Search

• Using magnetized water leads to lower standard consistency and longer setting times of the mortar mixes. • Magnetized water significantly improved the mechanical and durability properties of the mortar mixes. • Replacing cement with higher contents of MWD leads to lower strengths and durability properties of the mortar mixes. • The addition of 10% MWD to the mortar mixes significantly improved their hardened and durability properties. In this research, the simultaneous effect of marble waste dust (MWD) and magnetized water (MW) on the fresh, hardened and durability properties of mortar mixes were investigated. A total of 10 mortar mixes using different cement replacement ratios of MWD (0%, 10%, 20%, 30 and 40%) with regular tap water (RTW) and MW were prepared and tested. The standard consistency and setting characteristics, dry density, compressive and tensile strengths, water absorption and resistance to the acid attack of specimens were examined. The results showed that the fresh, hardened and durability properties of mortar mixes were improved by using MW. The results also revealed that the mortar mixes with either RTW or MW and 10% MWD as cement replacement displayed the most improvement in the hardened and durability performance compared to other mixes. However, using higher amounts of MWD leads to a lower strength and durability performance of the mortar mixes due to more porous microstructure. [ABSTRACT FROM AUTHOR]

Energy consumption of buildings is at the forefront of the total energy consumption list, and its environmental impact is increasing, thus making construction industry as a key player in energy. A systematic and comprehensive life cycle perspective assessment of building energy is crucial for maintaining project sustainability. Building energy analysis from life cycle perspective has been increasingly favoured by scholars. However, the links and contents of many literatures have not been summarized and lacking systematic literature research. This review-based research used a holistic analysis approach as the framework. Bibliometrics method in the first stage was used to select 255 papers published during 2009–2019 related to life cycle energy of buildings (LCE-B). Scientometric analysis in the second stage was adopted for identifying the journal sources, scholars, regions and articles that have been fruitful and influential in LCE-B research, and keywords analysis was proposed to preliminarily explore the research topics in the domain (e.g. analysis of optimisation). Results showed that BIM and multi-objective optimisation have become research hotspots recently. An in-depth qualitative discussion in the last stage was conducted to achieve three main objectives: (1) summarise mainstream research topics (e.g. calculation and parameter determination of embodied energy); (2) discuss existing research gaps (e.g. the spatial heterogeneity of embodied energy); and (3) identify future research directions. This study provides a comprehensive knowledge framework combined with philosophical theories that links current research fields with future research trends, providing researchers with multi-disciplinary guidance to gain insight into the latest research on LCE-B. • A three-stage holistic method consisting of bibliometric search, scientometric and qualitative analysis is used to review. • Visualisation of linkages among journals, authors, keywords, and regions of the LCE-B literature. • Classification of the existing LCE-B research topics based on a four-fold philosophical theory. • Summaries of the gaps in LCE-B research domain. • Framework for linking current research status to future research trends. [ABSTRACT FROM AUTHOR]

Information technologies are increasingly adopted across the world to promote the efficiency of construction and demolition (C&D) waste management and alleviate the environmental and social effects of waste disposal. In addressing management issues of C&D waste by information technologies, several studies have been published by international peer-reviewing journals related to construction management over the past decades. However, a systematic summary on the research development in information technologies used in C&D waste management discipline is lacking. Therefore, this study examines the latest research situation in this discipline by analysing published construction management research in peer-reviewing journals in the period of 2000–2019, and 57 related papers are collected by filtering. The characteristics of the collected papers are classified according to the following criteria: application scenarios in C&D waste management and different technologies. Eight categories of present advanced technologies used in C&D waste management are identified, namely, building information modelling, geographic information system, big data, radio frequency identification, image recognition technology, image analysis, global positioning system and barcode technology. A critical analysis of the identified technologies is conducted in accordance with their characteristics and applications. This study also performs the scientometric analysis of the collected papers by VOSviewer. The limitations of information technologies and the recommendations for potential future research directions are presented on the basis of the analytical review. [ABSTRACT FROM AUTHOR]

