Advanced Materials Research Vol. 723

Abstract: The deck of cement concrete bridge and the interface of asphalt pavement, and these two combined items have a direct effect on the useful life of asphalt pavement. According to the indoor shear test and pullout test, we could learn that the interlayer shear strength and the bond strength are strongly affected by temperature, and it is decreased with increasing test temperature. The pullout test analyses the variation regularity of bond strength between four adhesive layers and bridge panel at different temperatures, which proves that the bond strength is also decreased with increasing test temperature. The research suggests that the shear test and pullout test is worthy of evaluating the interface performance between deck and asphalt pavement under the high stability and low temperature conditions.

Abstract: Concrete pavements are usually selected by pavement engineers for roads subjected to heavy traffic loading and feature high maintenance and construction costs. As such, the structural behaviour of concrete pavements with doweled joints is evaluated herein using Finite Element Method. The pavement system is modelled using three-dimensional brick elements and five loading cases are applied to replicate realistic vehicular loadings approaching and leaving the joint. The structural behaviour of the pavement at the doweled joint is investigated for: (1) pavement with and without voids, and (2) different dowel bar spacing. The amount of load transfer was obtained from the shear force in the beam elements that simulate dowels. Results show that the voids underneath the joint causes an increase in the vertical displacement of the concrete slab and vertical stress at concrete/dowel bar interface which may result in crushing of the concrete and dowel loosening. Wider dowel spacings result in increased shear forces and the size of the region containing engaged dowels does not change significantly with dowel spacing, only effecting the distribution of shear forces. The study shows that the dowel bars perform effectively as a load transfer device in the concrete pavement system even under severe conditions.

Abstract: In this paper, strain and displacement for FLAC3D numerical simulation analysis of the whole weathering granite improved soil subgrade in train dynamic load of the stress is conducted, subgrade under repeated load test data and software simulation data is contrasted, the center of subgrade vertical settlement and the center of the subgrade stress change situation is researched.Through the research proves the whole weathering improved soil subgrade can ensure the high-speed safety, comfort and use requirement.

Abstract: This study has developed a relationship between the Dynamic Modulus (E*) and the Indirect Tensile Strength (ITS) of Hot-Mix Asphalt (HMA) using standard laboratory tests programs. Two types of SuperPave (SP) mixtures were considered namely, SP-III with 15% Reclaimed Asphalt Pavement (RAP) materials and SP-III with 35% RAP materials. Cylindrical samples of 100 mm diameter and 150 mm height were prepared. The samples were then tested for |E*| value at 210C at several loading frequencies following the AASHTO TP 62-07 test protocol. Next, the samples were cut into circular pieces of 38 to 50 mm thickness using laboratory saw. The samples are then tested for ITS value by applying a deformation rate of 50 mm per minute (AASHTO T 283 protocol). The ITS was calculated following the AASHTO T 283-07 test standard. The |E*| values (MPa) of SP-III with 15% RAP at 25, 10, 5.0, 1.0, 0.5, 0.1 Hz are measured to be 65, 59, 52, 34, 31, and 18 times of ITS (psi) respectively. The |E*| values (MPa) of SP-III with 35% RAP at 25, 10, 5.0, 1.0, 0.5, 0.1 Hz are measured to be 41, 38, 33, 24, 20, and 14 times of the ITS (psi) respectively. This study also draws a conclusion that increase in RAP has resulted in increased stiffness and strength.

Abstract: Differences in fatigue behavior among Gussasphalt, SMA and AC under different strain levels were studied by means of the four-point flexural fatigue test under strain-controlled mode. The results showed: Compared with SMA and AC, GA is qualified with higher bending stiffness modulus and excellent in load dispersibility and bending deflection resistance, thus its deformation resistance and stress dispersibility are more excellent in all conditions. The analyses based on viscoelasticity showed: Initial and fatigued lag angles of Gussasphalt are bigger than SMA and AC, and the viscoelasticity is more obvious when loading. Besides, the bigger lag angles, the better fatigue resistance.

