Advanced Materials Research Vol. 723

Abstract: Under normal atmospheric pressure conditions, volume suddenly increases about 11% when the water freezes and decreased when the ice melts. The pressure can reach up to 2500 times of atmospheric pressure in the closed space when the water freezing. This is a very important characteristic of the natural world and the industrial. In low temperature condition, the snow on the pavement is easy to melt and freeze, and it will affect the road safety, increase the cracking of the road and accelerate asphalt pavement water damage. Bitumen is a mixture consisting of some extremely complex polymer hydrocarbons and hydrocarbon derivatives of non-metallic (oxygen, sulfur, nitrogen). Deicing salt is used to prevent freezing in that area, chloride salt is its main ingredient. When the water melting point reduced, it is not easy to icing but to penetrate the asphalt pavement. If the temperature is continued to reduce, salt solution will still freezing. At last, the pavement will form water damage in repeated freeze-thaw cycles conditions.

Abstract: There is no temperature stress and temperature curling according to the present cement concrete pavement design, when the temperature gradient of cement concrete pavement in service is zero, and it does not consider the effect of Built-in curling caused in early-age setting process of cement concrete to cement concrete pavement in service. In fact, there is Built-in curling in cement concrete slab when it is after the completion of the cement concrete slab is poured, and the curling is mainly upward. It is in the setting process, when cement concrete is on the final set, the cement concrete is at the critical moment when is just able to bear load, and it exists temperature gradient but no strain in the pavement slab, the temperature gradient is known as "Built-in construction temperature gradient" in AASHTO2002 design guidance, and it is the important part of the Built-in curling. In this paper, cement concrete beam specimens were poured in outdoor and temperature sensor and strain sensor were buried in the cement concrete specimens to detect early-age internal temperature field and strain field, and then the study of Built-in curling and Built-in construction temperature gradient were carried out.

Abstract: in this paper the surface temperature of test specimens which were water-saturated were measured after different exposure time in the lamplight. The relationship can be set up among surface temperature,air viods and water permeability coefficient. This research demonstrated that there is good correlation. So when the pavement is in the sunshine for a time after a rain,asphalt pavement areas with different water permeability coefficient can be distinguished by using infra-red technology to measure the surface temperature.Compaction of asphalt pavement can also be evaluated. This way was used and checked up in shanghai-chengdu highway project. This is a new method what is very convinently and quickly to evaluate the compaction and homogeneity of asphalt pavement.

Abstract: The permanent deformation is the key failure of asphalt pavements, especially for long sustained slope sections, and it is necessary to research the delimitation criterion of long sustained slope sections. Firstly, the disease survey of long sustained slope sections is carried out, the change of truck speed and load are described and its impaction on rutting failure is analyzed. Finally, continuous speed of heavy truck is point out to be used as the delimitation criterion, based on a new model of continuous speed of heavy truck which developed and optimized according to permanent deformation.

Abstract: To solve the problems in the current deterministic method of a maximum speed limit for expressway, a method of dynamic speed limit on expressway under complex climate was presented which was based on pavement skid-resistant performance. Firstly, the variation of pavement skid-resistant performance under complex climate conditions was analysed based on research results and certain experimental statistic data. By analysing the influence rule of AC-16 and SMA-16 pavement texture, pavement temperature, water film thickness, ice thickness, vehicle speed to pavement Skid-Resistant Performance, pavement actual friction coefficient calculation model and reference standard were established under different pavement condition Then, by analysing the geometry line indexes, pavement conditions and vehicle dynamics, the critical sideslip speed and critical longitudinal-driving safety speed was formulated; therefore, with critical speed as a constraint of safety driving and interval classification of complex climatic conditions, the dynamic speed calculate method and safety speed control standard were proposed under various pavements conditions, visibilities and traffic environments. This method for overcoming the weakness of a maximum speed limit of expressway operation and improving traffic safety is helpful.

Abstract: A crucial part of any maintenance strategy is an intricate understanding of the material characteristics of the pavement, so that the current level of damage may be accurately assessed and an appropriate plan implemented. Advances in the precision to which these parameters can be determined, as well as improvements in how these results are interpreted under varying conditions of measurement and analysis, are essential in the effective execution of a maintenance strategy. Results from Falling Weight Deflectometer (FWD), which is a Non-Destructive Testing (NDT) device, can be used to predict elastic modulus of any layer by comparing measured deflection data to calculated values through an iterative process referred to as back-calculation. This paper presents a comparison between static and dynamic back-calculation procedures, specifically with regard to typical South African inverted pavements. The analysis indicates a dynamic analysis provides results of greater accuracy than a static analysis, although the effect of the difference requires further investigation.

Abstract: As China's economic development, substantial growth in traffic, the importance of subgrade in road construction is escalated. Under the vehicle load, subgrade deformation will continue to accumulate and ultimately lead to subgrade permanent deformation. Excessive permanent deformation of subgrade soil will cause enormous economic losses, especially in rutting deformation, and have a direct impact on road performance in safety and comfort. Meanwhile, permanent deformation of subgrade will affect the structural performance of pavement, causing the other forms of damage. For example, the emergence and strengthening of reflective cracking, or accelerated fatigue failure because of too heavy tensile strain (or tensile stress) on the underside of the surface layer, and then caused great negative impact on the pavement structure and service performance. This article examines the role of high-speed heavy traffic load characteristics, and set up finite element model analysis for semi-rigid road structure, the most widely used internal road style, to obtain the mechanical response characteristics under high-speed heavy traffic loads.

Abstract: In this paper, on the basis of investigating the traffic capacity and cross-sectional form of the concrete strip roads, the technological and economical possibility of concrete strip roads replacing the forth class full width concrete and asphalt pavement was discussed. By analyzing structural combination and drainage characteristics of the concrete strip roads, the structure combination forms were recommended. Then the mechanical characteristics of the concrete strip roads were analyzed. Finally, the design method for thickness of concrete strip slab and the relevant design nomogram were presented.

Abstract: In order to evaluate the bearing capacity and the compaction performance of subgrade in a reasonable way, according to the time history results of pressure and displacement tested with the PFWD (Portable Falling Weight Deflectometer), the extraction methods of time history data were put forward to use for the backcalculation. Combined with the analytic solutions of dynamic response of vertical displacement on the half-space surface under the impact loading of semi-sine wave in the circular rigid vertical distribution for the dynamic half-space theory, the mathematical models of subgrade dynamic backcalculation were established based on the least square criterion, then the corresponding backcalculation flow and method were proposed in accordance with the modified Gauss-Newton algorithm. Firstly the pressure time history was fitted as a semi-sine wave to obtain the two backcalculation parameters of impact load, i.e. the angular velocity and the nonresponsive period. Secondly the displacement time history was fitted to obtain the two subgrade dynamic parameters, i.e. the dynamic modulus and the dynamic density. Lastly, through comparing the dynamic backcalculation to the static backcalculation from the tested data, the results show that the dynamic modulus is substantially equal to the static modulus, and there are the well correlations between the dynamic density and the dry density and the moisture content measured with the sand replacement method. Therefore, the PFWD can simultaneously test the design index (modulus) and the construction index (compactness) for the subgrade to achieve the both unified evaluation.

Abstract: The pavement performance of AC-20 asphalt mixture added with certain polyester fiber or the anti-rut agent are studied in this paper. By analyzing the high temperature stability and water stability of asphalt mixture through the indoor test, it can be concluded that: after adding polyester fiber and anti-rut agent, the pavement performance of asphalt mixture has the remarkable enhancement, it can be better adapted to our heavy traffic requirements.