Alexander J. Moseson

Bio: Alexander J. Moseson is an academic researcher from Drexel University. The author has contributed to research in topics: Life-cycle assessment. The author has an hindex of 1, co-authored 1 publications receiving 25 citations. Previous affiliations of Alexander J. Moseson include Purdue University.

Effects of composition and transportation logistics on environmental, energy and cost metrics for the production of alternative cementitious binders

Abstract: The production of cement, the primary ingredient in concrete, is responsible for 5–10% of anthropogenic GHG emissions. Numerous studies have investigated ordinary portland cement (OPC) alternatives with the goal of reducing GHG emissions. This life cycle assessment (LCA) adds transportation as a focus of the assessment, in addition to the process steps from cradle to the gate of finished cementitious product. GHG emissions and cost are assessed for five cement types with comparable performance (1) OPC; (2) blended OPC with slag (SC); (3) blended OPC with fly ash (FAC); (4) metakaolin-based geopolymer (MKG); and (5) high volume limestone alkali-activated slag cements (HLAASCs). Transportation logistics are known to be critical for the cement industry, and this holds true for alternative cements. The influence of feedstock source location and transport mode within the supply chain significantly affect both environmental impacts (up to 80% of GHG emissions) and production cost (up to 65%), and should thus be a major consideration. All OPC alternatives reduce GHG emissions, even at the least beneficial points of their ranges. HLAASC reduces GHG emissions and energy consumption in all cases studied, by up to 95% and 83%. SC and FAC have comparable reductions in GHG emissions and energy, and their ranges overlap. MKG reduces GHG emissions but not energy input for the cases studied, however the energy demand may be closer to the other binders studied where the mineral is available and from low grade sources.

Life cycle assessment of geopolymer concrete

Abstract: The Life Cycle Assessment (LCA) of a Geopolymer Concrete (GC) was elaborated after scaling up the Life Cycle Inventory (LCI) from laboratory scale to industrial scale. The most relevant raw materials and processes contributing to its environmental performance were identified. Besides, the influence in the environmental impacts of both, the electricity generation mix considered (2012 and 2018 energy mix for Ecuador), and the source of alkali activators (produced in Ecuador and imported from Europe), was demonstrated. The production of sodium hydroxide is the most relevant process in all life cycle impact categories. An energy mix with a higher contribution of hydroelectricity (2018 energy mix: 85% hydroelectricity) entails favorable results. The differences between locally produced and imported sodium hydroxide are the energy mix considered (Ecuadorian vs. average European), and the type of sodium chloride used as raw material (obtained through seawater evaporation in Ecuador vs. solution and rock mining in Europe). GC entails an environmental performance advantage compared to a conventional concrete (CC) if the following two conditions are applied: sodium hydroxide is produced using local solar salt, and the electricity mix is the expected energy mix for 2018 in Ecuador. Under this condition, Global Warming Potential (GWP) characterization for GC is 64% lower than CC.

Geopolymers in construction - recent developments

Abstract: Geopolymers are inorganic materials that result from the alkali activation of aluminosilicates. The aluminosilicates source materials can either occur naturally (e.g. kaolin, metakaolin, rice husk ash, volcanic rock powders) or are produced by industrial processes (e.g. fly-ash, blast furnace slag). While the potential application of geopolymers as construction materials (e.g. concrete manufacturing and soil stabilization) has been studied in the past, their widespread use has been limited. This is mainly because the technology is still relatively new and research in this field is still emerging. However, the use of geopolymers in lieu of conventional binders (e.g. cement and lime) has substantial environmental advantages particularly in terms of the energy expended for their production and greenhouse gas emissions. The current trend to enhance sustainability practices in the construction industry has recently driven research in this area. This paper aims to offer a comprehensive overview of past studies on geopolymers synthesised from various precursors, the factors affecting geopolymerisation process, their microstructural characteristics as well as mechanical, chemical, thermal and environmental properties of geopolymers. Further, recent developments associated with the use of geopolymers as construction materials in civil engineering applications have also been discussed. Research findings show that geopolymers can achieve comparable or superior performance to conventional binders and/or concrete in terms of shear strength and durability but with a reduced environmental footprint.

