Cement-based composites with waste expanded perlite - Structure, mechanical properties and durability in chloride and sulphate environments

Abstract

Implementation of fine, dusty materials generated during the production of expanded perlite is a challenge from the waste disposal point of view. However, after proper treatment, it is possible to use them in the composite building materials manufacturing where they can play a role of so-called pozzolanic additive, strengthening setting and hardening process when mixed with cement. In this study waste expanded perlite – Portland cement composites were exposed to the action of sodium chloride, sodium sulphate and magnesium sulphate solution. The results show that the durability of cement composites with waste expanded perlite is significantly improved; the lifecycle of these materials would be markedly enhanced. Due to the pozzolanic reaction between the vitreous aluminosilicate component of perlite and calcium hydroxide released from cement clinker, the phase assemblage of hardened cement matrix is changed towards the partial replacement of calcium hydroxide by the C-S-H phase. The amount of calcium hydroxide is therefore markedly reduced, as well as the pore refinement and compact microstructure of products is observed. As a consequence, the compressive strength increases, the permeability of final material decreases. Therefore the durability of Portland cement - perlite mortars is significantly improved. The reference mortars with cement subjected to the sodium and magnesium sulphate started to expand after 200 and 100 days of curing respectively. They were destroyed after about a year, while the samples containing 20% of WEP exhibited no expansion after 5 years of storage in corrosive solutions.