• International Journal of Concrete Structures and Materials
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• 제4권2호
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• pp.97-104
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• 2010

The crushed limestone sand is an abundant material in Tunisia, which induces many environmental problems. Indeed, available stocks of siliceous sand drastically decrease because of its massive use in hydraulic concrete. Some recent research works, carried out in Tunisia, concluded that crushed limestone sand may be used in concrete manufacture instead of siliceous sand traditionally used. In this context, an experimental study was achieved in order to quantify the influence of a partial or total substitution of siliceous sand by crushed limestone sand on hydraulic concrete performances. Preliminary chemical and physical tests on crushed sand indicated that it presented the minimum requirement for its use as aggregate in hydraulic concrete. 79 concretes were then prepared with siliceous sand, crushed limestone sand and a mix of the two sands. Their slump value and compressive strengths were measured on plain concretes. Complementary structural tests on reinforced concrete beam were also performed. The results proved that crushed limestone sand concretes showed workability and mechanical performances closed to those of siliceous sand concretes.

• International Journal of Concrete Structures and Materials
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• 제4권2호
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• pp.105-108
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• 2010

In order to determine the effect of the use of limestone sand on chloride ion ingress in mortar, specimens were cast with two different sands: siliceous sand (used as reference) and limestone crushed sand (used for this study). To compare and assess the resistance of this mortar to chloride penetration, two different diffusions tests were employed: slow migration and rapid migration (AASHTO test). In this study, calculation of the effective diffusion coefficient is proposed using a model based on Nernst. Planck equation. The diffusion coefficients from each sample were compared. The results for all tests show that the diffusion coefficients for siliceous sand mortar are larger than those obtained with limestone sand. It appears also that the diffusion coefficient varies as a function of the W/C ratio.

• International Journal of Concrete Structures and Materials
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• 제4권2호
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• pp.109-112
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• 2010

Part I of this study was devoted to the electrical accelerated chloride diffusion in mortars. In this second part, natural chloride diffusion has been investigated for four types of mortars under exposure to a 0.5 mol/L NaCl solution for a period of up to 35 days. Two different types of sand were used for the production of test samples: siliceous sand (used as a reference) and limestone sand (used in this study). The effect of water to cement ratio and exposure time on the diffusion coefficients of mortars was also investigated. In this study, the total and free chloride content and penetration depth of mortar were measured after immersion, and Fick's second law of diffusion was fitted to the experimental data to determine the diffusion coefficient. Their results show that the use of crushed limestone sand in mortar had a positive effect on the chloride resistance. The apparent diffusion coefficient in all specimens was smaller than that in siliceous sand mortar. However, the chloride penetration of these mortars was increased as exposure time progressed.

• Advances in concrete construction
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• 제7권2호
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• pp.87-96
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• 2019

Self-compacting concretes (SCC) are highly fluid concrete which can flow without any vibration. Their composition requires a large quantity of fines to limit the risk of bleeding and segregation. The use of crushed sand rich in limestone fines could be an adequate solution for both economic and environmental reasons. This paper investigates the influence of quarry limestone fines from manufactured crushed sand on rheological, mechanical and durability properties of SCC. For this purpose, five mixtures of SCC with different limestone fines content as substitution of crushed sand (0, 5, 10, 15 and 20%) were prepared at constant water-to-cement ratio of 0.40 and $490kg/m^3$ of cement content. Fresh SCC mixtures were tested by slump flow test, V-funnel flow time test, L-box height ratio, segregation resistance and rheological test using a rheometer. Compressive and flexural strengths of SCC mixtures were evaluated at 28 days. Regarding durability properties, total porosity, capillary water absorption and chloride-ion migration were studied at 180 days. For the two test modes in fresh state, the results indicated compatibility between slump flow/yield stress (${\tau}_0$) and V-funnel flow time/plastic viscosity (${\mu}$). Increasing the substitution level of limestone fines in SCC mixtures, contributes to the decrease of the slump flow and the yield stress. All SCC mixtures investigated achieved adequate filling, adequate passing ability and exhibit no segregation. Moreover, the inclusion of limestone fines as crushed sand substitution reduces the capillary water absorption, chloride-ion migration and consequently enhances the durability performance.

