Journal of building engineering最新文献

Researchers are exploring local, recycled, and waste materials for construction to address environmental concerns. Concrete heavily depends on cement, contributing to energy consumption and greenhouse gas emissions. Substituting cement with alternatives like recycled materials can cut energy use and minimize the environmental impact on concrete production. This research represents the first investigation into using Dillenia Suffruticosa (DS) and Acacia Auriculiformis (AA) leaf ash as sustainable alternatives to cement in producing eco-friendly mortar, an area that other researchers have not previously explored. The study aims to investigate using DS and AA leaf ash as sustainable alternatives to cement in mortar production. In this study, the incorporation of DS and AA leaf ash as a partial replacement for cement was systematically varied in increments of 5 %, ranging from 5 % to 40 % of the total mortar volume. The ash was systematically incorporated into the mortar in increments of 5 %, ranging from 5 % to 40 % of the total mortar volume. The study further conducted a comprehensive investigation into the physical properties of the mortar, including consistency, bulk density, dry density, water absorption, and flow characteristics, alongside an analysis of its compressive strength. Microstructural behaviour was assessed using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis to provide a comprehensive analysis. Results indicate that the enhancement in compressive strength of DS ash specimens, relative to AA ash, ranged from 1.32 % to 24.49 % at 7 days, 5.81 %–16.86 % at 14 days, and 1.87 %–11.91 % at 28 days. Furthermore, the highest enhancement in compressive strength is observed with a composition containing 10 % DS ash and 5 % AA ash content, underscoring the superior performance of DS ash compared to AA ash. The mineralogical characteristics of DS and AA leaf ashes illustrate their effectiveness as supplementary cementitious materials in sustainable construction. The significant advantages of using DS and AA leaf ash as a cement substitute are environmental sustainability, innovative materials use, and contribution to sustainable construction.

Air source heat pumps (ASHP) are considered worldwide as an effective alternative to heating with fossil fuels. With the improvement of heating performance under low temperature conditions and the continuous development of advanced defrosting methods, the deterioration of partial load performance in heating applications has become more and more obvious. Many researchers have found that performance in field testing is lower than performance tested in steady-state laboratory operation. This article summarizes the research of the past decades on the aspects of the partial load efficiency loss phenomenon, the magnitude, the influencing factors and improvement strategies, and the efficiency improvement methods for existing ASHP heating systems could be divided into three categories: 1.Improving the thermal inertia of the system, 2.Reducing the deviation between heating capacity and building load, 3.Reducing the water pump performance. It is hoped that with the continuous improvement of the energy efficiency of ASHP units, more attention will be paid to the influencing factors and improvement methods of systems.

Auxetic cementitious composites (ACC) made of embedded auxetic materials into cementitious matrix are gaining attention due to their enhanced mechanical properties caused by using high shock absorbing auxetic metamaterials as reinforcing medium. 3D printed auxetics can be tuned to achieve the required properties of ACC, by using different printing filaments, and cell geometries. In this research, three different types of re-entrant chiral auxetic (RCA) geometries in the form of reinforcing meshes were developed by 3D printing using Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) filaments. The effect of re-entrant cells orientation was investigated to select a suitable orientation by testing the RCA meshes under uniaxial tension. Based on which, the horizontally celled RCA meshes were employed to develop and characterise ACC samples. The ACC samples were prepared by embedding all three types of 3D printed RCA meshes into two different kinds of mortar matrices of low and high tensile strengths. The ACC made of high strength mortar embedded with TPU-RCA mesh with densest cell geometry exhibited highest tensile strength (11 MPa) and ductility (ultimate strain/cracking strain = 20). The shear bond characteristics of developed ACC was also investigated through testing ACC strips bonded with masonry substrate under shear lap testing arrangement. The ACC made of high strength mortar embedded with PLA-RCA mesh exhibited highest shear bond strength of 0.44 MPa. The RCA meshes did not de-bond from the ACC during the shear testing, and failure occurred due to extension or fracture of embedded RCA meshes. The results prove the applicability and benefit of employing ACC as protective strengthening materials for masonry and other cementitious structures.

