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To study the effect of SAP incorporation on the early shrinkage of SAP internally cured concrete with the aim to solve the problems of early shrinkage and cracking of bridge leveling-layer concrete, using the SAP incorporation method as a parameter, the mechanical properties test of internally cured concrete, the shrinkage performance test of ring restraint and the scanning electron microscope observation test were carried out. The effects of the SAP content and incorporation method on the flowability, mechanical properties, shrinkage performance and microstructure of internally cured concrete were analyzed. The experimental results show that when the content of the SAP in concrete is 0.2% of the mass of cementitious materials, it has the least influence on the compressive strength of concrete. The addition of preabsorbed water to the SAP can delay early cement hydration, increase the later cement hydration rate and final hydration degree, and improve the concrete strength. Preabsorbed water mixed with an SAP can effectively improve the shrinkage of concrete, and the shrinkage reduction effect is more obvious than that from the dry addition of the SAP; the early cracking risk of concrete without an SAP is high, and it will crack before day 28. The addition of an SAP can strengthen the microstructure of concrete and improve its density and crack resistance, effectively avoiding concrete cracking. It is recommended that the water-absorbent resin be incorporated in a preabsorbent manner, and the SAP preabsorbent ratio is equal to the maximum water storage rate of the SAP. [ABSTRACT FROM AUTHOR]

To promote the construction of environmentally friendly, sustainable pavements and solve the impact of the scarcity of asphalt resources on highway development, bio-mixed asphalt (BMA) modified by SBS and polyphosphoric acid (PPA) was prepared, and the influence of the ratio of bio-asphalt (BA) replacing petroleum asphalt on different PPA/SBS blending schemes was explored through conventional property tests. According to each PPA/SBS blending scheme, the optimal replacement ratio of bio-asphalt was optimized, and the microstructure and distribution morphology of different PPA/SBS-modified BMA were evaluated. Conventional property test results show that with the same PPA/SBS content, the replacement ratio of bio-asphalt has a significant impact on the conventional performance of composite-modified asphalt, but the appropriate replacement ratio of bio-asphalt can improve the storage stability and conventional performance of composite-modified asphalt; in micromorphological analysis, it was found that the number of bee-like structures on the surface of the modified BMA decreased significantly, which indicated that the molecular heterogeneity of various components in the asphalt was reduced. In addition, bio-asphalt changed the particle morphology and improved the dispersity of SBS in asphalt. The composite-modified BMA had a lower SBS content, but its conventional performance was still excellent—so it has significant application prospects in road engineering. [ABSTRACT FROM AUTHOR]

To study the leaching characteristics of a cement-stabilized macadam base with fly ash, a calcium leaching test, using varying cement and fly ash dosages in an ammonium chloride solution, was designed to obtain the rate of calcium ion leaching, porosity, and permeability coefficient of cement-stabilized macadam with leaching time. The results showed that the number of leached calcium ions increased with the cement dosage in the leaching of cement-stabilized macadam. With an increase in the cement dosage, the leaching rate of calcium ions decreased, and the leaching process of the material was delayed. The incorporation of fly ash could effectively slow down the degree of calcium ion leaching. The permeability coefficient increased gradually with the extension of leaching time, and the increase in fly ash content had a more significant effect on the improvement of the permeability coefficient than the increase in cement dosage did. [ABSTRACT FROM AUTHOR]

Improper handling of waste printed circuit boards (PCBs) can cause serious pollution to the water and soil environments. In order to explore a new method of recycling waste PCBs, this study investigated the effect of PCBs and butadiene styrene rubber (SBR) on the rheological properties of neat bitumen. The dynamic shear rheological (DSR) test was used to study the effect of different PCB contents on the high-temperature rheological properties of SBR-modified bitumen. Fluorescence microscopy and Fourier-transform infrared spectroscopy were used to study the microstructure change law and modification mechanism of PCB and SBR composite modified bitumen. Finally, the feasibility of the bitumen properties was verified through a test of the bituminous mixture properties. The DSR test results showed that the addition of PCBs improves the elastic recovery modulus, dynamic shear modulus, and rutting factor of SBR-modified bitumen, indicating that the high-temperature properties were improved. Infrared spectroscopy analysis revealed that a new absorption peak was generated in the infrared spectrum of the compound bitumen after the addition of PCBs, and the intensity of the original absorption peak also changed, indicating that PCBs and SBR-modified bitumen were mainly physically blended and accompanied by a weak chemical reaction. It was further found that the absorption peak of the unsaturated C=C double bond was significantly enhanced, and the increase in the content of the unsaturated bond C=C in the main chain of the polymer significantly increases the stiffness of the bitumen. Macroscopically, the high-temperature rutting resistance was improved to a certain extent. The fluorescence diagram shows that when PCBs do not exceed 10%, the PCBs can form a homogeneous structure and be dispersed in SBR-modified bitumen. The road test of PCBs and SBR composite modified bituminous mixtures showed that PCBs can significantly improve the rutting resistance and water stability of SBR-modified bitumen at high temperatures at the recommended optimum content. The crack resistance at low temperatures is weakened but still meets actual engineering requirements. The correlation analysis between the properties of bitumen and bituminous mixtures is carried out based on grey correlation theory. The results show that the index of modified bitumen has a very good guiding effect on the bituminous mixture properties. The development of PCBs and SBR composite-modified bitumen provides a new practical method for recycling waste PCBs. [ABSTRACT FROM AUTHOR]

Effective approaches are required to be developed to solve the poor compatibility and thermal stability problems of crumb rubber-modified asphalt (CRMA). This study focuses on a method called microwave activation. However, seldom researches pay attention to the properties of MACRMA after aging. The objective of this study was to prepare microwave-activated CRMA (MACRMA) and investigate the performance of asphalt after aging. The samples were subjected to thin-film oven test (TFOT) at different times and temperatures. The effect of heat aging on the properties of MACRMA was evaluated by three indicator tests: viscosity, dynamic shear rheology test (DSR), and repeat creep recovery test (RCRT). The test results indicated that the MACRMA after two aging conditions had noticeably lower performance values (e.g., penetration, ductility) compared to unaged samples, and thus, the need to control temperature and time for mixing and construction was verified to be important. In addition, the G*/sin δ and phase angle values were largely influenced by the TFOT aging temperature and time. The MACRMA's ability to recover was improved after aging. Compared with the aging temperature, the aging time had a more significant effect on the deformation and recovery ability of MACRMA. [ABSTRACT FROM AUTHOR]