Chloride ingress and carbonation assessment of mortars prepared with recycled sand and calcined clay-based cement

Abstract

A promising and economical route for the reduction of the environmental impact generated by Ordinary Portland Cement (OPC) and Construction and Demolition (C&D) waste could be possible using Recycled Sand (RS) with Limestone Calcined Clay Cement (LC3). This research study presents an experimental investigation based on the comparison between LC3 and CEM II binders mixed with natural sand and two types of recycled sand (substitution rate 50 vol%). Mechanical and durability properties of the different mortars were examined through compression and flexural strength tests, capillary water absorption, Mercury Intrusion Porosimetry (MIP), fog chamber salt spray exposure and immersion in chloride solution condition to evaluate water-soluble and acid-soluble chloride contents, and carbonation assessment by natural and accelerated methods. According to experimental results, LC3 containing 70 % of clinker and a calcined clay to limestone ratio of 2:1 exhibits superior compressive strength compared to CEM II for both natural and recycled sands and significantly enhances the resistance against chloride ions ingress and carbonation. These results demonstrate that LC3 binder with 70 % clinker is a promising material to produce LC3 blends with adequate durability against carbonation and chloride ions ingress, particularly when recycled sand is used as a source of fine aggregate.