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RISS 인기검색어
- 검색키워드
- 저자 : Khuram Rashid (검색결과 3 건)
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Khuram Rashid,Tabasam Rashid 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.6
This work is conducted with the aim of using waste material to reserve the natural resources. The objective is accomplished by conducting experimentation and verify by modeling based on fuzzy logic. In experimentation, concrete is casted by using natural/river sand as fine aggregate and termed as control specimen. Natural sand is conserved by replacing it with used foundry sand (UFS) by an amount of 10, 20 and 30% by weight. Fresh and hardened properties of concrete are investigated at different ages. It is observed that compressive strength and modulus of elasticity reduced with the increase in amount of UFS. Furthermore, concrete compressive strength is predicted by using fuzzy logic model and verified at different replacement ratio and age with experimental observations.
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Appraisal of geopolymer lightweight aggregates sintered by microwave radiations
Nimra Saleem,Khuram Rashid,Noor Fatima,Sadia Hanif,Ghinwa Naeem,Aamna Aslam,Miral Fatima,Kiran Aslam 아시아콘크리트학회 2020 Journal of Asian Concrete Federation Vol.6 No.2
This work was designed for the production of geopolymer based lightweight aggregate (LWA) using industrial by-products. Combination of fly ash (FA) and silica fume (SF) were used as precursors, whereas, combination of sodium hydroxide and sodium silicate were used as activator. Small amount of sodium bicarbonate was also used for surface hardening and early strength development. Pellets of dif-ferent sizes were crafted manually and cured by microwave radiations just for 5 minutes. The physico-mechanical properties of produced pellets (LWA) were discussed in light of: morphology, density, water absorption, specific gravity, porosity, aggregate impact value, and particle crushing strength. The prop-erties of LWA were also compared with literature reported synthetic LWAs cured with different tech-niques. The water absorption and specific gravity of LWAs were within the specified range provided by ACI standard. Mechanical strength properties briefed that the produced LWAs were strong enough to resist compressive load comparable to natural LWAs and many other synthetic LWAs. Thus, proposed curing method, microwave irradiation, has been found to be a sustainable and fast curing technique than conventional energy-intensive curing regimes. The results also confirmed that produced LWAs have po-tential to replace natural LWAs both in cast-in-place and precast concrete elements with possible eco-nomic, environmental, and technical benefits.
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Zafar, Idrees,Tahir, Muhammad Akram,Hameed, Rizwan,Rashid, Khuram,Ju, Minkwan Techno-Press 2022 Advances in concrete construction Vol.13 No.1
Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.
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