ADVANCES IN CONCRETE TECHNOLOGY IN THE MIDDLE EAST:

SELF-CONSOLIDATING CONCRETE

Kamal H. Khayat

Editor

i

PROCEEDINGS OF

THE SECOND INTERNATIONAL CONFERENCE ON

ADVANCES IN CONCRETE TECHNOLOGY IN THE MIDDLE EAST:

SELF-CONSOLIDATING CONCRETE

December 8-10, 2009

Rotana Beach Hotel

Abu Dhabi, UAE

ii

Organizing Committee

Chairman

Kamal H. Khayat

Universit de Sherbrooke, Canada

Secretary

Rabih Fakih

Grey Matters, UAE

Treasurer

Fouad Yazbeck

Readymix Abu Dhabi, UAE

Advisory Committee

Osama Abdulbari

Sodamco, UAE

James Aldred

GHD, UAE

Hussein Basma

PCFC-Civil Engineering Department, UAE

Tarek Fransawi

Sodamco, UAE

Abdel Kader Trabulsi

Al Falah Readymix, UAE

Sponsored by: ACI International

Organized by: Grey Matters Group of Companies

iii

PREFACE

The Committee for the Organization of ACI International Conferences is very

pleased to sponsor the Second International Conference on Advances in Concrete

Technology in the Middle East: Self-Consolidating Concrete, which will be held

December 8-10, 2009 in Abu Dhabi, United Arab Emirates.

This conference dedicated to self-consolidating concrete (SCC) in Abu Dhabi is a

follow up of the CANMET/ACI International Conference that took place in Dubai

in November 2008 highlighting recent advances in concrete technology in the

Middle East.

The papers assembled here, submitted by industrial and academic researchers

from acoss the world cover a wide range of topics highlighted at the conference,

among them material selection and mix design, workability and rheology, test

methods and processing, production and quality control, engineering and

durability, structural performance and design, fibre-reinforced SCC, experience

and case studies, specifications, and economic and environmental benefits.

The organizing committee would like to thank all of the authors, as well as the

session chairpersons for their participation. Special thanks are also extended to all

the sponsors for their generous support.

It is our hope that this compendium may become a useful resource for the

concrete construction industry in the Middle East and help promote a better

understanding of the opportunities and challenges presented within the scope of

this conference.

Kamal H. Khayat

Editor and Conference Chair

Universit de Sherbrooke, Canada

November 2009

iv

CONTENTS

Organizing Committee ......................................................................................... iv

Preface................................................................................................................... v

Past, Present, and Future of SCC

Shigeyoshi Nagataki, Toru Kawai, and Hiromi Fujiwara .................................... 1

Guidelines for Design and Construction of Self-Consolidating Concrete for

Precast, Prestressed Concrete Members

Kamal H. Khayat, Soo-Duck Hwang, Gillaume Lemieux, and Wu Jian Long ... 27

Friendlier Self-Compacting Concrete through Smart Dynamic Construction

Bryan Barragan, Joana Roncero, Roberta Magarotto, S. Moro, and

R. Khurana ......................................................................................................... 73

Performance-Based Specifications for Self-Compacting Concretes in the Gulf

Region Determined

Jon C. Knights and Don Wimpenny ................................................................... 97

Future Trends in the Processing of Ready-Mixed High-Strength Self-Compacting

Concrete

Harald Beitzel ................................................................................................... 123

Water in Self-Consolidating Concrete Production Its Importance, How to

Accurately Measure it and the Benefits of Automated Water Control

David Serra ....................................................................................................... 133

Pumping of Self-Consolidating Concrete under Extreme Conditions

Harald Beitzel ................................................................................................... 145

Pumpability Assessment of C90 SCC

Said Ahmeed Jodeh and Gabriel E. Nassar ...................................................... 155

Can Ordinary Vibrated Concrete and Self-Consolidating Concrete be Treated

in the Same Way Concerning Pumpability?

Dimitri Feys, Geert De Schutter, Ronny Verhoeven, and Kamal H. Khayat .... 177

v

Self-Compacting Concrete: Properties, Development and Code Recommendations

Joost Walraven.................................................................................................. 201

Practical and Successful SCC Application in the Precast Concrete Industry

F. Surico, A. Gasperi, R. Marino, and J. Perazzoli .......................................... 229

Evaluation of SCC Formwork Pressure

Kamal H. Khayat and Ahmed F. Omran........................................................... 243

Al Turki Business Park Self-Consolidating Concrete: From Head to Toe

Redwan Amin Hameed and Narasimhulu Gary ............................................... 261

Laboratory Testing and Field Monitoring of Self-Consolidating Concrete (SCC)

Drilled Shafts

Hani Nassif, Nakin Suksawang, Kagan Aktas, and Husam Najm ................... 279

In-Situ properties of Self-Consolidating Concrete in a Thick Concrete Raft in

Dubai

James Aldred ..................................................................................................... 297

Environmentally Sustainable Self-Consolidating Concrete A Case Study

Abu Saleh, Mamo Kebede, and Nagham Yacoub ............................................. 307

Rheology of Self-Compacting Concrete and Eco-SCC

Olafur Wallevik, Florian V. Mueller, and Bjrn Hjartarson ............................ 339

1

PAST, PRESENT, AND FUTURE OF SCC

Shigeyoshi Nagataki, Toru Kawai, and Hiromi Fujiwara

Synopsis: In Japan, self-compacting concrete/self-consolidating concrete (SCC)

practical use and increased its results.

Under this situation, the Japan Society of Civil Engineers (JSCE) set up

- in April 1994 and

published State of the Art-Report on Self-Compacting Concrete in December

1996. Based on the report, JSCE published

application of self- Classified types are

explained and self-compactability is clearly defined.

On the basis of the recommendation, SCC has been frequently applied mainly for

the work where vibrating compaction is difficult. Furthermore, SCC has been

made more useful and more applicable through the technology development of

materials, construction method and specific design of mixture proportions.

However the share of SCC has not always been more than 3% of total produced

amount of concrete. On the other hand, some countries in Europe have

considerably higher shares of SCC than Japan. The reason must be investigated in

detail.

Recently in Japan, some researchers have been continuing their study to establish

the prediction method of self-compactability. By establishing this method, it is

considered the reliability of self-compactability of SCC will be much improved.

Keywords: plastic viscosity, pressure loss, reactive powder concrete, self-

compactability, self-compacting concrete, self-consolidating concrete,

superplasticizer, viscosity- agent, yield value

2

ACI honorary member Shigeyoshi Nagataki is a Professor of Aichi Institute of

Technology, Emeritus Professor of Tokyo Institute of Technology. He was

President of Japan Concrete Institute from May 2004 to 2006. He received his

Doctor of Engineering degree (1966) from the University of Tokyo, Japan. He is

also honorary member of JCI, JSCE and JSMS.

Toru Kawai is a senior research engineer of Shimizu Corporation. His research

interests include concrete materials and concrete construction methods. He

received his Doctor of Engineering degree (1996) from Tokyo institute of

Technology. He is member of JCI and JSCE.

Hiromi Fujiwara is a professor of Utsunomiya University. His research interests

include fresh properties of concrete and developing new cementitious materials.

He received his Doctor of Engineering degree (1996) from Tokyo Institute of

Technology. He is member of JCI and JSCE.

INTRODUCTION

Recent years have seen large number of concrete structures with increasing height

and overall size in Japan, resulting in an increasing demand for a wider diversity

of types of highperformance concrete. In efforts to meet these needs, high-

strength, high-durability and high-fluidity concretes, among others, have been

studied.

In Japan, self-compacting concrete/self-consolidating concrete (referred to as

[1], and SCC was put

is not necessary. The development of SCC was initiated from an increasing

demand for improving the reliability of concreting work in Japan. The

background of SCC development in Japan can be seen from the following

information.

The topography of Japan comprises many precipitous mountains and rugged

valleys; thus it is often the case that concrete placement must be carried out under

extremely difficult circumstances. Further, the increasingly complex shape of

concrete structure is making it more difficult to use a vibrator, while the more

densely arranged reinforcing bars resulting from the increasing high-rise concrete

buildings make consolidation more difficult to carry out.

3

In addition, the following reasons have been cited for the increasing demand for

SCC:

1) There have not been enough workers to carry out compacting work at construction sites.

2) Vibrating compaction of concrete is extremely noisy and deleterious to the health of workers, as well as an annoyance to people in the surrounding

neighborhood.

3) Vibrating compaction of concrete is costly and time-consuming.

SCC not only alleviates these problems, but also improves the efficiency of

construction. In other words, the use of SCC requires only the setting up of forms

and placement of concrete by pumping, and eliminates the previously required

hard, labor-intensive work of compacting and the related setting up of scaffolding.

For these reasons, it had been expected that the use of SCC would become

widespread.

