Research on pore-clogging behavior and mechanism in pervious concrete prepared with recycled aggregate

Abstract

The application of construction waste as recycled aggregate (RA) to prepare pervious concrete (PC) for urban pavements is an important means for comprehensively alleviating ecological and environmental problems such as urban flooding and excessive construction waste. This paper focuses on the long-term decrease of permeability performance of recycled aggregate pervious concrete (RAPC) and the change in pore characteristics under clogging conditions to reveal the clogging mechanism of RAPC. The suitability of different methods for cleaning clogged materials were also evaluated. The results showed that the incorporation of RA reduced the effective porosity of the PC and thereby reduced its water permeability at 50% additional water. In addition, the greater the proportion of RA, the worse the permeability of RAPC and the more obvious the reduction of permeability during long-term clogging. Simultaneously, increasing the target porosity has the opposite effect because it increases the pore volume and pore connectivity. However, both factors are detrimental to the mechanical properties of RAPC. Furthermore, the clogged area of RAPC is divided into three main zones. The pores in region I have a funnel shape with additional concentrated clogging material and severe clogging, and the pore rate, pore number, and pore maximum Ferret diameter are all significantly reduced compared to the unclogged RAPC. Fewer clogging materials can reach region II, and thus there is significantly less clogging than in region I. The clogging material is unable to reach region III; thus there is almost no clogging, and the pore characteristics are unchanged from those in the original material. In addition, high-pressure flushing has a better cleaning effect for removing dusty soil from clogged pores, while vacuum suction has a better cleaning effect for removing sandy soil. The reason for this result is that the two cleaning methods have different mechanisms. This study reveals the pore structure evolution and permeability decrease in RAPC during long-term clogging by particles in road runoff and recommends cleaning methods for different clogs to ensure the long-term preservation of the permeability of RAPC and prolong the service life of RAPC pavements.