Abstract: An experimental measurement of dynamic properties, including dynamic modulus and phase angle, of asphalt mixtures with varying saturation levels of moisture has been carried out in the study. The specimens of asphalt mixture were compacted with three different air void contents and two different levels of moisture saturation. The relaxation modulus expressed by Prony series was estimated from the Prony series expression of dynamic modulus. The purpose of this study is to identify the effect of air voids on dynamic properties that affect and control moisture susceptibility of asphalt mixtures and then compare the stress relaxation behavior of asphalt mixtures between dry and moisture conditioning. The results show that dynamic properties are quite sensitive to temperature and loading frequency in dry and different saturation levels of moisture. Moreover, and the smaller the air voids and saturation level, the greater the increase in dynamic modulus and rate of stress relaxation, indicating better resistance to cracking and less moisture susceptibility.

Abstract: Asphalt hardens as a result of an aging process. This study was undertaken to determine the effect of field aging simulated by laboratory aging method of different hot mix asphalt (HMA) mixture. Three types HMA mixtures were used for this study namely Asphaltic Concrete with 10 mm nominal maximum aggregate size (AC 10), Aspaltic Concrete 28 mm (AC 28) and Porous Asphalt 10 mm (PA 10). The resilient modulus test was carried out as an indicator of the performance at a 25 °C and 40 °C. Generally, all samples show similar trend which aged mixture produced slightly higher resilient modulus compared to unaged mixture while an increase in temperature from 25 °C to 40 °C might reduced the resilient modulus up to 88%. This study also found that the difference increment of resilient modulus after the aging process attributed by asphalt content, air void and gradation of respective mixtures.

Abstract: This study investigated the influence of individual constituents of calcined shale or hybrid constituents of calcined shale and fly ash or silica fume on the workability and compressive strength. Calcined shale is heat treated in a kiln and then ground to a finer powder and the calcination temperatures of 800 °C were used. The test results demonstrated that the workability and compressive strength decreased with the inclusion of calcined shale increased and the compressive strength of the specimens containing calcined shale all lower than that of the control specimens. It might be due to the higher water demand and lower CaO value. However, the hybrid batches with calcined shale and fly ash or silica fume enhanced better performance on compressive strength than individual constituents of calcined shale. The combination of 10 % calcined shale and 10 % silica fume in concrete seemed to give superior compressive strength and gave the highest value in the testing series. Finally, the inclusion of calcined shale is help to reduce the emissions of CO₂ and revealed an ecological advantage for concrete containing a binder blend of cement and calcined shale.

Abstract: Induction heating consists in adding electrically conductive fibers to the asphalt mixture and heating them with an induction heating device. But still, the factors that affect the increase of temperature are not well-known. With this purpose, 25 different mixtures, with the same aggregates distribution and amount of bitumen, but with 2 different lengths, 4 different quantities, and 4 different diameters of steel wool fibers have been considered. The influence of fibers on the air void content, electrical and thermal conductivity and on the induction heating of dense asphalt concrete has been studied. It was found that steel wool fibers increase slightly the electrical and thermal conductivities of dense asphalt concrete. Finally, it has been observed that the temperature reached due to the induction heating, increases with the number of fibers in the mixture and with their diameter.

Abstract: The aim of this paper is to investigate the rheological properties of Multi-Walled Carbon NanoTube (MWCNT) enhanced bitumen. The rheological properties of bitumen samples with a range of MWCNT applications are evaluated. The shear complex modulus of the samples increased after ageing, and also increased as the percentage of MWCNTs increased. The viscous component of the complex shear modulus was found to be dominant at higher temperatures, but as the concentration of MWCNTs increased, it was found that the elastic portion started to dominate at higher temperatures. At higher temperatures a change in the phase angle was found, with increased concentrations of MWCNTs causing a decrease in δ, representing a more plastic sample. It is shown that addition of MWCNTs as a modifier did not increase the cracking resistance of the bitumen. Thus, if fatigue cracking is of concern in a certain area it is not recommended to use MWCNTs as a modifier. As the quantity of MWCNTs increased, the temperature at which rutting would start to occur, increased.