• Computers and Concrete
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• v.13 no.1
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• pp.17-30
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• 2014

This research presents the effect of various ground pozzolanic materials in blended cement concrete on the strength and chloride penetration resistance. An experimental investigation dealing with concrete incorporating ground fly ash (GFA), ground bottom ash (GBA) and ground rice husk ash (GRHA). The concretes were mixed by replacing each pozzolan to Ordinary Portland cement at levels of 0%, 10%, 20% and 40% by weight of binder. Three different water to cement ratios (0.35, 0.48 and 0.62) were used and type F superplasticizer was added to keep the required slump. Compressive strength and chloride permeability were determined at the ages of 28, 60, and 90 days. Furthermore, using this experimental database, linear and nonlinear multiple regression techniques were developed to construct a mathematical model of chloride permeability in concretes. Experimental results indicated that the incorporation of GFA, GBA and GRHA as a partial cement replacement significantly improved compressive strength and chloride penetration resistance. The chloride penetration of blended concrete continuously decreases with an increase in pozzolan content up to 40% of cement replacement and yields the highest reduction in the chloride permeability. Compressive strength of concretes incorporating with these pozzolans was obviously higher than those of the control concretes at all ages. In addition, the nonlinear technique gives a higher degree of accuracy than the linear regression based on statistical parameters and provides fairly reasonable absolute fraction of variance ($R^2$) of 0.974 and 0.960 for the charge passed and chloride penetration depth, respectively.

• Geomechanics and Engineering
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• v.19 no.6
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• pp.543-554
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• 2019

İzmir Bay reserves high amount of residual alluvial deposits generated by Meles River at its stream mouth. These carried sediments with high water content and low bearing capacity are unsuitable in terms of engineering purposes. In-situ soil stabilization with deep soil mixing method is considered to improve properties of soil in this location. This method is widely used especially over Scandinavia, Japan and North America. Basically, the method covers mixing appropriate binder into the soil to improve soil profile according to the engineering needs. For this purpose, soil samples were initially provided from the site, classification tests were performed and optimum ratios of lime and cement binders were determined. Following, specimens representing the in-situ soil conditions were prepared and cured to be able to determine their engineering properties. Unconfined compression tests and vane shear tests were applied to evaluate the stabilization performance of binders on samples with different curing periods. Scanning electron microscope was used to observe time-dependent bonding progress of binders in order to validate the results. Utilization of 4% lime and 4% cement mixture for the long-term performance and 8% lime and 8% cement mixture for short term performance were suggested for the stabilization of Meles Delta soils. Development of CSH and CAH in a gel form as well as CSH crystals were clearly observed on SEM images of treated specimens.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.318-321
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• 2000

Most compressive strengths commonly used in the construction field are in a range of 240 to 300 kgf/$\textrm{cm}^2$ at 28 days. To get this rage of strengths, however, high-flowing concrete requires cementitious binders more than 400 to 450 kg/$\textrm{cm}^2$ for preventing segregation and sedimentation of aggregates. This amount of cementitious binder generates a large emission of excessive hydration heat, which may consequently induce harmful cracks in concrete structure. In order to reduce excessive hydration heat, thus, this paper aims at fabricating a high-flowing concrete under the condition that cement content is kept as low as 350kg/$\textrm{cm}^3$ by using viscose agents. In a parametric study, effects of cement types such as a ternary blended cement and Type V on he physical characteristics of high-flowing concrete were evaluated. In addition, the influence of viscosity was also investigated by applying two different viscose agents, one in a range of 6,000 to 10,000 cps and the others of 10,000 to 14,000 cps. In terms of chemical admixtures used in concrete mixture, the superplasticizer was Sulfonated Melamine-Formaldehyde Condensate with about 30,000 of molecular weight, and main component of viscose agent was HPMC (Hydroxy Propyl Methyl Cellulose). Slump flow was fixed at 50cm with different dosages of superplasticizer in weight.

• Advances in concrete construction
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• v.5 no.4
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• pp.391-405
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• 2017

Cement acts as the most important component of concrete as it binds and holds the concrete together. But it is one of the major $CO_2$ emitters all over the world, during manufacturing (900 kg of $CO_2$ per 1000 kg). Some of the modern construction methods aim at reducing the amount of usage of cement and came out with numerous solutions for replacement of the same. One such supplement in current trend is the Steel dust or the Electric Arc Furnace Dust (EAFD), which is a waste product from the electric arc furnace when the scrap metal is melted. When the concrete containing steel dust is exposed to atmosphere, the environmental oxygen and moisture play role to form rust and ultimately the member becomes harder. As Cement is the binder of conventional concrete, only certain percentage of the same could be replaced by the new material, steel dust. Tests were conducted for the 28 days cube strength of M45 grade (suitable for prestressing) concrete which has 0%, 10%, 20%, 30%, 40% and 50% steel dust instead cement. From the test, the optimum percentage replacement of steel dust was obtained, for which the beams and overhead poles were cast, prestressed and tested for the failure load and deflections. A conventional concrete beam and overhead pole were also cast, prestressed and tested to compare the results with those of the beam and pole that contained steel dust. The load vs. deflection plot and other results from the test is also discussed.