Construction and demolition waste (C&DW) as a direct consequence of rapid urbanization is increasing around the world. C&DW generation has been identified as one of the major issues in the construction industry due to its direct impacts on the environment as well as the efficiency of construction industry. It is estimated that an overall of 35% of C&DW is landfilled globally, therefore, effective C&DW management is crucial in order to minimize detrimental impacts of C&DW for the environment. As the industry cannot continue to practice if the resources on which it depends are depleted, C&DW management needs to be implemented in an effective way. Despite considering many well-developed strategies for C&DW management, the outputs of the implementation of these strategies is far from optimum. The main reason of this inefficiency is due to inadequate understanding of principal factors, which play a vital role in C&DW management. Therefore, the aim of this research is to critically scrutinize the concept of C&DW and its managerial issues in a systematic way to come up with the effective C&DW management. In order to achieve this aim, and based on a systematic review of 97 research papers relevant to effective C&DW management, this research considers two main categories as fundamental factors affecting C&DW management namely, C&DW management hierarchy including reduce, reuse, and recycle strategies, and effective C&DW management contributing factors, including C&DW management from sustainability perspective, C&DW stakeholders' attitudes, C&DW project life cycle, and C&DW management tools. Subsequently, these factors are discussed in detail and findings are scrutinized in order to clarify current and future practices of C&DW management from both academic and practical perspectives. [ABSTRACT FROM AUTHOR]

• Hydration of OPC is accelerated by S-water, due to the chloride promoting the precipitation. • Hydration rate of C 3 S is greatly affected by the concentration of chloride in solution. • Compressive strength of OPC mortar increased rapidly by the rapid hydration in S-water. • Chloride in S-water promoted the hydration reaction and affects hydrate assemblage. • In later age, mass of C-S-H in OPC paste with S-water is 10% lower than that with D-water. Using seawater for concrete manufacturing promisingly provides significant economical and environmental benefits. In this study, ordinary Portland cement (OPC) hydration in distilled water and seawater and the corresponding evolution of solid phases was investigated by heat evolution, hydrated phase, hydration kinetics, and microstructure characterization. The results show that seawater can promote the early hydration of tricalcium silicate (C 3 S) during the hydration acceleration period. The hydrated phase assemblage was affected by the dissolved ions in seawater. Friedel's salt was detected as a specific hydration phase in seawater, which was formed by chemical combination between the aluminate ferrite monosulfate (AFm) phase and chloride ions. The monocarboaluminate can be converted into a stable phase as Friedel's salt in the seawater, due to the reaction with chloride ions. Furthermore, the ettringite becomes more stable when coexists with Friedel's salt than that with monocarboaluminate, and thus ettringite formed in seawater remains 67% higher than that formed in distilled water at the later curing age. Moreover, additional unhydrated cement and less amorphous calcium silicate hydrate (C-S-H) were formed in seawater, which might be responsible for the slightly lower compressive strength of cement mortar prepared by seawater and sea sand. A modeled evolution of the solid phase and pore solution have been established, which agrees well with the characteristics of the dissolution of mineral phase, precipitation of hydration products and changes of pore solution. The related results can provide an insight into the applications of seawater and sea sand concrete for marine infrastructures. [ABSTRACT FROM AUTHOR]

• The interaction of OPC and CSA at early age hydration results in rapid-hardening structure. • CSA prolongs the induction period of hydration, due to the effect of aluminum phase. • The CSA can reduce frost damage, because of the high early age strength to resist frost damage. • Calcium nitrite can prolong duration of hydration and increase strength in sub-zero condition. This study investigated the hydration mechanism and mechanical properties of ordinary Portland cement (OPC) blended with calcium sulfoaluminate (CSA) cement. Heat evolution, hydration products, pore size distribution, and microstructure were investigated for OPC-CSA blends concrete with different contents of CSA cement. Macroscopic properties, such as internal temperature, dynamic elastic modulus, and compressive strength, are also studied through concrete subjected to early frost conditions. The results show that the OPC-CSA blended cement displayed a higher early strength and exhibited enhanced resistance to the early frost damage compared to OPC. The OPC-CSA blended cement also exhibits a higher hydration rate and a larger amount of heat of hydration than that in the OPC at the early stage. The increased heat of hydration can effectively prolong the hydration duration at sub-zero temperatures. However, incorporating CSA delayed the hydration of C 3 S at the late stage, thus affecting the development of compressive strength and dynamic elastic modulus. On the other hand, the hardened blended cement exhibited an higher porosity, which was corresponding to the increasing proportion of macropores (diameter over 1000 nm). If concrete directly is suffered from early frost after casting, blended cement with 20% of CSA can effectively reduce strength loss from frost damage by 100% at −5 °C, and that from frost damage by 80% at −15 °C respectively. Furthermore, when the calcium nitrite is incorporated as the antifreeze admixture with OPC-CSA blended concrete, the early stage frost resistance of concrete infrastructures can be significantly improved. [ABSTRACT FROM AUTHOR]

