Microwave Curing Techniques for Manufacturing Alkali-activated Fly Ash

Alkali-activated fly ash (AAFA) has been identified as a low-carbon alternative to Portland cement (PC). However, conventional thermal oven curing, typically at 85ºC, is commonly required to firstly initiate and then accelerate the chemical reaction, which may result in more energy consumption, offsetting the environmental benefits which could be obtained from AAFA.

In this study, the potential of using microwave as an alternative low-energy thermal curing method for manufacturing AAFA has been explored. A microwave curing regime based on a control strategy using temperature feedback data was developed and evaluated in the manufacture of AAFA. The temperature profile within the AAFA sample produced under microwave curing was obtained by using an embedded optical fibre temperature sensor, which was thus used to adjust the microwave power in real-time in order to achieve a desired internal temperature. The AAFA samples manufactured by microwave curing were characterized using compressive strength, XRD, NMR, MIP and SEM, which were also compared with the samples from thermal oven curing. The results indicated that the AAFA manufactured with microwave curing not only showed an equivalent performance, similar reaction products and microstructure, but also showed dramatic reduction in energy consumption.