MODELING THE EARLY AGE BEHAVIOR OF SELF-COMPACTING CONCRETE USING COAL ASH IN VIETNAM

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1 MODELING THE EARLY AGE BEHAVIOR OF SELF-COMPACTING CONCRETE USING COAL ASH IN VIETNAM M. K. Sam*, Papua New Guinea University of Technology, Papua New Guinea Troung Thi Hong Thuy, Institute of Building and Science Technology (IBST), Vietnam Nguyen Thien Rue, Hanoi University of Civil Engineering, Vietnam 28th Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2003, Singapore Article Online Id: The online version of this article can be found at: This article is brought to you with the support of Singapore Concrete Institute All Rights reserved for CI Premier PTE LTD You are not Allowed to re distribute or re sale the article in any format without written approval of CI Premier PTE LTD Visit Our Website for more information

2 28 th Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2003, Singapore MODELING THE EARLY AGE BEHAVIOR OF SELF-COMPACTING CONCRETE USING COAL ASH IN VIETNAM M. K. Sam*, Papua New Guinea University of Technology, Papua New Guinea Troung Thi Hong Thuy, Institute of Building and Science Technology (IBST), Vietnam Nguyen Thien Rue, Hanoi University of Civil Engineering, Vietnam Abstract Self-compacting concrete (SCC) is one of the newest forms of high performance concrete. Its unique properties, e.g. high flow value, and resistance to segregation are of considerable interest to the whole field of concrete construction. In the present study, data on slump flow up to 150 minutes and shrinkage up to 24 hours for self-compacting concrete with a fixed water/binder ratio of 0.31 using coal ash as a cement replacement material were collected. The slump flow was determined by the conventional slump test by measuring the average base diameter of the concrete. The specimens (100 x 100 x 300 mm) for shrinkage were sealed with nylon sheet to prevent evaporation and stored at room temperature (20-25 C). The aims of the present study are: (1) To model the slump flow loss; and (2) To model the early age shrinkage of self-compacting concrete. The study showed that it is adequate to predict the slump flow using a simple linear regression (y = a + bt) whilst a non-linear regression is needed for shrinkage data. It was also showed that the rectangular hyperbolic model (tis = a + bt) can fit the shrinkage data very well (R 2 > 0.99) for t ~ 9 hours KEY WORDS: Self-compacting concrete, slump flow, shrinkage, water/powder ratio. 475

3 1. INTRODUCTION Self-compacting concrete (SCC) is one of the newest forms of high performance concrete. Its unique properties, e.g. filling and passing ability, and resistance to segregation are of considerable interest to the whole field of concrete construction. In this study, the early age effects of the slump flow and shrinkage of self-compacting concrete using locally available materials in Vietnam were investigated. Data were collected from an experimental program conducted at the Institute of Building and Science Technology (lbst), Vietnam. 2. EXPERIMENTAL DETAILS The properties of the materials used are summarized in Tables 1 and 2. The mix proportions were selected based on the Japanese Method [Okamura and Ozawa, 1995]. Concretes containing 20%, 30%, 40% and 50% of coal ash in total powder (OPC + Coal Ash) with water/powder ratios of 0.29, 0.30 and 0.31 were prepared and tested for Slump Flow using a conventional slump apparatus and Filling Height using the L-Box-shaped apparatus. The volume ratio of coarse aggregate to concrete was kept constant at The mix proportions and experimental results were summarized in Table 3. Table 4 summarizes the slump flow results during the first 150 minutes. Table 5 summarizes the shrinkage of 100 x 100 x 300 mm samples during the first 24 hours. Table 1 - Chemical Composition and main characteristics of Ordinary Portland cement (OPC) and Coal Ash in Vietnam. Type CaO Si02 AI20 3 Fe203 MgO Na20 K20 S0 3 Density Specific (g/cm3) Surface (Blaine) (cm2/g) OPC Coal Ash Table 2- Properties of the aggregates and Superplasticizer. Property Fine Aggregate Coarse Superplasticizer (River sand, Aggregate max. 5 mm (Crushed size) limestone, max. 20 mm size) Unit weight at dry state, Polycarboxylate acid-based g/cm 3. with specific gravity of 1.1 Unit weight at SSD, g/cm"' g1cm 3. Absorption capacity, % Fineness modulus

