Variability of environmental impact of ready-mix concrete: a case study for Brazil

Abstract

Life Cycle Assessment is a powerful tool towards sustainable construction, but it often relies on average impact results, failing to identify the dispersion of environmental impact among construction product manufacturers. This work presents cradle-to-gate impact results for ready-mix concrete production, based on primary data provided by several plants in Brazil, and the associated variability among plants and in the upstream processes of cement and sand production. Four compressive strength classes are considered. Concrete, cement and aggregates inventories are modeled with Brazilian information and other upstream processes are based on ecoinvent. EN 15804 impact categories are assessed. The ranges between minimum and maximum impact values can be as large as 7.2 times the average impact result of the analyzed sample, which shows that the variability among manufacturers is high and decisions based on average impacts may be highly misleading. For some impact categories, the differences among concrete plants (mix design, cement type and operational conditions) represent the highest contribution for variability, while for others the dominant variation comes from upstream processes, especially clinker production. These results indicate a high potential for process improvement and that manufacturer selection based on environmental performance can be an effective strategy for sustainable construction.

The Environmental Profile of Clinker, Cement, and Concrete: A Life Cycle Perspective Study Based on Ecuadorian Data

“…Figure 5 shows a comparison of Global warming potential-GWP100 results between this research and previous results in the literature with compressive strengths of 20 to 70 MPa [49][50][51][52]54]. The study by Hossain et al [48] of concrete in China analyzes compressive strengths between 59 and 70 MPa.…”

“…The values of this study for characteristic compressive strengths between 21 and 50 MPa are 0.55-0.83 kg SO 2 -Eq/m 3 of ready-mixed concrete, lower than studies from Colombia, Peru, South Africa, Brazil, and Canada for the same compressive strengths. The value of TAP100 varies from 0.622 at 1.73 kg SO 2 -Eq/m 3 of ready-mixed concrete [50][51][52]54], due to low levels of SO 2 in flue gas from the production of clinker, due to the composition of fossil fuels and use of alternative fuels in kilns. This is reflected in the value chain of cementitious materials, such as concrete production, having lower TAP100 values than the literature reviewed.…”

“…The second process is transport, contributing between 3.72 and 20%; this result varies depending on the distance between the concrete plant and the cement factory. According to previous literature, characteristic compressive strengths between 21 to 50 MPa are 6.93 × 10 −6 to 9.2 × 10 −5 kg CFC −11 -Eq/m 3 of concrete ready-mixed [50][51][52]54]; in this research, those values are similar for characteristic compressive strengths between 21 and 50 MPa, which is 1.50 × 10 −5 to 2.23 × 10 −5 kg CFC −11 -Eq/m 3 of ready-mixed concrete.…”

“…Regarding ready-mixed concrete (RMX), studies from Europe and Asia have analyzed conventional concrete and concrete environmental improvements by adding waste, recycled components, using fly ash, slag, or combining these options [46][47][48][49], resulting in GWP reductions between 1 and 23% in similar, characteristic, compressive strength. For North America, South America, and South Africa, life cycle inventories [50][51][52] and LCA [53,54] for conventional concrete with characteristic compressive strengths produced results between 20 and 50 MPa.…”

Contextualizing embodied carbon emissions of concrete using mixture design parameters and performance metrics

“…This trend has been known and confirmed in numerous studies. 13,28,40,41 The industry-average concrete EPD from the National Ready-Mixed Concrete Association (NRMCA), for instance, indicates that Stage A1 of concrete production, namely raw material processing, is the most intense in terms of environmental impact. 42 A strong linear trend between cement content and GWP is additionally supported by the fact that a single dataset for cement was utilized in the LCAs for all mixtures, following the requirements of the current EPD program in the United States.…”