Firstly, this paper introduces classification of SCC and verification of self-

compactability prescribed in -

compac established by Japan Society of Civil Engineers (JSCE).

Secondly, this describes technology transition of materials and mixture

proportions, and shows typical examples of SCC applications. Finally, future

research on the estimation of self-compactability of SCC is described.

PAST AND PRESENT OF SCC

Recommendation for self-compacting concrete by JSCE

Details to publish the recommendation I

results gradually in Japan, therefore, the Concrete Committee of the Japan Society

-Compacting

in April 1994 and published State of the Art-Report on Self-

Compacting Concrete [2] in December 1996. The subcommittee published

practical application of self-

the report and accumulated research results in July 1998 [3]. The article includes a

recommendation, a manual for mixture proportioning, a manual for production

and placement, standard test methods and collected data for practical application.

Classification of SCC

In this recommendation, SCC is classified into three types, i.e., Powder-type,

Viscosity agent-type and Combination-type.

4

Powder-type: SCC proportioned to provide the required self-compactability not

by using a viscosity agent but primarily by reducing the water-powder ratio (in

effect increasing the powder content) to impart adequate segregation resistance

and using an air-entraining and high-range water-reducing admixture to impart

high deformability.

Viscosity agent-type: SCC proportioned to provide the required self-

compactability by the use of a viscosity agent to impart segregation resistance and

air-entraining and high-range water-reducing admixture to impart high

deformability.

Combination-type: SCC proportioned to provide the required self-compactability

primarily by reducing the water-powder ratio (in effect increasing the powder

content) to impart adequate segregation resistance and using an air-entraining and

high-range water-reducing admixture to impart high deformability. A viscosity

agent is also added to reduce the quality fluctuation of fresh concrete, so as to

facilitate the quality control of concrete.

In this recommendation, it is recommended that a suitable type should be selected

from these three types of SCC in consideration of the type of the structures,

structural conditions, types of materials available and limitations at concrete

production plants.

This classification is applied to Guidelines for Design and Construction of Self-

Consolidating Concrete for Precast, Prestressed Concrete Menbers [4] .

Classification of self-compactability of SCC

Furthermore, in this recommendation, according to the geometry and

reinforcement conditions of the structure to which SCC is to be applied, the

required self-compactability of SCC is classified into three levels, i.e., Rank 1,

Rank 2 and Rank 3 as follows.

Rank 1: Self-compactability into members or portions having complicated shapes

and/or small cross-sectional areas with a minimum steel clearance in the range of

35 to 60mm.

Rank 2: Self-compactability into reinforced concrete structures or members with a

minimum steel clearance in the range of 60 to 200mm.

Rank 3: Self-compactability into members or portions having large cross sectional

areas and a small amount of reinforcement with a minimum steel clearance of

more than 200mm.

It is recommended that the self-compactability level of general reinforced

concrete structures or members should be Rank 2.

5

Ranks 1 to 3 are set as the levels of self-compactability of concrete. These ranks

are set based on the dimensions and reinforcement conditions of the structures or

members.

Rank 2 is defined as the capability of concrete with which it can be self-

compacted through minimum bar clearance of 60 to 200mm. This normally

corresponds to a steel content of 350 to 100kg/m3. Rank 1 is a level on which

concrete meets severer requirements than Rank 2, and it can be self-compacted

through the minimum bar clearance is less than 60mm and the steel content is

more than 350kg/m3. Rank 3 is a level on which concrete meets easier conditions

than Rank 2, demonstrating self-compactability where the minimum bar clearance

is more than 200mm and maximum steel content is less than 100kg/m3.

Verific ation of self-compactability

The designed SCC is required to be verified by suitable methods in regard to the

attainment of the established performance. Verification of self-compactability of

fresh concrete is important for ensuring the performance of structures. The

verification should be carried out by preparing full-scale forms of the structure or

members or model forms representing the portions where the placing is

considered most difficult, placing the proportioned concrete in them according to

the assumed construction plan and confirming the state of filling of the concrete.

Where the concrete is placed under standard construction conditions, verification

by the tests specified in JSCE Standards is permitted. These are passability tests

using a filling tester, shown in Fig.1, according to the Rank of the concrete

established in consideration of the structural conditions. When Rank 2 self-

compactability is required, the concrete is judged as satisfying the requirement, if

its filling height is not less than 300mm by a filling tester with obstacle R 2.

When Rank 1 self-compactability is required, the concrete is judged as satisfying

the requirement, if its filling height is not less than 300mm using obstacle R 1.

The methods for concrete of Rank 3 include testing by a filling tester without any

obstacle.

Methods of proportioning SCC

In this recommendation, the methods of proportioning each type of SCC are

described to satisfy the self-compactability requirement corresponding to the rank

for the structures. Especially, maximum size and unit content of coarse aggregate

are specified. For maximum size of coarse aggregate, it is described that it should

be 20mm or 25mm. And for coarse aggregate content, standard values (unit

absolute volume of coarse aggregate) are little different depending on type of

SCC and required rank of self-compactability as shown in Table 1.

6

Application of SCC

Technology transition of materials and mixture proportions

The most different feature between SCC and ordinary concrete is that SCC has

sufficient self-compactability in the fresh state as before mentioned. Principal

technologies which have been developed to realize the self-compactability of SCC

in terms of materials and mixture proportions are introduced here.

Superplasticizer: The most remarkable development of material for SCC is the

invention of superplasticizer [5]. Dr. Hattori developed formaldehyde condensates

of beta-naphthalene sulfonates with the primary aim of significantly reducing the

water demand of concrete to produce high-strength concrete [6]. Water reduction

of up to 30 percent was achieved with the use of this superplasticizer called

Mighty 150. This admixture was introduced into the Japanese concrete industry as

-range water-

Since then, it has greatly contributed to production of high-strength concrete.

In Germany, Dr. Aignesberger and his colleagues developed the melamine-based

superplasticizer having nearly the same performance as the beta-naphthalene-

based one [7]. These two superplasticizers, however, have one common defect

that the loss in slump is considerably large.

Therefore, these superplasticizers were mainly used for factory production where

the problem of loss in slump during transportation is negligible. Another

approach was to add superplasticizer right before placing concrete at site.

To solve this problem, new technology of slump control with a reactive

polymeric dispersant [8], -

entraining and high-range water-

superplasticizer is mixed into concrete at the mixing plant even for in-situ casting

because the loss in slump during transportation is relatively small.

In terms of rheological aspect, by adding conventional superplasticizers, SCC

shows a small yield stress but it shows a relatively high plastic viscosity due to a

low water-cement (binder) ratio. This too much high plastic viscosity generally

makes it difficult to achieve the easy placement.

A new type of polycarboxylate-based air-entraining and high-range water-

reducing admixture has been developed on the basis of steric hindrance theory in

Japan. This polycarboxylate-based superplasticizer imparts the SCC with high

deformability and adequate plastic viscosity in the period immediately after

initial mixing until placement, even when the water-binder ratio is 30% or lower.

Under the circumstances, airentraining and high-range water-reducing

admixture was specified in JIS A 6204 (Chemical admixtures for concrete) in

7

1995. Since its introduction, this superplasticizer has dramatically increased in

use for achieving SCC and high-strength concrete.

The share of superplasticizers used for SCC in Japan around up to 1998 is

described in Fig. 2. It is clearly understood that polycarboxylate-based one was

commonly used. In recent years (after 1998 to 2009), almost all the

superplasticizers used for SCC were polycarboxylate one or its modified ones in

Japan.

Here, Fig. 3 [9] shows the share of the superplasticizers used for placed-in-situ

concrete in each country. In hot-climate countries like Vietnam, Thailand, India,

Singapore and Malaysia, beta-naphthalene-based superplasticizer (BNS) is the

major one. The reason may be the higher performance of BNS in higher

temperature and its lower price. According to Fig. 3, the share of the

superplasticizers depends on the area of the world.

Principal materials and mixture proportions SCC contains much higher unit

content of powders compared with ordinary concrete. Here, powder means not

only cement but also mineral admixtures such as ground granulated blast-furnace

slag, flyash, limestone powder and expansive agent.

The addition of components other than cement is mainly for reducing the heat of

hydration of the cementitious materials because SCC, especially powder-type and

combination-type mixtures have high contents of powder. Common unit content

of powders in powder-type and combination-type mixtures is 500-575kg/m3,

while that of viscosity agent-type mixture is 400-500kg/m3.

Common water powder ratios of powder-type and combination-type mixtures are

30-40%, while that of viscosity agent-type mixture is 45-55%.

Application volume

The volume of SCC application in Japan since 1992 is shown in Fig. 4 [10]. In

recent years, the volume of SCC placed in situ has been exceeded by that for

factory product. The share of SCC placed in situ is approximately 0.1-0.2% of

total produced amount of ready-mixed concrete in Japan and that of factory

product is about 2-3%.