4 Table 3 Mix Proportions of Trial Mixes for Self.Compacting Concrete rln bold: Slump Flow ~ 650 mm and Filling Height ~ 300 mm)[ln italics, specimens ( 150 mm cubes) with average compressive strength ~ 50 N/mm 2 ] Sample Ref. NC S S1 40 S1-50 S S S S3 40 S3-50 Water- Water- Water Powder Aggregate SP Slump powder cement (11m 3 ) (kg/m 3 ) (k ~/m3) (kg/m 3 ) Flow ratio ratio Cement Coal Fine Coarse (mm)* Ash Filling Height (mm)* Blocked Table 4 51ump Flow (in mm) with respect to time for different coal ash contents (Fixed water/binder ratio = 0.310) [In bold, slump flow ~ 650 mm] Time Coal Ash Content %) (minutes) Table 5 Time (hours) Early Age Shrinkage (in mm/m or 10-6) with respective to time for different coal ash contents (Fixed water/binder ratio = 0.310; Specimens: 100 x 100 x 300 mm sealed with nylon sheet, stored at room temperature of C) Coal Ash Content(%)

5 3. DATA ANALYSIS The experimental data are analyzed statistically using a statistical software [Barnes, 1994]. Figure 1 shows the effect of different coal ash contents on slump flow over time. Figure 2 shows the effect of different coal ash contents on shrinkage over time. Figure 3 shows the plot of time/shrinkage vs time for t ;:: 8 hours. Figure 4 shows the plot of time/shrinkage vs time for t ;:: 9 hours. Table 6 summarizes the results from the multivariate regression analysis on slump flow with respect to coal ash content and time. Table 7(a) summarizes the results from multivariate regression analysis on shrinkage with respect to coal ash content and time. Table 7(b) summarizes the results from simple regression analysis on shrinkage using the rectangular hyperbolic model. 90~ ~ 580 "= l -+-NC ~ _2O%Coal J70.. ".~Coa ~o.), ::~=.-.=.-= 40 t----~ ~-... ", :::"- -:or- ~50* ~~-~ =-~-~ ~~~-----I 30 ~ ~~~~ ~ 10t =====~~====~----~ O ~ ~------~ ~------~ ~ o Time, min. Figure 1 - Effect of Coal Ash Contents on slump flow over time. 478

6 Time, hours o ~--~~~r ~ r ' e ~--~~~~~~==~ ~--~... ~ os ~ t f ~ l-----~~. ~::~============~::::1~~-~ ri.l =.:~~~ ===~~~_/ -+-NC _ 30%coal ash ""';~~" 50% coal ash *-40% coal ash --*-20% coal ash Figure 2 Effect of different coal ash contents on shrinkage (10-3 mmim) over time. 0, Time/Shrinkage Vs Time for 8 Hrs or m~ I 0% Coal Ash, II 20% Coal Ash 30% Coal Ash CD CD cu % Coal Ash.:.: c c.c t/) -CD ,200 '" 50% Coal Ash --Linear (O% Coal Ash) E 0,150 i= -- Linear (20% Coal Ash) 0, linear (30% Coat Ash) Linear (40% Coal Ash) Time in Hrs --linear (50% Coal Ash) j <~ J Figure 3 Plot of Time/Shrinkage vs Time for t ~ 8 hours. 479

7 Time IShrinkage Vs Time for 9hrs or more Q) g» O.3()O ~ E 0250 Ii : O%CoaIAsh «II 20% Coal Ash 30% Coal Ash t""'" 40% Coal Ash :t: 50% Coal Ash --Linear (20%,Il% em Coal Aoh, Ash)! LInear (30% Coal ASh)...- LInear (40% Coal Ash) i - Linear (~% C~ Ash} I Timetn hrs Figure 4 Plot of Time/Shrinkage vs Time for t ~ 9 hours. Table 6 Model No Legend Summary of Results from MRE on Slump Flow with respect to Coal Ash Content and Time. [W/p = 0.31] Prediction Equations R" Y = X X X Y = X X Y = X X Y = X Y X Y = Slump Flow, in mm. [~ 650 mm : good fluidity.] X1 = Coal Ash Content, in % of total powder; X 2 = time, in minutes; X3 = (X2)2. 480

