Effect of Various Admixture-Binder Combinations on Workability of Ready-Mix Self-Consolidating Concrete

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Title: Effect of Various Admixture-Binder Combinations on Workability of Ready-Mix Self-Consolidating Concrete

Author(s): S.-D. Hwang and K.H. Khayat

Publication: Special Publication

Volume: 233

Issue:

Appears on pages(s): 25-44

Keywords: admixture-binder combination; binder; concrete-equivalent-mortar; rheology; self-consolidating concrete (SCC); workability

Date: 3/9/2006

Abstract:
An experimental investigation was carried out to evaluate the effect of high-range water reducing admixture (HRWRA), viscosity-enhancing admixture (VEA), andbinder type on key workability characteristics of self-consolidating concrete (SCC),including retention of deformability, passing ability, and stability. Concrete-equivalent mortar (CEM) mixtures were prepared to evaluate the effect of admixture-binder combinations on flow characteristics, including minimum water content (MWC) toinitiate flow and relative water demand (RWD) to increase a given fluidity. Fourpolycarboxylate-based HRWRAs, a polynaphthalene sulfonate-based HRWRA, four types of VEAs, and three blended cements were evaluated. In total, 16 SCC mixtureswith initial slump flow consistency of 660 20 mm and air volume of 6.5 1.5%, and 17CEM mixtures were investigated. Flow characteristics of SCC and CEM mixtures made with a number of admixture-binder combinations indicate that the efficiency of admixture-binder combination depends on water-to-cementitious material ratio (w/cm), type of binder, and type of admixtures. TheCEM approach can be used to evaluate the effect of admixture-binder combination on flow characteristics because the increase in MWC to initiate flow of CEM corresponds tohigher demand in HRWRA in SCC mixtures. Binder type was shown to have marked influence on the retention of slump flow, L-box and V-funnel passing ability, fillingcapacity, and surface settlement characteristics. The binder type also affects HRWRA and air-entraining admixture (AEA) demand. As established from CEMs, B3 quaternary cement with the smallest 50% passing diameter had the highest MWC (lowest packingdensity) needed to initiate flow and the highest RWD (highest robustness to changes in water). SCCs made with such quaternary cement and polycarboxylate-based HRWRA also exhibited the highest HRWRA demand compared those prepared with other blended cements. Both sets of SCCs made with 0.35 w/cm and 0.42 w/cm plus VEA had similar HRWRA demand and static stability when the polycarboxylate-based HRWRA was used.