Life cycle assessment (LCA) of benchmark concrete products in Australia

Abstract

A comprehensive Life Cycle Assessment (LCA) study was performed to investigate the environmental impacts associated with the manufacture of fourteen benchmark concrete products in Australia including concrete, mortar, grout and render. This study provides datasets for the reference cementitious construction materials which aid the construction industry to evaluate the environmental impact of construction more consistently. In addition, an appropriate formulation for the manual calculation of the environmental impacts of customised concrete mix-designs was investigated. Benchmark products were defined based on the average mix-design currently applied by the concrete industry and in compliance with the Australian cement and concrete standards. Normal and special grade concretes with strength in the range of 20 MPa to 100 MPa, mortars type M1 to M4, as well as grout and render were defined. The cradle-to-gate LCA model for each product was defined based on the ISO Standards 14040 and 14044 frameworks and in conjunction with modules A1 to A4 of European Standard EN 15804. GaBi software program version 7.2.2 was applied to ensure consistency and reproducibility of the environmental impacts for each product. The major impact classes were determined and discussed using Life Cycle Impact Assessment (LCIA) CML 2001 classification. Results showed that in all cases cement had the highest contribution to the impacts of concrete products. Using less cement in concrete products either by substitution of it with supplementary cementitious products or manufacturing cement with increased mineral additions has the potential to reduce environmental impacts. It was found that the Global Warming Potential (kg CO2-Eq per cubic metre) of the products ranged from 209 to 521 kg. Other regional environmental impacts, such as acidification, ozone layer depletion, and eutrophication, were also investigated and reported for each product. It was found that acidification was in the range of 0.670 to 1.609 kg SO2-Eq, and eutrophication was in the range of 0.108 to 0.259 kg Phosphate-Eq per cubic metre of concrete products in Australia. Establishing the industry reference point for cementitious products supports sustainability in production and enables tracking of future changes in the emissions of cementitious construction materials to ensure that concrete products are the responsible choice for construction. The decrease of cement clinker content through increasing mineral (limestone) addition is strongly suggested. In addition, the reported method for approximating environmental impacts of other concretes with customised mix-designs was found accurate and applicable.