• Computers and Concrete
• /
• v.4 no.6
• /
• pp.499-510
• /
• 2007

The densified mixture design algorithm (DMDA) was employed to manufacture high-performance lightweight concrete (LWAC) using silt dredged from reservoirs in southern Taiwan. Dredged silt undergoing hydration and high-temperature sintering was made into a lightweight aggregate for concrete mixing. The workability and durability of the resulting concrete were examined. The LWAC made from dredged silt had high flowability, which implies good workability. Additionally, the LWAC also had good compressive strength and anti-corrosion properties, high surface electrical resistivity and ultrasonic pulse velocity as well as low chloride penetration, all of which are indicators of good durability.

• Computers and Concrete
• /
• v.21 no.2
• /
• pp.139-147
• /
• 2018

Due to enhanced construction requirement, ready mixed concrete are being popular day by day. The current study aimed to develop ready mixed concrete using GBFS contained cement and determine its properties of fresh and hardened states. A real scale experiment was set up in a ready mixed plant for measuring workability and compressive strength. The workability was tested after mixing (within 5 minutes), 30, 60, 90, 120 and 150 minutes of the running of bulk carrier. The ready mixed carrier employed spinning motion i.e., rotating around its axis with 20 RPM and running on road with 1km/h speed. The mixing ratio of cement: sand:gravel, water to cement ratio, super plasticizer were, 1:1.73:2.47, 0.40 and 6% of cement, respectively. The chemical composition of raw material was determined using XRF and the properties of cements were measured according to ASTM standards. The experimental results confirm that the cement with composition of 6.89% of GBFS, 4% of Gypsum and 89.11% of clinker showed the good compressive strength and workability of concrete after 150 minutes of the spinning motion in bulk carrier.

• Computational Structural Engineering
• /
• v.1 no.2
• /
• pp.131-142
• /
• 1988

This study was carried out to investigate the long-term deformation of superplasticized concrete. Compressive strength, shrinkage, creep and creep recovery of concretes with and without the superplasticizing admixture have been compared for one year. The test results on creep of superplasticized concrete were also compared with three methods of predicting creep; the ACI model, the CEB model and the BP model. According to test results, superplasticized concrete has good results in compressive strength at an age of 28 days of more than 22%, drying-shrinkage cured at air-conditioned storage less than 15%, creep deformation in air conditioned storage and loaded at an age of 28 days to 15% of compressive strength less than 11% of control concrete.

• Korean Journal of Materials Research
• /
• v.29 no.10
• /
• pp.603-608
• /
• 2019

Plastic waste is becoming a problem in various countries because of the difficulty of natural decomposition. One type is PET plastic(Polyethylene Terephthalate), which is often used as a bottle for soft drink packaging, and LDPE(Low Density Polyethylene), which is also widely used as a food or beverage packaging material. The use of these two types of plastic continuously, without good recycling, will have a negative impact on the environment. Building material waste is also becoming a serious environmental problem. This study aims to provide a solution to the problem of the above plastic waste and building material waste by making them into a mixture to be used as bricks. Research is carried out by mixing both materials, namely plastic heated at a temperature of $180-220^{\circ}C$ and building material waste that had been crushed and sized to 30-40 mesh with homogeneous stirring. The ratios of PET and LDPE plastic to building material waste are 9 : 1, 8 : 2, 7 : 3, 6 : 4 and 5 : 5. After heating and printing, density, water absorption and compressive strength tests are carried out. Addition of PET and LDPE plastic can increase compressive strength, and reduce water absorption, porosity and density. A maximum compressive strength of 10.5 MPa is obtained at the ratio of 6 : 4.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.05a
• /
• pp.46-47
• /
• 2013

This study investigates the effect of a grading of aggregate on the properties of concrete. It is a common sense in Korea that the production of coarse aggregate in ready mixed concrete industry excludes particular aggregate size ranged from 5 mm to 13 mm for saving the production cost. This causes a gap grading of the aggregate for concrete, which can lead to the increase of unit water, the development of drying shrinkage-induced crack and the reduction of compressive strength. In this study, conventional aggregate obtained from a ready mixed concrete factory and the aggregate with a modified grading produced in lab. condition were prepared. Results showed that a good grading of aggregate (i.e., the ratio of 5~13 mm and 13~25 mm is 6 to 4) produced in the lab. condition significantly improved the slump and the compressive strength of the concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2006.05a
• /
• pp.19-22
• /
• 2006

