Potential use of lightweight aggregate (LWA) produced from bottom coal ash for internal curing of concrete systems

A Study on the Thermal Properties of High-Strength Concrete Containing CBA Fine Aggregates

“…Mangi et al [23,24] investigated the effect of CBA on the concrete strength properties under sulfate and chloride environments. Balapour et al [25] performed an experimental program to investigate the potential use of CBA for the internal curing of concrete systems. They indicated that CBA exhibited a low oven dry-specific gravity, which makes it capable of storing the amount of water needed for concrete internal curing.…”

Thermochemical principles of the production of lightweight aggregates from waste coal bottom ash

“…Two types of bottom ash, NV (low-calcium) and WP (highcalcium), were used in this study for LWA production. 5,12 The LWA manufacturing procedure started by drying the raw ash material, followed by sieving to the appropriate particle size distribution. Afterward, the prepared ash was mixed with various NaOH solutions (molarities of 2.5, 6.25, and 10 mol/L) to achieve mass concentrations (mass of solid NaOH per mass of bottom ash) of 4%, 10%, and…”

“…NaOH solutions with a liquid to solid ratio of 0.4 were used for geopolymerization during the curing period as well as to serve as a fluxing agent to reduce the melting temperature of the mixture. 5,12 The mixture was then pelletized into spherical shape and cured at 40°C and 30% relative humidity (RH) for 24 hours. Finally, the pellets were sintered at 1160°C to produce SPoRA.…”

“…The X-CT was carried out using a Zeiss Versa XRM 500 system. 5 The x-ray tube was set for a voltage of 80 kV and a current of 87 mA. The exposure time per step for 360° rotation was ≈0.6 second.…”

“…Previous studies of LWA production from various starting waste materials 5‐11 have suggested that a successful production of sintered LWA requires a sintering mechanism where three crucial conditions are reached concurrently during sintering 7,12 : (a) sufficient liquid/molten phase amount formation on the aggregate surface to maintain a viscous state for the LWA, (b) attaining an appropriate viscosity in the liquid‐solid suspension to enable the entrapment emitted gas during sintering while preventing extreme LWA deformations under gravitational forces, and (c) appropriate amount of gaseous phase emission during sintering to form entrapped pores in the liquid phase that will result in successful bloating and LWA formation. Providing a balance among these three conditions can lead to successful design and production of functional LWA having desirable engineering properties for different industrial applications.…”