On the other hand, Europe has a different trend of share of SCC depending on the

country as shown in Table 2 [11]. Shares of SCC of three countries in Table 1 are

considerably higher than those of Japan, possibly due to the difference in cost and

required performance between Japan and those countries. However, the real

reason must be investigated in detail. Information on the application volume in

North America and Asian countries has not been gained.

8

Examples of SCC applications

Anchorages at Akashi Kaikyo Bridge [12] (Large volume construction): Akashi

Kaikyo Bridge is a suspension bridge described in Fig. 5. The center span length

is 1990m, which is the longest one in the world. The main towers are

approximately 300m high. In the anchorages, cable anchor frames made with steel

member to fix the cables from the bridge were installed. The anchorages were

enormous volume of massive concrete structures.

Total 290 thousand cubic meters of SCC were placed at two anchorages 1A and

4A. The anchorage was composed of reinforced concrete part and cable anchor

frame part with densely arranged by steel frames. 1900m3

of SCC was placed in

one day.

Under the condition that sufficient number of workers to carry out vibrating

compaction for large volume construction could not be prepared for the project,

SCC was adopted because it needs no worker for compaction work. The SCC was

manufactured in properly assembled mixing plant at the site. This plant is for the

exclusive use of SCC. To control the quality fluctuation of fresh concrete, fine

aggregate was dewatered through the centrifugal rotating apparatus, for ensuring

the surface water content of fine aggregate of 4.5-5.1%.

Powder type mixture proportions applied to the project are shown in Table 3. The

cement for 1A was low heat cement composed of low-heat portland cement

(25%), ground granulated blast-furnace slag (55%) and fly ash (20%). The cement

for 4A was low heat cement composed of moderate-heat portland cement (21%),

ground granulated blast-furnace slag (59%) and fly ash (20%). Unit cement

content was maintained less than 260kg/m3 to satisfy the criteria that ultimate

adiabatic temperature rise should not be larger than 25oC. 150kg/m

3 of lime stone

powder was used to obtain a suitable viscosity for the placing without viscosity

agent. Maximum size of coarse aggregate of 40mm was selected to increase unit

weight of concrete larger than 2.3t/m3 as required in design.

To avoid the occurrence of thermal cracks, several measures were conducted.

Fresh concrete was cooled down by the spraying liquefied nitrogen gas onto the

concrete right after mixing. Pipe cooling method after placing concrete was also

carried out.

Requirements for concrete were as follows;

1) Unit weight : Not less than 2.3t/m3

2) Specified design strength: 24MPa at the age of 91days.

3) Air content : 1.5 % - 3.5%

4) Slump flow: 550 - 650mm at mixing plant and 450 - 600mm at placing spot.

9

Tunnel Anchorage at Kurushima Ohashi Bridge[13] (Compaction difficulty):

Tunnel anchorage of Kurushima Ohashi Bridge (area of a standard cross section

was approximately 80m2) was installed into the earth at a 40-degree incline as

shown in Fig. 6. Concrete was planned to be placed into the tunnel anchorage

where cable anchor frames and reinforced steel members were complicatedly

installed. Considering that sufficient vibrating compaction could not be easily

achieved because setting up the scaffolding for each lift in the tunnel was costly

and time-consuming, SCC was applied to the project.

Since the concrete was manufactured at an ordinary mixing plant, combination-

type SCC containing viscosity-agent was adopted to reduce the quality fluctuation

of fresh concrete due to the change of surface water content of fine aggregate.

Requirements for concrete were as follows;

1) Unit weight : Not less than 2.3t/m3

2) Specified designed strength: 24MPa at the age of 91days.

3) Air content : 1.5 % - 3.5%

4) Slump flow: 550-650mm at discharging spot.

5) Level of self-compactability : Rank 2 (see Section 1.3)

Mixture proportions applied to the project are shown in Table 4. The cement was

low heat cement composed of moderate-heat portland cement (23%), ground

granulated blast furnace slag(50%) and flyash(27%). Unit cement content was

maintained less than 260kg/m3 to satisfy the criteria that ultimate adiabatic

temperature rise should not be larger than 25oC. Viscosity agent was non-

adsorbed glycol type one in the liquid state.

Around 13,000m3 of SCC were used for 2 tunnels. SCC was pumped into the

tunnel and poured from the bottom to the top of the tunnel through two pipes

installed along the tunnel. Quality control tests were conducted at the mixing

plant, at the discharging spot near the entrance of the tunnel and at the placing

spot inside the tunnel.

Viaducts of Railway (Densely arranged reinforcing bars): In the last decade,

seismic design has been changed with strict criteria to endure the supposed great

earthquakes in Japan. As a result, in structure like viaducts of railway, especially

at the intersectional part of column, beam and slab, very densely arranged steel

reinforcing bars as shown in Fig. 7 have become common.

Mass of reinforcement at the intersectional part often exceeds 500kg/m3 and

sometimes reaches 600kg/m3. Minimum clearance between reinforcing bars was

40mm or so, vibrator can not be easily inserted through reinforcing bars. In these

10

cases, Rank 1 SCC (see Section 1.3) is often utilized instead of ordinary concrete

to attain the required quality. Mixture proportions depend on the requirements.

Coarse aggregate with maximum size of 15mm is preferred and often used to

enhance the self-compactability.

Application to CFT: Concrete-

-strength SCC

made it possible to fill the concrete completely into a steel tubular column having

a number of diaphragms inside (see Fig.8). CFT structure has rapidly been

prevailing in Japan with the strength requirements for concrete becoming more

demanding. In this section, an application record of CFT structure with high-

strength SCC to a high-rise building [14] is reported.

Building A is a 47-story high-rise condominium located in Tokyo. Columns up to

90m above ground were designed in CFT structure using SCC with a specified

design strength of 100MPa. The cross-section of the main columns was a square

measuring 900 by 900mm. Square columns were strengthened with internal

diaphragms, each having a round opening in the center with a diameter of 200 to

400mm, through which SCC passed. SCC was pumped from the ground (see

Fig.9) to the allowable level at which the lateral pressure was expected to reach

the permissible stress of the welds. After aforementioned SCC hardened, concrete

buckets were used for filling SCC into the remaining upper parts of square

columns. Circular columns with a diameter of 800mm were partially used. Since

circular columns were found strong against the lateral pressure, SCC was placed

into circular columns by pumping from the ground to a height of 90m in a single

lift.

Table 5 shows the mix proportions of the high-strength SCC with water binder

ratio of about 20% and slump flow of 650mm. The binder was 70% ordinary

portland cement, 20% blast-furnace slag and 10% silica fume.

Application to high-strength steel fiber reinforce concrete: In Europe, high-

performance steel fiber reinforced cementitious composite referred to as Reactive

Powder Concrete (RPC) was developed [15]. The RPC is a sort of SCC since it

needs no vibrating compaction during placement. Steam curing at 90oC and the

densest packing design enable to produce precast concrete having high-

performance and ultra high-strength of around 200MPa. The actual applications

of RPC have been done by 35 projects in the world. Recently some applications

have been done in Japan and related recommendations have been established by

JSCE [16]. In this section, main features as to mixture proportions, properties in

fresh and hardened states, mechanical properties and construction method of the

first application to pre-stressing concrete bridge in Japan is reported.

11

Table 6 shows the mixture proportions. Water-cement ratio is around 23% and

water-binder ratio is 12%. Cement, quartz and silica fume particles are well

balanced to obtain the densest packing described in Fig. 10. This packing design

helps achieve high-strength and high durability. RPC shows good self-

compactability for casting into thin or complicated shaped mold. It takes 8-14

minutes of mixing to get the specified flowability even by the revolving-blade

mixer.

The compressive strength of RPC is 200-240MPa and the tensile strength is

around 9MPa after 90oC heat curing for 48hours. The high tensile strength

combined with enough ductility makes conventional reinforcement unnecessary.

The 15mm long steel fibers inside of the mortar matrix act as reinforcement to

resist tensile stress.

RPC premix, water and a superplasticizer were mixed as a primary mixing. After

checking the flow value, steel fibers were added to the mixture and it was mixed

as a secondary mixing for 7 min. Then, the flow value was checked again (see

Fig. 11). Mixed RPC was placed through a tremie pipe attached to the hopper

outlet to manufacture the precast blocks described in Fig. 12. After placing, the

block was cured by sheets to prevent water evaporation as a primary curing. For

secondary curing, 90oC steam curing was conducted for 48 hours in a house. The

rate of rising and dropping temperature were controlled to15oC/h and 7 to 10

oC /h,

respectively to prevent the cracks due to temperature difference in the blocks.

Transverse wet jointing of blocks was conducted in the plant prior to installation.

