislava, 2005, 90 pp. (In Slovak)

2 Pytlík, P.: Ekologie ve stavebnictví. (Ecology in Civil Engineering) In: Scripts, ČVUT, Prague, 1997, pp. 98 – 135 (In Czech)

3 Recyklace stavebných materiálů. (Recycling Construction Materials) In: Stavební kontakt 4/98, Brno,1998, pp. 33 – 37 (In Czech)

4 Kňazeva, V., Skanavi, N.: Koncepce ekologického hodnocení stavebných hmot ze suro-viny vyrobené recyklací. (Concept of Ecological Evaluation of Construction Matters of Raw Materials Manufactured by Recycling.) In: Seminar proceedings ”International Scientific Conference” VUT, Brno, 1999, pp. 67 – 70 (In Czech)

5 Vyhláška MŽP SR, ktorou sa ustanovuje kategorizácia odpadov a vydáva Katalóg odpadov č. 19/1996 Z. z. (Decree of the Ministry of the Environment of the Slovak Republic, stating categorisation of wastes and issuing a Catalogue of Wastes No. 19/1996 of the Collection of Laws), 1996 (In Slovak)

6 Grünner, K.: Súčasný stav normalizácie v oblasti kameniva u nás. (Present Condition of Normalisation in the Area of Aggregate in Our Country.) In: Seminar proceedings ”Technology aggregates 98 ”, Stará Lesná, 1998, pp. 69 – 72 (In Slovak)

7 Matesová, D. a kol.: Využití betonu z recyklovaného kameniva pro konstrukční účely. (Using Concrete of Recycled Aggregate for Construction Purposes In: Seminar proceedings ”RECYCLING 2001 ”, Brno, 2001, pp. 34 - 41 (In Czech)

8 Hyben, I. a kol.: Optimalizácia umiestnenia recyklačnej linky. (Optimisation of Locating a Recycling Line.) In: Seminar proceedings ”RECYCLING 2005 ”, Brno, 2005, pp. 89 – 95 (In Czech)

9 Šenitková, I., Števulová, N.: Recyklácia v stavebníctve z pohľadu energetických úspor. (Recycling in Civil Engineering from Perspective of Economic Energ.) In: Acta Montanistica Slovaca, Košice, 3/1998, pp. 318 – 322 (In Slovak)

10 Haburaj, F.: Recyklace stavebních a demoličních odpadů. (Recycling of Construction and Demolition Wastes.) In: Termwork, UP, Faculty of Transport JP, Pardubice, 2004, pp. 1 – 25 (In Czech)

11 Klímek, V.: Základy stavebného inžinierstva. (Fundamentals of Civil Engineering.) In: Scripts SvF SVŠT Bratislava, 1985, pp. 45 – 80 (In Slovak)

12 Rockstroh, W.: Technologické projekty I, II. (Technological Designs I, II.). In: Alfa 1972, Bratislava, pp. 34 – 56 (In Slovak)

13 RISO – www.riso.sk – údaje uvedené v elektronickej forme. (Data provided in electronic form.) Bratislava, 2005 (In Slovak)

14 SAŽP – www.sažp.sk – údaje uvedené v elektronickej forme. (Data provided in electronic form.) Bratislava, 2005 (In Slovak)

15 Prokopčáková, K.: Projektovanie mechanizovaných stavebných procesov. (Designing Mechanised Construction Processes.) In: Proceedings of ”11th International Scientific Conference”, VUT Brno, 1999, pp. 137 – 140 (In Czech)

ledererova.indd 40 28. 6. 2006 9:24:31

optimization of the technology for recycling concrete ... · the usage of recycled concrete as an...

Documents