Alkaline activation of Blended cements with calcined illitic clay using glass powder wastes

E.F. IRASSAR; TREZZA M.A.; RAHHAL V.F.

new Delhi

Congreso; 3rd International Conference on Calcined Clays for Sustentaible Concrete; 2019

LC3

The illitic calcined clays have a slowly pozzolanic reaction and their contribution to the strength of the blended cement occurs at later ages. On the other hand, limestone filler addition stimulates the initial hydration of Portland clinker phases increasing the compressive strength at early ages, but it can reduce the later strength due to the dilution effect. Consequently, the complementary effect of the incorporation of both additions to portland cement can provide a blended cement with an acceptable development of strength and porosity.In this paper, the combined action of limestone filler (LF) and illicit calcined clays (ICC) as partial replacement of Portland cement are systematically studied using a Composite Central mix design. The studied domain is restricted by 0 to 20% of LF and 0 to 35 % of ICC. The studied responses are the mini slump spread, the compressive strength and the volume of permeable pores at 2, 7, 28 and 90 days in standard mortar, and the non-evaporable water content. Complementary, the CO2 emission is calculated and the eco-efficiency to obtain a MPa at 28 and 90 days is analysed.Results show that the contribution of LF to hydration degree of portland cement at 2 days increases the early strength of blended cements containing up to 20% LF and 0?15% ICC. At later ages, the LF content is limited to the adverse effect caused by dilution on the strength. The later pozzolanic reaction of ICC contributes to obtain a ternary blended cements with comparable compressive strength than Portland cement at 28 and 90 days. According to the statically model, the action of both addition is complementary, while the synergic effect is negligible, Finally, the use of ternary blended cements (PC?LF?IC) provides an eco-efficient solution obtaining a reduction of CO2 emission with comparable water demand and later strength performance.