Optimization of coal-based solid waste ceramsite foam concrete mix proportions and performance study

To recycle coal-based solid waste, this study used coal-based solid waste ceramsite with a density grade of 500 as coarse aggregates to manufacture ceramsite foam concrete. The concrete mix design was optimized using response surface experiments. Pore structure characteristics were analyzed to elucidate the connection between thermal conductivity and porosity. Microscale investigations were carried out employing a Vickers hardness tester, optical microscope (OM), scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and thermogravimetric analysis (TG) to offer distinct insights into the fundamental physicochemical mechanisms that govern the evolution of structural performance. The results show that with a foam content of 43 %, a water-to-binder ratio of 0.31, and a fly ash content of 15 %, the concrete produced meets the A10 grade standard. A high coefficient of determination (R2 > 0.96) highlights the validity and goodness of fit of the quadratic regression model. The average pore size and roundness of ceramsite foam concrete increase as the foam content rises but decrease with higher fly ash content. The established three-dimensional series thermal conductivity model demonstrates greater precision. A “locking” interface structure develops between ceramsite coarse aggregates and the cementitious matrix, which strengthens the transition zone. With a fly ash content of 15 %, the cementitious matrix contains the highest amount of flocculent C-S-H gel, leading to the highest compressive strength. Thermogravimetric analysis verifies the exceptional thermal stability of ceramsite foam concrete.