Pervious concrete with secondarily recycled low-quality brick-concrete demolition residue: Engineering performances, multi-scale/phase structure and sustainability

Brick-concrete demolition residue after the primary recycling is generally discarded due to its low quality. Secondary recycling of the brick-concrete demolition residue is urgently required to be solved at present in China due to the large scale constructions and demolitions, and remains a challenging task. In this work, a brick-concrete demolition residue from an urban-fringe of Hangzhou, China, was secondarily recycled as the fine aggregate to fabricate sustainable pervious concrete after systematic characterization of its physical and chemical properties. In order to improve the engineering properties of the pervious concrete, natural aggregate and sand were used. Multi-scale structure in terms of pore size distribution, skeleton morphology, and matrix-aggregate interfacial transition zone were systematically characterized using X-ray computed tomography and backscattered electron imaging tests. Results show that the increase of the natural aggregate replacement ratio and sand ratio always increases the compressive strength and density, but decrease the water permeability. Incorporation of the secondary brick-concrete demolition residue in concrete increases the total porosity and connected porosity of the pervious concrete, and helps form a Calcium-enriched matrix-aggregate interfacial layer zone. Use of the secondarily recycled brick-concrete demolition residue in pervious concrete manufacture at the optimal mix brings the CO2 emissions reduction by 107 kg/m3 and costs reduction by 30.3 USD/m3. The findings of this work provide a sustainable route to secondarily recycle low-quality brick-concrete demolition residue for constructions.