Quality Control and Robustness of SCC, Part 1. Outline

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Gervais Cain
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1 Quality Control and Robustness of SCC, Part ACI Spring 22 Convention March 8 2, Dallas, TX Peter Billberg PhD (Civil Eng.), is a Senior Researcher at the Swedish Cement and Concrete Research Institute. For over 5 years, Peter has focused on rheology and workability of fresh cementitious materials and various aspects of self-consolidating concrete (SCC). Such aspects include mix design, test methods, thixotropy, formwork pressure, robustness and training. Throughout 27 and 28, he worked as postdoctoral fellow with Professor Kamal H. Khayat at the Université de Sherbrooke (Canada). Peter's research interests currently focus on robustness of SCC mixtures and the influence of thixotropy on casting results. Peter is active in several international technical committees, serving as chair of RILEM TC 233-FPC (Formwork Pressure Generated by Fresh Concrete) and as secretary of ACI 238 Workability. Fresh Property Responses of Powder-, VMA- and Combination type SCC to Varying Aggregate Moisture Peter H Billberg Outline Parameters influencing SCC fresh properties Materials Test methods Evaluation methods Mixture designs Results Correlations Slump Construction Site Robustness Slump-Flow after transportation (mm) 44 mm (8 in) - 85 mm (33.5 in) Too stiff! Perfect! Segregation! Batch No. Sidan

2 Response to varying parameters Solid Materials Decreasing Slump-Flow Yield Stress (Pa) Sand moisture ± 3 % Fine sand ± 7 % Temperature ± C Change in (Moisture %, Fine sand <.25%, Temp C) Correkt Moisture, Temp=2 C, Sand 7 %<,25 mm Cement: CEM II/A-LL 42.5 R (app. 3% limestone) Aggregate: -8 mm and 8-6 mm, glaciofluvial origin Powder materials: LP: Crystalline limestone, D.5 = 4 microns LP2: Crystalline limestone, D.5 = 25 microns P. Billberg, M. Westerholm (28) Chemical Admixtures Slump Flow Superplasticizers: SP: PCE, 35% solids SP2: PCE, 3% solids SP3: PCE, 35% solids Configured also for stability (VMA?) Viscosity Modifying Admixtures: VMA: Modified starch VMA2: Microbial anionic polysaccharide VMA3: High molecular weight ionic polymers VMA4: Polysaccharide Viscometer ConTec 4 Filling Capacity Shear stress [Pa] pl Stress s Shear rate [s - ] Strain % Sidan 2

3 Slump Flow Area - + Dynamic Yield Stress, (Pa) Dynamic Yield Stress Area - + Correlation Slump Flow - Yield Stress Yield stress (Pa) y =.9x x + 89 R² = Filling Capaciaty (%) Correlation Slump Flow - FC y =.22x-7 R² = T 5 Sidan 3

4 Shear Stress [Pa] Yield Stress Shear Rate [s - ] Plastic Viscosity T 5 Yield Stress (Pa) Rheology Area T 5 Plastic viscosity (Pa s) Mix Design - Reference Mixtures Material Kg/m 3 Cement Water 2 88 W/C.7.5 Coarse Aggregate 3% 4% SP Type SP SP Powder Type LP/LP2 LP/LP2 Powder weight 2 Slump Flow Responses - Refs LP - W/C.5 LP - W/C.7 LP2 - W/C.5 LP2 - W/C Slump Flow Area vs. Yield Stress Area Yield Sress Area 3 Reference SCCs LP2/.5 25 LP2/.7 2 LP/.5 5 R² =.99 5 LP/ Slump Flow Area Powder/Comb./VMA Mixtures Cement = 375, W/C =.5, Powder = LP2 SCC Type Powder Comb. VMA LP2 weight 5 - CA 4% 35% 3% SP Type, 2, 3 SP SP VMA Type, 2, 3, 2, 3, 4, 2, 3, 4 low, various, dosages Sidan 4

5 Rheology Area (Pa x Pa s) Rheology Area 4 Comb. Powder SCC 2 VMA 8 Refs SP LP2/.5 SP Type VMA Type SBU Area (Pa/s) Structural Build-up, SBU, Area Refs LP2/.5 Powder SCC SP Comb. VMA N/A SP Type VMA Type (Pa) Correlation SBU S@min 2 8 R² = SBU 2 S@min Time 2.5 at rest 3 Static yield stress [Pa] Structural Build-up (Pa/s) SI (Pa x Pa/s) Correlation S@min -SI R² =.98 SBU 5 S@min 5 Time at rest 5 Static yield stress [Pa] S@min (Pa) Conclusions The more free water (higher W/C or coarser powder) the more robust the SCC becomes. SP type important for robustness. SP2 and SP3 better than SP due to enhanced stabilizing ability. Except for the SCCs with VMA, the powder type SCC is generally more robust. For the powder type SCC, VMA3 performed best (slump flow, yield stress, SBU, FC) Strong correlations: slump flow vs. yield stress and FC, and initial static yield stress vs. SBU and SI Thank you! Sidan 5

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