The quantity of Recycled concrete powder is increased, because it hal been ever so often crushing for production of a good quality recycled aggregates This Study is on the Development of Concrete-Product by Using Recycled Concrete Powder and alto for know performance of concrete-producted having low water contents and it is to know for all of performance of concrete-producted having low water contents The conclusions of this study are following. The use of replacement cement is not effective, because it has strengh of less than 10MPa But It is possible to develop high strength concrete-producted having 39MPa above compressive strength by using recycled concrete powder. Because strength enhancement effects by recycled concrete powder are responsible to optimum grading. The conclusions of this study are following. The use of replacement cement is not effective, because it has strengh of less than 10MPa. It is possible to develop high strength concrete-producted having 39MPa above compressive strength by using recycled concrete powder. Because strength enhancement effects by recycled concrete powder are responsible to optimum grading.

• Steel and Composite Structures
• /
• v.29 no.5
• /
• pp.659-667
• /
• 2018

This paper deals with the experimental study on strength the strength and deformation characteristics of short circular Concrete Filled Steel Tube (CFST) columns. Effect of vertical stiffeners on the behavior of the column is studied under axial compressive loading. Intermittently welded vertical stiffeners are used to strengthen the tubes. Stiffeners are attached to the inner surface of tube by welding through pre drilled holes on the tube. The variable of the study is the spacing of the weld between stiffeners and circular tube. A total of 5 specimens with different weld spacing (60 mm, 75 mm, 100 mm, 150 mm and 350 mm) were prepared and tested. Short CFST columns of height 350 mm, outer tube diameter of 165 mm and thickness of 4.5 mm were used in the study. Concrete of cube compressive strength $41N/mm^2$ and steel tubes with yield strength $310N/mm^2$ are adopted. The test results indicate that the strength and deformation of the circular CFST column is found to be significantly influenced by the weld spacing. The ultimate axial load carrying capacity was found to increase by 11% when the spacing of weld is reduced from 350 mm to 60 mm. The vertical stiffeners are found to effective in enhancing the initial stiffness and ductility of CFST columns. The prediction models were developed for strength and deformation of CFST columns. The prediction is found to be in good agreement with the corresponding test data.

• Advances in concrete construction
• /
• v.8 no.1
• /
• pp.47-54
• /
• 2019

Portland cement pervious concrete has been expected to have good water permeability, mechanical properties and abrasion resistance at the same time when Portland cement pervious concrete is applied to the actual vehicle pavement. In this study, the coarse aggregate and cement were replaced by the fine aggregate and the silica fume to improve actual road performance Portland cement pervious concrete. The Mechanical properties, the water permeability and the abrasion resistance of Portland cement pervious concrete were investigated. The results show that the compressive strength, the flexural strength and the abrasion resistance are increased when the fine aggregate and the silica fume are added to Portland cement pervious concrete separately. However, the porosity and the water permeability are decreased simultaneously. With assistance of silica fume and fine aggregate simultaneously, Portland cement pervious concrete could achieve a higher strength. The compressive strength, the flexural strength and the abrasion resistance of Portland cement pervious concrete mixed with 5% fine aggregates and 8% silica fume are increased by 93.1%, 65% and 65.2%, respectively. The porosity and the water permeability are decreased by 22.4% and 85% when Portland cement pervious concrete is mixed with 5% fine aggregate and 8% silica fume. Therefore, the replacement ratio of the fine aggregates and the silica fume should be considered comprehensively and determined on the premise of ensuring the water permeability coefficient.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.5
• /
• pp.153-160
• /
• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Explosives and Blasting
• /
• v.21 no.4
• /
• pp.23-35
• /
• 2003

This study is to clarify the comparative relationship and a mechanical anisotropy of rock on the subject of granite distributed in the Namwon area Uniaxial compressive and Brazilian strengths with respect to the horizontal and vertical axes of granite are shown the linear relation. In the case of the result of the p-wave velocity measurement. it is represented that the velocity of vortical direction is faster about 10 to 15% than other two horizontal directions. The difference between velocities is caused by a developmental pattern of microcracks distributed in rock. Moreover, this result is very consistent with the result investigated through thin sections. The proportion of uniaxial compression strength to Index of point load strength ($Is_{(50)}$) is 18~20 times in case of granite. Uniaxial compressive strength is relatively good relationship with point load strength, Schmidt hammer rebound value, and tensile strength point load strength of them is the best comparative relationship. It is indicated that point load test is the most useful tool to estimate uniaxial compressive strength, comparing with other experimental methods.