Mechanical and Durability Properties of Reactive MgO-Based Concrete Produced with Calcined Kaolinitic Clay and Zeolites

Abstract

The search for environmentally friendly concrete has led to the development of several potentially viable binder systems. Reactive magnesia (MgO) has been widely investigated with aluminosilicates, which, compared with silica fume (SF), provide reactive alumina in addition to silica and offer greater flexibility in formulating MgO-based binders. Metakaolin (MK) is a highly reactive supplementary cementitious material (SCM) used in MgO-based binders, but its high cost and water demand can limit practical application. Calcined clay (CC) and natural zeolites may offer more widely available and potentially less expensive alternatives with lower admixture demand. This study investigated the fresh, mechanical, and durability-related properties of concrete mixes containing reactive MgO and MK, CC, zeolite, or calcined zeolite. Hydromagnesite (HY) was also incorporated into selected calcined-zeolite mixes. Mechanical performance was evaluated using compressive strength, splitting tensile strength, flexural strength, and elastic modulus, while durability-related performance was assessed through porosity, electrical resistivity, oxygen permeability, and drying shrinkage. The MgO-MK mix showed the best overall performance. However, mixes containing calcined zeolite and HY also demonstrated potential as viable alternatives. Moreover, zeolite calcination reduced the required SP dosage and improved several mechanical and durability-related properties of the MgO-based concrete.