Multi-objective optimization of mix proportions for mass concrete with enhanced resistance to cracking and reduced temperature rise

Abstract

The objective of this study is to investigate the influence of fly ash (FA), granulated blast furnace slag (GBFS), and a high-efficiency crack-resistant agent (HECRA) on the workability, mechanical properties, hydration heat (HH), adiabatic temperature rise (ATR), and volume stability of mass concrete (MC). Preliminary experiments determined that the total replacement of FA and GBFS in dual blending should be within 35% to 40%, with the GBFS content not exceeding 15%. A total of 16 concrete mix designs (MD) were formulated, including a control mix (comprising only cement (C)) and ternary blends (comprising C, FA, and GBFS), with the HECRA added at 0%, 4%, and 8% of the mass of cementitious materials. The workability of the MC was assessed through tests for air content (AC), bulk density (BD), slump, flow, and setting time. The mechanical strength, HH, ATR, and shrinkage rate of the MC were individually evaluated through compressive strength (CS) tests, HH experiments, ATR tests, and shrinkage measurements. A grey relational evaluation model was employed to establish correlations between C, FA, GBFS, and the HECRA concerning overall performance. Supported by the entropy value method, a comprehensive performance evaluation model was created. The results indicate that, compared to the control mix, the other groups exhibited reductions in mechanical performance, rates of HH, cumulative ATR, and increased self-volume deformation (SVD). These findings suggest that including FA, GBFS, and a HECRA can mitigate the HH and SVD of MC, albeit at the expense of its strength. According to the comprehensive performance evaluation model, when the C-to-FA-to-GBFS ratio is 6:3:1, and the HECRA constitutes 8% of the mass of cementitious materials, the specimens demonstrate the best overall performance. At 28d, the CS is 48.46 MPa, satisfying the design strength requirements for C35 concrete. The comprehensive performance of the large volume crack-resistant concrete with low temperature rise (LCCT) produced in this study meets engineering needs. It provides theoretical references for the mixed design of MC.