To further improve the utilization of recycled fine aggregates (RFA) obtained from construction and demolition in ultra-high performance concrete (UHPC), this work aims to adopting the nano-silica (NS) to develop a UHPC incorporating RFA with high strength and low shrinkage. A series of experiment evaluation on the workability, compressive strength, autogenous shrinkage and resistance to chloride penetration of UHPC are conducted. The hydration products, pore structure, and microstructure of UHPC are analyzed using isothermal calorimetry, thermogravimetric analysis, scanning electron microscopy, and mercury intrusion porosimetry, respectively. Results indicate that the addition of RFA decreases the flowability and early compressive strength of UHPC. However, it effectively mitigates autogenous shrinkage and compensates for the later-stage strength loss. NS significantly enhances the early compressive strength and resistance to chloride penetration in UHPC containing RFA. The combined incorporation of 20 % RFA and 3 % NS leads to 65.6 % reduction in the autogenous shrinkage within 7 days, 12.1 % improvement in compressive strength and 16.5 % decrease chloride diffusion coefficient of UHPC specimens at 28 days. Furthermore, the synergistic effects of RFA and NS promote the cement hydration, reduce the porosity and further refine the pore structure, and improve the interface transition zone in UHPC. This provides valuable insights for advancing the development of environmentally sustainable which collaborative utilization of RFA and NS in the manufacture of UHPC with reducing carbon footprint.

The load flexibility of domestic water heaters was explored considering various demand-side management (DSM) strategies and seasons in this study. Physics-data driven models for electric resistance water heaters (EWHs) were developed. A data-driven approach was proposed to identify the model parameters of EWH models, enabling the inference of model parameters without knowledge of the detailed specific physical parameters of EWHs. This method provides substantial convenience for the application of the developed models in practical engineering. The model validation results indicate the accuracy of the developed EWH model, with a relative root mean square error of 1.9 %. Based on the validated model, the load flexibility potential of EWHs was quantified under seven DSM strategies and on five typical seasonal days, utilizing four evaluation indicators. Additionally, an integrated quantification index was proposed to compare the load flexibility of EWHs under various strategies and seasons. Results show that EWH's load flexibility is the greatest on a typical summer day, with the integrated quantification index being 50.3 %, while it is 37.2 %, 35.0 %, 30.1 %, and 20.5 % on the other four typical seasonal days. Recommendations for the application of the seven DSM strategies in different seasons were provided, offering guidance for the demand-side management of EWHs in real-world settings. Two suggestions for the improvement of EWH products were offered to enhance the load flexibility of EWHs based on the sensitivity analysis results, providing guidance to EWH manufacturers for the further development of EWH products.

This study conducted a four-point bending experiment investigation on the flexural performances of the RC beams strengthened with various CFRP schemes. Four beams were employed, i.e., the ordinary RC beam (L0), the RC beam bonded with CFRP sheet (L1-C), the CFRP U-wrapped RC beam (L2-U), and the RC beam using CFRP rivets (L3-A). Test results highlighted the obvious improvement in the flexural performances of CFRP-strengthened beams in terms of enhancing load-carrying capacities and limiting overall deformations compared to beam L0. In addition, end anchorage systems, including CFRP U-hoop and CFRP rivets, changed the failure mode, restricted crack propagation, and mitigated the bottom CFRP sheet debonding effectively. The ultimate loads of beams L1-C, L2-U, and L3-A were 27.4 %, 36.4 %, and 41.6 % higher than beam L0, respectively, indicating that CFRP rivets performed the best in improving the beams' flexural properties. Finite element analysis was developed to simulate the bending experiment process. The numerical results comply well with the experiments in terms of the crack distribution pattern and bending force history. Then, parametric studies for the design suggestions with the use of the modes reveal that the implementation of the CFRP rivet with a depth of 80 mm and a diameter of 10 mm seems to be an ideal optimization plan for the beams herein.

