Selection of low impact concrete mixtures based on life-cycle assessment mixtures

M G Silva,M R M Saade,V Gomes

doi:10.1590/s1983-41952018000600010

Abstract

Abstract Over the past decades, extensive research has been carried out to reduce the environmental impacts associated with the cement and concrete production. Life-cycle assessment (LCA) enables the quantification of the environmental loads and offers a useful perspective to scientifically support such studies. In this paper, we demonstrate LCA’s contribution to the selection of low environmental impact concretes, using breakwater coreloc components as a case study. A detailed experimental study was designed for the selection of an alkali activator for blast furnace slag (bfs) to produce concrete suitable for breakwater structures; for the evaluation of concrete properties and for the performance assessment of full scale elements in the field, as well as in the laboratory. Sodium silicate-activated bfs concrete mixtures achieved the best results in terms of performance requirements. Our cradle-to-gate life-cycle assessments showed that, though this chemical activator indeed produces lower global warming potential mixtures than the reference portland CP V-ARI concrete, it induces relevant impacts in several environmental categories. Such information is critical when selecting and optimizing low-impact concrete mixture design, and would not be detected in typical experimental studies that are exclusively guided by compliance with performance requirements.

Highlights

Portland cement contributes with 74 to 81% of concrete CO2 emissions [1]
A detailed experimental study was designed to select an alkaline activator for bfs concrete adequate to this application, and to assess physical, mechanical and durability properties, based on laboratory tests of specimens produced with activated blast furnace slag (AAbfs) binders
Among the alternatives to reduce the environmental impacts of cements and concretes, especially those related to CO2 emissions, the use of mineral admixtures as clinker replacement and the development of alkali-activated binders have attracted research in various parts of Brazil and the world

Summary

Introduction

Portland cement contributes with 74 to 81% of concrete CO2 emissions [1]. On its turn, portland clinker is responsible for approximately 90% of cement’s CO2 emissions, due to limestone decarbonation and intensive fossil fuel use in the kiln [2][3]. The study concluded that in the 20 to 30 years, two approaches can contribute to significantly reduce cement and concrete production and use-related emissions: increased proportion of mineral admixtures as partial clinker replacement in portland cement; and more efficient use of clinker in mortars and concretes [6]. Scrivener et al (2016) [6] argue that the contribution of such binders to CO2 emission mitigation depends, first, on the availability of the material to be activated – like fly ash, calcined clay and bfs, whose use as portland cement (mineral admixture) replacement is much simpler – and, on the other hand, on technologies that produce less cost-, energy- and emission-intensive alkaline activators. This paper demonstrates how life cycle assessment can complement the traditional performance-oriented approach and provide essential environmental information for selecting low impact concrete mixtures

Methods

Results

Conclusion