After blocks were fixed on both sides, RPC was poured from the bottom slab to

the top slab. The joints were heat-cured by electrical heaters and insulation. The

strength was achieved as temperature between 70 and 90oC was maintained at

joints. A general view of Sakata Bridge constructed with PRC is shown in Fig. 13.

FUTURE OF SCC

Future research on SCC

In Japan, recently some researches have been working to estimate the self-

compactability, especially the pressure loss between obstacles when SCC is

flowing in formworks [17].

Background of researchRecently in Japan, ordinary concrete can not be applied

to construction of concrete structures on some conditions that densely reinforcing

bars are arranged. Concrete cannot flow through these reinforcing bars. In these

cases, it is difficult to use vibrators and to check state of concrete compaction

directly. Therefore, in case of SCC, a perfect concrete compaction inside

12

formwork is expected. However, the required self-compactability is not always

attained.

Therefore, to study the reason of this lack of self-compactability, it is necessary to

clear the mechanism and to establish the prediction method of self-

compactability.

It is considered that this lack of self-compactability is caused by the pressure loss

between obstacles when SCC is flowing in formworks.

Fig. 14 shows the image of the pressure loss. If concrete is a Newtonian body, the

height difference between two surfaces of concrete in tank A and tank B does not

exist. However, the height difference always exists due to the yield value, because

concrete is a Bingham body.

This height difference is explained by pressure loss of concrete flowing. A

potential energy of concrete is decreased with flowing, because the energy is

spent for friction loss between concrete and surface of formwork, contact loss

with coarse aggregate each other when concrete passes through steel bars, and

transformation loss of concrete with flowing. This energy loss appears as a height

Estimated result for the pressure loss

To investigate a mechanism of pressure loss, it is used the visual testing method

by using model fresh concrete for the pressure loss test; model concrete is

skeleton concrete composed of transparent liquid of Bingham body and artificial

light weight coarse aggregate, and behavior of coarse aggregate is observed. By

using this method and image analysis, continuous change of coarse aggregate

distribution and locus of each coarse aggregate particle can be observed.

From results of these investigations, it is clear that pressure loss has a good

relationship with unit volume of coarse aggregate and clearance between steel

bars (see Fig. 15). As unit volume of coarse aggregate increases and/or as

clearance between steel bars decreases, the pressure loss increases.

In a process of increase pressure loss, flowing velocity of coarse aggregate

particles around steel bars is getting slow or stopping, then only the model liquid

flows through coarse aggregate particles. Then, number of coarse aggregate

particles around steel bars increases. At last, in some cases, around steel bars,

coarse aggregate particles make blockage and this blockage stops the whole

concrete flow.

Mechanism of the pressure loss

Mechanism of causing the pressure loss is considered as follows.

13

[Step 1] Flowing velocity of coarse aggregate in flowing SCC decreases in

upstream area of steel bars

When SCC flows through the interspaces between vertical steel bars in the

formwork, the flowing line of SCC changes from being linear to curved around

the steel bars, and flow of coarse aggregate around the steel bars is obstructed and

the flowing velocity of coarse aggregate is decreased.

[Step 2] Volume of coarse aggregate increases in front of the obstacle

Volume percentage of coarse aggregate particles in SCC increases in upstream

area of steel bars due to the phenomenon described in [Step 1].

[Step 3] The stress transfer mechanism changes in SCC

In SCC, it is considered that the sheer stress and shearing stress act on the

surfaces of the coarse aggregate particles, as shown in Fig.16. In the case of SCC

having low volume of coarse aggregate particles, shearing stress has no influence

on sheer stress.

However, as the volume ratio of coarse aggregate particles to mortar increases,

coarse aggregate particles come into contact with each other easily. As a result, it

is considered that the mechanism of the stress transfer model changes and the

relationship between and becomes linear, as shown in Fig.17.

[Step 4] Sheer stress at the surface of coarse aggregate particles increases

and then yield value of SCC increases partially around steel bars

The shearing stress increases with increasing sheer stress. Thus, the deformation

resistance force of SCC also increases. This means that the yield value of SCC

increases.

[Step 5] The pressure loss increases

When SCC flows through the interspaces between the steel bars, a balance of

dynamic is shown in Fig. 18 and Equation (1). This equation shows that pressure

loss increases as the yield value of SCC increases.

c

LD

DP

2 (1)

Where,

c : Yield value of SCC

P : Pressure difference between the steel bars

D: Diameter of the steel bars

14

L : Clearance between steel bars.

Estimated results and needed research in future

Fig. 19 shows the comparative results of measured pressure loss and estimated

one based on the pressure loss mechanism. From this figure, the relationship

between measured pressure loss and estimated one depends on the dosage of

viscosity agent. The pressure loss is influenced by both rheological properties

such as yield value and plastic viscosity. Therefore this difference occurs from the

reason why this model considers the effect of only yield value but does not

consider viscosity.

Therefore it is necessary to improve the model and establish the accurate

predicting method for the pressure loss in the near future.

REFERENCES

1. Nagataki, S. and Fujiwara, H., -Compacting Property of Highly-Flowable

, Proceedings, Second CANMET/ACI International Symposium on

Advances in Concrete Technology, ACI SP-154, pp.301-314, 1995

2. State of the Art-Report on Self-Compacting

Concrete, Concrete Engineering Series, No. 15, 1996 (in Japanese).

3.

self- (in Japanese).

4. Khayat, K. H., et al, Guidelines for Design and Construction of Self-

Consolidating Concrete for Precast, Prestressed Concrete Members,

Supplemental Papers, Ninth ACI International Conference on Superplasticizers

and Other Chemical Admixtures in Concrete and Tenth ACI International

Conference on Recent Advances in Concrete Technology and Sustainability

Issues, pp.441-474, 2009.

5. Kawai, T.,

Severe Conditions, pp.291-302, 1995.

6. -62,

pp.37-66, 1979.

7. -Based Superplasticizer as a

-68, pp.61-80, 1981.

15

8.

of Third International Conference on Superplasticizers and Other Chemical

Admixtures in Concrete, ACI SP119-1, pp.243-264, 1989.

9. Yamada, K. -National Comparison of Concrete

Materials and Message for Future, -Results of International Questionnaire Survey-

, Keynote Lecture 2, 4th International Conference on Construction Materials:

Performance, Innovations and Structural Implications, pp.71-80, 2009.

10. of Concrete Technology, Vol.27, No.2.,

2008 (in Japanese).

11. Ouchi, M., International Information:Tangible difference between the

definition and the real state of SCC- 5th International RILEM Symposium on Self -

Compacting Concrete- , Vol.46, No.2, pp.89-91, 2008 (in Japanese).

12. Yasuda, M., et al, Construction of Anchorage with Highly Workable Concrete

Capable of Casting 1900 Cubic Meter Per Day/ Akashi Kaikyo Bridge

& Concrete, No.558, pp.60-64, 1993 (in Japanese).

13. Okada, R., et al, Application of Self-Compacting Concrete to Tunnel

pp.44-51, 1996 (in Japanese).

14. Jinnai, H., -rise Buildings: Applications

, Technical report, Taisei Corporation, 2005 (in

Japanese).

15. Richard, P., with High Ductility and 200-

800 -144, American Concrete Institute,

pp.507-517, 1994.

16. and

Construction of Ultra High Strength Fiber Reinforced Concrete Structures

.

17. Maruoka, M., et al, Experimental investigation of estimating method of

pressure loss of self-compacting concrete pass through the gaps between re-bars ,

JSCE Journal of materials, concrete structures and pavement, No.795/V-68,

pp.111-126, 2005 (in Japanese).

16

Table 1 - Standard values of unit absolute volume of coarse aggregate

Table 2 - Share of SCC in Europe

Table 3 - Mixture proportions (powder -type)

Slump

flow

(mm)

Gmax (mm)

W/C

(%)

s/a

(%)

Air

(%)

Unit content (kg/m3)

W C LP S G SP

1A 450-

600 40 55.8 45 2.5 145 260 150 769 965 6.355

4A 450-

600 40 55.8 36 2.5 145 260 150 609 1121 7.8

LP:Lime stone powder

Self-compactability Unit absolute volume of coarse aggregate (m

3/m

3)

Powder-type Viscosity agent-type Combination-type

Rank 1 0.28-0.30 0.28-0.31 0.28-0.30

Rank 2 0.30-0.33 0.30-0.33 0.30-0.33

Rank 3 0.32-0.35 0.30-0.36 0.30-0.35

Country

Share

Placed in situ Factory

product

Denmark 28%(2006)

24%(2005)

50%(2005)

Sweden 5%(2003) 50%(2003)

Netherland No information 70%(2005)

17

Table 4 - Mix proportions (combination-type )

LP: Lime stone powder

Table 5 - Mixture proportions

Fc

(MPa)

Slump

flow

(mm)

Gmax (mm

)

W/B

(%)

Air

(%)

Unit content (kg/m3)

W B S G SP

100 600-

700 20 20 2.0

15

5

77

5 634

86

2 13.6

B: Ordinary Portland cement 70%, GGBF Slag 20%, Silica fume 10%

Table 6 - Typical mixture proportions

Comp.

strength

(MPa)

Flow

value

(mm)

Steel fiber Unit content (kg/m3)

Dia.

