In this paper, Fourier-transform infrared (FTIR) spectroscopy was used to evaluate the effects of diatomite on aging properties of an asphalt binder. The modified asphalts included 5%, 10%, and 15% diatomite, and were prepared in the laboratory. The changes in functional groups of asphalt were employed to investigate the aging mechanisms of the modified and control asphalts. Effects of diatomite on the anti-aging properties of asphalt were analyzed via the changes in intensity of the absorption peaks. Results showed that there were no new functional groups generated after diatomite mixing with asphalt. This indicated that the process of diatomite modification was just physical mixing. Furthermore, parts of saturates and aromatics were volatilized in the aging process of modified asphalt. Polar molecules reacted with oxygen in aging. Meanwhile, carbonyl (C=O) and sulfoxide (S=O) were also generated. The aging resistance of modified asphalt was the best when the diatomite content was 10%. The work of this paper may provide a new perspective to evaluate asphalt aging.

This study aims to adopt the acoustic emission (AE) technique to evaluate the reinforcing effect of basalt and steel fibers on the fracture resistance of asphalt concrete (AC) under indirect tension (IDT) testing at low temperature. Control asphalt concrete (CAC) with no fibers was also tested for comparison. The AE counts and durations were recorded and analyzed to characterize the fracture processes of basalt fiber reinforced asphalt concretes (BFRAC) and steel fiber reinforced asphalt concretes (SFRAC), which were compared with the results from static displacement and strain data obtained through digital image correlation (DIC). The results revealed that the low-temperature fracture processes of BFRAC and SFRAC could be effectively divided into four stages according to the evolutions of AE parameters and corresponding cumulative AE parameters. AE properties could effectively evaluate the reinforcing effects of basalt and steel fibers on the low-temperature fracture resistance of AC, whereas static displacement and strain failed to identify the effects. BFRAC with a fiber length of 12 mm (BFRAC-12) had favorable ductile property at the final failure stage, whereas BFRAC with a fiber length of 6 mm (BFRAC-6), SFRAC with a fiber length of 6 mm (SFRAC-6), and SFRAC with a fiber length of 12 mm (SFRAC-12) exhibited brittle characteristics based on variations of AE parameters. Good correlations between the curve characteristics of AE parameters and the failure loads of AC specimens can be observed. The AE technique demonstrated great potential for the damage fracture characterization of asphalt materials.

Erosion effect of chloride ions from the marine, deicing salt, saline-alkali land and some industrial environments will cause the corrosion of rebar in concrete, which is one of the most harmful factors affecting the durability of concrete structure. It had been proved that the incorporation of rubber aggregates increase the capillary saturation of cement concrete and reduce the corrosion degree of rebar. This paper investigated the rebar corrosion behavior in rubber aggregate concrete under the chloride electro-accelerated corrosion condition and such an investigation has not been seen in any public literature. Two water-cement ratios (0.45 and 0.55) and four rubber contents (0, 50, 100, and 150 kg/m³) were selected for experiment. Four-point bending tests of concrete beam were conducted before and after chloride ion erosion in order to determine effect of rubber aggregate on the durability of rebar. Results showed that rebar corrosion degree decreased with the increase of rubber aggregate in concrete. Besides, the more the dosage of rubber is, the better the anti-crack performance of cement concrete. This will postpone the crack development and reduce the peak of rebar corrosion.

The amount of boron waste increases year by year. There is an urgent demand to manage it in order to reduce the environmental impact. In this paper, boron waste was reused as an additive in road base material. Lime and cement were employed to stabilize the waste mixture. Mechanical performances of stabilized mixture were evaluated by experimental methods. A compaction test, an unconfined compressive test, an indirect tensile test, a modulus test, a drying shrinkage test, and a frost resistance test were carried out. Results indicated that mechanical strengths of lime-stabilized boron waste mixture (LSB) satisfy the requirements of road base when lime content is greater than 8%. LSB can only be applied in non-frozen regions as a result of its poor frost resistance. The lime–cement-stabilized mixture can be used in frozen regions when lime and cement contents are 8% and 5%, respectively. Aggregate reduces the drying shrinkage coefficient effectively. Thus, aggregate is suggested for mixture stabilization properly. This work provides a proposal for the management of boron waste.

Moisture migration in pavement leads to the loss of strength of asphalt mixture. However, moisture profile measurement inside of the mixture can be challenging. In this paper, a new experimental method is proposed to measure the moisture profile; this method is based on the principle that white anhydrous copper sulfate powder turns blue with water. The influences of asphalt content, gradation, indoor compaction, temperature and pressure on moisture diffusion depth and strength loss are also discussed. The results show that the proposed method successfully reveals the moisture profile of the asphalt mixture. High temperature and pressure accelerate the moisture diffusion process. A large filler-bitumen ratio and high content of coarse aggregate result in a large diffusion depth. The rolling compacted mixture demonstrates better resistance to moisture diffusion than the Marshall mixture. It is inferred that the rainfall’s influence on the asphalt layer is mainly within a depth of 23 mm below the surface. The strength attenuation of asphalt mixture after damage is mainly affected by compaction method and external pressure, while filler-bitumen ratio affects the attenuation trend of the mixture strength. The proposed method in this paper has the advantages of easy operation and in-field application potential.

Short fibers have been widely used to prepare the fiber reinforced asphalt concrete (FRAC). However, internal interactions between fiber and other phases of asphalt concrete are unclear although experimental methods have been used to design the FRAC successfully. In this paper, numerical method was used to investigate the reinforced mechanism of FRAC from microperspective. 2D micromechanical model of FRAC was established based on Monte Carlo theory. Effects of fiber length and content on stress state of asphalt mortar, effective modulus, and viscoelastic deformation of asphalt concrete were investigated. Indirect tensile stiffness modulus (ITSM) test and uniaxial creep test were carried out to verify the numerical results. Results show that maximum stress of asphalt mortar is lower compared to the control concrete when the fiber length is longer than 12 mm. Fiber reduces the stress level of asphalt mortar significantly. Fiber length has no significant influence on the effective modulus of asphalt concrete. Fiber length and content both have notable impacts on the viscoelastic performance of FRAC. Fiber length should be given more attention in the future design of FRAC except the content.