: Durability of concrete modified with acid leached calcined kaolinitic clay

Abstract

Calcined or thermally treated kaolinitic clay (CKC) was leached by sulphuric acid to extract aluminum in the manufacturing of aluminum sulfate coagulant.The residual of this process is called low alumina calcined kaolinitic clay or Acid-Leached Calcined Kaolinitic Clay (ALCKC).ALCKC was investigated as a supplementary cementing material by mixing with Ordinary Portland Cement (OPC) and the durability of the concrete was assessed.The experimental protocol included optimization of the mixes of ALCKC/OPC containing 0, 10, and 15 ALCKC for the production of hardened concrete, and in this work, the durability against chlorides, sulfates solutions, heating, and seawater was studied.It was found that the addition of ALCKC to cement/concrete caused slight expansion of concrete within the limits and there was no significant effect on the alkaline silica reaction or alkalinity of the concrete medium.When using ALCKC in plain concrete, the ratio of 10% ALCKC/OPC achieved higher resistance against the negative effect of salt solutions attack.The ratio 10% of ALCKC to OPC is the optimum ratio that achieved high-performance plain concrete with compressive strength greater than the reference OPC by 24.7% and the ratio of 15% achieved 17.9% after aging of 90 days and this performance was better than that achieved by the ratio of 20% therefore for this reason this ratio was excluded.The ratio of 10% LACKC/OPC achieved high resistance to heat exposure keeping high compressive strength.The total porosity for the concrete vaccinated with ALCKC was minimal, resulting in protecting the concrete from aggressive solutions.Passivation potential measurements proved the vaccination gained by inoculation of ALCKC.