• Advances in concrete construction
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• 제16권4호
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• pp.177-188
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• 2023

In the context of the shortage of river sand, two types of manufactured sand (MS) were used to partially replace river sand (RS) to design manufactured sand concrete (MSC). A total of 81 specimens were designed for uniaxial compression test and beam flexure test. Two parameters were considered in the tests, including the types of MS (i.e. limestone manufactured sand (LMS), pebble manufactured sand (PMS)) and the MS replacement percentage (i.e., 0%, 25%, 50%, 75%, 100%). The stress-strain curves of MSC were obtained. The effects of these parameters on the compressive strength, elastic modulus, peak strain, toughness and flexural strength were discussed. Additionally, the sensitivity of particle size distributions to the performance of MSC was evaluated based on the grey correlation analysis. The results showed that compared with river sand concrete (RSC), the rising slope of the stress-strain curves of limestone manufactured sand concrete (LMSC) and pebble manufactured sand concrete (PMSC) were higher, the descending phrase of LMSC were gentle but that of PMSC showed an opposite trend. The physical and mechanical properties of MSC were affected by the MS replacement percentage except the compressive strength of PMSC. When the replacement percentage of LMS and PMS were 50% and 25% respectively, the corresponding performances of LMSC and PMSC were better. In generally, when the replacement percentage of LMS and PMS were same, the comprehensive performance of LMSC were better than that of PMSC. The constitutive model and the equations for mechanical properties were proposed. The influence of particle ranging from 0.15 mm to 0 mm on the performance of MSC was lower than particle ranging from 4.75 mm to 0.15 mm but this influence should not be ignored.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.177-180
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• 2000

The objective of this study is to analyze the degree of surface-glossing of cement mortar with the grading of aggregate and contents of limestone powder. According to the experimental results, degree of surface-glossing of cement mortar using river sand is higher than that of crushed sand. As F.M of aggregates is less than 2.78, degree surface-flossing of cement mortar has better performance, Also, as the contents of limestone power increase, degree of surface-flossing is shown to be improved, And it shows that degree of surface-glossing decrease with elapse of age.

• 한국농공학회논문집
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• 제55권3호
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• pp.123-128
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• 2013

This study was performed to evaluate the slump flow, air content, setting time, compressive strength, adiabatic temperature rise and diffusion coefficient of chloride used ordinary portland cement, crushed coarse aggregate, crushed sand, river sand, fly ash, limestone powder, blast furnace slag powder and superplasticizer to find optimum mix design of low carbon green concrete for structures. The performances of low carbon green concrete used fly ash, limestone powder and blast furnace slag powder were remarkably improved. This fact is expected to have economical effects in the manufacture of low carbon green concrete for structures. Accordingly, the fly ash, limestone powder and blast furnace slag powder can be used for low carbon green concrete material.

• 한국농공학회논문집
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• 제55권6호
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• pp.11-17
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• 2013

This study was performed to evaluate the chlorine ion penetration resistance, chemical resistance and freezing and thawing resistance used ordinary portland cement, crushed coarse aggregate, crushed sand, river sand, fly ash, limestone powder, blast furance slag powder and superplasticizer to find optimum mix design of low carbon green concrete for structures. The performance of low carbon green concrete used fly ash, limestone powder and blast furnace slag powder were remarkably improved. This fact is expected to have economical effects in the manufacture of low carbon green concrete for offshore structures. Accordingly, the fly ash, limestone powder and blast furnace slag powder can be used for offshore structure materials.

• Advances in concrete construction
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• 제10권5호
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

• 분석과학
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• 제13권1호
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• pp.5-11
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• 2000

시운전중인 국내 최대 규모의 유동층 보일러에서 발생한 크링커의 생성원인을 규명하기 위해 현장에서 크링커 및 사용중인 무연탄의 회, 모래, 석회석을 채취하였다. 발전소에서 시행중인 운전조건을 고려하여 이들에 대한 비율별 및 온도 조건 변화에 따른 각 시료의 성분 분석, 표면형상 관찰, 열특성 분석 및 결정구조 분석을 실시하였다. 크링커는 횐 색과 검은 색 및 갈색 부분으로 되어 있었으며 이를 색깔별로 크게 흰 색 및 검은 색으로 구분하여 실험을 하였다. 그 결과 검은 색은 모래, 흰 색은 무연탄 회에 보다 유사한 특성을 지녔고, 온도에 따른 실험 결과, 모래의 소결온도는 $1,200^{\circ}C$ 이상의 고온인 반면에 모래에 석회석을 혼합할 경우, 소결온도가 낮아짐을 알 수 있었다. 따라서 크링커의 생성원인은 유동층 보일러 내에 고온부가 형성되어 모래와 석회석이 용융 또는 소결된 상태에 무연탄회가 부착되어 형성된 것으로 판단되었다.