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The construction industry is one of the main sources of greenhouse gas emissions, and portland cement production is responsible for approximately 8% of anthropogenic CO2 emissions. Microbially induced calcium precipitation (MICP) has the potential to partially replace cement or modify the properties of materials that would otherwise not find use in construction, for example, in concrete recycling. MICP might be an environmentally friendly method to improve the properties of recycled aggregates and form conglomerates from the finest fractions. In this paper, factors influencing MICP's ability to solidify recycled concrete fines are thoroughly investigated. Calcium carbonate precipitate crystals produced by the bacterium Sporosarcina pasteurii were analyzed using scanning electron microscopy and energy dispersive spectroscopy. [ABSTRACT FROM AUTHOR]

Buildings consume over half of annual energy supply as embodied and operating energy in their construction and operation releasing harmful emissions to the atmosphere. Over 90% of the embodied energy is attributed to construction materials used in building structure, envelope, and interiors that must be reduced to minimize material use. Concrete is one of the major materials that contributes significantly to the energy and carbon footprint of buildings, as it is responsible for 5-9% of global carbon emission. Because most of the concrete use in the building sector occurs in building structures, assessing how building design parameters influence its environmental sustainability is important. One of the design parameters that impact the sustainability of buildings is the aspect ratio, which is defined as the ratio of horizontal to vertical surface area of a building. A building with the same floor area can be designed horizontally or vertically with different aspect ratios, which will influence its structural design and eventually the amount of concrete used in the building. In this paper, we examine how aspect ratio may affect the environmental sustainability of a buildings foundation, structural framing, and slab. We model the structure of a generic building with different aspect ratio to analyze if aspect ratio can help reduce the energy and carbon embodied in reinforced concrete structures. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) could be a solution that uses a cementless binder and recycled materials for producing concrete, while reducing the carbon dioxide emission and the demand for raw materials. In addition to the environmental aspect, previous studies on GPC showed that it can achieve mechanical characteristics higher than those of ordinary Portland concrete (OPC) such as greater strength a few days after casting, and it can be suitable for structural applications. In this paper, the state-of-the-art review of GPC is presented through an extensive literature analysis to determine the most recent information regarding the engineering properties of geopolymer concrete and the critical issues that prevent its widespread use and to put forward suggestions for future research. In particular, the physical properties in both fresh and hardened states and the mechanical characteristics are investigated; the structural performance of geopolymer concrete elements is also outlined. [ABSTRACT FROM AUTHOR]