Study On Preparation And Application Of Warm Mix Asphalt Additives

Warm mix asphalt (WMA) is a new kind of asphalt mixtures with energy saving and environmental protection. Warm mix asphalt is mixed and compacted at temperatures in the range of 10 to 60℃lower than typical hot mix asphalt, without compromising the performance of the asphalt pavements. Warm mix asphalt technology has the potential for being one of the most important breakthroughs for the asphalt industry. Compared with hot mix asphalt, the construction costs of warm mix asphalt are more expensive because of the warm mix asphalt technologies, which has became a key problem restricting the progress of warm mix asphalt concrete. Based on the existing principle of the warm mix asphalt technologies in this paper, it was found that the structural characteristics of zeolite 4A make it to a potential warm mix asphalt additives. Hence, the zeolite 4A was synthesized and the effect of zeolite 4A on the temperature parameters and performance of asphalt mixture were analyzed.Zeolite 4A containing crystal water was synthesized from coal fly ash by fusion with sodium hydroxide prior to hydrothermal reaction. The influence of some factors was investigated by orthogonal then the synthesis conditions were optimized. The results indicate that the best technological conditions of synthesizing zeolite 4A containing crystal water with coal fly ash are the mole ratio of SiO2/Al2O3 is 1.9; the mole ratio of Na2O/SiO2 is 2.0; the mole ratio of H2O/Na2O is 50; under the aging temperature of 65℃, the optimum aging time is 3h; under the crystallization temperature of 90℃, the optimum crystallization time is 4h.Based on the synthesis of 4A zeolite, the effect of zeolite 4A on the performance of asphalt mixture was analyzed. The influences of zeolite 4A volume of voids were researched and the dosage and decreased temperatures were identified. Water damage resistance property was evaluated adopting Marshall Water Submerged Stability test and Freeze-Thaw Split test; adopting bending test the lower-temperature cracking resistance of asphalt mixture was evaluated; indirect tension fatigue tests were also carried out and adopting rutting test the higher-temperature deformation resistance of asphalt mixture was evaluated. The results indicate that the mixing and compaction temperatures of warm mix asphalt with 0.3%zeolite 4A containing crystal water was 20℃lower than the traditional hot mix asphalt without sacrificing the quality of the pavement performance, indicating synthetic zeolite is a warm mix asphalt additives.At last, a comprehensive analysis of the principle of the zeolite 4A as warm mix asphalt additives and the energy-saving environmental benefits were performed and the results show that the compaction properties of asphalt mixtures at low temperature can be improved by the crystal water of zeolite 4A, which can be used to produce warm mix asphalt. With energy saving and environmental protection, warm mix asphalt has significant social benefits.