New analytical wake models are derived from the soft computing technique, called Genetic Programming (GP) to predict wake velocities and turbulence intensity. The design of the wind farm's appropriate layout is essential for minimizing cost and maximizing the wind farm power generation. This needs a precise wake velocity model to simulate the wake effect of the wind farm within a limited time duration. Furthermore, prediction of turbulence in the wake due to ambient flow and rotor-generated is extremely crucial owing to its contribution to fatigue loads and structural failures of the downstream wind turbines. This article discusses the classical to the recent analytical wake velocity and turbulence intensity models derived based on hard computing techniques in detail and their limitations. The significant constraints are the consideration of uniform inflow without integrating Atmospheric Boundary Layer (ABL) impacts for the forecast of wake velocity and estimation of single value of turbulence intensity while it radially varies at distinct downstream distances of the wind turbine. Eventually, these constraints are tackled and new analytical models for wake velocity and turbulence intensity profiles are formulated for both uniform and ABL inflows. The existing and proposed models are compared with the previous NREL Phase VI wind turbine CFD study for uniform and ABL inflows and it was observed that the proposed models are precise. • Adoption of modern artificial intelligence-based method to derive empirical relationships. • Extensive details about ancient classic to recent analytical models of wake velocity. • Discussion on the key factors to be considered in modelling the wake turbulence intensity. • Expression for a radially varying profile of turbulence intensity in contrast to current models' single value estimation. • Integration of impact of wind velocity varying with altitude owing to ABL and terrain roughness length in the proposed analytical models. [ABSTRACT FROM AUTHOR]

Carbon capture and storage is becoming increasingly feasible. This study provides a novel quantitative analysis of the global CO 2 mitigation potential through accelerated carbon sequestration in concrete debris separated from construction and demolition waste. We consider the economic and environmental tradeoff. Based on data collection from 14 large regions and countries, we created a method to estimate and project the generation of concrete debris, recycling and carbonation rates, and cost. The overall concrete debris generation was more than 3.0 (± 0.6) billion tonnes (Bt) in 2017 worldwide, mainly from emerging countries such as China and India. This debris has the potential to mitigate 62.5 (± 8.9) million tonnes (Mt) CO 2 under optimal carbonation conditions determined by pressure, temperature, humidity, time, CO 2 concentration, and debris size. Our scenario analysis reveals that the global cumulative carbonation of concrete debris could be as high as 3.0 Bt CO 2 between 2018 and 2035, which equals approximately one third of the total CO 2 emissions from fuel combustion of China in 2016. In our scenarios, the economic benefits of storing CO 2 by concrete debris are mainly from recycled concrete aggregate rather than carbon sequestration, but also consider the current carbon price in major carbon markets. These findings highlight an effective and practical approach to reuse concrete debris as well as enhancing economic benefits. This approach could be helpful to better manage the fast-growing concrete debris and need for carbon mitigation as well as bridging the gap of CO 2 sequestration by concrete debris between research and application. • The tradeoff between environmental and economic benefits has been determined. • 62.5 Mt CO 2 could have been sequestered with profit of 3.3 billion USD in 2017. • Cumulative CO 2 mitigation potential could be as high as 3.0 Bt from 2018 to 2035. [ABSTRACT FROM AUTHOR]