Addition of active micro-nanomaterials in recycled aggregate concrete (RAC) is a potential strategy to improve the mechanical properties and durability of RAC. The calcined layered double hydroxides (CLDHs) with special composition, structure and memory effects, exhibit great adsorption and binding capacity to anions. Therefore, the CLDHs were prepared and utilized for inhibiting chloride attack in interfacial transition zone (ITZ) of RAC. The structural transformation characteristics of CLDHs experienced various calcination temperatures were firstly investigated, and the reconstruction performances and Cl- adsorption capacity of CLDHs in solution with different anions, pH and temperature were then explored in detail. The microstructure and chloride erosion resistance property of ITZ in RAC incorporated with CLDHs were further investigated. The results demonstrated that CLDHs exhibited excellent reconstruction performance and Cl- adsorption capacity when LDHs were calcined above 500 degrees C, and the maximum chloride adsorption capacity of the CLDHs was 86.82 mg/g. It was noteworthy that the reconstruction and Cl- adsorption performance of CLDHs will be distinctly suppressed when the pH > 10, in contrast, increasing the ambient temperature promoted the reconstruction and Cl- adsorption performance of CLDHs. Additionally, the width of ITZ in the RAC were significantly reduced and the porosity had decreased by 32.5 % with incorporation of 3 % CLDHs in RAC. The good filling effect and superior chloride adsorption capacity resulted in the significantly decreased free chloride content in RAC.

由于再生骨料存在自身的缺陷，再生混凝土容易遭受到侵蚀环境的影响。偏高岭土作为矿物掺合料，可以在早期促进水泥水化，最终产物以离子键和共价键为主，范德华键为辅，因而较其他掺合料具有更优越的性能。以偏高岭土为掺合料对再生混凝土进行改性，分析实海暴露环境侵蚀下的再生混凝土界面区的劣化演变过程。研究结果表明，当偏高岭土掺量为4%、7%、10%时，抗压强度分别较基准混凝土提升了11.1%、19.4%、8.3%。当受到海水侵蚀时，各界面过渡区性能都随着时间的推移先增强后减弱。新砂浆-骨料界面、新砂浆-旧砂浆界面对于海水侵蚀较为敏感，而旧砂浆-骨料界面在海水侵蚀下表现出更稳定的性能，旧砂浆以及新旧砂浆界面为薄弱部位。

Concrete structures are vulnerable to environmental erosion during long-term service, leading to durability degradation and raising demands for high-performance repair materials. Although polyacrylate incorporation enhances the mechanical properties of cement-based systems, their bonding performance remains insufficient in practice. In this study, molecular dynamics simulations and experimental tests were combined to elucidate the interaction mechanisms between copolymer monomers and the cement matrix. The ion-exchange functionalized waterborne acrylate copolymer-modified mortar achieved a 67 % increase in interfacial shear strength, 53.6 % improvement in flexural bond strength, and 75.5 % and 54.2 % gains in compressive and flexural strength, respectively. Durability was also markedly enhanced, with 77.75 % and 49.81 % reductions in chloride migration coefficient and carbonation depth. These improvements arise from ion-exchange reactions between the copolymer and cement hydration products, forming a chemically bonded interpenetrating network that densifies the microstructure and strengthens interfacial adhesion. This work demonstrates that the copolymer significantly optimizes both bonding performance and durability through multi-scale mechanisms, while molecular dynamics simulations provide molecular-level insights into the microscopic interactions of polymer-modified cement-based materials. © 2025 Elsevier Ltd.

Recycled concrete aggregate (RCA) is an important form for reusing of waste concrete. However, the presence of corrosive ions, specifically chloride ions, which are absorbed on the surface of RCA or infiltrated from the external environment, significantly affects the mechanical performance and durability of recycled aggregate concrete (RAC). This paper aims to suppress the erosion and diffusion of chloride ions in RAC by adding calcined layered double hydroxides (LDOs), utilizing the restructuring and anions exchange properties of LDOs. The dissolution ratio of chloride ions carried by RCA and the adsorption efficiency of LDOs on the leaching ions were analyzed using the silver nitrate titration method. The maximum chloride adsorption capacity of the LDOs is 31.052 mg/g. Additionally, the inhibitory effect and mechanism of LDOs on chloride ion attack were detailed evaluated by the techniques combining mercury intrusion porosimetry (MIP), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM and EDS), rapid chloride migration coefficient method (RCM), and electrochemical impedance spectrum. The results indicate that LDOs exhibit a good adsorption effect on chloride ions leaching from RCA, and the adsorption efficiency is negative correlation with the pH value. Furthermore, the small size effect of LDOs plays a filling role in the pores of concrete, increasing the compactness and penetration resistance of chloride ions of RAC. This work provides a promising approach to enhance the mechanical and durability properties of RAC by incorporating with LDOs utilizing its chloride ion capture feature and nano-filling effect. And the findings of this research can also be extended to the use of LDOs for treatment of other corrosive anions, such as SO42− and CO32− in RAC, demonstrating its applicability in a broader context. © 2024 Elsevier Ltd

