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Influence of Mix Design on Physical, Mechanical and Durability Properties of Multi-Recycled Aggregate Concrete
The decrease in the quality of recycled aggregate due to an increase in the number of recycling is a primary factor that limits the multi-recycling of concrete. This degradation adversely affects concrete performance; thus, the characteristics of recycled aggregate should be considered during the mix design stage, but little research has taken that into account. This study investigates the effect of the equivalent mortar volume (EMV) mix design on some physical, mechanical and durability properties of concrete made of multiple recycled coarse aggregates at 50% and 100% replacement ratios compared to concrete made by the conventional mix design (CMD). The results showed that the performances of concrete by the CMD decreased with an increasing number of recycling cycles. The properties of EMV-based concrete deteriorated with an increase in the number of recycling cycles at 100% replacement ratio due to poor workability caused by a shortage of fresh mortar. However, at 50% replacement, the EMV-based concrete exhibited similar performance across the three cycles of recycling, as well as improved properties over natural aggregate concrete. This study demonstrated that an appropriate mix design and optimal aggregate replacement ratio can offset the property loss of multiple recycled aggregate concrete.
Examining Key Barriers and Relevant Promotion Strategies of Green Buildings Adoption in Tanzania
Green buildings (GBs) offer significant potential to address environmental challenges and support nations to meet their sustainable development goals. Numerous developed countries have prioritized green building technologies (GBTs) adoption in their construction industry, whilst other nations are still hampered by several issues that slow down the level of their adoption. To effectively promote the adoption of GBTs, it is crucial to identify the key barriers and to prioritize relevant promotion strategies suitable to be emphasized towards specific geographic locations. This study aims to examine the key barriers hindering the adoption of GBTs and recommend suitable strategies to promote GBT adoption in the context of Tanzania. A questionnaire survey was carried out with 61 experts (architects, engineers, urban planners, economists, and green technologists) from Tanzania working in the field related to green buildings. A ranking analysis technique was used to rank the barriers and relevant promotion strategies to be prioritized. Measures of descriptive statistics, including mean and standard deviation, were carried out to sort the barriers and promotion strategies in the order of their potentiality. A Spearman’s rank correlation test was conducted to verify the consistency of the mean scores and derived ranks, and cluster analysis was also performed to group factors that share similar characteristics into the same clusters. Unfamiliarity with GBTs; a lack of expertise or few professionals in the GB field; the presence of few successful demonstrative projects to convince clients; and a low promotion of GBTs together with limited user knowledge were noted as the most critical barriers hindering the adoption of GBTs in Tanzania. Cluster analysis shows that knowledge-related barriers are majorly hindering the adoption of GBTs in Tanzania. Thus, a multi-faceted approach of institutional interventions and broadening public awareness should majorly be taken into account simultaneously to enhance adoption rates. The analysis also revealed that the establishment of an institutional framework; educational programs for policymakers, developers, and contractors related to GB guidelines; providing awareness to clients through advertisements; and imposing mandatory regulations in shifting towards GBTs are the most relevant promotion strategies to widen the adoption of GBs. The findings of this study provide valuable insights to various stakeholders for policy development in the construction industry and the future implementation of GBs in Tanzania.
Some Remarks on New Trends in Using Waste Aggregates in Civil Engineering: An Overview
The extensive development of construction, in which cement concrete remains the key composite, enforces the need for particular environmental concerns. This applies to aspects, including ecological challenges in the cement industry and the rational use of natural construction aggregates. This review article focuses on new trends in the use of waste aggregate, with particular emphasis on concrete recycled aggregate and waste sands. The state of the art was analysed, including many years of own studies on modification of properties of waste aggregate and concrete composites made from it. It was assessed that among possible ways of quality improvement of RCA, the most promising for the macro scale seems to be carbonation, unlike biodeposition. The latter, novel and undoubtedly interesting from a scientific viewpoint, has not been studied sufficiently, and the real obstacle is the cost of its implementation in practice. Multi-recycling, the pioneering proposal of recycled concrete aggregate management, can be viewed only in the ecological context for the moment. The use of waste sands from hydroclassification combined with steel fibres is the closest to implementation for constructional purposes in engineering practice.