Self-compacting concrete (SCC) has great potentials as it offers several environmen-tal, economic and technical benefits. Moreover, the use of fibers extends its possibil-ities since fibers arrest cracks and retard their propagation. Incorporation of Quarry Dust (QD) in SCC help to reduce environmental hazards during the production of QD. This study evaluated the fresh and hardened properties of steel fiber self-compacting concrete (SFSCC) incorporating QD. The optimum fiber and QD contents with no ad-verse effects on fresh and hardened properties were determined. A comparative study on behavior of SCC and SFSCC mixtures in terms of workability, compressive strength, compressive strength development ratio, tensile, flexural and energy ab-sorption capacity was carried out. Test results showed that compressive strength in-creased with increase in QD contents at fixed fiber content by mass of Portland ce-ment (PC) and then decreased. Strength development ratio (C28/C7) for SCC was 1.13, while it was 1.06, 1.08, 1.10 and 1.01 after reinforcing with 0.10, 0.20 and 0.30 contents of fiber. The compressive, tensile, flexural and energy absorption capacity or Toughness of SFSCC increased with the inclusion of the aforementioned contents of steel fiber up to 0.20 % volume of total binder at constant QD content and then decreased when compared with control SCC values. From these results, optimum value for the variables studied was obtained from mix QD20 + 0.2fr. Hence, steel fiber and QD could be successfully used in SCC production not minding the slight draw back on workability of SCC caused by inclusion of steel fiber, but with a modified dos-age of super-plasticizer (SP), fresh and hardened properties, in accordance with spec-ifications in relevant code(s) can be achieved.
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Researchers and decision makers are continuously looking out to determine the po-tential and effectiveness of fly-ash as a partial replacement of cement in concrete. The current study is carried out to check the optimum or nearly optimum quantity of fly-ash with which cement should be replaced to get most of the properties of concrete enhanced and to give the idea about the quantities of fly-ash that can be used in a better way and better cause so that a proper management scheme of its usage and disposal can be implied. Further, a comparison is given between normal concrete and fly-ash concrete to show the properties which can be enhanced by proper utilization of fly-ash as a partial replacement of cement. After carrying out the lab experiments, it has been seen that the replacement of fly-ash in concrete has resulted in general increase in compressive strength, flexural strength and splitting tensile strength up to 15% replacement and after then the strength is decreased considerably than that of normal concrete. Addition of fly-ash in concrete has resulted in decrease in the water absorption of concrete and hence decreases in permeability of concrete. There is a progressive increase in workability with increase in percentage of fly-ash in con-crete. The current study has led to a conclusion that in order to achieve best results in use of fly-ash concrete, the fly-ash used for replacing cement in concrete should have the required properties as specified by the standards and proper techniques of processing fly-ash as well as mixing of fly-ash with cement must be employed.
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Polymer materials are used in different engineering applicationsbecause of their ex-cellent engineering properties. Theuse of thesematerials in different engineering fields has increased in recent years. It is predicted that polymermaterials will be one ofthemost remarkable and popular engineering materials in the near future becauseof their unique properties. This paper focuses on Methyl Ethyl Ketone Peroxide (MEKP), which is oneof the main catalysts and investigate its effect on the mechani-cal properties of Polymer Concrete (PC).The main aimsof the study are to under-stand the mechanical properties of the polymer concreteincluding different amount of MEKP and to investigate the influence of MEKP on the mechanicalcharacteriza-tions of the PCs. For this purpose, five different samples containing 0.15%(Mixture-1), 0.25% (Mixture-2), 0.35% (Mixture-3), 0.45% (Mixture-4) and 0.55% (Mixture-5) MEKP ofthe total weight were prepared and some experimental studieswere per-formed on the prepared mixtures.The obtained strength values were discussed and evaluated effect of MEKP on mechanical properties ofPCs.
