• Computers and Concrete
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• 제21권2호
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• pp.149-156
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• 2018

This paper investigated the influence of binary and ternary blends of mineral admixtures in self-compacted mortar (SCM) on the fresh, mechanical and durability properties. For this purpose, 25 mortar mixtures were prepared having a total binder content of $640kg/cm^3$ and water/binder ratio between 0.41 and 0.50. All the mixtures consisted of Portland cement (PC), fly ash (FA) and silica fume (SF) as binary and ternary blends and air-entrained admixture wasn't used while control mixture contained only PC. The compressive and tensile strength tests were conducted for 28 and 91 days as well as slump-flow and V-funnel time tests whilst freeze-thaw (F-T) resistance and capillary water absorption tests were made for 91-day. Finally, in general, the use of SF with FA as ternary blends improved the tensile strength of mortars at 28- and 91-day while the use of SF15 with FA increased the compressive strength of the mortars compared to binary blends of FA. SCM mixtures with ternary blends had lower the sorptivity values than that of the mortars with binary blends of FA and the control mixture due to the beneficial properties of SF while the use of FA with SF as ternary blends induced the F-T resistance enhancement.

• Advances in concrete construction
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• 제4권2호
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• pp.145-160
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• 2016

Marble is a metamorphic rock used widely in construction which increases amount of marble powder obtained from it. Marble powder is a waste product obtained from marble during its processing. Marble waste is high in calcium oxide content which is cementing property but it creates many environmental hazards too if left in environment or in water. In this research, partial replacement of cement and sand by waste marble powder (WMP) has been investigated. Seven concrete mixtures were prepared for this investigation by partially replacing cement, sand with WMP at proportions of 0%, 10% and 15% by weight separately and in combined form. To determine compressive strength, flexural strength and split tensile strength of concrete made with waste marble powder, the samples at the curing ages of 7, 28 and 90 days was recorded. Different tests of durability were applied on samples like ultrasonic pulse wave test, absorption and sorptivity. For further investigation all the results were compared and noticed that WMP has shown good results and enhancing mechanical properties of concrete mix on partially replacing with sand and cement in set proportions. Moreover, it will solve the problem of environmental health hazard.

• Advances in concrete construction
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• 제7권4호
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• pp.231-239
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• 2019

The present study deals with the development of metakaolin-based geopolymer concrete (GPC) and thereafter studying the effects of adding ultra-fine slag on its mechanical and permeability characteristics. The mechanical characteristics including compressive, split tensile, flexural strengths and elastic modulus were studied. In addition, permeability characteristics including water absorption, porosity, sorptivity and chloride permeability were studied up to 90 days. The results showed the effective utilization of metakaolin for the development of elevated temperature cured geopolymer concrete having high 3-day compressive strength of 42.6 MPa. The addition of ultra-fine slag up to 15%, as partial replacement of metakaolin resulted in an increase in strength characteristics. Similar improvement in durability properties was also observed with the inclusion of ultra-fine slag up to 15%. Beyond this optimum content of 15%, further increase in ultra-fine slag content affected the mechanical as well as permeability parameters in a negative way. In addition, the relationship between various properties of GPC was also derived.

• Advances in concrete construction
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• 제7권3호
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• pp.143-150
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• 2019

This study presents the fracture properties of nano modified medium strength concrete (MSC). The nano particle used in this study is nano silica which replaces cement about 1 and 2% by weight, and the micro steel fibers are added about 0.4% volume of concrete. In addition to fracture properties, mechanical properties, namely, compressive strength, split tensile strength, and flexural strength of nano modified MSC are studied. To ensure the durability of the MSC, durability studies such as rapid chloride penetration test, sorptivity test, and water absorption test have been carried out for the nano modified MSC. From the study, it is observed that significant performance improvement in nano modified MSC in terms of strength and durability which could be attributed due to the addition pozzolanic reaction and the filler effect of nano silica. The incorporation of nano silica increases the fracture energy about 30% for mix without nano silica. Also, size independent fracture energy is arrived using two popular methods, namely, RILEM work of fracture method with $P-{\delta}$ tail correction and boundary effect method. Both the methods resulted in nearly the same size-independent $G_F$ irrespective of the notch to depth ratio of the same specimen. This shows evidence that either of the two procedures could be used in practice for analysis of cracked concrete structures.

