Journal of Materials in Civil Engineering

With many advantages such as high skid resistance, low noise, and less splash and spray, porous asphalt pavement can significantly improve driving quality in wet weather condition and is used widely in Europe, the United States, and Japan. The early research in China on porous asphalt pavement was started in the 1980s. Due to the hot weather, overloaded traffic and poor material properties, the porous asphalt pavement paved in that time is not quite successful. This paper deals with the present research, especially the material composition and its impacts on the performance of porous asphalt pavement. In this study, the empirical equation of air void versus gradation was derived from uniform experimental analysis so that the target gradation could be achieved by using the formula. In addition, the quantitative relationship between air void and drainage efficiency is obtained by a series of experimental studies, and the performances of porous asphalt mixture with three types of bitumen are evaluated to analyze the influence of asphalt property on that of the asphalt mixture. Finally, the binder requirement of porous asphalt for China’s weather and traffic condition is proposed.

The slipform paving technique has been utilized widely in the construction of high-class highway cement concrete pavements in China, resulting in increased use of complex admixtures. Complex admixtures usually contain various components that may have potential compatibility issues, not only between admixtures and cement, but also between admixture components. In order to alleviate or eliminate potential incompatibility problems, it is necessary to adjust the mix proportions and admixture chemical components by taking into account the real-life materials and surrounding conditions. An optimum dosage of the complex admixture should be determined according to the specific job requirements and construction technique. Compatibility issues always arise between admixtures and cements. It was found that ${\mathrm{Na}}_2\mathrm{S}{\mathrm{O}}_4$ and $\mathrm{Ca}{\mathrm{Cl}}_2$ may increase the early strength, but also may reduce the slump of the mix. When the resin-based air-entraining agent and water reducers were used together, they produced a large amount of residue. Water-retaining polymer can be used as the plasticizing ingredient to slow down hardening without sacrificing slump loss and setting time. It is necessary to reduce the ${\mathrm{C}}_3\mathrm{A}$ content so as to enhance the compatibility between retarders and cements. Retarding admixtures based on lignosulphonic or hydroxylated carboxylic acids can delay the setting of cement paste, but also may accelerate the setting when the dosage is high. Blended cements require much more air-entraining agent than Portland cements. The air content decreases as the alkalinity and fineness of cement increase.

The coupled action from alternating stresses and corrosion agents is the main driving force deteriorating concrete performance. The writers carefully devised some test equipment to investigate the flexural strength of high-performance concrete (HPC) subjected to the action of sodium sulfate $\left({\mathrm{Na}}_2\mathrm{S}{\mathrm{O}}_4\right)$ solution and alternating stresses applied by a third-point loading equipment. The chloride diffusion in the HPC was also studied at different deterioration stages of the test specimens. The influence of water/cement ratio and the dosage of the mineral admixture on the corroded and fatigued concrete were analyzed. By introducing the corrosion factor and the corrosion fatigue factor, the writers developed a method to evaluate the concrete resistance to chemical corrosion agents and/or fatigue loadings. The results show that under the same condition, the corrosion fatigue factor is much smaller than the corrosion factor and the maximum difference between them exceeds 20%. In addition, both water–binder ratio and fine mineral admixture have notable influence on the corrosion factor and the corrosion fatigue factor. Decreasing water dose of concrete, adopting low water–binder ratio, or mixing about 20% fly ash can evidently improve the corrosion fatigue resistance of HPC.

Engineering problems with expansive soils in subgrades complicate highway construction in expansive soil areas of China. To research and solve the engineering problems, a Chinese research group carried out extensive research as part of the construction of a highway in Ningming Basin, a typical expansive soil area in China. The research on Ningming expansive soils is presented, including laboratory studies of soil properties, modified California bearing ratio tests for evaluating the bearing capacity, and wet compaction tests for obtaining the parameters to control field compaction when using expansive soils as embankment fill. The field investigations of slope failures also are introduced, including analysis of the investigations. New techniques for using expansive soils in embankments, and stabilizing cut slopes consisting of expansive soils, were developed and applied into the trial sections of the highway by the research group, based on their research and investigations. The measures proved successful and were used to solve the technical problems related to the NanYou Highway subgrade construction. The outcomes of the research also may prove useful in the construction of such projects as railway and hydraulic works.