(mm)

Length

(mm)

Vol.

(%) W C

Grain

(quartz,

sand etc.)

Steel

fiber SP

200-240 240-

260 0.2 15 2 180 774 1523 157 22

Slump

flow

(mm)

Gmax (mm)

W/C

(%)

s/a

(%)

Air

(%)

Unit content (kg/m3)

W C LP S G Va SP

600-700 20 62.5 49.6 2.5 162.5 260 210 823 880 4.06 7.8

18

Fig. 1 - Shapes and dimensions of apparatus for self-compactability test

Fig. 2 - Share of superplasticizers in Japan(up to 1998)

19

RMC SP

0%10%20%30%40%50%60%70%80%90%

100%

Ja

pa

n

Ko

rea

Ch

ina

Vie

tna

m

Th

aila

nd

Ind

ia

Sin

ga

po

re

Ma

laysia

Ne

wZ

ea

lan

d

Au

str

alia

US

A

Ca

na

da

Ge

rma

ny

Ra

tio

PC-based BNS-based MM-based

Sh

are

Fig. 3 - Share of superplasticizers in each country

Fig. 4 - Volume of SCC application in Japan

20

Fig. 5 - Outline of Akashi Kaikyo Ohashi

Fig. 6 - Placement of SCC at tunnel anchorage

21

Fig. 7 - Intersectional part of column and beam (densely arranged

reinforcing bars)

Fig. 8 - Diagrams in the CFT

Fig. 9 - Placing with a concrete pump

22

Densest

packing

Fig. 10 - The densest packing design

Fig. 11 - Measurement of flow value

Fig. 12 - Precast block

Porosity Cement

Silicafume

Cement

Quartz

23

Fig. 13 - General view of completed bridge (Sakata Mirai Bridge)

Figure 14 - Image of the pressure loss

Fig. 15 - Relationship among unit volume of coarse aggregate Xv, clearance

L, and pressure loss

concrete

concreteconcrete

Tank A Tank A Tank A

Tank B Tank B Tank B

h

ha

hb

Steel bars

partition gate

0.26 0.28 0.30 0.32 0.340

500

1000

1500

2000BlockageClearance: L

30mm 35mm 40mm 45mm

Pres

sure

Los

s P

(Pa)

Unit volume of coarse aggregate Xv (m3/m3)

24

Fig. 16 - Concept of sheer and shearing stress

Fig. 17 - Concept of change in stress transfer mechanism

Fig. 18 - Concept of dynamic balance between steel bars

Shearing stress:

Coarseaggregate

Steel bar

Sheer stress:

Concrete flow

Sheer Stress :

Shea

ring S

tres

s :

By increasing of volume

of coarse aggregate

D

P

SCC

D+L

Yield stress

Steel bar

Concept of the dynamic balance

Distribution of shearing stress

c=P(D+L)

2D

25

Fig.19 - Relationship between measured and estimated pressure loss

0 50 100 150 200 2500

50

100

150

200

250

Measured Pressure Loss (Pa)

Est

imat

ed P

ress

ure

Loss

(P

a)

Vis.=12.5%Vis.=15.0%Vis.=17.5%

Dosage of viscosity agent

26

27

GUIDELINES FOR DESIG N AND CONSTRUCTION OF SELF-

CONSOLIDATING CONCRE TE FOR PRECAST, PRESTRESSED

CONCRETE MEMBERS

Kamal H. Khayat, Soo-Duck Hwang, Gillaume Lemieux, and Wu Jian Long

Synopsis: Self-consolidating concrete (SCC) is a specially proportioned hydraulic

cement concrete that enables the fresh concrete to flow easily into the forms and

around the reinforcement and prestressing steel without segregation. Use of this

type of high-performance concrete for the manufacture of precast, prestressed

bridge elements provides the benefits of increased rate of production and safety,

reduced labor needs, and lower noise levels at manufacturing plants. In spite of its

benefits and widespread use in Japan and Europe, the use of self-consolidating

concrete in the United States has been limited because of concerns about certain

design and construction issues that are perceived to influence the structural

integrity of the bridge system. These issues include workability, strength

development, creep and shrinkage properties, durability, and other factors that

influence constuctibility and performance.

An extensive laboratory evaluation was carried out to develop guidelines for the

use of SCC in precast, prestressed concrete bridge elements, including

information on material selection, mixture proportioning, and workability

evaluation. Key engineering properties, durability characteristics, and structural

performance of SCC were also investigated.

Guidelines for the use of self-consolidating concrete in precast, prestressed

concrete bridge elements were developed and relevant changes to AASHTO

LRFD bridge design and construction specifications were proposed. These

guidelines should provide highway agencies with the information necessary for

considering concrete mixtures that are expected to expedite construction and yield

economic and other benefits.

Keywords: creep; guidelines; mechanical properties; precast; prestressed

concrete; self-consolidating concrete; shrinkage; workability.

28

Kamal Henri Khayat is Professor of Civil Engineering and Director of the

Integrated Research Laboratory in the Valorization of Materials and Innovative

and Durable Structures at the Universit de Sherbrooke in Canada. He is Fellow

of the American Concrete Institute and serves on several technical committees of

ACI, RILEM, and CSA, including Chairman of ACI 237 on SCC and RILEM TC

on Mechanical Properties of SCC.

Soo-Duck Hwang is a Research Assistant at the Universit de Sherbrooke,

Sherbrooke, Quebec, Canada. His research interests include workability, transport

properties, and visco-elastic properties of self-consolidating concrete used in

repair applications and precast/prestressed elements.

Gillaume Lemieux is an engineer at Euclid Canada. He received his M.S. in Civil

Engineering from Universit de Sherbrooke. His research interests include

workability and mix design of self-consolidating concrete.

Wu Jian Long is R&D Manager at Haozhuoyinghua Technology Development

Co. Ltd, Beijing, China. He received his Ph.D. in Civil Engineering from

Universit de Sherbrooke. His research interests include workability, mechanical

properties, and visco-elastic properties of self-consolidating concrete.

INTRODUCTION

The competitive situation in the precast concrete construction market is

significantly affected by price and cost factors as well as by productivity and

quality. This environment is characterized by ever-shorter construction times,

rising labor costs, as well as greater demand for high workability, strength, and

durability. Technological developments and methods of production that can lead

to improved concrete quality and savings are therefore becoming increasingly

important. Self-consolidating concrete (SCC) represents a significant

advancement in concrete technology that provides great potential for efficiency

and economy in concrete construction.

29

SCC is a highly workable concrete that can flow through densely reinforced or

geometrically complex structural elements under its own weight without

mechanical consolidation and adequately fill the formwork with minimum risk of

segregation. The flowability of SCC is higher than that of normal high-

performance concrete typically used in precast, prestressed concrete plants. This

characteristic of SCC, coupled with the absence of the noise associated with

vibration, make SCC a desirable material for fabricating prestressed bridge

elements. The use of SCC in the precast, prestressed applications can therefore

enable complex precast concrete members to be prefabricated with greater ease,

speed, economy, and higher surface quality. This can be achieved even in tightly-

spaced areas or congested reinforcement, such as columns, cap beams and

superstructure elements and lead to providing uniform and aesthetically pleasing

surfaces. The quality control and quality assurance measures used for producing

SCC will also help achieve structures with the desired durability and service life.

Properly designed SCC is expected to provide similar properties as the

conventional counterparts except for the high workability. However changes in

mix design and fluidity of SCC can result in SCC with hardened properties and

performance that are different from that commonly expected from conventional

concrete. Proper selection of material constituents and proper proportioning are

necessary for achieving the desired workability and performance of SCC. The

factors that significantly influence the design, constructability, and performance

of precast, prestressed bridge elements with SCC need to be researched. It is also

necessary to develop guidelines for the use of SCC in bridge elements and to

recommend changes to AASHTO LRFD bridge specifications. These guidelines

will provide highway agencies with the information necessary for considering

concrete mixtures that are expected to expedite construction and yield economic

and other benefits that are associated with SCC (surface finish, labor cost, etc.).

For successful design of SCC, some factors require greater attention than that

required for conventional concrete, including type and size and grading of coarse

aggregate, composition and content of binder, and w/cm. Proper selection of

material constituents is necessary for workability and performance of the

hardened concrete.

