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This paper summarizes an investigation of the performance of the recycled asphalt concrete with stable crumb rubber asphalt (SCRA) binder. Both the normal recycled asphalt mixtures and the SCRA recycled asphalt mixtures were prepared with the 0%, 30%, 50% content of the reclaimed asphalt pavement (RAP). Laboratory tests were carried out to compare the performance of different mixtures and the comprehensive recycling effect of the SCRA and rejuvenator were evaluated further. The performance evaluations included the dynamic stability (DS) by wheel-tracking test, failure strain by low-temperature bending beam test, Marshall strength ratio (MSR) by the immersion test and fatigue life by four-point bending beam test, which represented the high-, low-temperature performance, moisture stability and the fatigue resistance respectively. The testing results indicated that as the RAP content increased, the recycled asphalt mixtures showed a better high-temperature stability but a worse low-temperature property, moisture stability and fatigue life for both VA and SCRA recycled mixtures. The SCAR is much better than the virgin asphalt (VA) in recycling the aged asphalt mixtures with large RAP content which could reach 50%. The rejuvenator has a positive effect on the low-temperature performance, moisture stability and fatigue resistance. By the combining the use of the SCRA and rejuvenator, the low-temperature performance of the SCRA recycled asphalt mixtures could be improved further while the other performance retained a high level at the same time, which was enough for the engineering applications completely.

Microbial induced calcite precipitation (MICP) can bond sand particles together to improve the mechanical properties of sandy soil. This environmental-friendly technique has potential applications on construction materials such as bio-bricks and bio-beams. This study is to investigate the flexure resistance performance of bio-beams by adding discrete randomly distributed fiber and bamboo materials with multiple immersing MICP treatment. Different fiber proportions (0.1%, 0.2%, 0.3% and 0.4% by weight of dry sand) were used. MICP treated bio-beams were also reinforced by five different arrangements of bamboo strips. Four-point bending tests were conducted to evaluate the flexure behavior of fiber reinforced and bamboo reinforced bio-beams. Results showed that adding fiber in the MICP treated bio-beams can increased the ductility. The optimum fiber content was around 0.3%. Addition of 0.3% fiber can significantly prevent the post peak flexure strength loss and improved the ductility of bio-beams which had 400 kPa residual strength at 15% failure strain. Bamboo reinforced bio-beam can improve the flexure strength from 890 kPa to 1750 kPa. Meanwhile, multiple immersing MICP treatment can significantly improve the flexure strength of bio-beams up to 3.0 MPa, but the ductility of fiber reinforced bio-beam reduced after multiple treatment.

Evotherm is one of the chemical warm mix asphalt (WMA) technologies that has been widely used in sustainable asphalt pavement construction. But the long-term performance of such warm mix asphalt pavement has not been studied comprehensively. This study investigated the field-aged asphalt binder performance with three different Evotherm additives (ET, DAT and 3G) based on fourteen field projects across the United States. Their performance was compared with corresponding HMA control binder. Asphalt binders were extracted and recovered, and were subjected to tests including continuous grading high temperature and low temperature, multiple stress creep recovery, and fracture. The results showed that after 2–6 years of field aging, the HMA binder had relative higher continuous grading high temperature than the Evotherm binder. All HMA and Evotherm binders regardless of types were m-value controlled, indicating of a significant aging level. The thermal cracking resistance of both HMA and Evotherm binders were similar and quite poor. The failure strain value of HMA binder is comparable with that of Evotherm binder at 20 °C as well as at 5 °C. The addition of Evotherm additive did not compromise the elastic response of polymer-modified binders.

Cold-recycled mixture with asphalt emulsion (CMAE) has been widely used in pavement rehabilitation due to its environmental and economic advantages. Curing condition and compaction method can both affect the volumetric and mechanical properties of CMAE. The main objective of this paper is to propose a relative reasonable fabrication method of CMAE in consideration of curing and compaction history in the laboratory. The two fast curing conditions (single curing: 2 days curing at 60 °C and mixed curing: 3 days curing at 20 °C followed by 2 days curing 60 °C) and three impact compaction methods (single compaction-50 blows, single compaction-75 blows and double compaction) using Marshall compactor were used to evaluate the volumetric and mechanical properties of CMAE with different cement contents. The result analysis indicates that the single curing condition is beneficial to decreasing the voids content and increasing the indirect tensile strength (ITS), failure strain and critical strain energy density (CSED) of CMAE with low cement content. However, the mixed curing can decrease the voids content and greatly improve the ITS and CSED of CMAE with high cement content. This is because the single curing is better for the film formation of asphalt emulsion but more harmful to the cement hydration than the mixed curing. It is recommended to adopt single curing under relatively low cement content and mixed curing under relatively high cement content in the laboratory. Meanwhile, increasing the number of compaction blows and employing double compaction can greatly reduce the voids content and improve the ITS and CSED with different cement contents, which is beneficial to the mechanical properties of CMAE. Since the double compaction can better simulate the field construction, it is recommended to employ the double compaction to fabricate specimens in the laboratory.

