A comparative study on the role of metakaolin and diatomite in the performance of eco-friendly dolomite waste-based alkali-activated binder

The production process of dolomite aggregate yields a huge content of the rejected size, namely dolomite waste. This waste causes many environmental problems including increasing the wastage area, disposal of landfill, and increasing the air pollution. This work pay attention to the sustainable disposal of this waste in the production of an innovative binder using chemical exchange reaction. This work aims to examine the role of metakaolin (MK) and diatomite (DT) in enhancing the physicochemical properties of alkali-activated binder-based dolomite waste (AADW). The DW powder was combined with varying weight percentages of MK and DT. The resultant admixtures were activated via Na2SiO3, followed by curing at room temperature. The fabricated mixtures possess a wide range of compressive strength values, dependent on the contents of the additives (MK and DT). AADW without any additives represents a compressive strength of 34.6 MPa. DT was found to have a minimal effect on early compressive strength but significantly enhanced later strength. In contrast, incorporating MK into the alkali-activated system materially improved the early compressive strength, while it recorded 28-day strengths similar in hardness to the hardened sample with DT. Specifically, AADW-DT10 and AADW-MK10, which contain 10 wt% DT and MK, respectively, exhibited 7-& 28-day compressive strengths of 14.4 MPa & 32.1 MPa and 57 MPa & 56.2 MPa, respectively. Replacing DW with DT reduced drying shrinkage of the resultant hardened alkali-activated materials. However, incorpo-rating MK up to 10 wt% reduced the drying shrinkage of AADW, while the sample with 15 wt% recorded the highest drying shrinkage. Nonetheless, AADW-DT exhibited lower drying shrinkage than that of AADW-MK at all curing ages up to 90 days. Overall, the result indicated that the higher reactivity and high alumina content of MK provide suitable conditions for synthesizing hardened materials with better physical and mechanical properties when compared to AADW-DT.