A number of test methods have been used to characterize workability of SCC. No

single test method has been found to fully characterize all relevant workability

aspects of SCC. Selection of proper combined test methods can facilitate

workability testing protocol and provide means for quality control of field

applications.

Knowledge of the compressive strength, elastic modulus, and flexural strength of

concrete is required for estimating camber of prestressed members at the release

of the prestressing load, and for determining elastic deflections caused by dead

30

and live loads, axial shortening and elongation, and prestress losses. Literature

review showed that a loss of up to 20% in the modulus of elasticity could be

obtained compared to the high-performance concrete of normal consistency

because of the lower coarse aggregate volume of SCC [Holschemacher and Klug,

2002]. However, under air-drying conditions, the elastic modulus of SCC can be

higher than that of normal concrete at long term.

Typically, SCC mixtures are proportioned with higher binder content and lower

coarse aggregate volume and maximum size which increase the risk of thermal,

autogenous and drying shrinkage, and creep leading to loss of prestress and

excessive deflections and elastic shortening. Therefore, creep and drying

shrinkage characteristics of SCC need to be considered in the design of precast,

prestressed bridge elements to account for losses in prestress and avoid cracking

of concrete.

According to the literature survey, there seems to be some discrepancy regarding

the visco-elastic properties of SCC because of differences in mix design (w/cm),

type and content of coarse aggregates, type of chemical admixture, and testing

exposure. It is reported that the creep potential of SCC appears to be slightly

higher than that of conventional concrete made with the same raw materials and

having the same 28-day compressive strength [Attiogbe et al., 2002; Pons et al.,

2003; Byun et al., 1998]. Depending on the selected binder, w/cm, and ambient

temperature at the precasting plant, the use of new generation HRWRA may

eliminate the need to use radiant heat or steam curing.

SCC used in precast, prestressed applications is typically proportioned with a low

w/cm (0.32 to 0.36) to enhance stability of the plastic concrete. Relatively low

w/cm values, coupled with high content of binder lead to greater degree of

autogeneous shrinkage than conventional concrete. Such type of shrinkage also

increases with the fineness of the binder and fillers in use. Therefore, drying

shrinkage, autogeneous shrinkage, and thermal contraction have to be managed in

the mix design process and in the structural detailing of the prestressed element.

Studies have shown that the scatter between measured and predicted drying

shrinkage values is greater in the case of SCC than that for normal concrete.

Experimental shrinkage strains for SCC were found to be larger than those

estimated by various prediction models [Byun et al., 1998]. Also, comparison of

experimental creep data to those obtained from major creep-prediction models

indicated differences. Work is required to compare creep and shrinkage data of

SCC mixtures made with representative mix designs and the material constituents

available in the United States to those obtained from prediction models.

The stability of SCC is a key property in ensuring uniform mechanical properties

and adequate performance of precast, prestressed bridge girders. Properly

31

designed SCC mixtures can exhibit uniform distribution of in-situ compressive

strength. Bond strength and its uniformity along the height of cast girders can be

influenced by flow properties of the SCC, grading of the aggregate, and content of

fines. Some studies have found that bond strength of SCC to reinforcement can be

lower than that of normal concrete [Koning et al., 2001; Hegger et al., 2003].

Other studies, however, have shown that for a given compressive strength,

reinforced concrete members made with SCC can develop higher bond strength

than in the case of normal concrete [Dehn et al., 2000; Chan et al., 2003]. Bond

strength that can be developed between SCC and prestressed strands and its

uniformity along the height of cast wall elements were investigated in this project.

The structural design concerns related to the use of SCC for constructing

prestressed girders include the likely lower modulus and greater shrinkage of SCC

and the possible larger prestress losses, and the reduced shear resistances resulting

from the use of a smaller maximum aggregate size or a smaller volume of coarse

aggregate.

PROJECT OBJECTIVES AND SCOPE

The aim of the proposed research carried out as a USA National Cooperative

Highway Research Program (NCHRP) Project 18-12 (Self-Consolidating

Concrete in Precast, Prestressed Concrete Bridge Elements) carried out at the

Universit de Sherbrooke in collaboration with McGill University in Canada

[NCHRP Report 628, 2009] is to develop guidelines for use of SCC with precast,

prestressed bridge elements, including recommended changes to the Load and

Resistance Factor Design (LRFD) Bridge Design Specifications of the American

Association of State Highway and Transportation Officials (AASHTO), hereafter

referred to as the AASHTO LRFD Specifications. Such guidelines will provide

highway agencies with the information necessary for considering SCC mixtures

that are expected to produce a uniform product, expedite construction, and yield

economic and other benefits. Accomplishing this objective will require a research

effort to:

develop material properties and performance criteria for SCC used for precast, prestressed concrete bridge elements.

evaluate key engineering properties, durability characteristics, and structural performance of such concrete.

propose relevant changes to AASHTO LRFD Bridge Design and Construction Specifications.

Specifically, this project aimed at:

32

developing SCC mixtures that can be produced consistently in the field;

identifying test methods for use in SCC mix design;

identifying test methods for use for quality control in precasting plants;

developing specifications and criteria for SCC mixtures for precast, prestressed concrete bridge elements;

determining the influence of mix parameters, such as raw materials, mixture proportioning, mixing, production, placement, and characteristics of the cast

element;

comparing performance of precast, prestressed concrete elements made with SCC with those made with conventional high-performance concrete;

preparing guidelines for testing, proportioning, and casting SCC bridge elements;

investigating applicability of current models recommended by AASHTO LRFD Bridge Design and Construction Specifications and suggest revisions

whenever applicable.

The paper presented here summarizes the guidelines for the use of SCC in precast,

prestressed bridge girders. The guidelines include information on the selection of

concrete constituents and proportioning of concrete mixtures, workability

characteristics, testing methods, mechanical properties, visco-elastic properties,

production and control issues, and durability of SCC.

SELECTION OF CONSTIT UENT MATERIALS

The production of SCC requires uniform quality of all constituent materials, and it

is therefore necessary that these materials meet standard specifications. A choice

of suitable constituent materials is vital to the optimization of SCC mix design for

different applications. Constituent material qualification for SCC designated for

precast, prestressed concrete bridge elements generally follows the requirements

of AASHTO LRFD Bridge Design [2004] and Construction [1998]

Specifications. It is important to continually check for any change in materials or

proportions that will affect surface appearance, strength, or other characteristics of

SCC that may affect its overall performance.

Cement and Cementitious Materials

One must ensure that material additions do not adversely affect the desired

architectural appearance, where appearance is a design requirement.

Cement and blended cement

33

All cements which conform to the AASHTO M 85 or ASTM C 150 standard

specifications can be used for the production of SCC. The correct choice of

cement type is normally dictated by the specific requirements of each application

or by the availability. For SCC applications where visual appearance is important,

adequate cement content and uniform w/cm should be adopted to minimize the

color variation. Therefore, the cement should be from the same mill and of the

same type, brand, and color.

Selection of the type of cement will depend on the overall requirements for the

concrete, such as compressive strength at early and ultimate ages, mechanical

properties, durability, and color considerations in architectural applications where color

and color uniformity are important. Blended hydraulic cements which conform to the

AASHTO M 240 or ASTM C 595M can also be used. Unless otherwise specified,

Types I, II, or III cement; Types IA, IIA, or IIIA air-entrained cement; or Types IP

(portland-pozzolan cement) or IS (portland blast-furnace slag cement) blended

hydraulic cements can be used for the construction of precast, prestressed concrete

elements. Types I, II or III cements can be used with some replacements by

supplementary cementitious materials and other hydraulic binders. In general, fly ash

and slag replacement values shall not exceed 20% and 40%, respectively, to ensure

high-early strength for satisfactory release of strands.

The total content of cementitious materials used in prestressed concrete for a 28-

day design compressive strength of 4,000 to 8,000 psi (28 to 55 MPa) can vary

from 600 to 1,000 lb/yd3 (356 to 593 kg/m

3) [PCI Bridge Design Manual, 1997].

The AASHTO LRFD Bridge Design Specifications [2004] suggest that the sum

of portland cement and other cementitious materials should not exceed 800 lb/yd3

(475 kg/m3), except for Class P concrete where the total cementitious materials

should not exceed 1,000 lb/yd3 (593 kg/m

3). These values for SCC designated for

precast, prestressed applications shall range between 650 and 800 lb/yd3 (386 and

475 kg/m3) [ACI 237R-07].

