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Concrete has always been indispensable as a material for the engineering and construction of hydraulic structures (e [...]

Abstract Approximately 5%–7% of global Carbon Dioxide (CO2) emissions can be attributed to Ordinary Portland Cement (OPC), which has traditionally been used as the primary binder in concrete. Geopolymer concrete has been widely claimed to have lower global warming potential than OPC concrete, and this claim has formed the basis of many studies examining mix designs and mechanical properties of geopolymer concretes. A major limitation with the vast majority of existing studies is a lack of the direct quantification of the global warming potential of the materials developed. That is, the underlying assumption in the majority of these studies is that geopolymer concrete is more sustainable than OPC based concretes. The aim of this paper is to quantify the CO2 equivalent (CO2-eq) emissions associated with production of a large number of previously developed mix designs (1404 mix designs from 110 studies) including the impacts of curing, allocation and transportation and allowing for variation in energy grid source and the production of the activator solution. When considering the impact of transportation, a case study based on five major capital cities in Australia is presented and the critical transport distances at which the manufacture of geopolymers becomes more emissions intensive than conventional concrete is identified. The results show that the relative CO2-eq emissions of geopolymer and OPC based concretes of the same strength, are highly dependent on the system boundary for analysis, the type of allocation scenario and material transportation distances and mode, and further, that depending on these factors geopolymer concretes can either have significantly lower, or significantly higher CO2-eq emissions than OPC concretes of the same strength. It is expected that the findings of this work can aid in specifying the optimal concrete types for reducing CO2-eq emissions considering the intended use of the concrete.

Trillions of cigarette butts (CBs) are being littered every minute, causing a global cigarette butt pollution problem. Because of having cellulose acetate based polymeric structure, CBs take years to biodegrade and leach toxic chemicals and heavy metals in due process. Researchers have made several attempts to recycle cigarette butts in different construction materials, developed a novel encapsulation technique for CBs, and incorporated bitumen and wax encapsulated cigarette butts in dense graded asphalt preparation. As a continuation and expansion of the parent research, this paper focused on the in-depth volumetric analysis of asphalt prepared with bitumen encapsulated cigarette butts, thermal conductivity, and potential for energy savings. Volumetric analysis assessment demonstrated the potential of material saving and energy saving during transportation of construction materials. Thermal conductivity test results have indicated that bitumen encapsulated cigarette butts (BECB) modified asphalt have better resistance to damage due to temperature variations. The use of up to 1% BECB in asphalt by maintaining air void has been advised based on the laboratory investigation, and recommendations have been made for the further expansion of the research.

Geopolymer concrete is preferred over OPC due to its use of energy waste such as fly ash, making it more sustainable and energy-efficient. However, limited research has been done on its seismic characterization in confined masonry, highlighting a gap in sustainable earthquake-resistant structures. Our study compares the performance of alkali-activated fly-ash-based geopolymer concrete bare frame and confined masonry wall panels with conventional concrete. Experimental results showed that geopolymer concrete bare frame has 3.5% higher initial stiffness and 1.0% higher lateral load-bearing capacity compared to conventional concrete. Geopolymer concrete confined masonry exhibited 45.2% higher initial stiffness and 4.1% higher ultimate seismic capacity than traditional concrete. The experimental results were verified using a numerical simulation technique with ANSYS-APDL, showing good correlation. Comparison with previously tested masonry walls revealed that GPC confined masonry has similar structural behavior to cement concrete masonry. This study demonstrates that geopolymer concrete made from waste energy such as fly ash is a sustainable and low-energy substitute for OPC concrete, particularly in highly seismic-prone areas, for a cleaner environment.

The construction industry represents one of the greatest contributors to atmospheric emissions of CO2 and anthropogenic climate change, largely resulting from the production of commonly used building materials such as steel and concrete. It is well understood that the extraction and manufacture of these products generates significant volumes of greenhouse gases and, therefore, this industry represents an important target for reducing emissions. One possibility is to replace emissions-intensive, non-renewable materials with more environmentally friendly alternatives that minimise resource depletion and lower emissions. Although timber has not been widely used in mid- to high-rise buildings since the industrial revolution, recent advances in manufacturing have reintroduced wood as a viable product for larger and more complex structures. One of the main advantages of the resurgence of wood is its environmental performance; however, there is still uncertainty about how mass timber works and its suitability relative to key performance criteria for construction material selection. Consequently, the aim of this study is to help guide decision making in the construction sector by providing a comprehensive review of the research on mass timber. Key performance criteria for mass timber are reviewed, using existing literature, and compared with those for typical concrete construction. The review concludes that mass timber is superior to concrete and steel when taking into consideration all performance factors, and posits that the construction industry should, where appropriate, transition to mass timber as the low-carbon, high performance building material of the future.

