Recycling waste tire rubber by incorporating it into concrete has become the preferred solution to dispose of waste tires. In this study, the effect of the volume content of crumb rubber and pretreatment methods on the performances of concrete was evaluated. Firstly, the fine aggregate and mixture were partly replaced by crumb rubber to produce crumb rubber concrete. Secondly, the mechanical and durability properties of crumb rubber concrete with different replacement forms and volume contents had been investigated. Finally, the crumb rubber after pretreatment by six modifiers was introduced into the concrete mixture. Corresponding tests were conducted to verify the effectiveness of pretreatment methods as compared to the concrete containing untreated crumb rubber. It was observed that the mechanical strength of crumb rubber concrete was reduced, while durability was improved with the increasing of crumb rubber content. 20% replacement of fine aggregate and 5% replacement of the total mixture exhibited acceptable properties for practical applications. In addition, the results indicated that the modifiers had a positive impact on the mechanical and durability properties of crumb rubber concrete. It avoided the disadvantage of crumb rubber concrete having lower strength and provides a reference for the production of modified crumb rubber concrete.

Waste utilization has gained more and more interest. In this study, crumb rubber and diatomite were used to modify asphalt binder and the short-term aging effects on the properties of modified asphalts were evaluated. Three kinds of modified asphalt were prepared; they are diatomite modified asphalt (DA), crumb rubber modified asphalt (RA), and diatomite and crumb rubber compound modified asphalt (DRA). Thin film oven test (TFOT) was used to simulate short-term aging in the laboratory. Penetration, softening points, ductility, viscosity, elastic recovery, low temperature creep, and rutting susceptibility were tested and analyzed before and after TFOT. The results indicated that the softening point, viscosity, elastic recovery, creep stiffness, and G*/sinδ of DA, RA, and DRA are all linearly increased with increasing age, while the penetration and ductility are linearly decreased with increasing age. High temperature properties of asphalt are obviously improved by the addition of crumb rubber. Low temperature properties of asphalt are affected more seriously by the addition of diatomite. DRA could combine the advantages of diatomite and crumb rubber and achieve better performance in short-term aging resistance than DA and RA.

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.