Effects of the addition of inertized MSW fly ash on calcium aluminate cement mortars

Abstract

The large urban development carried out in the cities has promoted the increase of municipal solid wastes (MSW). While the incineration process is considered as the best possible method to manage this waste, however, among all the incineration products, MSW fly ashes produce the greatest environmental problems. The inerting of this hazardous toxic waste, as well as its valorization as a by-product is achieved due to its stabilization in the form of insoluble carbonates. In this way, a new “raw material” is produced and available at low cost, and the toxic and hazardous waste is eliminated by its subsequent encapsulation in mortar matrixes. Consequently, conservation of alternative natural resources is strengthened. In this research, calcium aluminate cement (CAC) mortars have been developed incorporating treated fly ash as filler, assimilating 10% in weight of the aggregate and adding it into the mortar dosage as a new formulation. The amount of 10% was chosen taking into account the positive outcomes in the bibliography. Likewise, samples tested covered different cement proportions, both using aggregates with different diameters (0/2 mm and 0/4 mm), and using different cement/aggregate ratios (1/1 and 1/3) of the stated CAC. After having analyzed the physical/mechanical properties of these mortars, the conclusions drawn are that the tested mortars are technically acceptable, with a much shorter workability period than the reference mortars. They also present better dimensional stability and an increase in bulk density. Mercury intrusion porosimetry displays a porosity decrease. In addition, the contribution of CaCO3 develops calcium monocarboaluminate hydrate (C3A·CaCO3·11H2O) which increase the resulting mixtures-those made with CAC·0/4·1/1-compressive strengths up to 48.62% more than the reference mortars.