Evaluation of thermal and freeze-thaw resistances of the concretes with the silica fume addition at different water-cement ratio
Dashdondog Oyunbileg, J. Amgalan, Tsegmid Batbaatar, Jadambaa Temuujin
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. • The mechanical strength and durability of the ordinary concrete can be significantly increased by silica fume addition. • Silica fume addition improved pozzolanic reaction of cement leading to increased formation of secondary gel of C-S-H phase. • The SF added concrete shows freeze-thaw resistance of 420 cycles, a water impermeability of W20 and higher density.. • The residual strength of the 600 °C calcined concrete may be used for approximate determination of the freeze-thaw cycles.