Rheological Properties of Cemented Paste Backfill with Alkali-Activated Slag

Abstract: This study investigates the time-dependent rheological behavior of cemented paste backfill (CPB) that contains alkali-activated slag (AAS) as a binder. Rheological measurements with the controlled shear strain method have been conducted on various AAS-CPB samples with different binder contents, silicate modulus (Ms: SiO2/Na2O molar ratio), fineness of slag and curing temperatures. The Bingham model afforded a good fit to all of the CPB mixtures. The results show that AAS-CPB samples with high binder content demonstrate a more rapid rate of gain in yield stress and plastic viscosity. AAS-CPB also shows better rheological behavior than CPB samples made up of ordinary Portland cement (OPC) at identical binder contents. It is found that increasing Ms yields lower yield stress and plastic viscosity and the rate of gain in these parameters. Increases in the fineness of slag has an adverse effect on rheological behavior of AAS-CPB. The rheological behavior of both OPC- and AAS-CPB samples is also strongly enhanced at higher temperatures. AAS-CPB samples are found to be more sensitive to the variation in curing temperatures than OPC-CPB samples with respect to the rate of gain in yield stress and plastic viscosity. As a result, the findings of this study will contribute to well understand the flow and transport features of fresh CPB mixtures under various conditions and their changes with time.

Preparation of geopolymer concrete using Egyptian kaolin clay and the study of its environmental effects and economic cost

Abstract: Concrete is the basic building material in the world, and cement is the main material used in the production of concrete. However, there is an urgent need to reduce the consumption of cement, where cement production leads to 5–8% of global emissions of carbon dioxide. Geopolymer concrete is an innovative building material produced by alkaline activation of pozzolanic materials such as fly ash, granulated blast furnace slag, and kaolin clay. Geopolymers are widely used in the production of geopolymer concrete due to their ability to reduce carbon dioxide emissions and reduce high energy consumption. During the present study, the environmental impact of two strength grades (30 MPa and 40 MPa) of metakaolin geopolymer concrete (GPC) was evaluated to study its applicability in the construction sector. The kaolin clay extracted from the Aswan quarries was activated by a mixture of sodium hydroxide and sodium silicate solution. To introduce geopolymer concrete in the Egyptian industry sector, its environmental performance, together with its technical performance, should be competitive to the cement concrete used mainly for the time being. The cost of this new concrete system should also be evaluated. The environmental impact of GPC was evaluated and compared with cement concrete using life cycle assessment analysis and IMPACT 2002+ methodology. The cost of production was calculated for 1 m3 of geopolymer concrete and conventional cement concrete. Metakaolin geopolymer concrete achieved a high compressive strength of ~ 56 MPa, splitting tensile strength of 24 MPa, and modulus of elasticity of 8.5 MPa. The corrosion inhibition of metakaolin geopolymer concrete was ~ 80% better than that of conventional cement concrete. Geopolymer concrete achieved a reduction in global warming potential by 61% and improved the human health category by 9.4%. However, due to the heavy burdens of sodium silicate, the geopolymer concrete negatively affected the quality of the ecosystem by 68% and showed a slightly higher impact than cement concrete on the resource damage category for low strength grade of 30 MPa. The high cost of the basic ingredients of the geopolymer resulted in a high production cost of geopolymer concrete (~ 92 US$) that was three times that of cement concrete (~ 31 US$). Based on the environmental results, geopolymer concrete based on locally available metakaolin clay can be applied in the construction sector as a green alternative material for cement concrete.

Comparative study on the effect of fiber type and content on the performance of one-part alkali-activated mortar

Abstract: One-part alkali-activated material (AAMs) have proven to be an environment-friendly and sustainable alternative for the Ordinary Portland Cement (OPC) whose production is associated with high carbon footprint. Alkali activated materials have good strength and durability properties. However, they exhibit relatively low flexure strength, tensile strength, strain capacity and brittleness, which in some cases limits their application. In this article, the behavior one-part alkali-activated fly ash slag-based mortar reinforced with Micro-steel, PVA and Basalt Fiber is investigated. The effect of fiber type and content on one-part alkali-activated composites in terms of slump flow, water absorption, compressive strength, flexure strength, splitting tensile strength, load deflection curve under flexure and splitting tensile strength was evaluated. The results depicted an improvement in the mechanical performance of the one-part alkali-activated mortar with inclusion of all three types of fibers. Micro-steel fibers were most beneficial in improving displacement capacity under tensile load while PVA fibers addition significantly improved the strength properties of the mix. Basalt fibers also yielded positive results in terms of mechanical properties and showed potential to be a good enhancer of mechanical properties in one-part alkali-activated composites.