Experimental study of the porosity and microstructure of self-compacting concrete (SCC) with binary and ternary mixes of fly ash and limestone filler

• Binary and ternary mixes of fly ash and limestone filler of self-compacting concrete (SCC).
• Analysis of the porosity and microstructure of these mixes.
• The durability properties studied are strongly affected by the type and quantity of additions.
• The use of ternary mixes also proves to be extremely favourable.

Self-compacting concrete (SCC) can soon be expected to replace conventional concrete due to its many advantages. Its main characteristics in the fresh state are achieved essentially by a higher volume of mortar (more ultrafine material) and a decrease of the coarse-aggregates. The use of over-large volumes of additions such as fly ash (FA) and/or limestone filler (LF) can substantially affect the concrete’s pore structure and consequently its durability.In this context, an experimental programme was conducted to evaluate the effect on the concrete’s porosity and microstructure of incorporating FA and LF in binary and ternary mixes of SCC. For this, a total of 11 SCC mixes were produced: 1 with cement only (C); 3 with C + FA in 30%, 60% and 70% substitution (fad); 3 with C + LF in 30%, 60% and 70% fad; 4 with C + FA + LF in combinations of 10–20%, 20–10%, 20–40% and 40–20% fad, respectively.The results enabled conclusions to be established regarding the SCC’s durability, based on its permeability and the microstructure of its pore structure. The properties studied are strongly affected by the type and quantity of additions. The use of ternary mixes also proves to be extremely favourable, confirming the beneficial effect of the synergy between these additions.