This paper presents a comprehensive study to evaluate the characteristics of polymer-modified asphalt binders and mixes using both the conventional and SuperPave tests. The polymers investigated included styrene–butadiene–styrene, styrene–butadiene–rubber, and complex polymers (or C-polymer). It is shown that the characteristics of polymer-modified asphalt binders and mixes may vary with the polymer type, polymer dosage, asphalt source, aggregate type, and mix type. As the polymer dosage increases, the high- and low-temperature characteristics of the asphalt binder become better, the creep stiffness decreases, the $m$ -value may increase, and the aging characteristics improve. The use of a polymer can enhance the dynamic stability of asphalt mix and the use of the rut depth can better measure the rut resistance. The presence of a polymer can also enhance the bending behavior of the asphalt mix at low temperatures. It is concluded that the AC-13 mix may generate better pavement performance than the AC-16 mix. The C-polymer has shown promising results in improving the characteristics of hot-mix asphalt.

Geocell flexible retaining wall is a new type of retaining structure constructed by stacking three-dimensional network geocells filled with soil or gravel. The writers analyzed the interaction among wall, reinforced layers, and fill using the finite element software, MARC, and evaluated the stress distribution of the geocell flexible retaining wall. Field testing was conducted to measure the lateral earth pressure of a geocell flexible retaining wall constructed on an expressway in central north China’s Shanxi Province. It was shown that the deformation of flexible retaining wall was significantly influenced by the width of wall, distance between adjacent reinforced layers, and foundation modulus. The width of wall affected the stress level noticeably. The horizontal displacement of reinforced layers increased as the external load applied on the fill behind the wall increased. The horizontal stress of tied reinforced layers developed in three phases: bending, stretching–bending, and stretching as the external load increased. Economic analysis demonstrated that the cost of geocell flexible retaining wall can be reduced by 24%, which brings about remarkable economic benefits.

Fiber-reinforced polymer (FRP) strap is one of the FRP forms. Its width is small and its thickness is large. The wave-shaped-gear-grip anchorage (WSGG) was developed specifically for the FRP strap. A brand-new method has been developed for externally anchored FRP sheet prestress strengthening, which makes full use of the features of WSGG anchors by fixing both ends and then fastening the middle to force FRP sheets to elongate geometrically and generate a pretension. Worn bridge members (solid RC plates of $8\mathrm{m}$ long) removed from the Cheng-Yu Expressway were used in this experiment of externally anchored CFRP strap prestressed strengthening. The experiment results demonstrated that the proposed method for the application of prestressing FRP straps is very simple, easy, and technically practical, and can significantly enhance the effectiveness of strengthening. It was also shown that the proposed method will have broad applications.

As one of the main distresses that may occur in asphalt pavements, rutting affects pavement performance the most significantly. This paper presents the investigation of the contributions of the structural layers to the total rutting in the asphalt pavements with semirigid bases through in situ excavation of transverse trenches and cores taken in the selected typical pavements on a real-world expressway. The selected pavements exhibited different depths of rutting. Laboratory rut testing was conducted on the core samples. Statistical analysis was undertaken to evaluate the effects of the layer properties sensitive to the variations of temperature on the rutting. The results indicated that the high temperature stability of the asphalt intermediate course had the greatest effect on the rut development. This paper presents the regression relationship established between rut depth and dynamic stability for each structural layer in asphalt pavements. In addition, the criteria for the dynamic stability are provided for asphalt base courses on different longitudinal grades.

Incidents may arise in road tunnels, in particular at the tunnel entrance and exit. Investigation conducted in the road tunnels in the provinces of Guizhou and Yunnan in China showed that the concrete pavement surface skid resistance decreased rapidly inside the tunnels and was significantly different from that outside the tunnels. Pavement surface skid resistance is one of the most important factors that affect travel safety, in particular wet weather skidding accidents. Countermeasures are necessary to enhance the skid resistance on concrete pavements in tunnels. The writers made an effort to investigate possible pavement surfaces to provide long-lasting skid resistance, including porous concrete surface and open graded friction course (OGFC) surface. Porous concrete was paved directly on the regular concrete pavement and OGFC was paved on the existing surface of concrete pavement to provide sufficient skid resistance. Accelerated abrasion devices have been developed to evaluate the skid resistances of the porous concrete and OGFC, respectively. Regular asphalt materials will burn easily and emit toxic gas in fire, which may reduce the survival rate for tunnel users involved in fire accidents. Fire-retardant asphalt has been developed to reduce the tendency of asphalt materials to burn and reduce emission.