A comparative study on concrete slurry waste: performance optimization from the wet-milling process

Concrete slurry waste (CSW) is a mixture of fine aggregates, cement hydration products and residual cement particles obtained from the sedimentation pits during the production of concrete. In the present study, CSW with different grinding durations were evaluated; the properties of the CSW and the CSW-cement composition were compared under the influence of wet-milling. The results indicated that the particle size of the CSW decreased and the dispersion stability of the slurry was improved after wet-milling treatment. The increasing ettringite peak suggested that the mineral admixture hydrated during wet-milling. However, carbonization also occurred during the process. The nucleus effect of wet-milled CSW not only increased the hydration heat and compressive strength of cement, but also significantly enhanced the pore structure and chloride penetration resistance of the mixtures. Although the gel pore volume fraction for the mixture containing original CSW is higher than that of the reference mixtures, the compressive strength and chloride penetration resistance are weak due to the loose structure caused by the dilution effect.Web of Science545art. no. 18

Preparation and Experimental Investigations of Low-Shrinkage Commercial Concrete for Tunnel Annular Secondary Lining Engineering

Secondary lining concrete is frequently used in underground tunnels. Due to the internal restriction of the annular concrete segment, micro-cracks may be caused by temperature stress and volume deformation, thus affecting the safe transportation of the tunnel. The purpose of this study is to provide a concrete experimental basis with low hydration heat and low shrinkage for tunnel engineering with different construction requirements. Different amounts of expansion agent (EA), shrinkage-reducing agent (SRA), and superabsorbent polymer (SAP) were considered in commercial concrete. It was found that EA elevated the degree of hydration and the hydration exothermic rate, while SRA and SAP showed the opposite regularity. SRA has the optimum shrinkage reduction performance with a 79% reduction in shrinkage, but the strength decreases significantly compared to EA and SAP groups. The effect of the combination of different shrinkage reducing components in commercial concrete is instructive for the hydration rate and shrinkage compensation in secondary lining engineering

Harnessing ultrasound in photocatalysis: Synthesis and piezo-enhanced effect: A review

The photocatalytic technique has drawn far-ranging interests in addressing the current issues; however, its property suffers from the limited visible light response and rapid recombination of carriers. To address these issues, two specific approaches have been proposed to enhance the photocatalytic activity: (1) ultrasound-assisted synthesis has been utilized to prepare photocatalysts, resulting in refined grain size, increased specific surface area, and reduced photogenerated carrier recombination; (2) sonophotocatalysis and piezoelectric enhanced photocatalysis have been developed to accelerate the reaction, which utilizes the synergism between ultrasound and light. On one side, sonophotocatalysis generates cavitation bubbles which induce more reactive radicals for redox reactions. On the other side, ultrasound induces deformation of the piezoelectric material structure, which changes the internal piezoelectric potential and improves the photocatalytic performance. Currently, intensive efforts have been devoted to related research and great progress has been reached with applications in pollutant degradation, new energy production, and other fields. This work starts by elucidating the fundamental concept of ultrasound-assisted photocatalyst synthesis and photocatalysis. Then, the synergistic behavior between ultrasonic and light in ultrasonic-assisted photocatalysis has been thoroughly discussed, including pollutant degradation, water splitting, and bacterial sterilization. Finally, the challenge and outlook are investigated and proposed