This study focuses on the core economic zone of East China, utilizing the decoupling model to investigate the relationship between carbon emissions and economic development in the construction industry. Furthermore, it analyzes the driving factors through the application of the logarithmic mean index method. The findings reveal that, firstly, Zhejiang and Jiangsu provinces exhibit higher total carbon emissions in the construction industry. Except for Fujian Province, the other regions exhibit a downward trend after 2019. Secondly, there is considerable spatial variability in carbon emissions in the construction industry within the core economic zone of East China, and it gradually decreases over the study period. While economically developed regions like Zhejiang and Jiangsu provinces tend to concentrate and consume more resources and energy, their impact on surrounding neighboring provinces or cities is relatively limited. Thirdly, carbon emissions from the construction industry in the core economic zone of East China show a development trend shifting from weak decoupling to strong decoupling, indicating a healthy growth in the construction industry. Specifically, different regions show different trends. Lastly, regarding influencing factors, the impact direction of carbon intensity on total carbon emissions shows instability. Energy intensity consistently exhibits inhibitory effects, and the economy and the population scale act as driving forces.

With the increasing trend of office buildings towards high-rise, multifunctional, and structurally complex architecture, the difficulty of engineering cost management has increased. Accurately estimating costs during the decision-making stage is crucial for ensuring the overall project’s financial viability. Therefore, finding straightforward and efficient methods for cost estimation is essential. This paper explores the application of algorithm-optimized back propagation neural networks and support vector machines in predicting the costs of office buildings. By employing grey relational analysis and principal component analysis to simplify indicators, six prediction models are developed: BPNN, GA-BPNN, PSO-BPNN, GA-SVM, PSO-SVM, and GSA-SVM models. After considering accuracy, stability, and computation time, the PCA-GSA-SVM model is identified as the most suitable for office building cost prediction. It achieves stable and rapid results, with an average mean square error of 0.024, a squared correlation coefficient of 0.927, and an average percentage error of 5.52% in experiments. Thus, the model proposed in this paper is both practical and reliable, offering valuable insights for decision-making in office building projects.

Fine gold tailings particles generated from gold mining and refining have the potential to replace high-cost quartz sand in the preparation of economical ultra-high-performance concrete (ECO-UHPC) due to their large stockpiles, low cost, and elimination of grinding. In this study, ECO-UHPC was prepared by substituting quartz sand with gold tailing sand (GTS) at substitution rates of 0%, 25%, 50%, 75%, and 100%. The mechanical properties of ECO-UHPC, including its cubic compressive strength, elastic modulus, and prismatic compressive strength, as well as its leaching toxicity, were experimentally analyzed under various early curing experiences such as ambient-water curing (WC), hot-water curing (HWC), hot-air curing (HAC), and combined curing (CC). Additionally, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were employed to interpret the macroscopic behavior of ECO-UHPC. The results indicate that the incorporation of waste GTS slightly reduces the fluidity of fresh ECO-UHPC, decreasing it by approximately 6.1% at a full 100% replacement. As a result of waste GTS substitution, the cubic strength of ECO-UHPC experiencing the WC environment during early curing is reduced by 0.7–12.2%. However, the strength of thermally cured ECO-UHPC is comparable to or even higher than that of pure quartz-based G0, with the maximum value occurring in G-50. Specifically, the strength of G-50 cured with HWC, HAC, and CC varies by +20.0%, +40.2%, and +57.7%, respectively, as compared to that of G-50 cured with WC. The evolution of the elastic modulus and the prismatic strength of ECO-UHPC under different early curing conditions and GTS replacement rates aligns closely with that of its cubic strength. In addition, the implementation of thermal curing conditions also limits the leaching of heavy metals from ECO-UHPC, with the best effect observed under CC. This is because appropriate thermal curing promotes the densification of a cementitious substance and the bonding of GTS-cementitious material. Overall, this study demonstrates the feasibility of utilizing waste GTS as a partial or full replacement for quartz sand in ECO-UHPC while maintaining desirable mechanical performance and environmental safety. The findings provide valuable insights into the influence of GTS substitution and early curing regimes on ECO-UHPC properties, highlighting the potential of thermal curing to enhance strength and mitigate leaching risks. Future research should further explore the long-term durability of GTS-based ECO-UHPC and its broader applicability in sustainable construction practices.

This paper presents a technique for enhancing the cracking resistance of reinforced concrete (RC) beams through the external application of liquid rubber. To evaluate the influence of this coating on flexural performance, four-point bending tests were conducted on seven RC beams, comprising six coated beams and one uncoated control beam. The effects of coating position (beam soffit, beam sides, or both) and number of coating layers (3 or 6) on the flexural response were investigated. The results indicate that the external application of liquid rubber improves the cracking load and ductility of the RC beams to some extent, and the degree of improvement is related to the number of coating layers. Moreover, the application of liquid rubber to the tensile zone of the RC beams can moderately restrain tensile deformation of the concrete. When the coating was applied only to the beam soffit, the concrete strain at the soffit was lower than that in the tensile zone on the beam sides, resulting in a non-linear distribution of tensile strain along the section height within the pure bending region.