The application of fly ash in the pavement base is mainly concentrated in two aspects: fly ash (lime and fly ash) stabilized materials and cement fly ash stabilized materials. These two materials have been compiled into national standards, the technology is relatively mature, and there are many practical applications. The application of fly ash on pavement surfaces is mainly asphalt mixture surface and cement concrete surface. Jiao Hua of Chang’an University’s research in his master’s thesis shows that when fly ash replaces all ore powder in AC-16 asphalt mixture, it has poorer low-temperature crack resistance and better high-temperature stability than that mixed with ore powder. , the water stability has been improved but the effect is not outstanding. Xie Jun, Wu Shaopeng, and others studied the effect of surface treatment fly ash and coupling agent on moisture damage of asphalt mixture. Combining filler with a coupling agent and fly ash is called a composite fly ash modifier. The properties of the composite fly ash modifier were mainly characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. As a filler, its effect on the moisture sensitivity of asphalt mixtures was evaluated by indirect tensile stiffness modulus tests, static creep, and indirect tensile fatigue tests. The results show that the asphalt mixture with composite fly ash modifier has high indirect tensile strength and tensile strength ratio during frost and has excellent moisture sensitivity. In addition, the composite fly ash modifier modified asphalt mixture showed better stiffness modulus, resistance to permanent deformation, and fatigue life after specific moisture damage treatment. Conclusion: The composite fly ash modifier can effectively improve the moisture sensitivity of the asphalt mixture.
Fly ash embankments are also widely used in road engineering, especially in soft soil foundation road sections. It can make full use of the light weight of fly ash to reduce the embankment’s own weight and the additional stress of soft soil foundation, thereby reducing total settlement and improving embankment stability. Similarly, filling fly ash with the high-filling soil at the bridgehead can improve the bridgehead jumping problem caused by the settlement caused by the self-weight of the high-filling soil at the bridgehead. Liu Tiejun studied the mechanical properties of fly ash used as embankment filler and came to the following conclusions: the dry density of fly ash showed a trend of increasing first and then decreasing with the increase of moisture content, and the maximum dry density of moisture content was 19%; The permeability coefficient of coal ash decreases exponentially with the increase of dry density. When the dry density of fly ash is less than 1.35g/cm3, the dry density has almost no effect on its permeability coefficient; the cohesion of fly ash increases with the water content When the moisture content of fly ash increases and decreases, and the decrease is slow when the moisture content is less than 26%, otherwise it decreases faster; when the moisture content of fly ash increases by 1%, the internal friction angle decreases by about 0.25°; The cohesion of coal ash increases linearly with the increase of compaction degree, while the internal friction angle of fly ash increases exponentially with the increase of compaction degree; the moisture content of fly ash The closer to the optimum moisture content or the closer to 100% compaction, the smaller the decrease in cohesion and internal friction angle with the increase of vibration times, and it is easier to reach a stable state in the early stage of vibration. Chen Yunyong and Gao Liang also conducted indoor model tests on reinforced fly ash embankments. According to the principle of similarity, the two men scaled down the actual embankment at a ratio of 1:8 and used bidirectional geogrid as the reinforcement material, and carried out experimental research on the stress and strain of the fly ash reinforced embankment. The results show that the uneven settlement of the fly ash embankment can be significantly reduced by geogrid reinforcement, and the bearing capacity of the embankment can be significantly improved.
Content source: Fly Ash Industry Alliance
Post time: Jul-10-2023