Abstract
Pervious concrete is a kind of porous and permeable material for pavements and slope protection projects, etc. In this paper, a kind of pervious concrete was prepared with Portland cement, silica fume (SF), polycarboxylate superplasticizer (SP), and limestone aggregates. The performance of concrete, such as its porosity, pore distribution, permeability coefficients, and mechanical properties, were studied through laboratory tests. The volumetric porosity was measured by the water displacement method, and the planar porosity and pore size distribution were determined using image processing technology. A permeameter with a transparent sidewall and an exact sidewall sealing method were used to measure the permeability coefficients accurately. The results show that the segregation index and flow values of pastes increased with the increase of SP and water cement ratio (W/C). The measured porosity (volumetric porosity and planar porosity) of pervious concrete with a single-size aggregate was closer to the design porosity than that with the blended aggregate. Compared with the design porosity selected in this study, aggregate size was the main factor influencing the pore distribution of pervious concrete. The standard deviation of the permeability coefficient was less than 0.03 under different hydraulic gradients. It was found that the relationships between the permeability coefficient and volumetric porosity (or effective pore size d50) approximately obey polynomial function. Based on the test results, the optimized parameters were suggested for practical engineering: W/C of 0.26–0.30; 0.5% SP content; 5% SF content; 15–21% design porosity; and aggregate sizes of 4.75–9.5 mm and 9.5–16 mm.
Highlights
With the rapid development of economy and the increment of urban populations, many large-scale infrastructures and impermeable roads have been built, which has caused more and more serious environmental problems, such as urban hot island phenomena and the disappearance of groundwater.Pervious concrete, referred to as porous ecological concrete, is a porous media material which consists of cement, water, aggregates, and admixtures, etc
The permeability coefficient was measured by the permeameter that was designed with The permeability coefficient was measured by the permeameter that was designed with transparent plexiglass by our group
Thisinmight be attributed to the fact that the pervious concrete with a larger design porosity only resulted in a larger number of open and connected pores, but had little effect on the pore size of the concrete
Summary
With the rapid development of economy and the increment of urban populations, many large-scale infrastructures and impermeable roads have been built, which has caused more and more serious environmental problems, such as urban hot island phenomena and the disappearance of groundwater. Pervious concrete has a large porosity and its permeability can reach up to about 2–6 mm/s [1]. Rainwater can penetrate into pervious concrete quickly, so groundwater can be replenished and stored effectively. It can reduce city temperatures and alleviate urban hot island phenomena [2]. The properties of pervious concretes have been studied in many laboratories, including mixing design, conservation method, porosity characteristics, strength and durability, etc. Many researches on pervious concretes have been conducted, studies concerning the properties of paste, as well as the accurate determination of the permeability coefficient and pore structure, are still limited. A visual permeameter and an exact sidewall sealing method were established to measure the permeability coefficients accurately. The mechanical behavior, such as the compressive strength, was measured
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