Bowen Guan

HIGH TEMPERATURE STABILITY OF BRUCITE-FIBER-REINFORCED ASPHALT CONCRETE

As a natural alcaline mineral fiber applied in the asphalt pavement, brucite fiber has not been investigated systematically on its excellent physical and mechanical properties and environmental friendliness up to now, including the functions of fine thermal stability and reinforcement in the asphalt concrete. By virtue of awl-shear test, the temperature sensitivity of shear strength was put forward to evaluate the temperature sensitivity of the brucite fiber asphalt mortar. Through the rutting test, the high temperature stability of brucite fiber asphalt concrete is investigated, in contrast with the lignin fiber and basalt fiber. Results show that brucite fiber can increase the viscosity of asphalt, decrease the temperature sensitivity property of asphalt, improving the high temperature stability of asphalt mortar. In additon, the high temperature stability of asphalt concrete can be greatly improved with the addition of brucite fiber. The optimum dosage of brucite fiber is about 0.4 wt.% of asphalt concrete. The high-temperature reinforcing effect of brucite fiber is better than lignin fiber and similar to the basalt fiber in the asphalt concrete.

Influence of Macrotexture and Microtexture on the Skid Resistance of Aggregates

This article intends to study the influence of macrotexture and microtexture on the skid resistance of four types of aggregates. For this purpose, fractal dimension (D), root mean square height (Rq), and Polished Stone Value (PSV) were tested. The Pearson correlation coefficients between PSV and D or Rq in the interval of different polishing cycles were calculated and analyzed with correlation analysis. The relationships between PSV and Rq were also established. The results showed that the PSV development was approximately divided into 3 stages including accelerated attenuation stage, decelerated attenuation stage, and stabilization stage. There is a critical point of the entire polishing cycles. When the number of the polishing cycles exceeds this critical point, microtexture replaces macrotexture to play a major role in the skid resistance of aggregates. In the accelerated attenuation stage, macrotexture plays a major role in the skid resistance of aggregates. In the decelerated attenuation stage and stabilization stage, microtexture gradually plays a major role in the skid resistance of aggregates. Because of roughest microtexture in the stabilization stage, bauxite can provide the highest levels of skid resistance for high friction surface treatment over the long-term period.

Developing a Model for Chloride Ions Transport in Cement Concrete under Dynamic Flexural Loading and Dry-Wet Cycles

Chloride ions attack is the main factor leading to the degradation of concrete durability, while the diffusion process would be significantly aggravated under the dynamic flexural loading and dry-wet cycles. In this paper, the influence coefficients of dynamic flexural loading on chloride/water diffusion coefficients were established, based on the relationship between the dynamic flexural loading and the chloride ions diffusion coefficient of concrete. Based on the model of chloride ions transporting in dry-wet cycle environment, the transport model of chloride ions in concrete under the dynamic flexural loading and dry-wet cycles was established. The effects of different factors on the chloride ions transport law in concrete were analyzed through laboratory test. The results showed that the model was in good agreement with the experimental results. The theory and assumptions proposed applied in the model of chloride ions transport in concrete under the dynamic flexural loading and dry-wet cycles had certain rationality and scientificity.

Road Performance of Brucite Fiber Asphalt Concrete

As a new type of pavement material, brucite fiber asphalt concrete has been never studied at home and abroad. Laboratory experiments are made on the brucite fiber asphalt concrete. Effects of the dosage of the brucite fiber on the physical properties such as the bulk density, volume of air voids, voids filled with asphalt, voids in mineral aggregates, optimum asphalt content and the strength are also studied by the Marshall test. The contrast tests on road performance are made between the brucite fiber asphalt concrete and the ordinary asphalt concrete by low temperature bending test, wheel rutting test and water stability test. Test results show that addition of brucite fibers in asphalt concrete can change the physical properties significantly, especially the volume indexes and the strength. According to the Marshall test results, the optimum quantity of brucite fiber is about 0.4 wt.% of asphalt concrete. Based on the contrast test, the brucite fiber asphalt concrete is better than the ordinary asphalt concrete on the anti-crack properties in low temperature, the stability properties in high temperature and the stability properties in water.