Globally, coal mining wastes (CMWs) are associated with significant environmental and economic costs. Processing CMW into an ingredient of foam concrete is a promising solution but the behaviour of this particular construction material has not been sufficiently evaluated, especially during the initial period of cement hydration. The purpose of this paper is to present novel laboratory set-up and experimental procedures designed to investigate the early age behaviour of hydrating foam concrete samples made with a CMW from Poland. Two types of tests were devised to simulate air-curing conditions and water-curing conditions, respectively. These tests were carried out in custom-built unsaturated oedometer cells, and the matric suction in the test samples was monitored for approximately 14 days, using Warwick high capacity tensiometers. Experimental results show that in both curing conditions, a higher matric suction during cement hydration corresponds to a denser sample at the end of the monitoring period. A comparison of water-cured and air-cured samples also reveals different responses to CMW inclusion in their mix designs. The responses can be convincingly explained based on complementary test data and idealised capillary tube models adapted for the hydrating foam concrete samples. •A novel laboratory set-up, incorporating high capacity tensiometers (HCTs) into purpose-built unsaturated oedometer cells, is proposed to investigate the curing behaviour of foam concrete during early age hydration. The incorporation of the HCTs made it possible to directly monitor the matric suction evolution of the mix and the corresponding interplays depending on the foam concrete samples’ (water- or air-) curing conditions.•The influence of natural sand replacement by coal mining waste (CMW) in the foam concrete mix has been studies, together with the corresponding effects on the evolutions of matric suction and porosity during the early age hydration.•Two different types of tests were devised for measuring the impacts of different curing environments on foam concrete properties. The first type was adapted for a water-curing condition and is akin to a chemical shrinkage test. The second type was adapted for an air-curing condition where water inflow was not permitted into the hydrating foam concrete sample over the monitoring period. In both cases. The evolution and interplays of matric suction were studied in correspondence with formation/stabilisation of the pore networks.•Simplified capillary models are proposed that meaningfully describe the rather complex kinetics of foam concrete hydration associated to the matric suction variations.