Advanced Materials Research Vols. 243-249

Abstract: Dry shrinkage performance of ferrous mill tailings stabilized with inorganic binding materials with the optimal ratio is studied through laboratory test. The curves of water loss-time and dry shrinkage strain-time are obtained. The comparisons to that of soil-lime are also made. It shows that the largest for water loss ratio and dry shrinkage strain is soil-lime, its dry shrinkage performance is the worst. The dry shrinkage strain of ferrous mill tailings stabilized with lime added a small amount of cement is increased, however, the compaction is increased and the amount of lime and cost is greatly reduced. The dry shrinkage performance of those materials: ferrous mill tailings stabilized with lime the best, then ferrous mill tailings stabilized with lime (cement), ferrous mill tailings stabilized with cement, soil-lime.

Abstract: Asphalt Pavement was damaged more seriously in longitudinal Gradient than common segment because of its special load bearing conditions. This paper establishes a 3D Visco-elasto-plastic Finite Element to analyses the stress respond of pavement structure, calculating the discipline of stress behaviors under different gradient. Burgers model was used to study the factors which can influence on tracking, for example longitudinal Gradient, speeds and frequency of axle load. Result of calculation show that the maximum shear stress grows as the gradient increases. Rutting of pavement was small before a certain number of axle loads, but when beyond the certain number, the rutting incense notably, and the slower speed the vehicle has, the deeper tracking the pavement responds.

Abstract: Two kinds of warm additives, Sasobit and Evotherm DAT, were used to develop warm stone mastic asphalt (SMA) mixture. The test results showed that compaction temperature of SMA can be decreased by 30-40°C when using Sasobit or Evotherm DAT. Then, to compare the mechanical performance properties of SMA and warm SMAs, mechanical properties of pavement mixture, including Marshall stability, retained Marshall stability, tensile strength ratio, Cantabro loss, rutting dynamic stability and low temperature flexural strength, were tested in laboratory. The results indicated that Sasobit can decrease obviously the moisture resistance ability and low temperature cracking resistance ability of SMA. Therefore, the pavement performance properties of Sasobit warm SMA are inferior to those of Evotherm DAT warm SMA, which has the nearly same performance properties as hot SMA.

Abstract: after reasonably analyzing characteristics of flexible fiber reinforcement fragile material, the mechanical model of individual fiber is established while being pulled out from asphalt; the spherical coordinates is adopted to establish the calculation model for short fiber bridging stress evenly distributed in space to calculate the value of bridging stress generated by short fibers while asphalt is breaking; the fiber asphalt sample in big size is adopted to perform low temperature tensile failure test to practically measure bridging stress of short fiber; fit the calculated value and measured value of bridging stress by adjusting parameters in the calculation model to check the rationality of fiber bridging stress in calculation method and model.

Abstract: To study the influence mechanism of the excavation stability of the debris accumulation body by the expansive fine grain, it has used by Particle Flow Code, based on indoor test, the fine-grain expansive effect has divided into fine-grain intensity attenuation and volume expansion, and it has linear decreased down from the surface on the accumulation body. Based on the contrastive analysis between simulated result and traditional finite element, the Particle Flow Code is more accurate and true. The analysis result has suggested that when consider the expansive action, the damage model is changed into surface sliding from part slump, and the X-direction stress added 20kPa in the interior of the accumulation body, and the whole sliding force added 30% more or less. At present, the field excavation situation is consistent with the calculation result.

Abstract: The benefit using BOF slag on Perpetual Pavement that has been developed in United States and Europe recently, will effectively increasing Rutting and Skid Resistance of Pavement, reducing the amount of asphalt that used on Mix Design that will reduce the overall construction cost. The character of BOF slag has higher density and Hydrophilic, this study applied it to porous pavement. It compared with the performance of traditional aggregates. Based on the result, there are no significant differences. The BOF slag will be expansion with water, it was bad in pavement construction. Through swelling pressure test, the BOF slag with new process is no significant change in water. So, BOF slag is suitable in porous pavement.

Abstract: Low temperature cracking is the main distress in asphalt pavements in winter. As asphalt rubber course is increasing, there is no standard method to characterize the resistance to cracking of asphalt rubber mixtures. This paper investigates the use of a Semi Circular Bend (SCB) test as a candidate for a low-temperature cracking specification. Based on the SCB test, this paper presents the findings of a laboratory study that aimed to evaluate the effects of recycled tire rubber on the Low temperature cracking properties of asphalt mixtures. Three mix types, a conventional hot-mix asphalt concrete, a dry process rubber modified asphalt concrete, and a wet process asphalt-rubber asphalt concrete, were included in the investigation. It is found that the asphalt mixtures produced by the wet process showed much better low temperature crack resistance, the binder effect modified by rubber was significant.

Abstract: The effect of sasobit’s quantity exerted on the asphalt viscosity was researched firstly in this paper, and the mixing temperature of warm mix recycled Asphalt mixture was determined. Then, the technical performances of warm mix recycled asphalt mixture on high temperature, low temperature and water stability were studied through systematic experiments. And compared the technical indexes with that of hot mix asphalt. The results showed that sasobit could reduce asphalt viscosity significantly, so it could lower the mixing and compaction temperatures of the recycled asphalt mixture. The technical indexes of warm mix recycled asphalt mixture conform to the current specifications, so it can be used in many pavement structures.

Abstract: The settlement cntrol of high-speed railway is a key technology in embankment engineering. In order to reveal the engineering characteristics of the deep completely decomposed granite soil in Hainan east loop line, a passenger dedicated line, four groups of centrifuge model tests were conducted to study the settlement properties of the subsoils untreated, treated by dynamic compaction, and reinforced with cement-mixed piles, under the action of the embankment, especially the relationship between settlement and time, including the settlement during and post-construction. The results show that the Weibull model can describe the relationship between embankment settlement and time well, and that the post-construction settlements of the subsoil meet the requirements of the relevant code. Among the two foundation treatment measures, dynamic compaction is more effective than reinforcement with cement-mixed piles, and the pressure on the contact surface between embankment and subsoil was obviously different from the commonly used calculated values.

Abstract: To study the mechanical properties of high modulus asphalt mixtures, dynamic modulus and phase angle of these two mixtures are tested with Simple Performance Testing System under different temperatures, loading frequencies and confining pressures. Testing results show the superiority of high modulus asphalt mixture in aspect of high temperature performance. Furthermore, the changing rules of dynamic modulus and phase angle are also discussed.