• 한국토양비료학회지
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• 제28권3호
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• pp.249-255
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• 1995

사토, 사양토, 양토, 식양토의 4개 토양에 Polyvinyalcohol(PVA), Polyacrylamide(PAM) 및 Bitumen을 분무처리하여 토양의 입단형성과 수분특성에 미친 영향을 조사하였으며 한편, Pot 재배 시험을 통하여 PAM 처리가 상추의 발아율과 생육에 미친 효과를 검토하였다. 2mm 이상의 입단함량(粒團含量)은 Soil conditioner를 처리하지 않은 토양에서 사토 0%, 사양토 45%, 양토 80%, 식양토 90%이었고 PVA, PAM 및 Bitumen의 처치에 의해서는 사도 20~52%, 사양토 55~76% 범위로 증가되었으나 양토와 식양토에서는 변화가 적었다. Soil conditioner 처리에 의해 내수성(耐水性) 입단(粒團)이 증가되었고 입단의 불안정성(不安定性)은 감소되었다. 토양(土壤)의 습윤각(濕潤角)은 PAV와 PAM 처리에서는 거의 변화가 없었으나 Bitumen 처리에 의해서는 무처리토양과 비교하여 크게 높아져서 소수성이 증가되었다. 침수성과 흡수성은 Bitumen 처리에 의해 모든 토성에서 물의 이동이 나타나지 않았으며 PVA와 PAM 처리에 의해서는 사토를 제외할 토성에서는 큰 변화가 없었다. PAM 처리에 의하여 상추의 발아율. 뿌리무게와 지상부 건물중이 무처리에 비해 크게 증가되고 그 효과는 사양토와 미사질양토에 비하여 사토에서 매우 컸는데 이는 PAM 처리에 의해 토양의 보수력과 기상비율이 함께 증가되어 상추생육을 촉진한 결과로 판단된다.

• Advances in concrete construction
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• 제5권5호
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• pp.423-436
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• 2017

Today, pozzolans are widely used in construction for various reasons such as technical and economic efficiency. In this research, in order to evaluate some of important properties of concrete, silica fume and fly ash have been used as a replacement for cement in different mass percentages. Concrete mixtures were made from a water-cement ratio of (0.45) and cured under similar conditions. The main focus of this study was to evaluate the permeability and mechanical properties of concrete made from binary and ternary cementitious mixtures of fly ash and silica fume. In this study permeability of concrete was studied by evaluating the sorptivity, water absorption, water penetration depth, electrical resistivity and rapid chloride permeability (RCP) tests. Mechanical properties of concrete were evaluated with compressive strength, splitting tensile strength and modulus of elasticity. Scanning electronic microscopy (SEM) was used to characterize the effects of silica fume and fly ash on the pore structure and morphology of concrete with cement based matrix. The results indicated that the incorporation of silica fume and fly ash increased the mechanical strength and improved the permeability of concrete.

• 한국토양비료학회지
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• 제19권3호
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• pp.251-268
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• 1986

Selecting a site for the safe disposal of radioactive waste requires the evaluation of a wide range of geologic, mineralogic, hydrologic, and physicochemical properties. Although highly diverse, these properties are in fact interrelated. Site requirements are also diverse because they are influenced by the nature of the radionuclides in the waste, for example, their half-lives, specific energy, and chemistry. A fundamental consideration in site selection is the mineralogy of the host rock, and one of the most ubiquitous mineral groups is clay minerals. Clays and clay minerals as in situ lithologic components and engineered barriers may playa significant role in retarding the migration of radionuclides. Their high sorptivity, longevity (stability), low permeability, and other physical factors should make them a very effective retainer of most radionuclides in nuclear wastes. There are, however, some unanswered questions. For example, how will their longevity and physicochemical properties be influenced by such factors as radionuclide concentration, radiation intensity, elevated temperatures, changes in redox condition, pH, and formation fluids for extended periods of time? Understanding of mechanisms affecting clay mineral-radionuclide interactions under prevailing geochemical conditions is important; however, the utilization of experimental geochemical information related to physicochemical properties of clays and clay-bearing materials with geohydrologic models presents a uniquely challenging problem in that many assessments have to be based on model predictions rather than on experiments. These are high-priority research investigations that need to be addressed before complete reliance for disposal area performance is made on clays and clay minerals.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.620-623
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• 2004