The burning or accumulation of a large number of corn cobs in the countryside not only pollutes the environment but also takes up land, and it is of great significance to use agricultural solid waste to prepare green ecological construction materials for liveable villages. Therefore, in this study, the agricultural solid waste-corn cob is used as coarse aggregate, the recycled sand as fine aggregate, and industrial solid waste-mineral powder is used as cementitious material to prepare a green low carbon recycled concrete (LCRC). Regarding the alkali exciter concentrations, fine aggregate type and pre-wetting degree of aggregate as key variables, the time-varying laws of mechanical property, thermal insulation property, drying shrinkage property and CO2 emission of LCRC were studied. The results show that LCRC with a higher concentration of alkali exciter has better mechanical and thermal insulation properties, but poorer shrinkage properties. The mechanical property and shrinkage property of LCRC by manufactured sand are more excellent but poor insulation property. 80% pre-wetted LCRC has better mechanical and shrinkage properties, but lower thermal insulation property. The 28 days compressive strength and flexural strength of LCRC can reach up to 11.6 and 1.6 MPa. The bending compression ratio and 90 days shrinkage of LCRC are between 0.07 and 0.18 and 625.9∼977.7 × 10−6, which are comparable to or even better than normal concrete. The thermal conductivity of LCRC ranges from 0.108 to 0.300 W/(m·K) and can be used as a preparation insulation material. Meanwhile, LCRC can reduce carbon emissions by up to 31% than ordinary cement. © 2022 The Author(s)

The poor performance of recycled aggregate concrete (RAC) limits its application on wide filed. This paper attempted to study the influence of fly ash (FA), slag powder (SP) and silica fume (SF) on the performance of RAC from a microscopic point of view. The compressive strength and chloride resistance were evaluated when FA, SP and SF were used. Then the evolution of ITZ performance with different admixtures was observed by backscattering scanning electron (BSE) microscopy image, Mercury intrusion porosimetry (MIP), microhardness and so forth. Results indicate that, (1) the supplementary cementitious materials (SCMs) can improve the compressive strength and chloride penetration resistance of RAC, with a certain dosage range for different SCMs; (2) the SCMs can refine the pore structure of ITZs for RAC, increase the microhardness and modify the phases around ITZs; (3) the three SCMs both fill the cement paste voids and promote the compactness of ITZ structure by reacting with calcium hydroxide to generate C[sbnd]S[sbnd]H gels, which in turn enhance the macroscopic performance of RAC. The results of this research can provide a meaningful reference for further study of SCMs to improve the ITZs structure of RAC. © 2022 Elsevier Ltd

掺加矿物掺合料是降低高贝利特硫铝酸盐水泥（HB-SAC）混凝土的生产成本并改善其凝结硬化性能的有效措施。研究了水灰比为0.5时，矿粉（MP）、粉煤灰（FA）对高贝利特硫铝酸盐水泥抗压强度、砂浆流动度、标准稠度用水量、凝结时间的影响；并通过XRD、SEM对掺加不同矿物掺合料的高贝利特硫铝酸盐水泥净浆进行分析。结果表明：掺加矿物掺合料延长了高贝利特硫铝酸盐水泥的凝结时间；水泥浆体标准稠度用水量随矿物掺合料掺量的增加呈先减小后增大趋势，掺量为10%时达到最小值；掺加矿物掺合料后水泥砂浆流动度变大，粉煤灰对砂浆流动度的影响显著；当掺量从0增加至30%时，掺加矿粉抗压强度降低15.4%，掺加粉煤灰抗压强度降低27.6%；掺矿粉、粉煤灰后，水泥浆体中C-S-H凝胶数量增加，其他水化产物无明显变化。

Applying recycled aggregate (RA) aligns with the development concept of green and environmental protection. Nevertheless, introducing RA has resulted in a complex interface structure, which will deteriorate the performance of recycled aggregate concrete(RAC). To investigate the influence of the properties of the interfacial transition zones(ITZs) on the performance of RAC, and the digital image correlation(DIC) technology was used to track the strain variation law of each interface during the failure process. The porosity and mechanical properties of the ITZs were quantitatively characterized by backscattered electron(BSE) imaging and microhardness testing. By controlling a single variable, the different ITZs of RAC were improved by targeted strengthening, including mortar and aggregate strengthening.The influence of the ITZs properties on the macroscopic properties and mesoscopic failure behavior of RAC was analyzed. The experimental results show that the mechanical properties of the ITZs were enhanced and the porosity was reduced. Strengthening treatment improved the strength of target interface, causing a change in the relative strength of the internal interface of concrete, and reducing the probability of failure of the strengthened interface. This is consistent with the results observed in SEM images, the more compact and stable the structure at the interface, the lower the probability of failure under load. A comprehensive evaluation of mortar strengthening and aggregate strengthening was carried out with the help of the linear weighted sum method, and the results showed that the mortar strengthening was more effective. © 2023 Elsevier Ltd

