Pervious concrete is widely used in various fields because of its high permeability. Strength and permeability are two important design parameters for pervious concrete, but limited research has been conducted so far on their mutual relationship. A series of laboratory tests are carried out to demonstrate the effects of water–cement ratio, aggregate–cement ratio, and porosity on the properties of pervious concrete including strength and permeability in this study. In addition, a modified permeability testing method for pervious concrete is developed, as the existing permeability testing devices for pervious concrete have not considered the specimen–container interface leakage induced by the large number of open pores on the surface of specimen, thus affecting the testing precision of permeability.

Pervious concrete pavements have good drainage capabilities; however, storm water runoff during extreme events can cause the pores clogging in permeable pavement. This study aims to preliminarily reveal the mechanism of sediment clogging in the pores of the pervious concrete pavement under storm water runoff. An innovative continuous permeability measurement system combined with the electrical conductivity measurement is developed. Laboratory simulation tests are conducted with this system to demonstrate the effects of four factors on the permeability reduction. The tests indicate that the pore clogging process generally includes three phases, i.e. quick clogging, temporary mitigation of clogging and progressive clogging. The clogging is more prone to occur in specimens with large porosity. Meanwhile, the variation of electrical conductivity of pervious concrete can accurately reflect the clogging process of pervious concrete. A rapid clogging model has been developed and validated. Research results obtained are important in optimising the design and evaluation of pervious concrete pavement.

Having the advantages of high permeability and high strength, pervious concrete is suitable for improving ground-bearing capacity. In the Yellow River Delta, a pervious concrete pile (PCP) composite foundation has been constructed to reduce settlement of an expressway embankment. To study the working mechanism of PCPs, a numerical model was constructed based on the finite-difference method and Biot’s consolidation theory, which was validated by data from in situ tests. The excess pore-water pressure, pile–soil stress ratio, lateral displacement, and settlement of the PCP composite foundation under the loading of the road embankment were numerically calculated and compared with those of gravel pile and low-grade concrete pile composite foundations. Comparisons show that the dissipation of excess pore-water pressure in the PCP composite foundation was fastest, which implied that PCPs can significantly mitigate the development of excess pore-water pressure and thus enhance subsoil strength. Furtherm...

In this paper, a diffuse interface model, namely, the phase-field model (PFM) is proposed to model asphalt concrete cracking subjected to shear loading (Mode II) at low temperature. This method describes the microstructure of asphalt concrete using a phase-field variable. To account for the growth of cracks, a nonconserved Allen-Cahn equation is adopted to evolve the phase-field variable. The whole PFM system is implemented and solved in a finite-element software program. The simulation results are then validated by semicircular bending (SCB) tests at $-20°\mathrm{C}$ and four-point bending tests at $-10°\mathrm{C}$ . It is discovered that PFM simulations of crack initiation and propagation in asphalt concrete at low temperature agree very well with the experimental results.

Estimation of unsaturated hydraulic conductivity could benefit many engineering or research problems such as water flow in the vadose zone, unsaturated seepage and capillary barriers for underground waste isolation. The unsaturated hydraulic conductivity of a soil is related to its saturated hydraulic conductivity value as well as its water retention behaviour. By following the first author’s previous work, the saturated hydraulic conductivity and water retention curve (WRC) of sandy soils can be estimated from their basic gradation parameters. In this paper, we further suggest the applicable range of the estimation method is for soils with $d_{10}$ > 0.02 mm and $C_u$ < 20, in which $d_{10}$ is the grain diameter corresponding to 10% passing and $C_u$ is the coefficient of uniformity ( $C_u=d_{60}/d_{10}$ ). The estimation method is also modified to consider the porosity variation effect. Then the proposed method is applied to predict unsaturated hydraulic conductivity properties of different sandy soils and also compared with laboratory and field test results. The comparison shows that the newly developed estimation method, which predicts the relative permeability of unsaturated sands from basic grain size parameters and porosity, generally has a fair agreement with measured data. It also indicates that the air-entry value is mainly relative to the mean grain size and porosity value change from the intrinsic value. The rate of permeability decline with suction is mainly associated with grain size polydispersity.

Moisture damage of hot-mix asphalt (HMA) pavement is an extremely complicated mode of distress. Previous researches on moisture damage mainly focused on the performances of undamaged pavement at the initial stage of opening to traffic. So with the permeability tests and the Hamburg Wheel Tracking Device (HWTD) tests, trial works were done to study the effect of traffic-load-induced mechanical damage on the evolution of moisture damage in HMA pavement. The monotonous uniaxial compression loading method and the repetitive compression loading method were employed to make the mechanical damages of the styrene–butadiene–styrene block copolymer-modified HMA specimens, respectively. Comparisons demonstrated that there were slight differences between the damages from the two kinds of damage making methods. The damages were characterised with two kinds of nondestructive testing methods (dynamic modulus testing method and ultrasonic wave testing method), and the relationship of the characterised damages with the two methods was obtained. The permeability tests of HMA showed that the coefficient of permeability initially decreases and then increases with the damage. HWTD test results implied that the mechanical damage had a significant influence on the moisture damage, especially in hot and humid environment. In HWTD test, the mechanical damage induced by the undesirable stress state in pavement accelerates the appearance of the striping inflection point and increases the cumulative deformation of HMA specimen. Therefore, in order to reflect the performance of asphalt pavement during its life cycle, the effect of mechanical damage on the evolution of moisture damage should be considered in pavement design and construction.