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Top-down cracking is a type of cracking that rivals the severity and prevalence of reflective cracking. It significantly reduces the pavement's quality service life. Yet the nature of top-down cracking has not been completely understood. Recent studies of the causes of top-down cracking have focused on identifying the mechanisms that induce tensile stresses at the surface by applying different combinations of surface tractions and the finite element method. Asphalt concrete is treated as a uniform linear elastic material. A new and different approach is presented for investigating the causes of top-down cracking by means of micromechanics. In this approach, asphalt concrete is viewed as a bonded granular material, and the microstructure, including aggregate particle configuration and mastic stiffness, is considered. Theories that predict the existence of tensile stress under compressive loading were reviewed. Both qualitative and quantitative experimental methods were developed to observe the location of top-down cracking and to measure the tensile strains in the pavement. The experimental results indicate the following: ( a) top-down cracking may initiate not only at the pavement surface but also at some distance down from the surface; ( b) both tensile-type and shear-type cracking could initiate top-down cracking; and ( c) top-down cracking may most likely initiate when the mastic is weaker or the pavement temperature is higher. Therefore, a mix sensitive to rutting may also be sensitive to cracking.

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Cementitious porous pavement (CPP) is a structural low‐impact development material for rainfall–runoff management. Both infiltration and filtration are critical functions for CPP stormwater quality and quantity control. In this study, three groups of CPP specimens exposed to rainfall–runoff for 4 years and experienced with different maintenance intervals (6, 12 and 48 months, respectively) were used to examine CPP infiltration and filtration performance. Particle mass strained on CPP surface, saturated infiltration rate If, temporal infiltration rate I(t), suspended sediment concentration (SSC) and turbidity (τ) were measured to evaluate the process of filtration/infiltration. I(t), SSC and τ were examined less than 50 mg/l of the suspended particle loading. It was found that the CPP surface cleaning methods used in the past 4 years, namely, high pressure wash followed by vacuuming with one atmosphere (100 kPa), were effective, and a 12‐month maintenance interval was verified suitable to maintain the pore structure an acceptable infiltration rate for stormwater management. It was also found that CPP infiltration and filtration process affect each other, and the two properties are coupled in urban stormwater quality and quantity control. On the basis of the experimental measurements, the temporal infiltration rate of the cleaned CPP under a certain particle loading could be simulated by a first‐order nonlinear rational model, and effluent turbidity–SSC relationship was found following a power law. Copyright © 2012 John Wiley & Sons, Ltd.