Waste concrete powder(WCP) has been estimated with a great value-added material as by-product of waste concrete manufactured to fine and coarse aggregate for concrete, because it is able to utilized for cement clinker and concrete admixture. In the experimental results for this study, chemical composition of WCP was similar to that of cement, and specific gravity of WCPs were 2.46 and 2.48 due to internal micro-void of WCP. Final setting of paste with WCP was delayed, and flow value of mortar with WCP was tendency to reduced in comparison with that of paste and mortar with only ordinary portland cement as replacement ratio of WCP increased. Furthermore, sorptivity of mortar with WCP was increased as replacement ratio of WCP increased. Compressive strength of mortar with $15\%$ WCP was developed about 27MPa at 28days.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.317-327
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• 2017

The addition of different types of polymers such as SBR, VAE, Acrylic, etc. in concrete and mortar leads to an increase in compressive, tensile and bond strength and decrease in permeability of polymer modified mortar (PMM) and concrete (PMC). The improvement in properties such as bond strength and impermeability makes PMM/PMC suitable for use as repair/retrofitting and water proofing material. In the present study effect of addition of fluoropolymer on the strength and permeability properties of mortar has been studied. In the cement mortar different percentages viz. 10, 20 and 30 percent of fluoropolymer by weight of cement was added. It has been observed that on addition of fluoropolymer in mortar the workability of mortar increases. In the present study all specimens were cast keeping the workability constant, i.e., flow value $105{\pm}5mm$, by changing the amount of water content in the mortar suitably. The specimens were cured for two different curing conditions. Firstly, these were cured wet for one day and then cured dry for 27 days. Secondly, specimens were cured wet for 7 days and then cured dry for 21 days. It has been observed that compressive strength and split tensile strength of specimens cured wet for 7 days and then cured dry for 21 days is 7-13 percent and 12-15 percent, respectively, higher than specimens cured one day dry and 27 days wet. The sorptivity of fluoropolymer modified mortar decreases by 88.56% and 91% for curing condtion one and two, respectively. However, It has been observed that on addition of 10 percent fluoropolymer both compressive and tensile strength decreases, but with the increase in percentage addition from 10 to 20 and 30 percent both the strengths starts increasing and becomes equal to that of the control specimen at 30 percent for both the curing conditions. It is further observed that percentage decrease in strength for second curing condition is relatively less as compared to the first curing condition. However, for both the curing conditions chloride ion permeability of polymer modified mortar becomes very low.

• Advances in concrete construction
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• 제12권6호
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• pp.479-490
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• 2021

Present research is mainly focused on, microstructural and durability analysis of Graphene Oxide (GO) in Wollastonite (WO) induced cement mortar with silica fume. The study was conducted by evaluating the mechanical properties (compressive and flexural strength), durability properties (water absorption, sorptivity and sulphate resistance) and microstructural analysis by SEM. Cement mortar mix prepared by replacing 10% ordinary portland cement with SF was considered as the control mix. Wollastonite replacement level varied from 0 to 20% by weight of cement. The optimum replacement of wollastonite was found to be 15% and this was followed by four sets of mortar specimens with varying substitution levels of cementitious material with GO at dosage rates of 0.1%, 0.2%, 0.3% and 0.4% by weight. The results indicated that the addition of up to 15%WO and 0.3% GO improves the hydration process and increase the compressive strength and flexural strength of the mortar due to the pore volume reduction, thereby strengthening the mortar mix. The resistance to water penetration and sulphate attack of mortar mixes were generally improved with the dosage of GO in presence of 15% Wollastonite and 10% silica fume content in the mortar mix. Furthermore, FE-SEM test results showed that the WO influences the lattice framework of the cement hydration products increasing the bonding between silica fume particles and cement. The optimum mix containing 0.3% GO with 15% WO replacement exhibited extensive C-S-H formation along with a uniform densified structure indicating that calcium meta-silicate has filled the pores.