Development of artificial leak-free phase change material (PCM) aggregates using emulsion technique, cementless binder, and cold-bonded pelletization

The present study developed new leak-free artificial PCM aggregates using an emulsion technique, cementless binder, and cold-bonded pelletization (hereafter, PCM-surfactant-aggregate) and significantly increased the PCM quantity in aggregates without PCM leakage, which was demonstrated from differential scanning calorimetric (DSC) and thermogravimetry (TG) results. The PCM-water-emulsion was produced by using a non-ionic surfactant, Pluronic P123, and used as mixing water to produce cementless artificial aggregates using Ca(OH)2-Na2CO3-activated fly ash and cold-bonded pelletization. The produced artificial PCM-surfactant-aggregates showed no material separation during preparation and no visual PCM leakage on the surface and were lightweight aggregates in terms of compressive strength (ASTM C330). In the concrete testing results, the 28-day compressive strength was 18.1 MPa when all fine and coarse aggregates were replaced with artificial PCM-surfactant-aggregates and the thermal conductivity decreased with increasing aggregate content. The testing on the heated concrete specimens having PCM-surfactant-aggregates indicated no PCM leakage, no dimensional change, and no strength reduction due to the PCM phase transition from solid to liquid. Overall, the concrete containing PCM-surfactant-aggregates showed an increase in the lowest temperature and a decrease in the highest temperature in the temperature profile of the indoor space in the dynamic heat flow test.