8 Table 7(a) - Summary of Results from MRE on Shrinkage with respect to Coal Ash Content and Time. [W/p = 0.31] Model No Prediction Equations R' 1 Y = Xl X X Y = Xl X Y = X ~ Y = Xl X Legend Y = Shrinkage, in mm/m or Xl Coal Ash Content, in % of total powder; X2 time, in hours; X3 = (X2{ Table 7(b) - Summary of Results from Simple Regression Analysis on Shrinkage with respect to Time using rectangular hyperbolic model. [W/p = 0.31] % Coal Ash Time,in Prediction Equations R' hours (Hyperbolic Model) Legend 0 t;:: 8 Y = t t;:: 9 Y = t t;:: 8 Y = t t;:: 9 Y = t t;:: 8 Y = t t;:: 9 Y = O.0044t t;:: 8 Y = t t;:: 9 Y = t t;:: 8 Y t t;:: 9 Y = t Y = tis = a + b.t, where s = shrinkage, in 10-6 ; t = time, in hours. 4. OBSERVATIONS AND DISCUSSION (1) Slump Flow: (a) As the coal ash content increases, the slump flow increases in general. [Fig. 1] (b) Coal ash (Xl) has greater effect on slump flow as compared to time (X2) for t ~ 150 minutes. [Table 6: Model no. 4, R2 = vs Model no. 5, R2 = ] (c) Multiple linear model is good enough for predicting the slump flow (Y) with respect to coal ash content (Xl) and time, e.g. Model no. 3 : Y = Xl X2 with R2= [Table 6] (2) Shrinkage (a) The relationship between shrinkage and time is non-linear at the different coal ash contents. [Fig. 2; Table 7(a)). (b) The rectangular hyperbolic model (tis = a + b.t) fitted the shrinkage data very well. In general, models for t ;:: 9 hours is better than models for t ;:: 8 hours ( s = shrinkage). [Table 7(b); Figure 3 and Figure 4.] 481

9 5. CONCLUSIONS From the present study, we can conclude that: (1) Coal ash is a beneficial material in controlling the slump flow of self-compacting concrete with respect to time. (2) The rectangular hyperbolic model can be used to predict the early shrinkage of selfcompacting concrete for t ~ 8 hours and upto 24 hours. REFERENCES 1. Barnes, J.w. (1994), "Statistical Analysis for Engineers - A Computer-based Approach", McGrawHill, New York, 1994, 385p 2. Hong Thuy, T.T., and Thien Rue, N. (2001),.. Investi~ation on the Cement Replacement by Coal Ash in producing Self-Compacting Concrete", 8 East Asia - Pacific Conference on Structural Engineering and Construction, 5-7 December 2001, Singapore. Paper No pp. 3. Okamura, H., and Ozawa, K. (1995), "Mix Design for Self-Compacting Concrete", Concrete Library International of JSCE, 1995, No. 25, pp Sam, MK (2002), "Predicting the Behaviour of Highly Flowable Underwater Concrete - A Process-based Model Approach", Proceeding of the World Conference on Concrete Materials and Structures, May 14-16, 2002, Sham Alam, Malaysia. Pp Thuy, NN., Tuan, L.A., and Chanh, N.V. (2001),.. Self-Compacting Concrete - A Rheological Approach", Proceeding of ICCMC/IBST 2001 International Conference on Advanced Technologies in Design, Construction and Maintenance of Concrete Structures, March 2001, Hanoi, Vietnam, pp

FUNDAMENTAL PROPERTIES OF CONCRETE WITH CEMENT DISPERSING AGENT FOR RETEMPERING

FUNDAMENTAL PROPERTIES OF CONCRETE WITH CEMENT DISPERSING AGENT FOR RETEMPERING K. Tokuhashi, Tsuruga Cement Co. Ltd., Japan M. Shoya, Hachinohe Institute of Technology, Japan M. Aba*, Hachinohe Institute