Effects of alkali-activated slag binder and shape-stabilized phase change material on thermal and mechanical characteristics and environmental impact of cementitious composite for building envelopes

Abstract

A tremendous quantity of energy has been used in the building and a huge amount of CO2 emitted to maintain comfortable indoor temperatures. In order to lower existing level of CO2 emissions, using eco-friendly alternative binders instead of ordinary Portland cement (OPC) and improving buildings’ energy efficiency are indispensable. The thermal characteristics of cementitious composite have been improved by the use of phase change materials (PCMs) via its latent heat capacity. PCMs can also be incorporated with alkali-activated binding materials of industrial by-products such as alkali-activated slag (AAS), which can result in an efficient carbon reduction compared to the use of ordinary Portland cement (OPC) as a binder. To better comprehend the practical feasibility of AAS in PCM-incorporated composites as an alternative building component, it is necessary to study the one-part AAS system holistically by assessing its fundamental material characteristics, environmental impact (CO2 emission), and energy efficiency. This work uses an experimental-computational method and a case study to evaluate the effects of one-part AAS binder and shape-stabilized PCMs on thermal and mechanical properties and environmental impact. The experimental results demonstrate that AAS binder can reduce thermal conductivity by up to approximately 20% compared to the OPC case. Incorporating thermal energy storage aggregate (TESA) in the AAS binder can further decrease the thermal conductivity. In addition, the AAS-based composite can significantly reduce CO2 emissions by more than 10% than the OPC-based case due to the improved thermal properties and the consequent reduction in carbon footprint from raw materials and annual energy consumption. The results of this study infer the feasibility of AAS binder and TESA as eco-friendly, energy-saving cementitious composites for building envelopes.