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Early distress in RCC (Reinforced Cement Concrete) structures in the recent times poses a major problem for the construction industry. It is found that in most of cases, distresses in reinforced concrete structures are caused by corrosion of rebar embed-ded in the concrete. The HYSD (High Yield Strength Deformed) rebars which are used to offer excellent strength properties is detrimental to durability due to action of ribs as stress concentrators. Nowadays, concept of PSWC rebars (plain surface with wave type configuration rebars, formerly known as C-bars/mild steel rebar with curvy profile) is emerging to have a compromise between strength and durability. This in-vestigation assesses the flexural behaviour of RCC elements reinforced with PSWC rebars. The flexural performance of RC beams of size 1000mm x 150mm x 150mm reinforced with PSWC rebars at 4mm and 6mm deformation level was studied by conducting test as per IS 516-1959 under four point loading. The performance of PSWC bar reinforced elements are compared with beams reinforced with mild steel rebars, HYSD rebars with spiral and diamond rib configuration to assess the viability of PSWC rebars to replace conventional reinforcement. The test results are validated by numerical analysis with the help of ANSYS software. Totally 15 beams are sub-jected to flexure test and the performance evaluators are first crack load, deflection at first crack load, ultimate load carrying capacity, deflection at ultimate load, load-deflection behaviour, load-strain behaviour and failure pattern. It is found that PSWC rebars as reinforcement in concrete beams enhanced the ductile behaviour of beams as compared to conventional HYSD and mild steel rebar beams. The energy absorbing capacity has increased significantly for beams reinforced with PSWC rebars when compared with conventional HYSD and mild steel rebar beams. The load-deflection behaviour and failure mode of PSWC rebars reinforced concrete beams were found to be similar to that of high yield strength rebars irrespective of deformation level. The analytical investigation from ANSYS software gave good agreement with the ex-perimental results. It is concluded that PSWC bar has the potential to replace conven-tional HYSD rebar. Further study needs to be done to optimize the profile level and stirrup locations; and usage with high concrete grade for effective exploitation.
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Tuba BAHTLİ, Nesibe Sevde OZBAY
Tuba BAHTLİ, Nesibe Sevde OZBAY
In this study, the effects of finely-milled bronze and waste tire on the mechanical properties of concrete have been investigated. Approximately 2.5% and 5% by weight for each additive (bronze sawdust and waste tire) were added to dry concrete. The open porosity, density, compressive strength values of cured concrete have been determined. In addition, the Schmidt rebound hammer (SRH) and the ultrasonic pulse velocity (UPV) tests, which are non-destructive test methods, were applied. The microstructure and fracture surfaces of these materials were characterized by scan-ning electron microscopy (SEM). It was observed that the density of pure concrete was 2.35 g/cm3 while the density was 2.19 g/cm3 for a C+5%B+5%T material. Simi-larly, pure concrete had an almost three times better compressive strength and a two times better SRH value than those of the C+5%B+5%T material. The density and me-chanical properties of concrete materials containing bronze and waste tire decreased due to micro crack formations, weak bonding and deep cracks forming especially be-tween the concrete and additives.
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The locations of structural members can be provided according to architectural pro-jects in the design of reinforced concrete (RC) structures. The design of dimensions isthe subject of civil engineering, and these designs are done according to the expe-rience of the designer by considering the regulation suggestions, but these dimen-sions and the required reinforcement plan may not be optimum. For that reason, the dimensions and detailed reinforcement design of RC structures can be found by using optimization methods. To reach optimum results, metaheuristic algorithms can be used. In this study, several metaheuristic algorithms such as harmony search, bat al-gorithm and teaching learning-based optimization are used in the design of several RC beams for cost minimization. The optimum results are presented for different strength of concrete. The results show that using high strength material for high flex-ural moment capacity has lower cost than low stretch concrete since doubly rein-forced design is not an optimum choice. The results prove that a definite metaheuris-tic algorithm cannot be proposed for the best optimum design of an engineering problem. According to the investigation of compressive strength of concrete, it can be said that a low strength material are optimum for low flexural moment, while a high strength material may be the optimum one by the increase of the flexural mo-ment as expected.
