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An inorganic polymer compound was used to coat lightweight expanded clay aggregates (ceramsites) with a thin layer. These modified aggregates were then used to manufacture modified ceramsite concrete specimens. The spalling and mechanical properties, including cube and cylinder compressive strengths, tensile strength, flexural strength, elastic modulus and stress–strain relationship, of the concrete specimens at room temperature and after exposure to high temperatures (200–1200°C) were tested. Furthermore, chemical changes of the inorganic polymer compound and macro- and microstructures of the concrete were also detected after exposure to the different temperatures by means of Fourier transform infrared spectroscopy, charge-coupled device high-temperature in situ digital image collection and scanning electron microscopy, respectively. Normal ceramsite concrete and crushed limestone concrete were also produced as references for comparison. It was found that only 4·2% of the modified ceramsite concrete specimens spalled, while 69·4% of the normal ceramsite concrete specimens and 33·3% of the crushed limestone concrete suffered spalling. After exposure to 1200°C, modified ceramsite concrete still had considerable residual mechanical properties. The polymer used as the modification material decomposed gradually with increasing temperature, which could generate channels for vapour release to reduce the possibility of concrete spalling.

In this study, the pore structure of a hardened phosphorous building gypsum body was optimised by blending an air-entraining agent with the appropriate water–paste ratio. The response surface test was designed according to the test results of the hardened phosphorous building gypsum body treated with an air-entraining agent and an appropriate water–paste ratio. Moreover, the optimal process parameters were selected to prepare a porous phosphorous building gypsum skeleton, which was used as a paraffin carrier to prepare energy-storage phosphorous building gypsum. The results indicate that if the ratio of the air-entraining agent to the water–paste ratio is reasonable, the hardened body of phosphorous building gypsum can form a better pore structure. With the influx of paraffin, its accumulated pore volume and specific surface area decrease, and the pore size distribution is uniform. The paraffin completely occupies the pores, causing the compressive strength of energy-storage phosphorous building gypsum to be better than that of similar gypsum energy-storing materials. The heat energy further captured by energy-storage phosphorous building gypsum in the endothermic and exothermic stages is 28.19 J/g and 28.64 J/g, respectively, which can be used to prepare energy-saving building materials.