Fiberglass/epoxy laminate or structures strengthened by fiberglass/epoxy laminate might be subjected to dynamic loadings such as impact and blast. Understanding the dynamic material properties of the fiberglass/epoxy laminate is important to predict the behavior of fiberglass/epoxy laminate or its strengthened structure against dynamic loading. In this study, unidirectional quasi-static and dynamic tensile tests on fiberglass/epoxy laminate were carried out to investigate its dynamic material properties. The strain rate for quasi-static and low velocity test varied from 2.08E-05 to 1.04E-01 s −1 . The high speed dynamic tests were conducted by INSTRON® VHS 160/100-20 machine at the strain rate from 2.75 to 115 s −1 . The strain rate effects on the tensile strength, failure strain and Young’s Modulus of fiberglass/epoxy laminate were investigated. Based on the testing data, empirical formulae were derived to predict the dynamic enhancement of tensile material properties of fiberglass/epoxy laminate as a function of strain rates, which can be used to model the dynamic material properties in the numerical simulation of structural responses.

Cold recycling with asphalt emulsion is an economical and environment-friendly technology for asphalt pavement maintenance and rehabilitation. This study aims to investigate the early-age strength and long-term performance of the asphalt emulsion cold recycled mixes with various cement contents, as well as the correlation between the early-strength and long-term performance. To achieve this objective, three research tasks were conducted, including: 1) quantifying the early-age strength of four types of asphalt emulsion cold recycled mixes by measuring their cohesive forces and raveling loss rates through the Hveem cohesion test and raveling test, respectively; 2) characterizing their long-term performance properties, including moisture stability, high-temperature stability, and low-temperature cracking resistance; and 3) developing the correlation models between the early-age strength and long-term performance of asphalt emulsion cold recycled mixes through regression analysis. It was concluded that adding cement in cold recycled mixes played positive effects on both its early-age strength and long-term performance. In addition, strong linear correlation was found between the early-age strength and long-term performance of asphalt emulsion cold recycled mixes.

With the development of low-carbon sustainability, the recycling of waste concrete and waste tires to produce rubber-modified recycled aggregate concrete (RRAC) has become imperative. The compressive properties of RRAC after exposure to elevated temperatures were investigated in this study. The stress–strain curve, compressive strength, deformation performance, and bursting resistance of RRAC samples with rubber contents of 0%, 4%, and 9% were studied after exposure to 20, 200, 400, and 600 °C for 60 min. Furthermore, a single equation for the stress–strain curve of RRAC was selected and compared with the experimental results. The results suggested that the addition of rubber particles could significantly reduce the mass loss, improve the relative compressive strength, and increase the failure strain of recycled concrete. When the rubber content was large, additional pores formed after rubber melting, which led to a higher porosity in the specimen. Meanwhile, the internal structure became excessively loose, which resulted in a decrease in strength. Based on the obtained results, a rubber content of 4% is recommended for use in RRAC.

The failure behavior of restrained cracking induced by temperature and/or shrinkage differs from that of direct tensile failure. To study the restrained cracking behavior and criterion, a self-developed temperature stress testing machine (TSTM) was utilized and found to have good performance when examining concentric deformation and reproducibility. Restrained cracking experiments were performed considering different mixtures, temperature histories, shrinkages, and loading ages. The results indicated that concrete would crack when the restrained tensile stress exceeded 76% of the direct tensile strength, while the failure strain was 103%–137% of the tensile strain capacity. A combined stress–strain failure criterion was proposed under the assumption of linearity, and the prediction errors range from −7.61% to 12.89%. The proposed criterion will aid evaluations of the safety of restrained concrete.