Book Chapters
Permanent URI for this collection
Browse
Browsing Book Chapters by browse.metadata.impactarea "Construction Materials"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Cradle-to-gate environmental life cycle assessment of limestone calcined clay cement (LC3)(Alive2Green, 2024-01) Dumani, Nozonke; Mapiravana, Joseph; De Jager, PetaThe manufacturing of cement contributes to approximately 5-7% of global anthropogenic carbon dioxide emissions, necessitating the need for reducing the environmental impact. Limestone Calcined Clay Cement (LC3) has emerged as a promising alternative to ordinary Portland cement (OPC), leveraging widely available resources like clay, limestone and gypsum to partially replace the carbon intensive Portland clinker. One ton of Portland cement is associated with about one (1) ton of CO2 . This study aimed to assess and compare the CO2 emissions of theoretical binary and LC3 cement types against 100% Ordinary Portland Cement (OPC). Considered were: OPC with 30% calcined clay replacement, and LC3, composed of 50% clinker, 30% calcined clay, 15% limestone, and 5% gypsum.Item Performance of geopolymer concrete subjected to mineral acid tests in static and dynamic conditions(52-69, 2024-01) Dlamini, Mandla N; Alexander, M; De Jager, PetaGeopolymer cements are an emerging alternative binder to Portland cements, characterised by an alumino-silicate polymer network nanostructure. These binders are purported to possess numerous beneficial properties such as acid resistance and a relatively low carbon footprint. This study sought to assess the performance of a fly ash-based geopolymer concrete developed at the CSIR, exposed to mineral acids (HCl and H2SO4) under static and dynamic exposure conditions. Portland cement and calcium aluminate cement concretes using calcareous aggregates (dolomite) were used as control specimens, while geopolymer cements were mixed with a range of calcareous and siliceous aggregates. The test results show that the resistance of geopolymer concretes exposed to hydrochloric acid in dynamic and static conditions is significantly higher than Portland cement and calcium aluminate cement concretes, where mass loss was used as a measure. The study also shows that the acid resistance of geopolymers can be further improved by combining them with siliceous aggregates instead of calcareous aggregates. Furthermore, a linear empirical relationship, between basicity (related to the major acidic and basic oxides established via XRF) and the rate of dissolution of concrete in acidic solutions was observed. Basicity was also related to preferential corrosion in concrete mixtures exposed to the dynamic HCl test, and it was found that the difference in the basicity of the paste and aggregate of concrete mixture was useful in determining the type and extent of preferential corrosion.Item Quantifying the environmental impacts of a sustainable concrete mix for a block paving system(Cape Town: Alive2Green, 2024-01) Dumani, Nozonke; Mokoena, Refiloe; Mgangira, MartinA sustainable concrete mix design, incorporating industrial by-products: fly ash and recycled plastic pellets, was developed, and optimized through laboratory performance-based testing trials. The primary objective of this investigation was to offer environmentally sustainable alternatives to conventional concrete mixes that can be used for concrete block paving and aligns with circular economy principles and fosters enhanced employment opportunities and poverty reduction. Following a laboratory investigation to optimise the quantities of fly ash and plastic pellets in the concrete mix, paving blocks were produced in the laboratory using the optimised mix. The blocks were also tested to ensure compliance with performance criteria stipulated in national specifications for concrete block paving. This chapter focusses on the comprehensive life cycle assessment (LCA) conducted to investigate the environmental impacts associated with the production of the optimised concrete mix design in comparison with two references mixes. All three mixes comprised varying quantities of cement, fly ash as a partial cement replacement, and plastic pellets as a partial substitute for sand. The analysis included concrete with 100% Portland limestone cement, concrete with 50% Portland limestone cement and 50% fly ash, and concrete with 50% Portland limestone cement, 50% fly ash, and plastic pellets. The study, limited to a cradle-to-gate analysis, utilized the life cycle assessment software tool SimaPro 8.1 with the Ecoinvent Database version 3. The life cycle inventory dataset for each material was compiled, and the CML-IA Baseline World 2000 method was employed to generate and report the results. The LCA study results demonstrated that adding fly ash as a cement substitution significantly reduced the environmental impacts of concrete mixes. However, the extent of this reduction depended on the type of allocation method used. Under no allocation and economic allocation scenarios, concrete mixes with fly ash exhibited lower environmental impacts than those without fly ash. Conversely, mass allocation scenarios indicated higher environmental impacts for concrete with added fly ash more than 35%. Additionally, it was noted that environmental impacts for fly ash concrete mixes with plastic pellets as a partial substitute for sand were marginally higher than those with fly ash concrete mixes using only sand.