Asphalt concrete has been widely used in road engineering as a surface material. Meanwhile, ultrasonic testing technology has also been developed rapidly. Aiming to evaluate the feasibility of the ultrasonic wave method, the present work reports a laboratory investigation on damage detection of asphalt concrete using piezo-ultrasonic wave technology. The gradation of AC-13 was selected and prepared based on the Marshall’s design. The ultrasonic wave velocities of samples were tested with different environmental conditions firstly. After that, the samples were destroyed into two types, one was drilled and the other was grooved. And the ultrasonic wave velocities of pretreated samples were tested again. Furthermore, the relationship between velocity and damaged process was evaluated based on three point bending test. The test results indicated that piezoelectric ultrasonic wave is a promising technology for damage detection of asphalt concrete with considerable benefits. The ultrasonic velocity decreases with the voidage increases. In a saturated water environment, the measured velocity of ultrasonic wave increased. In a dry environment (50 °C), the velocity the ultrasonic waves increased too. After two freeze-thaw cycles, the voidage increased and the ultrasonic velocity decreased gradually. After factitious damage, the wave must travel through or most likely around the damage, the ultrasonic velocity decreased. During the process of three point bending test, the ultrasonic velocity increased firstly and then decreased slowly until it entered into a steady phase. At last the velocity of ultrasonic wave decreased rapidly. In addition, the errors of the results under different test conditions need to be further studied.

Bitumen ageing is a very complex process and poses a threat to the performance of pavements. In the present work, a fluorescence spectrophotometer was employed to research the change rule of components and the structure of bitumen after the ageing process. The Thin Film Oven Test (TFOT) and Ultraviolet (UV) light treatment were carried out as ageing methods. The properties and components of bitumen were tested before and after aging. The 2D and 3D fluorescence spectra of bitumen were analyzed. The vector of fluorescence peak was calculated for evaluating the ageing process. The results indicated that the ideal concentration of bitumen- tetrachloromethane solution was 0.1 g/L or smaller for avoiding the fluorescence quenching. The coordinates of fluorescent peak appeared “blue-shift” after ageing due to the change of aromatics. In addition, bitumen has already occurred serious ageing when the magnitude of a vector is more than 36.

The aim of the test is to research the influence rules of TEAHCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what's more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEAHCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

This study addressed the issues of low grinding efficiency, insufficient early strength of cementitious materials, and poor volume stability in steel slag processing by developing four composite grinding aids. Through optimization of the synthesis process, grinding aid d - formulated with polycarboxylate polymer combined with sodium sulfate (71%), sodium carbonate (15%), and calcium chloride (4%) - demonstrated optimal performance. Experimental results revealed that the optimal grinding duration for steel slag was 45 min, with grinding aid d increasing the proportion of 0–30 μm particles to 66.77%, grinding aids a, b and c were increased to 61.34%, 63.65% and 63.37% respectively, showing significant improvement compared to the control group. The grinding aid d enhanced the 3-day compressive strength of steel slag-based cementitious materials by 21.04%, grinding aids a, b and c were increased by 16.07%, 16.19% and 12.37%, while effectively reducing free calcium oxide content through mechanical activation to improve volume stability. Microstructural analysis indicated denser hydration product structures, increased ettringite and calcium hydroxide crystal formation, and reduced porosity in samples treated with grinding aid d. The research confirmed a positive correlation between the 0–30 μm particle proportion and hydration degree of cementitious materials, providing theoretical support for steel slag resource utilization. Steel slag-based cementitious materials can effectively reduce costs, decrease environmental pollution, and enhance the long-term strength, durability, and workability of concrete.

Piezoelectric material has excellent characteristics of electromechanical coupling so that it could be widely applied in structural health monitoring field. Nondestructive testing of piezoelectric technique becomes a research focus on piezoelectric field. Asphalt concrete produces cumulative damage under the multiple repeated vehicle load and natural situation, so it is suited material and structure for nondestructive application. In this study, a test system was established by driving power of piezoceramic, laser displacement sensor, computer, and piezo‐embedded asphalt concrete. Displacement, hysteresis, creeps, and dynamic behavior of KNN piezoceramic element embedded in asphalt concrete were tested. The results indicate that displacement output attained 0.4 μm to 0.7 μm when the loads were from 0 N to 150 N. The hysteresis was not obvious when the load was from 0 N to 100 N, aside from higher loads. The creep phenomenon can be divided into two parts: uptrend and balance. The more serious the asphalt binder ageing is, the larger the displacement is, when piezo‐asphalt concrete has already been in serious ageing.

Current research on the microstructural mechanisms governing the stabilization of steel slag aggregates with inorganic binders remains limited. To address this knowledge gap, this investigation comparatively analyzes the interfacial transition zone (ITZ) in steel slag composites stabilized by cement versus solid waste-based alternative binder. Through microhardness testing and micro-region XRD characterization, distinct interfacial characteristics were identified: the steel slag-cement and steel slag alternative binder ITZ exhibited widths of approximately 60 μm and 200 μm, respectively. Phase composition analysis revealed enhanced complexity in ITZ regions. The cementitious ITZ contained supplementary Ca(OH) ₂ and tricalcium aluminate phases compared to the cement matrix, while the alternative binder-based ITZ demonstrated higher residual C ₂ S content relative to its matrix. The comprehensive evaluation combining unconfined compressive strength (UCS) and leaching tests shows that this alternative binder has certain performance advantages, especially in the later stage of strength development, it has obvious progressive advantages. The alternative binder-treated specimens achieved 56%, 60%, and 84% of cement-stabilized UCS values at 7d, 28d, and 90d respectively, while exhibiting superior frost resistance. Notably, chromium leaching concentrations were reduced to 79.58% of cement-stabilized levels and 23.20% of untreated steel slag.