• Architectural research
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• v.25 no.3
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• pp.53-59
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• 2023

Concrete is widely used in the construction industry; however, it has the disadvantage of deteriorating durability due to cracks occurring because of climate change and shrinkage. In addition, when cement is used as a binder, CO₂ emitted during the manu-facturing process accounts for ~8% of global CO₂ emissions. In this study, ecofriendly cementitious materials such as blast furnace slag powder and fly ash (FA) were used as cement substitutes in the production of mortar containing a chitosan-based polymer (CP), and their fluidity, compressive strength, and self-healing performance were examined. The 28-day compressive strength of the control sample was ~32.4 MPa (the lowest for all tested samples), while that of the sample containing 5% CP and 20% FA was ~49.6 MPa (the highest for all tested samples) and ~53.1% higher than that of the control sample. Even at a healing age of 56 days, the control sample exhibited the lowest healing performance, whereas the samples containing CP (5%, 10%) and 20% FA demonstrated excellent healing performance. After 28 days, the decrease in crack size for the control sample was minimal; however, for the sample containing only cement and CP, a significant decrease in crack size was observed even after 28 days. This study confirmed that the appropriate use of CP and cementitious materials improves not only compressive strength but also the selfhealing performance of mortar.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.309-310
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• 2023

Slag and ash generally have a higher powder degree than portland cement, so workability may deteriorate under the same unit quantity condition, and strength and durability decrease when the unit quantity is increased. At this time, if an aggregate having a low water absorption and an appropriate particle size is used to recover the loss of strength, it can contribute to reducing the unit quantity of the binder. Therefore, for the purpose of improving the workability and strength of non-sintered cement mortar using slag and ash, ferro nikel slag whose particle size was adjusted was used as an aggregate and its applicability was identified. In this experimental condition, it was confirmed that non-sintered cement mortar tends to improve workability and secure strength when ferro nikel slag having various particle size distributions is used as an aggregate. This can be analyzed as the effect of ferro nikel slag material properties including glassy properties and mixing conditions with a wide particle size distribution.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.385-393
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• 2009

This study grasped the relationship between relative humidity in concrete and concrete shrinkage followed by pre-absorbed water of porous lightweight aggregates through measurements of concrete shrinkage and humidity and comparisons with established research results. It was showed that shrinkage reduction effect of lightweight concrete is 36% at 7 days early ages and 25% at 180 days long-term ages when water-binder ratio is 0.3. It also showed that shrinkage reduction effect is 19% at 7 days and 16% at 180 days when water-binder ratio is 0.4 and 37%, 32% when water-binder ratio is 0.5. The moisture supply effect of lightweight aggregates was remarkable at early age within 7~10 days irrespective of water-binder ratio. In case of waterbinder ratio is 0.3, the relationship between shrinkage and internal humidity of concrete has been underestimated regardless of applied existing model type and in case of water-binder ratio is 0.4, 0.5, measurement values are relatively similar with existing model equations. Finally this study did regression analyses about the relation among the humidity change and the shrinkage strain as a high-degree polynomial and derived parameters that can connect moisture movement analysis with differential shrinkage analysis in case of considering relative humidity at the time by moisture movement analysis of concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.141-147
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• 2017

Recently, lots of researches on concrete with high volume mineral admixtures such as ground granulated blast-furnace slag(GGBS) have been carried out to reduce greenhouse gas. The high volume GGBS concrete has advantages such as low heat, high durability, but it has a limitation in practical field application, especially low strength development in early ages. This study investigated the compressive strength and hydration characteristics of high performanc and volume GGBS cement pastes with low water to binder ratio. The effects of fineness($4,330cm^2/g$, $5,320cm^2/g$, $6,450cm^2/g$, $7650cm^2/g$) and replacement(35%, 50%, 65%, 80%) of GGBS on the compressive strength, setting and heat of hydration were analyzed. Experimental results show that the combination of high volume slag cement paste with low water to binder ratio and high fineness GGBS powder can improve the compressive strength at early ages.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.6-11
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• 2007

The rheological properties of slag cement pastes by effect of particle size distribution of binder were investigated using a Rheostress 1 rheometer (Haake) with a cylindrical spindle and the relationship between fluidity particle size distribution using the Rosin-Rammler equation. Samples are combined the two types of slag powder and OPC, fine slag particles sized Elaine specific surface area $8,000cm^2/g$, coarse slag particles sized Elaine specific surface area $2,000cm^2/g$, intermediate OPC particles $3,450cm^2/g$, used to search for the combination that would yield the best quality product. The all flow curves which were measured by rheometer showed hysterisis and could be classified into 4 types. When the combination was based on a ratio of 15-20 vol% fine particles, 40-50 vol% intermediate particles, 30-40 vol% coarse particles of the total volume, a high fluidity and low yield-strength was achieved. The Rosin-Rammler function can explain aboved correlation flow curve types. On type 1, the n-value had a correlation with plastic viscosity however the blend of type 2 and 3 showed consistent n-value regardless of plastic viscosity. In addition, the blend in type 4 tended to a rise in fluidity according to the increase of the n-value.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.233-240
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• 2012

Hybrid SHCC is being researched actively for its excellent performance in controlling macro and micro cracks using macro and micro fibers, respectively. However, a significant autogenous shrinkage of SHCC is expected since it possesses high unit cement volume in its mix proportion, resulting in autogenous shrinkage cracks. Therefore, this study was performed to evaluate mechanical property of shrinkage-reducing type hybrid SHCC mixed together with steel fiber and PE fiber with excellent micro/macro crack controlling performance. In order to evaluate mechanical property of shrinkage-reducing type hybrid SHCC, replacement ratios of 0% and 10% of expansive admixture and water to binder ratios of 0.45, 0.3, and 0.2 were considered as variables. Then, shrinkage, compressive, flexural, and direct tensile tests were performed. The test results showed that mix proportion with W/B 0.3 significantly improved mechanical performance by using 10% replacement of expansive admixture.