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In this paper, the investigation of the optimum designs for two types of concrete can-tilever retaining walls was conductedutilizing the artificial bee colony algorithm. Sta-bility conditions like safety factors of sliding, overturningand bearing capacity and some geometric instancesdue to inherent of the wall were considered as the design constraints. The effect of the existence of the key in wall design on the objective func-tion was probed for changeableproperties of foundation and backfill soils. In optimi-zation analysis, the concrete of the wall, which directly affectsparameters such as carbon dioxide emission and the cost,was considered as the objective function and analyzes were performed according to different discrete design variables. The opti-mum concrete cantilever retaining wall designs satisfying constraints of stability conditions and geometric instanceswere obtained for different soil cases. Optimum designs of concrete cantilever retaining wall with the key were attained in some soil cases which were not foundthe feasible optimum solution of the concrete cantilever retaining wall. Results illustratethat the artificial bee colony algorithm was a favor-ablemetaheuristic optimization method togainoptimum designs of concrete canti-lever retaining wall.
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Glass Fiber Reinforced Plastic (GFRP) composites as rolled bars can be used as steel rebar to prevent oxidation or rust which is one of the main reasons concrete struc-tures deteriorate when exposed to chlorides and other harmful chemicals. GFRP is successful alternative for reinforcement with high tensile strength-low strain, cor-rosion resistance and congenital electromagnetic neutrality in terms of longer ser-vice life. The main goal of the study is to investigate the mechanical and bonding properties of GFRP bars and equivalent steel reinforcing bars then comparethem. GFRP and steel rebar are embedded in concrete block with three different levels. Me-chanical properties of GFRP and steel bars in terms of strength and strains are deter-mined. On the other hand; modulus of elasticity of GFRP and steel bars, modulus of toughness and modulus of resilience were calculated using stress-strain curves, as a result of the experiments. Pull-out tests are conducted on each GFRP and rebar sam-ples which are embedded in concrete for each embedment level and ultimate adher-ence strengths are determined in terms of bar diameter–development length ratio. Yield strength, strain and modulus of elasticities of GFRP samples are compared to steel rebar. According to the test results reported in this study, GFRP bars are used safely insteadof steel bars in terms of mechanical properties.
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This study presents a reliability analysis procedure fora reinforced concrete bridge exposed to different moving loads. Bridges are one of the important part of transpor-tation infrastructure systems. As bridges age, structural weakening due to heavy traf-fic and aggressive environmental factors lead to an increase in repair frequency and decrease in load carrying capacity. Therefore, bridges require periodic maintenance and repair in order to function and be reliable throughout their lifetimes. In other words, condition and safety of the bridges must be monitored at regular time inter-vals to avoid the disadvantages of deterioration. Otherwise, sudden collapse of a bridge may lead to irreversible loss oflife and property. Therefore, the importanceof the structural assessment of bridges is rapidly increasing in developed countries. In this study, reliability analysis which is one of the structural performance predic-tionmethod is applied to a reinforced concrete bridge subjected to the different mov-ing loads. The aim of this studyis to observe the safety of the bridge for the effect of the increasing traffic factor over the years.
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Design engineers may find various options of metaheuristic method in optimization of their problems. Because of the randomization nature of metaheuristic methods, solutions may trap to non-optimum solutions which are just optimums in a limited part of the selected range of the design variables. Generally, metaheuristics use sev-eral options to prevent this situation, but the same optimization process may solve different performances in every run of the process. Due to that, a comparative study by using ten different algorithms was done in this study. The optimization problem is the cost minimization of an L-shaped reinforced concrete (RC) retaining wall. The evaluation is done by conducting 30 multiple cycles of optimization,and comparing minimum cost, average cost and standard deviation values
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