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The use of industrial wastes such as coal fly ash (CFA) and carbide lime (CL) can enhance the long-term performance of recycled asphalt pavements under freeze–thaw conditions as well as reduce consumption of natural resources. Further improvement of the mechanical properties of such blends can be achieved by adding small quantities of sodium chloride (NaCl). Blends of recycled asphalt, CFA, CL and sodium chloride were therefore assessed in terms of their durability to freeze–thaw exposure. Additional splitting tensile tests were performed to evaluate strength improvements after adding sodium chloride. Specimens were moulded with three different dry unit weights and two different lime percentages, and cured for 7 d. The accumulated loss of mass was evaluated as a function of the porosity/lime index, which broadens the applicability of this index by demonstrating it, and influences not only strength but also long-term performance. The improvement in engineering properties provided by sodium chloride was found to be related to the formation of mineral phase thomsonite and to sodium chloride acting as a catalyser. [ABSTRACT FROM AUTHOR]

The long-term storage of coal ash in impoundments can lead to concerns of structural stability as well as trace element migration to local surface water and groundwater sources. Microbial induced calcium carbonate precipitation (MICP) offers a potential approach for minimising leachability of heavy metal trace elements from coal ash by calcium carbonate cementation. In this study, a protocol for MICP treatment of coal ash has been experimentally developed. The MICP treatment is applied to three coal ashes from different power plants, and their response to the developed treatment protocol is assessed. Possible factors affecting the MICP treatment of coal ash are discussed in terms of efficacey and inhibition of the stabilisation process. For this purpose, several approaches such as shear wave velocity, electrical conductivity, pH measurement, acid washing, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were implemented. The results indicated that carbon/carbide content of the fly ash material has an important role in the efficacey of the MICP treatment process. The most likely explanation is carbon/carbide aids in the nucleation of calcium carbonate precipitation. [ABSTRACT FROM AUTHOR]