Plastic and glass can be sorted using machines and recycled into new plastic and glass, as opposed to producing them from raw materials. However, contaminated plastic and glass, as well as certain types of plastic and glass, cannot be recycled using traditional methods and must be disposed of in landfill. Researchers have been looking into this and have tried a variety of solutions to convert this waste into functional products. The development of composite construction materials, based on these two materials was identified as a worthy solution. On the other hand, carbon dioxide is emitted during the cement manufacturing process and the use of that cement in the production of construction materials contributes 7% of total global greenhouse gas emissions. Hence, plastic sand/glass composite is environmentally friendly in two ways. It reduces landfill while also replacing the equivalent concrete product, lowering CO2 emissions. This paper examines the literature on the development of such materials, including technology, challenges, quality, and properties. At the raw material selection stage, the effect of sand grain sizes, gradation, plastic type, plastic mix, impurities, pre-processing, and cleaning was investigated. At the material processing stage, the filler to binder ratio, mixing temperatures, mixing methodology, and compaction were all examined. It was identified plastic type and a mix of plastic, as well as impurities did not affect the density or strength of the composite significantly. Also, the compressive strength of the composite products manufactured in the considered studies is comparable to C20/25 concrete.

The research work presented in this manuscript focused on the comparative examination of the influence of the Compression Casting Technique (CCT) and the conventional casting method (i.e., compaction through vibration) on the performance of 100% Recycled Aggregate Concrete (RAC). The minimum target compressive strength of 100% RAC was 15 MPa keeping in view its application in the manufacturing of load-bearing concrete masonry units. A total of 28 concrete compositions were prepared by varying the coarse to fine aggregates ratio (i.e., 70:30 and 60:40), cement content (10% and 15%) by weight of total aggregates, casting technique, and applied pressure for compression casting (i.e., 25, 35, and 45 MPa). The concrete compositions were tested to determine their density, compressive strength, Elastic Modulus (EM), and Ultrasonic Pulse Velocity (UPV). For comparison, samples of Natural Aggregate Concrete (NAC) were also tested for the same properties. The results highlighted the positive impact of CCT on the properties of 100% RAC. The compressive strength and EM of fully RAC was increased by 20–80% and 15–50%, respectively, by changing casting method from vibration to CCT. At casting pressure of 35 MPa and 15% cement, compressed 100% RAC exhibited compressive strength higher than vibrated NAC. The UPV value exhibited by 100% RAC was increased by changing the casting technique. The analytical models were proposed using regression analysis of experimental results to predict compressive strength and EM of compressed 100% RAC and NAC. These proposed models were evaluated using statistical parameters, i.e., average absolute error (AAE) and mean (M) and found to be able to predict the compressive strength and EM of RAC with reasonable accuracy as compared to the analytical models already existing in the literature. This study finally concluded that through CCT, 100% RAC with low cement content could achieve minimum target compressive strength of 15 MPa. The development and use of compressed load-bearing 100% RAC construction units would help to achieve sustainability in construction.

Cigarettes are one of the favoured commodities on our planet. However, the annual consumption of 5.7 trillion cigarettes and 75% littering rate results in cigarette butts (CBs) being one of the most critical environmental issues. The leachate of heavy metals and toxic chemicals is polluting our ecosystem and threatening the wildlife species. Therefore, it is crucial to find effective and efficient recycling methods to solve the growing CB waste issue. In this study, unglazed fired ceramic tiles were manufactured with 0%, 0.5%, 1.0%, and 1.5% shredded CBs by dry mass to investigate the feasibility of the proposed sustainable recycling method. The chemical and mineralogical characterisation, density, shrinkage, bulk density, breaking strength, water absorption, and modulus of rupture were investigated and compared with the Australian Standards for ceramic tiles (AS 4459). The results revealed that tiles incorporating 0.5% CBs by mass demonstrated the greatest performance compared to the other mixtures. The water absorption for all tile–CB mixtures was found to be greater than 10%, with a positive growth tendency. The addition of 0.5% CBs by mass slightly improved flexural strength from 15.56 MPa for control samples to 16.63 MPa. Tiles containing 0.5% CBs by mass satisfied the modulus of rupture and water absorption limits for group III class according to the Australian Standards (AS 13006), and they may be suitable to be used as wall tiles. The result of a simulation equation predicts that an energy savings of up to 7.79% is achievable during the firing process for ceramic tiles incorporating 1% CBs by mass.