A proposed performance based approach for life cycle assessment of reinforced blended cement concrete

Abstract

The use of supplementary cementitious materials (e.g. fly ash and ground granulated blast furnace slag) as a partial replacement of ordinary Portland cement (OPC) in blended cement (BC) concrete has been established in recent years. However, an optimum mix design of BC concrete should not only achieve the targeted mechanical properties but also aim at minimizing the cost as well as environmental impacts. The first step towards an accurate estimate of BC concrete's environmental impacts is to define an indicative functional unit. Unfortunately, most of the research that uses life cycle assessment (LCA) to compare OPC and BC concrete, selects a simple functional unit without taking into consideration the difference in mechanical properties and durability characteristics. Although several efforts were found integrating the durability characteristics in the environmental impact assessment over the whole life cycle, no consensus was found. In this study, a novel approach to quantifying the environmental impact of BC concrete compared to OPC concrete as a part of a decision making process on the type and mixing proportions of concrete to minimize its environmental impact. Using LCA, the method proposes that performance based parameters are defined: a targeted compressive strength and service life. Predictions should be made of these parameters based on generic user-input data like type of BC, water/binder ratios, binder content and OPC replacement rates. The comparative environmental impact is then quantified accordingly. It is believed that this novel approach allows the user to accurately select and proportion a blended cement concrete mix with the objective of minimizing its environmental impact.

A review of the efficiency of self-healing concrete technologies for durable and sustainable concrete under realistic conditions

“…System boundaries, as summarized in Figure 14, could be: (i) cradle-to-gate (referring to the production process), (ii) cradle-to-grave (including, besides the 'production phase' also the 'use' and 'end-of-life' stages) or, better, but not yet investigated for self-healing concrete (iii) cradle-to-cradle (which includes 'production', 'use', 'end of life' and 'recycling of the waste' phases) [371,372]. Wu et al [373] warned to exclude 'use' and 'end of life' stages according to the ISO 24067 standard only if they affect LCA results by less than 1%.…”

A Systematic Review of the Discrepancies in Life Cycle Assessments of Green Concrete

“…Not capping the performance nor the durability of the concrete being studied, though it maximizes the sustainability potential according to Muller et al [72], impinges upon the performance base specifications of the concrete. Instead, performance-based specifications similar to those in the framework proposed by Hafez et al [55] should be adopted. Finally, according to Sagastume-Gutiérrez et al [57], the comparison between the environmental impacts of two construction materials can be reliable, only after considering the combined effects of mechanical and durability characteristics.…”

“…First, goal and scope definition involves outlining the system boundary, the functional unit (FU) selection and any assumptions and/or limitations that need to be considered. A system boundary of a concrete product could be cradle-to-gate, which means including all processes and emissions until the production of its different constituents, or cradle-to-grave which includes the "Use" and "End-of-Life" phases as per Figure 2 [55]. A Cradle-to-Cradle LCA scope is that which assumes that all waste generated will be recycled in the future [23].…”

A whole life cycle performance-based ECOnomic and ECOlogical assessment framework (ECO2) for concrete sustainability

“…The environmental enhancements to Green concrete mixes could be, on the downside, associated with deterioration in the functional aspects and an increase in cost of concrete [19]. Sustainability, in general, is a multi-faceted notion that outlines the nature and impact of human activity on the current and future means of life [20].…”