Evaluation of thermal and freeze-thaw resistances of the concretes with the silica fume addition at different water-cement ratio

Abstract

The preparation of concrete with improved durability is an essential subject in the development of building and construction materials. This study presents the preparation and characterization of a high-strength concrete by activating ordinary 42.5 grade Portland cement (OPC) with silica fume (SF). The effect of the SF addition and water-cement (W/C) ratio on concrete durability including freeze-thaw, water permeability, mechanical and thermal resistance properties have been determined. When the water-cement ratio (W/C) in the SF added concrete is appropriately designed, for example, W/C 0.23, the compressive strength was 92.85 MPa, water absorption 0.7 %, 420 freeze-thaw cycles and water impermeability is W20. Residual strength of this concrete after thermal explosion at 600 °C for 2 h was 82 % of the original plain concrete, indicating that the obtained value is the true dense concrete. It also shows the concrete slump flow of 630 mm, which indicates its self-compacting behavior. The concrete prepared with W/C 0.29 achieved 365 freeze-thaw cycles, had 65.1 MPa compressive strength, W14 water impermeability, 1.8 % water absorption and 69 % residual strength after the thermal explosion at 600 °C. Concrete with washed aggregates has higher mechanical properties than concrete with unwashed aggregates. Freeze-thaw resistance has a direct relationship with the percentage of residual strength after explosion at 600 °C in all W/C ratios tested. Better durability and high resistance to temperature explosion was caused by the beneficial formation of the calcium silicate hydrate phase (C-S-H) in the silica fume added concrete.