Several studies have examined the impact of fabric roller shades on building energy consumption, visual, and thermal comfort. These works mainly focus on glare, outdoor view, and daylight availability. However, a review that comprehensively and jointly analyses the results obtained in the aforementioned studies is lacking. To address this gap, this paper conducts a literature-based review that aims to describe, analyse, and discuss a set of studies that examine the impact of fabric shades optical properties on glare, outdoor view, daylight availability, and colour, focusing on methodologies and results. Since the study concentrates on fabric optical properties and their impact on the mentioned daylight parameters, it excludes shade system dynamics and exclusively analyses conditions where roller shades are fully deployed. According to the paper findings, glare and outdoor vision clarity are the two parameters where the impact of the optical properties of fabric roller shades has been most extensively studied, including the efficiency of the metrics used to describe their performance. Regarding daylight availability, further research is needed using dynamic daylighting analysis. The colour-related parameters have received the least attention to date. Psychophysical research is required to determine whether current colour metrics are appropriate for testing the effects of fabric optical properties on chromaticity and colour rendition. Nevertheless, the conclusions reached in this paper can serve as guidelines for architects and building professionals and can guide the development of a fabric selection tool that includes all the analysed parameters.

Impressed current cathodic protection (ICCP) is an electrochemical technique employed to mitigate corrosion. The evaluation of its effectiveness has traditionally relied on qualitative criteria such as protection potential and potential decay. This study proposes a novel electrochemical setup to enable measurements during current-controlled ICCP treatment. The experimental outcomes demonstrate that the proposed approach, in conjunction with protection potential analysis, allows for the quantitative determination of the optimal ICCP current density. As the protection current density increased, the fitted charge transfer resistance (R_ct) initially showed an upward trend, followed by a gradual decline. To accurately interpret the results, it is crucial to discern whether the R_ct values correspond to oxidation reactions (referred to as corrosion reactions in this context) or reduction reactions. Furthermore, it was observed that the optimal current density was closely associated with the severity of initial corrosion, in line with previous findings. This consistency serves to further validate the efficacy of the proposed method.

The uncontrollable printability and structural integrity limit the development and application of 3D printed cement composites. In this study, the potassium and sodium-based electrolyzed water (KEW and NEW) were incorporated into the 3D printed ordinary Portland cement composites (OPCCs) to adjust rheological properties, aiming to improve printability and optimize the printed structure build-up. Experimental results show that the KEW can enhance the elastic modulus and decrease the strain notably as the applied shear stress increases. Compared with tap water (TW), the KEW and NEW increase the static yield stress based on oscillation-shear and creep-recovery protocol, and improve thixotropy. Besides, the structure deformation of 3D printed OPCCs with NEW and KEW decreases from 11.81 % to 8.34 % and 8.22 %, respectively, representing a margin of approximately 29.4 % and 30.4 %. Furthermore, the compressive and flexural strength of 3D printed OPCCs with KEW increases from 25.5 to 29.4 MPa and 3.55 to 4.04 MPa, respectively, benefitting from the lower porosity and higher hydration rate. In conclusion, the incorporation of electrolyzed water into 3D printed OPCCs demonstrates considerable potential, effectively enhancing printability and optimizing structure build-up.

Limestone calcined clay cement (LC³) is a promising solution for mitigating CO₂ emissions in cement production by substantially replacing clinker with widely available supplementary cementitious materials. While calcination is the conventional method for activating clay, there is a growing interest in mechanical activation. Incorporating mechanically activated kaolin into LC³ formulation would offer a novel approach to producing this cement. This study aims to assess the impact of replacing calcined clay (CC) with mechanically activated clay (MC) in LC³ properties and relevant features. Accordingly, LC³ with MC substitutions ranging from 0 to 100 wt% were formulated. The resulting cements were characterised to evaluate their physicochemical properties, microstructure, strength, and pore distribution. LC³ incorporating MC exhibited comparable crystalline and amorphous phases to LC³ containing CC. However, the incorporation of MC accelerated hydration, leading to the earlier formation of carboaluminates and consumption of portlandite, alongside enhanced compressive strength at early curing stages. At 28 days, LC³ with 100 wt% of MC displayed similar compressive strength (42 MPa) to LC³ with 100 wt% of CC (40 MPa) with comparable pore distribution and microstructure. These findings validate MC's potential to substitute CC in LC³, offering an alternative for activating clay.