Mortar and concrete with lime-rich calcined clay pozzolana: A sustainable approach to enhancing performances and reducing carbon footprint

Low environmental impact sustainable building materials have become a crucial requirement and challenges to the contemporary construction industry. This study is an extensive effort for the development of a green cementitious composite to limit extensive extraction and consumption of nonrenewable mineral resources and CO₂ emission generation by the reduction of clinker cement production. In this route, 10%, 25%, 35%, and 50% of CaO-based calcined clay were adopted as a partial replacement for ordinary Portland cement (OPC) in mortar mix. The raw clay was extracted from Nizwa city (NZS) and ground into particles with size less than 75 µm. As per its chemical composition, the clay was classified as cementitious and pozzolanic material as per ASTM C618 standard specifications. The mill was then calcined at different temperatures of 950 °C, 850 °C, and 750 °C. The blend mortar mixes were assessed in terms of their mechanical, microstructural, durability, and thermal performances using various experimental tests. The results indicated that replacement levels of lime-rich calcined clay varying from 10% to 35% of OPC could generally offer similar to better strengths, durability, and thermal performances to a plain mortar. The mortar flow was reduced when incorporating calcined clay, while density was unaffected. Meanwhile, CaO-based calcined clay generally exhibited better performance with regard to permeable voids, combined sulphate + chloride, sulfuric acid attacks, and chloride ions permeability. The outcome of the present work sheds light on the massive potential of calcined clay pozzolana to develop sustainable, affordable, and locally produced blend cement for a variety of infrastructure applications, including energy-efficient and sustainable development, to reduce the carbon footprint.