ASSESSMENT OF A METHODOLOGY FOR DESIGN OF SCC MIXES BY ROBUSTNESS STUDIES

A major deterrent to the large-scale use of self-compacting concrete (SCC) in the industry has been its limited robustness or susceptibility to deviate from expected performance with slight errors in the proportions of the constituents. In this study, a methodology for SCC mix design, which includes the empirical optimization of the phases, and subsequent assessment of the robustness of design SCC mixes by an experimental program, is presented. The mix design strategy involved separate optimization of paste and aggregate phases. The SCC mixes were developed with raw materials, including binders and aggregates, from two different geographical regions in India. Robustness assessment was done by varying the water content by ± 10 kg/m3, keeping all other proportions as constant. It was observed that the mixes developed are tolerant to an increase in water content up to 5 %, which is significant considering the fact that, in actual circumstances, errors in dosing of water are more common. It was also observed that mixes with higher water/ powder (w/p) ratio exhibit better robustness with both increase or decrease in water content, with respect to the base mix. The performance of the SCC mixes formulated suggests that the mix designs with a combination of high paste content and low water powder ratio may have low robustness. The results also indicate that the performance of the mix varied with other constituents except with the two superplasticizers (SP) used (which belong to the same family of polycarboxylic ether (PCE) but with different characteristics), indicating that the SPs are efficient for developing robust SCC.