Development of high-strength alkali-activated pastes containing high volumes of waste brick and ceramic powders

Abstract

The main purpose of this study was to develop a high-strength alkali-activated paste using a high volume of waste red clay brick powder (WBP) and waste ceramic powder (WCP) as source materials. The reference mixes in this study were prepared using 100% WBP and 100% WCP. In the trial mixes, the WBP and WCP comprised about 60% of the total weight of the starting materials, while fly ash (FA) and ground granulated blast furnace slag (GGBFS) comprised the remaining 40%. Increments of the latter in the different trial mixes varied from 10% to 30% of the total weight. A solution of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was used as the alkali activator. Alkali-activated paste (AAP) samples were prepared and cured at ambient temperature for 3, 7, 28, and 56 days. Workability, compressive strength, ultrasonic pulse velocity, thermal conductivity, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and Fourier transform infraredspectroscopy (FTIR) analyses were conducted in order to study the engineering and microstructure performance of these samples. The test results revealed that the fresh AAP mixtures were highly workable with measured slump flow values of 235–300 mm. Moreover, the hardened AAP samples obtained high compressive strength results measured in the range of 36–70 MPa. The AAP samples with WBP showed better mechanical strength performance and denser morphology than those with WCP. It is attributable to the enhancement of alkali activation of the AAP due to the finer particle size and higher CaO content of the WBP as compared to the WCP. The results of this study further demonstrate the strong potential of using recycled WBP and WCP in the production of high-strength AAP.