Developments in the Built Environment最新文献

A transversely isotropic structural model for wood, based on a polytope strength criterion, is proposed and deployed in the analysis of solid wood columna-capreoli A-trusses reproducing the geometry and connection details of those currently erected in the Aula Magna of the Monastery San Lorenzo ad Septimum in Aversa. The predictivity of the polytope strength criterion is assessed verifying its capability of identifying the closest crisis mode against experimental evidence from a simple flexural test, with minimal wood sacrifice. The model is employed in parametric optimization analyses to infer a design provision for the columna-capreoli connection which appears to be in reasonable agreement with the rule of the art empirically inferable from the observation of many samples of open-node King Post A-trusses belonging to the architectural heritage in Campania of historical and artistic value. A final discussion examines a perspective of extending these optimization analyses to the sustainability of the built environment.

Life Cycle Assessment (LCA) is widely accepted for evaluating a building's environmental footprint. Building Information Modelling (BIM) has become the go-to strategy for LCA during design. Still, despite BIM-LCA automating detailed quantity extraction, challenges persist, such as a lack of standardised geometry modelling and information management and a common language between LCA and BIM data.

This study proposes a method to assess embodied carbon from BIM models classified using a construction classification system that provides a data structure, maps BIM objects and environmental impacts in LCA databases and matches different levels of development (LoD) in BIM models. The method was tested on real-world models, resulting in 375 kgCO₂e/m² for the single residential and 426 kgCO₂e/m² for the multi-residential building. These findings revealed its ability to adapt to different LoD and modelling techniques, expedite assessing different design options, and potentially save up to 20 hours of work remodelling.

Modular construction (MC) plays a pivotal role in fostering sustainable development. However, the promotion of MC in many jurisdictions has been encumbered by its prevailing undeveloped supply chain. This study aims to systematically explore the drivers, opportunities, constraints, concerns, strategies, and measures with regard to enhancing the MC supply chain, using the empirical case of modular integrated construction in Hong Kong and the supply chain in the Greater Bay Area of China. The research was conducted through the combination of a literature review, a questionnaire survey with 244 effective responses, and 46 expert interviews. A systematic framework with foremost drivers, opportunities, constraints, concerns, strategies, and measures is proposed for guiding MC supply chain enhancement from technical, political and regulatory, socio-economic, and geographical perspectives. The findings contribute to better understanding the complexity and dynamics of the MC supply chain and guide stakeholders to work collaboratively for supply chain enhancement.

This study aims to develop an ambient-cured nano-engineered one-part alkali-activated materials with excellent thermal characteristics using graphene nanoplatelets (GNPs) and ternary precursors. Their compressive strength, thermal properties, microstructure, pore structure were characterised through visual observation, isothermal calorimetry, TGA, XRD, SEM/EDS and X-ray μCT after high temperature exposure to 200–800 °C. The research findings indicated high strength characteristics of the developed AAM (∼80 MPa) at ambient condition, which could further reach to approx. 100 MPa after being heated up to 400 °C. GNPs provided nucleation effects for promoting geopolymerisation and crystallisation. As observed from X-ray CT, a high extent of severe cracks initiated from the core and propagated towards the surface. From SEM/EDS analysis, high Na/Al and Na/Si ratios or low Si/Al and Ca/Si ratios highly correlated to thermal stability. Overall, the research outcomes implied the promising use of the nano-engineered AAMs for thermal energy storage (TES) at 400 °C.

To investigate the recovery effect of natural self-healing of freeze-thaw damage of cementitious material-poor hydraulic concrete, we carried out a natural self-healing test for hydraulic concrete damaged by up to 200 rapid freeze-thaw cycles. The self-healing effect of macro-mechanical properties of hydraulic concrete damaged by freeze-thaw cycles was quantitatively characterized by the recovery rate of the specimens which underwent different numbers of freeze-thaw cycles then continued the standard curing to 28 days. Next, the microscopic properties of damaged hydraulic concrete after self-healing were further investigated by combining XRD, SEM and nitrogen adsorption tests. Finally, a prediction model of the recovery rate of macro-mechanical properties was established by using the microscopic pore test results. The results showed that, when the hydraulic concrete undergoes the damage of different freeze-thaw cycles and continues to standard curing for 28 days, the concrete specimens manifest natural self-healing to some extent even if damaged by up to 200 freeze-thaw cycles.

Magnetic nanocomposites were fabricated by attaching surface-modified magnetite nanoparticles to the surface of reduced graphene oxide (rGO) in this study. By applying an external magnetic field, the rGO were highly aligned in the cement paste. The orientation factor of aligned rGO was found to be 0.71 by analyzing the polarized Raman scattering spectra. The alignment of the rGO contributed to both the mechanical and dielectric properties of the cement paste. The flexural strength of the specimen with aligned rGO improved by 48% compared with that of the cement pastes with randomly distributed rGO. The dielectric constant at 100 Hz of the specimen with aligned rGO was increased by 271% compared with that of cement pastes with randomly distributed rGO. A modified rule of mixtures was proposed to predict their mechanical and dielectric properties. This study offers insight on the development of nanofiller-incorporated cement-based materials with enhanced mechanical and dielectric properties.

Phosphogypsum-based cementitious material (PBC) is acknowledged as a low-carbon green composite material. The addition of lime to modify PBC has been found to significantly enhance PBC utilization rate. This study investigates the effects of varying lime contents in PBC on mechanical properties, volume expansion, hydration products, micromorphology, and pore structure of modified Phosphogypsum (PS). The results demonstrate that lime effectively counteracts the retarding effect of water-soluble impurities in PS, thereby reducing setting time. Additionally, the 7 days and 28 days strength of PBC initially increases and then decreases with increasing lime content, with the 28 days compressive strength of B₀ (0.5%) reaching 48 MPa. A 0.5% lime-modified PS proves beneficial in promoting PBC hydration, reducing pore size, densifying the microstructure, and enhancing mechanical properties. Moreover, the volume expansion results highlight the significant influence of the alkaline environment on both the generation and distribution of ettringite, consequently impacting PBC expansion.

Interfacial adhesion between surface coating and cement paste under aggressive environment is the most key properties that responsible the effectiveness of coating on cement paste. The present work is dedicated to an in-depth investigation concerning the temperature influence on the interfacial adhesion degradation between rubber nano-coating and Calcium-Silicate-Hydrate (CSH) paste under harsh environments. Results indicate that a well-distributed fully rubber nano-coating on CSH maintains its impermeability within temperature range of 260–373K for pure water molecules and up to 420K for salty water solution. However, the nano-coated structure loses its impermeability at 380K and 440K in pure water and salty water solution, respectively. The interfacial adhesion between rubber and CSH surface decreases with increasing temperature under both conditions. In addition, the effectiveness of the rubber nano-coating surface weakens due to temperature rising inducing the breaking of the hardest interfacial interatomic cao-c = bonds in both conditions.