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The recycling of inert construction and demolition materials (C&D) remains problematic if these materials are used to process high-quality recycled aggregates suitable for manufacturing new concrete. Even when selective demolition is employed, the crushing and classification of C&D produces recycled aggregates with an unacceptable level of impurities, with the content of gypsum being the biggest concern. Another concern is the percentage of brick content that decreases the density of the recycled aggregate as well as its homogeneity. The present work studies an air-jig sorting method to separate out concrete particles from a C&D mixture that contains high amount of gypsum (22% mass) and brick (24% mass) particles. The mixture of aggregates studied had a 4 to 20 mm grading. After sorting, the bottom third of the mixture had less than 1% mass of gypsum and more than 90% mass of concrete particles. In contrast, the upper third of the sorted material contained gypsum in proportion of nearly 80% mass. The separation mechanism appears to be governed by both particle density and bulk density of individual components. These results are very encouraging and prove that the air-jigging method is a promising technology for the use in C&D recycling plants. Further research is warranted. Highlights Sorting the recycled aggregates (RA) may improve the quality of this material. Air jig prospective test on RA provided better results than previous wet jig tests. RA resulting from the jigging are of suitable quality to be used for secondary concrete. Both particle density and bulk density govern the separation process.

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The interactions between kaolinite and a commercially available phosphinate-based flame retardant (Exolit® OP1311) were evaluated as flame retardant systems in Polyamide 6 (PA6). The thermal degradation and flammability of PA6 composites were studied by TGA and cone calorimeter tests. Characterizations were conducted using FTIR, EDX and XRD. Cone calorimeter results showed a reduction in peak heat release rate (pHRR) as a function of filler loading and type with a greater reduction for OP1311 containing composites. Interestingly, OP1311 can be partially substituted by kaolinite without detrimental effect on peak of release rate (pHRR) measured by cone calorimeter. FTIR, EDX and XRD analysis of cone calorimeter residues showed that kaolinite may trap some phosphorous compounds in condensed phase leading to the formation of a glassy structure on sample residue. To assess possible interactions between kaolinite and phosphinate, a controlled thermal degradation was carried out on kaolinite, OP1311 and kaolinite/OP1311 (50:50) blends. The residues were analyzed by EDX and XRD. Results showed that almost all phosphorous present in the initial sample remains in residue for Kaolinite/OP1311 blend versus only about 60% for OP1311 alone. Also, XRD results showed that during combustion, new crystalline phases can be formed in the sample when kaolinite is combined with OP1311. These results suggest that some interactions between both components may occur and could explain the observed fire behavior of the composites containing kaolinite and phosphinate.