Influence of cement on low-temperature property of granite asphalt mixtures
Combined with the application of granite asphalt mixtures in the pavement project along the Ma-Wu Expressway. In this paper, the amount of 20%, 40%, 60%, 80% cement was in equivalent replacement of common filler. The effects of cement on low-temperature property of granite asphalt mixtures were investigated by indirect tensile strength and three-point bend test, obtained the variation of cement with different admixture amounts influence on granite asphalt mixtures, than the optimum mix amount has been found. Experimental results showed that the cement additive improved the low-temperature property and the optimum mix amount of cement was 40%∼60%, which possesses guiding significance for ensuring bituminous pavement project quality.
The influence of aggregate, filler and bitumen on asphalt mixture moisture damage
Abstract Moisture damage in an asphalt mixture can be defined as the loss of strength, stiffness and durability due to the presence of moisture leading to adhesive failure at the binder–aggregate interface and/or cohesive failure within the binder or binder–filler mastic. Various test methods exist to identify the susceptibility of asphalt mixtures to moisture damage, such as the AASHTO T283 procedure. This paper describes a new combined ageing/moisture damage laboratory test known as the Saturation Ageing Tensile Stiffness (SATS) test that has been successfully used to quantify the moisture damage of a range of UK asphalt mixtures. The test consists of initial saturation prior to placing compacted asphalt mixture cylindrical specimens in a moist, high temperature and pressure environment for an extended period of time. The stiffness modulus measured after the test divided by the stiffness modulus measured before the test (retained stiffness modulus), and the specimen saturation after the test (retained saturation), are used as an indication of the sensitivity of the compacted mixture to moisture damage. In this paper, the sensitivity of the SATS test to different aggregates, fillers, binders and volumetric proportions as well as mixture types has been assessed. The results show that the SATS test is able to discriminate between different asphalt mixture combinations in terms of their moisture damage resistance. Compared to AASHTO T283, the SATS test was found to be a more aggressive conditioning protocol, although both tests ranked mixtures in a similar order with respect to moisture damage.
Experimental study on ground vibration of blasting the boulder with tandem shaped charging warhead
Hazardous effects of blasting the boulder with the new breaking-blasting equipment-tandem shaped charging warhead are mainly air shock wave, seismic wave and blast slung shot. Blast-induced ground vibration is one of the inevitable effects and may cause substantial damage to nearby structures. Started from the formation process and mechanism of ground vibration to study the seismic wave, the research attained curve of vibration velocity of monitoring points by TC-4850 and carried out differential and fast Fourier transform analysis of the curve. And the results concluded that blasting vibration with tandem shaped charging warhead mainly comes from prime charge; the attenuation law can be predicted by Sadev’s Formula. Explosion vibration frequency range is 20-150 Hz, while with the increase of distance from the blasting center, blasting vibration intensity attenuates rapidly, vibration duration increases and vibration frequency gradually reduces. Compared with general rock blasting, its attenuation rate of blasting vibration is faster with higher frequency and smaller impact on buildings, but the harm effects should not be ignored for the special application environment.