This study designed an eco-friendly pervious concrete (PC) product using waste glass cullet (WGC) and recycled concrete aggregate (RCA) by dry-mixed compaction technique. The mechanical properties, water permeability behavior and related pore structure characteristics, thermal conductivity of the PCs were determined. The experimental results showed that the use of silica fume in the cement paste was effective to compensate for the low compressive strength of the PCs due to the use of narrowed graded aggregates without the incorporation of fine particles (less than 2.36 mm). Although the incorporation of recycled aggregates (i.e. WGC and RCA) into the PCs led to reductions in compressive strength, the water permeability of the PCs was improved, especially for the PCs prepared with WGC, as the use of WGC was conducive to improving the water permeability due to the negligible water absorption nature and smooth surface of glass cullet. Another encouraging result indicated that the PCs comprising 50% WGC as the fine aggregate and 50% RCA as the coarse aggregates could achieve satisfactory strength and permeability, which could largely meet the requirement of the standard (JIS A 5371) for permeable pedestrian pavers. The appropriate blending of the selected size of WGC (2.36e5 mm) and RCA (5 e10 mm) to produce a desirable pore structure in the PCs were responsible for the good performance. In addition, the low thermal conductivity of the produced PCs provided an opportunity to use the PC as partition block materials for saving energy consumption of buildings.

Introduction

The use of pervious concrete (PC) is a unique and effective means to address several important environmental issues, including improving the recharge of groundwater, reducing stormwater runoff, promoting tree survival by providing air and water, improving water quality and reducing the heat island effect, etc. (Tennis et al., 2004). Especially, in Hong Kong, heavy rainfall could happen commonly (about 2400 mm per annum of rainfall are recorded on average) (DSD, 2018). How to manage the heavy rainfall becomes a crucial issue for Hong Kong due to the densely built up urban areas and the mountainous terrain which further exacerbates the risk of flooding. Hence, it is necessary to undertake flood and waterlogging mitigation measures to improve the flow capacity. The U.S. Environmental Protection Agency identified PC pavement as one of the effective Best Management Practices for stormwater management as PC has sufficient void space to allow rapid percolation of water through the pavement (Tennis et al., 2004; DEP, 2006). Therefore, PC pavement has been extensively applied in the parking lots, drainage layers in exterior areas, residential street parking lanes, walkways/sidewalks, bike paths and pavements with minimal heavy truck traffic. Usually, PC consists of Portland cement (supplementary cementitious materials sometimes are used), aggregates and water. The difference from conventional concrete is that PC contains no fine aggregates and a lesser amount of cement paste is used to fill the voids between the aggregate particles. As a result, open cells (pores) are formed and the induced high porosity of PC leads to good internal drainage and infiltration.