Fly ash

Pozzolans and slag meeting ASTM C 618, C 989, or C 1240 are supplementary

cementitious material and may be added to portland cements during mixing to

produce SCC with improved workability, increased strength, reduced

permeability and efflorescence, and improved durability. In general, Class F fly

ash has been shown to be effective in SCC providing increased cohesion and

robustness to changes in water content [European Guidelines, 2005]. Fly ash

should conform to the AASHTO M 295 or ASTM C 618 [AASHTO LRFD

Bridge Design [2004] and Construction [1998] Specifications]. In general, the

content of cement replaced with fly ash is 18% to 22% by mass [Florida DOT,

34

2004]. In some cases, higher level of fly ash replacement may reduce the ability

of SCC to flow. The replacement rate of fly ash also affects strength and

durability. Contribution of fly ash delays the hydration process and strength

development. Fly ash can also affect air entrainment since the carbon present in

fly ash can absorb air-entraining admixture and adversely affect the ability to

entrain air. Therefore, state specific limits on LOI indicative of the carbon

content. Fly ash shall not be used with Type IP or IS cements.

Silica fume

Silica fume conforming to AASHTO M 307 or ASTM C 1240 can be used as

supplementary cementitious material in the proportioning of SCC for improved

strength and durability. Silica fume also improves resistance to segregation and

bleeding. Special care should be taken to select the proper silica fume content. In

some cases, high level of silica fume addition besides increasing cost can cause

rapid surface crusting that leads to cold joints or surface defects if delays occur in

concrete delivery or surface finish. According to Florida DOT [2004], the

quantity of cement replacement with silica fume should be 7% to 9% by mass of

cementitious materials.

Ground granulated blast- furnace slag

Ground granulated blast-furnace slag (GGBFS) meeting AASHTO M 302 or

ASTM C 989 may be used as supplementary cementitious materials. GGBFS

provides reactive fines and due to large replacement rate usually about 40%

enables a low heat of hydration. Cement replacement by GGBFS is based on the

severity of the environment to which the concrete is exposed. The level of

GGBFS addition is 25% to 70% for slightly and moderately aggressive

environments, and 50% to 70% by mass when used in extremely aggressive

environments. A high proportion of GGBFS exceeding 40% may however affect

stability of SCC resulting in reduced robustness with problems of consistency

control while delayed setting can increase the risk of static segregation. When

used in combination with silica fume and/or metakaolin, GGBFS content should

be limited to 50% to 55% of the total cementitious content, by mass of binder

[Florida DOT, 2004]. However, in precast prestressed members, the amount of

slag is usually 40%. GGBFS shall not be used with Type IP or Type IS cements.

Fillers

The particle-size distribution, shape, and water absorption of fillers may affect the

water demand/sensitivity and suitability for use in the production of SCC. Calcium

carbonate-based mineral fillers can enhance workability and surface finish. The fraction

below 0.005 in. (0.125 mm) shall be of most benefit to SCC flow properties. Contents

of fillers should be evaluated to ensure adequate performance of concrete, including

strength development and durability.

35

OTHER SUPPLEMENTARY CEMENTITIOUS ADDITIO NS

Metakaolin, natural pozzolan, ground glass, air-cooled slag and other fine fillers

have also been used or considered as additions for SCC, but their effects need to

be carefully evaluated for both short and long term effects on the fresh and

hardened concrete.

Aggregate Characteristics

A well-graded combined aggregate with sufficient intermediate sizes is highly desirable

for improved stability. Also, if the proper particle shape and texture are selected,

combined aggregate grading can lead to large reductions in water, paste, and cement

contents leading to improved hardened concrete properties. The moisture content,

water absorption, grading and variations in fines content of all aggregates should

be closely and continuously monitored and must be taken into account in order to

produce SCC of constant quality. Changing the source of supply for aggregates is

likely to make a significant change to the concrete properties and should be

carefully and fully evaluated [European Guidelines, 2005]. Gravel, crushed stone,

or combinations can be used as coarse aggregate. In the case of fine aggregate,

natural sand or manufactured sand can be used. Coarse and fine aggregates should

conform to the grain-size distribution recommendations of the project

specifications.

Coarse aggregate

Unless otherwise specified in the contract documents, the recommendation is to

use normal-density coarse aggregate meeting the requirements of AASHTO M 80

or ASTM C 33. The use of continuously graded aggregates is recommended. The

nominal maximum-size of coarse aggregate (MSA) should be selected based on

mix requirements and minimum clear spacing between the reinforcing steel and

prestressing strands, clear cover the reinforcement steel, and thickness of the

member. The recommendations given in the PCI Bridge Design Manual [1997]

apply. Slightly gap-graded aggregates may lead to greater flowability than

continuously graded aggregate. Gap-graded aggregate can, however, increase the risk

of bleeding and segregation, and proper measures are needed to ensure adequate static

stability of the concrete.

In the design of SCC, typically the MSA values are smaller than those of

conventional vibrated concrete. The MSA is generally limited to to in. (12.5

to 19 mm). In the placement of SCC in highly congested and restricted section,

MSA value of 3/8 in. (9.5 mm) can be used.

If aggregates susceptible to alkali-aggregate reactivity are used, special precautions

must be observed. These include the use of low-alkali cement, blended cements, or

pozzolans and GGBFS.

36

Fine aggregate

For normal weight concrete, fine aggregates conforming to AASHTO M 6 are

appropriate for the production of SCC. Fine aggregate component should be well-

graded concrete sand. It may be beneficial to blend natural and manufactured sand

to improve plastic properties of SCC. Common concrete sand, including crushed

or rounded sand, siliceous or calcareous sands, can be used in SCC. Particle size

fractions of less than 0.005 in. (0.125 mm) should be considered as powder

material in proportioning SCC. Such fine content can have marked effect on

rheology. Fine aggregates for SCC should conform to the gradation requirements

of AASHTO M 6 or ASTM C 33, as presented in Table 1.

Chemical Admixtures

Chemical admixtures are used in precast, prestressed concrete to reduce water

content, improve filling ability and stability, provide air entrainment, accelerate

strength development, enhance workability retention, and retard setting time.

Because chemical admixtures can produce different results with different binders,

and at different temperatures, the selection of the admixtures should be based on

the plant materials and conditions that will be utilized in production. For

prestressed concrete, chloride-ion content in chemical admixtures should be

limited to 0.1%, by mass of the admixture [AASHTO LRFD Bridge Design

Specifications, 2004]. Incompatibility of admixtures with binders can lead to

improper air void system and delayed or accelerated setting time. Therefore,

before the start of the project, concrete with the job materials, including the

admixtures, should be tested to ensure compatibility. Such testing should be

repeated whenever there is a change in the binder and admixtures.

High-range water-reducing admixtures

High-range water-reducing admixtures (HRWRA) shall conform to the

requirements of ASTM C 494 Type F (water-reducing, high range) or G (water-

reducing, high range, and retarding) or ASTM C 1017. The admixture should

enable the required water reduction and fluidity during transport and placement.

The use of Type F or G HRWRA is essential to achieve SCC fluidity. Such

HRWRA can be used in combination with regular water-reducing admixtures or

mid-range water-reducing admixtures. There are mid-range water-reducing

admixtures that may be classified under ASTM C 494 as Type A or F depending

on dosage rate. The required consistency retention will depend on the application.

Precast concrete is likely to require a shorter retention time than cast-in-place

concrete.

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Viscosity-modifying admixtures

The use of a viscosity-modifying admixture (VMA ) for SCC proportioned with

w/cm higher than 0.40 is recommended to ensure stability of the fresh concrete.

VMA should not be added to SCC as a means for improving a poor mix design or

poor selection of materials. High dosage of VMA may lead to increased HRWRA

demand and in some cases, some delay in setting, and development of early-age

mechanical properties.

VMAs are used in SCC to enhance segregation resistance and to enhance

robustness by minimizing the effect of variations in aggregate moisture content,

temperature, etc. This can make the SCC less sensitive to small variations in the

proportioning and characteristics of material constituents. There are currently no

ASTM specifications for VMA. Producers should confirm by trial mixtures that

VMA does not adversely affect the hardened concrete properties.

Air -entraining admixtures

Air -entraining admixtures shall conform to the requirements of AASHTO M 154

or ASTM C 260. Air-entraining admixtures are used in concrete primarily to

increase the resistance of the concrete to freeze-thaw damage. Proper selection of

air-entraining admixture that can stabilize small bubbles and properly formulated

HRWRA that does not cause a large number of coarse air bubbles are needed to

design the SCC with adequate air-void system.

In some cases, high dosage of HRWRA coupled with the high fluidity of the

mixture can make it difficult to ensure the entrainment of a fine, stable air-void

system in the concrete. HRWRA can also entrain coarse air bubbles.

Compatibility evaluation between the air-entraining admixture and HRWRA is

therefore needed to achieve the targeted air-void characteristics.

Set-retarding and set-accelerating admixtures

An ASTM C 494 Type D set-retarding admixture may be used during hot weather

concreting or when a delay in setting is required, subject to acceptance by the Engineer.

Some water-reducing admixtures at high dosage rates can act as retarding admixtures.