赤泥是生产氧化铝过程中排出的红色淤泥状残渣。随着氧化铝的生产,产生的赤泥数量不断增加。赤泥成分复杂难以利用导致了大量的堆存,这不仅产生了大量的管理成本,而且造成环境污染威胁到人的生存与发展。本文在国家自然科学基金（51978353）的资助下完成。以拜耳法赤泥为主要原料,利用石油焦渣、电石渣和高贝利特水泥对拜耳法赤泥改性作用,制备赤泥基高活性粉体。然后使用热活化、机械活化和化学活化对赤泥基复合粉体进行激发活化,掺加辅助材料制备地聚合物。在此基础上,研究了不同龄期、养护制度、水灰比和胶砂比赤泥基地聚合物胶凝材料的性能。最后利用赤泥基地聚合物制备非烧结尾矿砖。主要包括以下几个方面:（1）石油焦渣单独掺加40%对拜耳法赤泥粉体具有较好的改性效果,制备的胶砂试件28d抗压强度为9.5MPa。电石渣单独对拜耳法赤泥改性效果较差,但电石渣与石油焦渣复合改性拜耳法赤泥制备胶砂试件可以得到较好强度。当拜耳法赤泥、石油焦渣和电石渣固相质量比为7:2:1,制备的胶砂试件28d抗压强度为11.0MPa。（2）将拜耳法赤泥、石油焦渣和电石渣混合进行煅烧,保持600℃煅烧180min,添加30%矿渣制备胶砂试件28d抗压强度为27.0MPa。比较高贝利特水泥、普通硅酸盐水泥、粉煤灰和矿渣四种辅助性胶凝材料。矿渣与拜耳法赤泥粉体复合激发可以得到较高的早期强度和稳定的后期强度。当拜耳法赤泥粉体、矿渣、石油焦渣和电石渣的固相质量比为49:30:14:7时,制备的胶砂试件28d抗压强度为22.4MPa。（3）将赤泥、矿渣、石油焦渣和电石渣按49:30:14:7比例混合作为胶凝材料,按照胶砂试验制备赤泥基地聚合物。制备的胶砂试件抗压强度随龄期增长不断提高。1d抗压强度可以达到28d抗压强度的63%,3d抗压强度达到28d强度的71%,7d抗压强度达到28d强度的84%。浸水养护和密封养护试件的28d抗压强度较高,抗压均高于26.0MPa。胶砂试件的水灰比对抗压强度有很大影响,水灰比为0.4试件的28d抗压强度为35.1MPa。灰砂比1:1,水灰比0.3的胶砂试件28d抗压强度为43.4MPa。（4）使用拜耳法赤泥基地聚合物制备免烧砖。最终确定胶凝材料中赤泥为49%、石油焦渣为14%、电石渣为7%、矿渣为30%,胶砂比为1:3,水胶比为0.5。制备的赤泥基非烧结尾矿砖28d抗压强度为21.8MPa,吸水率为8.4%,干燥收缩值为0.05%,浸水4d后强度未降低,经历25次冻融循环后质量损失为0%,强度损失为9.05%,各项性能均满足《非烧结垃圾尾矿砖》（JC/T422-2007）中MU15等级要求。利用拜耳法赤泥、石油焦渣、电石渣、矿渣和河砂制备非烧结尾矿砖。赤泥不需要高温煅烧和添加化学试剂可以得到较好性能的免烧砖。消耗了大量赤泥,推动铝工业发展,开发了赤泥的潜在经济价值。

This article introduces an ultra-compact four-way quadrature power splitter (4W-QPS) based on a novel transmission-line compression technique called double-path zigzag microstrip line (DP-ZML). Detailed design techniques with modular approach are disclosed for the state-of-the-art 5G low-band applications. The theoretical predictions are verified with experimental re-sults through a fabricated prototype that operates from 696.55 to 876.03 MHz with >15 dB return-losses and isolations, and 90 & DEG;& PLUSMN;4 & DEG; quadrature phase between ad-jacent outputs. The compact size of this 4W-QPS is achieved at 0.212,gx0.212,g at a center frequency of 786 MHz.