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Strength of Concrete Produced With Recycled Materials
Ali, Mohamed Emad
Ali, Mohamed Emad
Date
2019-12
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Advisor
Type
Thesis
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Description
A Master of Science thesis in Civil Engineering by Mohamed Emad Ali entitled, “Strength of Concrete Produced with Recycled Materials”, submitted in December 2019. Thesis advisor is Dr. Sherif Yehia and thesis co-advisor is Dr. Farid Abed. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form).
Abstract
Recent statistics predicts that the increasing demand of Natural Aggregate (NA) in construction industry to reach 66.2 billion metric tons by the year 2022. Several concerns were raised regarding the extinction of NA due to the increasing demand from the construction industry. Introducing Recycled Aggregate (RA), as replacement of NA, is certainly an important step towards sustainable development in the concrete industry and management of construction waste. RA from demolished concrete structures is an alternative to NA, which helps in the preservation of the environment. However, concrete produced by RA is affected by the variability of the aggregate properties. Properties of RA are influenced by previous loading, different environmental conditions, crushing process, contamination and impurities such as wood and plastic pieces. In addition, mortar adhered to RA lead to lower density, high absorption, and low resistance to degradation. Several research efforts indicated that concrete with comparable compressive strength to that achieved with NA could be produced by utilizing RA. However, durability and long-term performance of concrete made with RA need to be evaluated to ensure meeting the design requirements. The use of supplementary cementitious materials is one of the alternatives to improve concrete durability and cement replacement is another step towards sustainability. In this study, Ground-Granulated Blast-furnace Slag (GGBS) and Silica Fume will be used as partial replacement of cement to improve concrete made with RA. Several mixes with replacement of NA by RA will be prepared and exposed to three different conditions. Furthermore, as an approach to embrace sustainability, similar mixes will be prepared and evaluated using Treated Wastewater (TWW) that contains 670 ppm of dissolved solids. Based on the results the effect of replacing 50% of cement by GGBS and Silica increased the strength concrete by 17%. However, the effect of replacing 100% of NA with RA reduced the strength by 39%, in addition, the effect of replacing Tap Water (TW) with TWW in concrete mixing reduced the strength of NA concrete by 13% and RA concrete by 20%. The concrete where the concrete was produced with RA, GGBS/Silica, TWW and cured with TWW had a strength reduction of only 6% with respect to conventional concrete.