Chloride ingress and carbonation assessment of mortars prepared with recycled sand and calcined clay-based cement
Ahmed Jan, Lucia Ferrari, Nikola Mikanovic, Mohsen Ben Haha, Elisa Franzoni
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 (LC 3 ). This research study presents an experimental investigation based on the comparison between LC 3 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, LC 3 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 LC 3 binder with 70 % clinker is a promising material to produce LC 3 blends with adequate durability against carbonation and chloride ions ingress, particularly when recycled sand is used as a source of fine aggregate. • The durability of mixes with LC 3 and recycled aggregates is still almost uncharted. • LC 3 with recycled sand has better strength and durability than CEM II with natural sand. • LC 3 with 70 % clinker gives low capillary water absorption rates also with recycled sand. • LC 3 binders leads to a lower and refined porosity compared to CEM II. • The pH of the mortars with LC 3 was investigated by different methods and indicators.