ملخص البحث :

One of the major challenges faced by researchers is to recycle industrial wastes in a manner that reduces their environmental impact in nature. An experimental study was carried out to determine the suitability of using chopped tire rubber as reinforcements in green and sustainable geopolymer concrete, with the purpose of using them as nonstructural products. The geopolymer mixture was made by mixing of fly ash powder, fine aggregate, and Superplasticizer in Na2SiO3/NaOH solution. Mixtures were divided into four different groups, with constant water to fly ash ratio of 0.12 and alkaline dosage of 45% by weight of fly ash, based on the recycled chopped tire rubber (CTR) content: 0, 10, 20, and 30% by volume of fine aggregate with two maximum sizes (2 and 4 mm). Hardened properties of resulted geopolymer like compressive strength, density; and ultrasonic pulse velocity were examined at 28d. Besides that, X-Ray diffractometer and Scanning Electron Microscope were used in order to observe the microstructure of the resulted geopolymer concrete. In view of the consequences for this study, it is preferable to replace no more than 10% of fine aggregate in geopolymer concrete by CTR. In addition, according to SEM photographs, increasing the CTR content more voids will be pronounced and thus, decreasing the mechanical performance.

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Industrialwasteisconstantlyincreasing,someasures must be taken to recycle it in more practical and environmentally friendly ways. The aim of this study was to investigate the suitability of sawdust wasted particles for the production of cement bonded particleboards, and to enhance theircompatibility with cement byusing physical pretreatment processes, addition of nano slag and accelerated carbonation curing. All tests were carried out with different manufacturing parameters: sawdust/cement: (20%, 30% and 40%), treated and untreated wood, CO2 curing and the addition of nano slag. Experiments were performed to assess the mechanical properties of produced particleboards such as density (D), water absorption (WA), thickness swelling (TS), bending strength (BS), and microstructural properties of the cement particleboards. For treated sawdust, the outcomes demonstrated an enhancement in the mechanical and microstructural characteristics of produced cement bonded particleboards by using the accelerated CO2 curing method for sawdust particleboards. According to Scanning Electron Microscopy (SEM) micrographs, part of the carbonate crystals was found to be diffused into the cell walls and cavities and were found to protrude from sawdust surfaces

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Geometry, size, and shape of the surface pores, as well as, capillarity, and exposure environment are directly influence strength and durability of cementitious composites. The current research aimed to improve the resistance to abrasion and decrease the surface porosity of cement-based composites by nano surface coating technique. All samples were coated with a mixture of methanol alcohol, ordinary Portland cement and nano powder of (TiO2, MgO, ZnO and ZrO2) separately in percentages of (1, 1.5, and 2 %) by weight of cement. The hardness, abrasion, water absorption, density, porosity, and microstructural analysis: Scanning Electron Microscopy and X-Ray Diffraction (SEM & XRD) were studied for all coated and control specimens. Results showed an improvement in mechanical properties for all coated specimens as compared to control. The highest Vickers micro hardness value had reached 29%, while the largest value of abrasion resistance had increased by 39% for coated samples with 2% ZrO2. Also, the results showed a reduction in the porosity and water absorption of all coated samples, having highest scores obtained from the coated samples with 2% MgO. While the total water absorption rate decreased by 45% and the density had increased by 1% and the porosity had decreased by 46%. Additionally, the results of microstructural tests revealed pattern and images for each of SEM and XRD. Also, results indicated that the nano coating leads to signifcant consumption of Portlandite (CH) associated with production of a stable structure of CSH and reduction of voids, and this is evident from the enhancement in the physical properties.

ملخص البحث :

Carbon dioxide emissions and the consumption of natural resources related to the cement manufacturing have prompted the need to develop more sustainable and environmentally friendly types of concrete. Geopolymer concrete is considered eco-friendly concrete because it is free of cement. Otherwise, nanomaterials have been introduced into geopolymer concrete in previous works with the aim of improving its properties. However, very restricted studies have focused on the combined utilizing of nano-clay and nano-titanium in geopolymer concrete. Therefore, in the current research, geopolymer concrete was developed from industrial wastes (fly ash; FA) by using a novel mixture of different nanomaterials: nano-clay (NC) and nano-TiO2 (NT). Mixtures with constant water to FA (12 %), and different alkaline contents: (40 %, 45 %, and 50 %) by FA, were performed and divided into three groups. In the frst group, only FA was used as a binder, meanwhile, a combination of (FA+NC) and (FA+NT) was used separately in group two (binary). In the third group, (FA+NC+NT) were mixed together (ternary). Several hardened tests have been investigated: compressive, tensile strengths and density. Also, microstructural characteristics were monitored using XRD and SEM tests. The fndings revealed that the addition of nanomaterials obviously enhanced the density of the microstructure, reducing the pores of the produced geopolymer concrete. Moreover, the compressive strength was enhanced up to 38 % for NC, and 24 % for NT in the binary blends while the improvement reached 55 % in the ternary blends.