Journal of Building Engineering xxx (xxxx) xxx Please cite this article as: Shuen Simon Sui Jiang, Journal of Building Engineering, https://doi.org/10.1016/j.jobe.2020.101859 Available online 11 October 2020 2352-7102/© 2020 Elsevier Ltd. All rights reserved. Hygrothermal and mechanical performance of sustainable concrete: A simulated comparison of mix designs Shuen Simon Sui Jiang , Jian Li Hao * , Janaynna Nayami De Carli Department of Civil Engineering, Xi’an Jiaotong-Liverpool University Suzhou, 215123, China A R T I C L E INFO Keywords: Hygrothermal performance WUFI® plus Building energy Sustainable concrete Simulation ABSTRACT Given that concrete is the second most-consumed resource in the world after water, and that most buildings are constructed in whole or in part of this cement composite, it is important to understand the impact that this material has on energy performance. In order to evaluate the hygrothermal and mechanical performance of concrete when used in buildings, this study compared different sustainable concrete mix designs. Properties such as density, porosity, specifc heat capacity, and thermal conductivity of four different mixes were analyzed through hygrothermal simulations using WUFI® Plus software. Test results reveal that the hygrothermal per- formance of concrete can be enhanced without diminishing the value of its mechanical properties, while reducing CO 2 emissions at the same time. It was also found that the use of recycled aggregates coupled with supplementary cementitious materials can give a high strength concrete with lower environmental impacts in terms of energy consumption and carbon footprint. 1. Introduction It is estimated that the building sector accounts for 40% of the energy used globally [1], and that 60% of the energy consumed in buildings corresponds to heating and cooling of spaces, where heating has the greatest impact on energy consumption [2,3]. For this reason, signif- cant efforts have been made and several strategies implemented to decrease the use of energy intended for heating and cooling. As these strategies include designing buildings to be more isolated and air-tight in order to reduce heating energy loses, it is therefore important to consider the challenges involved in removing the consequential increased moisture inside buildings [4]. Since the levels of humidity inside a building can have a signifcant impact on the consumption of energy, especially when the relative hu- midity levels are out of the desired range, it is important to consider the infuence of moisture when evaluating the thermal and energy perfor- mance of a building. Methods and technologies to reduce energy con- sumption caused by undesirable indoor humidity have been investigated by applying novel control systems and strategies to heating, ventilation and air-conditioning (HVAC) systems, and by using innovative con- struction or insulation materials [5–7]. However, concrete is still the most widely used construction material globally, and because of its mechanical and cost-effective characteristics is unlikely to be fully replaced by other materials in the foreseeable future. It is therefore desirable to improve the capability of concrete to reduce energy consumption. Although the hygrothermal performance of concrete has a direct effect on a building’s indoor humidity level, the hygrothermal in- teractions are generally ignored or simplifed most of the time when the energy simulation of a building is carried out [8]. Moon et al. [9] found that energy consumption can increase by up to 4.4% when the effects of moisture are considered and that ignoring moisture transfer contributes to a signifcant error in the measurement of indoor humidity, which in turn greatly affects the energy count. Le et al. [10] studied the hygrothermal performance of a hemp concrete building envelope by employing a numerical heat and mass transfer model. Data from their lab experiments showed that hemp concrete produces better indoor relative humidity and reduces 45% of energy consumption compared to cellular concrete. Based on the outcome of the aforementioned study, Moujalled et al. [11] investigated the hygrothermal performance of hemp lime concrete with respect to relative humidity and temperature but not consider energy savings. Due to the sustainable benefts of concrete admixture, several re- searchers have considered applying concrete products with admixture and other materials to strengthen the energy performance of buildings [12–15]. Bagari´ c et al. [14] used recycled concrete aggregate (RCA) * Corresponding author. E-mail addresses: s.sui18@student.xjtlu.edu.cn (S.S. Sui Jiang), jianli.hao@xjtlu.edu.cn (J.L. Hao). Contents lists available at ScienceDirect Journal of Building Engineering journal homepage: http://www.elsevier.com/locate/jobe https://doi.org/10.1016/j.jobe.2020.101859 Received 13 November 2019; Received in revised form 14 August 2020; Accepted 29 September 2020