Abstract
Cement manufacture contributes about 5–7% of the global carbon dioxide emission. The fastest short-term remedy is to replace parts of ordinary Portland cement (OPC) in concrete with supplementary cementitious materials (SCMs) to reduce CO2 emissions. Calcined clay and limestone filler have proven to be potential substitutes to good quality SCMs such as fly ash and slag because of their abundance, low cost, and potential reactivity to calcium hydroxide to form calcium silicate hydrates (C-S-H) which are responsible for the strength and other mechanical properties of concrete. A life cycle assessment (LCA) to evaluate the environmental impact of mortar with calcined clay and limestone filler in reinforced concrete (RC) column retrofitting is carried out using data from a multi-purpose complex project in Rizal province in the Philippines. A total of four retrofitting methods are evaluated based on two retrofitting techniques (RC column jacketing and steel jacketing) with two material alternatives (pure OPC-based mortar and mortar with partial replacements). Results show that RC column jacketing using patched mortar with partial replacement of calcined clay and limestone fillers is the least environmentally damaging retrofit option. The use of these SCMs resulted in a 4–7% decrease in global warming potential and a 2–4% decrease in fine particulate matter formation. Meanwhile, RC column jacketing decreased the effect on human carcinogenic toxicity by 75% compared to steel jacketing.
Highlights
This paper primarily investigates the environmental impact of mortar with calcined clay and limestone filler as supplementary cementitious materials (SCMs) and compares it with ordinary Portland cement (OPC)-based mortar as applied in reinforced concrete (RC) column retrofit
Four retrofitting alternatives are considered: Method 1A—RC column jacketing with the use of mortar with ordinary Portland cement (OPC), Method 1B—RC column jacketing utilizing mortar with partial replacement of calcined clay and limestone filler, Method 2A—Steel jacketing with the use of OPC-based mortar, and Method 2B—Steel jacketing utilizing mortar with partial replacement of calcined clay and limestone filler
Results of the life cycle assessment (LCA) process network indicate that steel production constitutes the greatest environmental impact compared to Portland cement production, calcined clay, limestone filler, fine aggregates, and other energy resources such as electricity and diesel
Summary
There has been a widespread drive in the building industry to adopt more sustainable techniques [1]. This widespread adoption of sustainable practices is a result of climate change and the environmental implications of development [2]. While the UN’s sustainable development goals (SDGs) continue to emphasize the growth element in its interpretation of sustainable development, achieving such goals in the construction industry remains difficult [3]. One possible reason is the huge volume of materials used in the construction of the built environment especially on a global scale. It is estimated that about 40% of the global materials are accounted for by the construction industry [4]. In the manufacture of Portland cement alone, it is projected that the yearly global production is
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