Influence of supplementary cementitious materials in sustainability performance of concrete industry: A case study in Hong Kong

Abstract

Although the use of a few industrial by-products as supplementary cementitious materials (SCMs) is one of the most recognized solutions to produce more durable and sustainable concrete, cost-competitive supply of such materials is of great concern, especially for a resource-scarce city like Hong Kong. In addition, several factors including the mechanical performance, transport distance and allocation of upstream impacts, can offset the environmental gain of concretes produced with such by-products. Other potential material such as volcanic ash, can be an effective alternative of industrial SCMs. However, there is a need to comprehensively demonstrate how this material can enhance the sustainability performance of the concrete industry. In this study, the greenhouse gases (GHG) emissions of using volcanic ash is evaluated and compared with its counterparts such as fly ash and ground granulated blast furnace slag in concrete production using a lifecycle assessment (LCA) technique. Based on the bottom-up approach, an industry level evaluation on GHG emission saving due to the use of different SCMs is conducted. The results show that more than 80 % lower GHG emissions are associated with volcanic ash compared to other SCMs. For the same grade of concrete, volcanic ash can reduce up to 25 % and 19 % of total GHG emissions compared to ordinary Portland cement and SCM concretes, respectively (at the product level). Considering the assumptions described in this study, the results reveal that by substituting 10–50 % industrial SCMs with volcanic ash, 11–37 % more GHG emissions can be reduced from the concrete industry in Hong Kong (at the industry level). The analysis conducted in this study would help source alternative SCMs for further promotion of sustainability in the construction industry of Hong Kong, where majority of SCMs are sourced from different countries.