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Glazed hollow bead (GHB) is an innovative material that gives concrete very good thermal-insulation properties and improves concrete frost resistance, when used as a partial replacement of ordinary fine aggregate. The improvement in frost resistance under freeze-thaw cycles and the deterioration mechanisms of recycled aggregate thermoinsulating concretes (RATICs) is the objective of this study, after adding GHBs to the mix. Fifteen cubes and ninety prisms made of five RATIC mixes (GHB content = 0, 40, 65, 90 and 130 kg/m3) were tested in compression, to identify the optimum content of GHB. The degradation mechanisms of RATIC were identified based on mass loss, dynamic elastic modulus and uniaxial compressive strength. In addition, RATIC mesostructure was investigated by means of Computed Tomography Scanning, and the deterioration mechanisms by analyzing pore amount, average and maximum pore area and porosity. The experimental results demonstrate that adding glazed hollow beads to recycled aggregate concrete (RAC) moderately changes the mesostructure of the concrete, to the advantage of frost resistance, and that the optimum content of GHB is around 90 kg/m3.

A testing program including freeze–thaw cycles and flexural-loading combined action was designed to investigate the durability of recycled aggregate thermal insulation concrete (RATIC). The volume replacement ratios of recycled coarse aggregates (RCAs) were 0, 30, 50, 70, and 100%, and the flexural-load ratios were 0, 15, 30, 45%, and the glazed hollow bead particles (GHBs) with volume percentage of 130% were added. To evaluate the performance of RATIC, the relative dynamic modulus of elasticity (RDME) and mass loss rate (MLR) were estimated. The results show that the flexural-load stress exhibited an obvious negative effect on the freeze–thaw resistance of RATIC. With a 45% flexural-load ratio, RATIC fractured even before the load cycles reached 30. The decrease in the RDME was accelerated by the flexural-load stress, whereas this stress exhibited little effect on MLR. The durability performance of RATIC under combined actions decreases with the increase in the RCA replacement ratio, whereas the performance increased with the increment in the thermal insulation aggregate GHBs. Further to reveal the mechanism of RATIC under double actions, scanning electron microscopy, X-ray diffraction, and a new method of fluorescence analysis were employed. The results showed the existence of more micropores and micro-cracks in the tensile area. Further, compared to the new interfacial transition zones (ITZs), the micro-cracks in old ITZs caused by combined actions aggravated the damage caused in the freeze–thaw cycles.