They should be used with caution. Set-accelerating admixture (Type C) shall be used to

decrease setting time and increase the development of early-age mechanical properties.

The admixture is particularly beneficial in precast concrete construction to facilitate

early form removal and release of prestressing [PCI Bridge Design Manual, 1997]. In

the absence of accelerated radiant heat or steam curing, the use of set-accelerating

admixture in SCC may be beneficial in precast applications when using HRWRA,

especially the poly-naphthalene- or melamine-based products.

Shrinkage-reducing admixtures

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If a shrinkage-reducing admixture is specified in the contract documents,

verification of the air-void system, including air content in hardened concrete,

spacing factor, and specific surface, is recommended. It could be difficult to

entrain air and large dosages of air entraining admixture are needed when a

shrinkage reducing admixture is used.

Other admixtures

Corrosion-inhibiting admixtures can be incorporated to protect the reinforcement

from corrosion. Producers should confirm by trial mixtures that the addition of

any admixture does not adversely affect the hardened concrete properties.

Coloring pigments used in SCC shall conform to the requirements of ASTM C

979. All coloring admixtures required for a project shall be ordered in one lot and

shall be finely ground natural or synthetic mineral oxide or an organic

phothalocyanine dye with a history of satisfactory color stability in concrete

[European Guidelines, 2005]. The use of corrosion-inhibiting admixtures may

hinder the efficiency of other admixtures and cause non-uniformity in color of the

concrete surface (darkening and mottling). There are currently no ASTM

specifications for corrosion-inhibiting admixtures.

Fibers

Synthetic and steel fibers (hybrid fiber) can be used. The dosage rates of the fiber

in SCC ranges between 0.25% and 0.50%, by volume, depending on the type of

applications. The dosage of fibers should be determined given the workability

requirements of the mixtures, which should take into considerations element

characteristics and placement conditions. Changes in mixture proportioning may

be needed to secure good passing ability and filling capacity of the fiber-

reinforced SCC. The incorporation of synthetic fiber is recommended to reduce

the risk of cracking due to restrained or plastic shrinkage. The dosage of synthetic

fiber should not exceed the 0.50%, by volume, when casting complex and narrow

sections or highly-reinforced structures blocking risk increased.

SELECTION OF WORKABI LITY TEST METHODS

Workability describes the ease with which concrete can be mixed, placed, consolidated,

and finished. It describes the filling properties of fresh concrete in relation to the

behavior of concrete in the production process. Workability of SCC is described in

terms of filling ability, passing ability, and stability (resistance to segregation) and is

characterized by data that relates to specific testing methods [ACI Committee 237,

2007]. Various test methods have been used to assess the workability characteristics of

39

SCC. In general, test methods include the components required for evaluating

simultaneously the filling ability, passing ability, and static stability. Table 2

summarizes some of the main test methods that proposed for the evaluation of

workability of SCC. The filling capacity combines the filling and passing abilities

of SCC and can be tested using the caisson filling capacity [Yurugi et al., 1993].

Filling Ability

The ability of SCC to flow into and fill completely all spaces within the

formwork, under its own weight, is of great importance to SCC casting, distance

between filling points, etc. [ACI Committee 237, 2007]. Slump flow test [ASTM

C 1611] is used to assess the horizontal free flow of SCC in the absence of

obstruction. The test method is based on the test method for determining the

slump of a normal concrete. The diameter of the concrete circle is a measure of

the flowability of the SCC. In general, slump flow varies between 23.5 and 29 in.

(600 and 735 mm) for SCC used in precast, prestressed applications [NCHRP

Report 628, 2009]. When slump flow test is performed, the time needed for the

concrete to spread 20 in. (500 mm) is also noted. This test is called T-50 flow

time. Advantages and precautions of slump flow and T-50 flow test methods are

presented in Table 3.

Passing Ability

The passing ability tests evaluate the ability of concrete to pass among various

obstacles and narrow spacing in the formwork without blockage that can rise from

local aggregate segregation in the vicinity of the obstacles that give rise to

interlocking and blockage of the flow in the absence of any mechanical vibration

[ACI Committee 237, 2007].

The J-Ring test [ASTM C 1621] can be used to assess the restricted deformability

of SCC through closely spaced obstacles [Bartos, 1998]. In general, the maximum

difference between slump flow and J-Ring flow varies between 2 to 3 in. (50 to 75

mm) depending on the filling ability (slump flow) of the mixture. A difference

between slump flow and J-Ring flow less than 1 in. (25 mm) indicates good

passing ability and no visible blocking of the concrete. Difference greater than 2

or 3 in. (50 or 75 mm), depending on the slump flow value, reflects blocking of

the concrete.

In the L-box test, the vertical part of the box is filled with concrete and left at rest

for one minute. The gate separating the vertical and horizontal compartments is

then lifted, and the concrete flows out through closely spaced reinforcing bars at

the bottom. The time for the leading edge of the concrete to reach the end of long

horizontal section is noted. The heights of concrete remaining in the vertical

section and at the leaving edge are determined. The blocking ratio (h2/h1) is

calculated to evaluate the self-leveling characteristic of the concrete. A blocking

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ratio of 0.5 and higher is indicative of adequate passing ability. Higher values are

necessary in densely reinforced and thin sections.

The V-funnel apparatus consists of a V-shaped funnel with an opening of (2.55

3.0 in.) 65 75 mm at its bottom. The funnel is filled with concrete, then after

one minute, the gate is opened and the time taken for concrete to flow through the

apparatus is measured. In the case of structural applications, the V-funnel flow

time lower than 8 seconds indicates good passing ability [Hwang, 2006].

Advantages and precautions of the slump flow and J-Ring flow test, L-box, and

V-funnel methods are presented in Table 4

Filling Capacity

The property to completely fill intricate formwork or formwork containing closely

spaced obstacles is critical for SCC to achieve adequate in-situ performance. SCC

with high filling and passing abilities can achieve good filling capacity and spread

into a predetermined section to fill the formwork under the sole action of gravity

without segregation and blockage [ACI Committee 237, 2007].

Filling capacity test provides a small-scale model of a highly congested section

and is suitable to evaluate the filling capacity and its self-consolidating

characteristics [Ozawa et al., 1992; Yurugi et al., 1993]. For the caisson test, the

maximum size aggregate (MSA) is limited to in. (19 mm). In general, a filling

capacity higher than 70% is recommended for SCC used in precast, prestressed

applications. Advantages and precautions of the caisson filling capacity test are

presented in Table 5.

Static Stability

Static stability refers to the resistance of concrete to bleeding, segregation, and

surface settlement after casting while the concrete is still in a plastic state [ACI

Committee 237, 2007]. Surface settlement test method can be used to evaluate the

surface settlement of SCC from a plastic state until the time of hardening [Manai,

1995]. In general, a maximum surface settlement lower than 0.5% or a rate of

settlement after 30 minutes lower than 0.27% per hour is recommended for SCC

used in precast, prestressed bridge elements. Surface settlement test enables the

quantification of the effect of mixture proportioning on static stability. The

settlement is monitored until achieving a constant value.

The static stability of SCC can also be determined using column segregation test

[ASTM C 1610]. The coefficient of variation of the aggregate among the column

section can be taken as a segregation index (Iseg) [Assaad et al., 2004]. Another

index consisting of the percent static segregation (S) can be obtained by

measuring the difference between aggregate mass at the top and bottom sections

of the column. Column segregation test consists of casting concrete in a column

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divided into four sections along the concrete sample. From each section, the

concrete is weighed and washed out. Then, the coarse aggregate content is

determined for each section. In general, a segregation index (Iseg) lower than 5%

or a percent of static segregation (S) lower than 15% is recommended for SCC

used in precast, prestressed bridge elements.

The visual stability index (VSI) involves visual examination of SCC prior to

placement and after performance of the slump flow test. It is used to evaluate the

relative stability of batches of the same or similar SCC mixtures. The VSI

procedure assigns a numerical rating of 0 to 3, in 0.5 increments. The VSI test is

most applicable to SCC mixtures that tend to bleed [Daczko and Kurtz, 2001].

The test can be considered as a static stability index when it is observed in a

wheelbarrow or mixer following some period of rest time (static condition). VSI

value of 0 to 1 is recommended for SCC for precast, prestressed concrete bridge

elements. Advantages and precautions of surface settlement and column

segregation tests are presented in Table 6.

Dynamic Stability

Adequate resistance of concrete to separation of constituents upon placement and

spread into the formwork is required for SCC when flowing through closely

spaced obstacles and narrow spaces to avoid segregation, aggregate interlock, and

blockage [ACI Committee 237, 2007]. The caisson test measures the filling

capacity indicative of the filling and passing abilities; therefore, it is a good

indicator of the dynamic stability. Concrete wi