• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.431-440
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• 2011

Concrete structures exposed to fire produce changes in their internal structure, resulting in their service life reduction due to the deterioration of its strength and performance capacity. The deterioration level are dependent on the temperature, exposure time, concrete mix proportions, aggregate property, and material properties. This study was performed to evaluate the thermal behavior of ultra-high strength concrete for the parameters of water to cement ratio (compressive strength), fine to total aggregate ratio, and maximum coarse aggregate size. At room temperature and $500^{\circ}C$, tests of ultrasonic pulse velocity, resonance frequency, static modulus of elasticity, and compressive strength are performed using ${\varnothing}100{\times}200\;mm$ cylindrical concrete specimens. The results showed that the residual mechanical properties of ultra-high strength concrete heated to $500^{\circ}C$ is influenced by variation of a water to binder ratio, fine to total aggregate ratio, and maximum coarse aggregate size.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Advances in Computational Design
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• v.8 no.2
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• pp.113-131
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• 2023

The use of fibers has been commonly considered in engineered cementitious composites, but their behavior with coarse aggregate in concrete has not been studied significantly, which is needed to meet structural performance objectives for design, such as ductility. This research analyzes the behavior of fiber-reinforced concrete with coarse aggregate with 0.62%, 1.23%, and 2% PVA (Polyvinyl-alcohol) content, varying the maximum aggregate size. Tensile (direct and indirect) and compressive concrete tests were performed. The PVA fiber addition in coarse aggregate concrete increased the ductility in compression, especially for the fiber with a larger aspect ratio, with a minor impact on strength. In addition, the tensile tests showed that the PVA fiber increased the tensile strength of concrete with coarse aggregate and, more significantly, improved the ductility. A selected mixture was used to build short and slender reinforced concrete beams to assess the behavior of structural members. PVA fiber addition in short beams changed the failure mode from shear to flexure, increasing the deflection capacity. On the other hand, the slender beam tests revealed negligible impact with the use of PVA.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.577-584
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• 2011

A series of field and laboratory permeability tests were performed to investigate the pore-clogging phenomenon of porous concrete used for pavement materials of a road. The field permeability tests were conducted for 37 study points in Jeju city, using the porous concretes with 13mm of maximum coarse aggregate ($G_{max}$). The results show that the service life of porous concrete is about 22 months when the permeability of the porous concrete is designed for 0.01 cm/sec. Some specimens were made with the purpose of recreating pore-clogging phenomenon. Tests were done for injected concentration of pore-clogging materials or size of maximum coarse aggregates ($G_{max}$). The test results demonstrated that relatively long in service life experienced with small amount of injected concentration of pore-clogging materials, whereas relatively short in service life experienced with a reduction in size of maximum coarse aggregates ($G_{max}$). In conclusion, the service life of porous concrete is in proportion to the concentration of pore-clogging material but it is in inverse proportion to the size of maximum coarse aggregate ($G_{max}$). Thus, the persisting period of porous concrete can be determined with respect to concentration of pore-clogging materials or size of maximum coarse aggregates ($G_{max}$).

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.59-68
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• 2008

The experiment was carried out to investigate the influence of coarse aggregate, admixture, and accelerator on the properties of concrete. As the maximum size of coarse aggregate decreased from 13 mm to 8 mm, fluidity of fresh concrete declined but compressive strength and dynamic modulus of elasticity of hardened concrete increased remarkably. The mechanical properties of concrete substituted silica fume to the plain concrete improved, the compressive strength of that substituted blast furnace slag increased slightly. The hydration reaction and compressive strength of specimen with sodium luminate type accelerator were high at initial, but specimen with alkali free type accelerator improved largely in 28 days.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.169-175
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• 2011

Strength is one of the very important factors to evaluate the physical properties of concrete. Aggregate forms the most parts in concrete. Cement as a binder in concrete is also closely related to strength. This experiment was tested to understand the effect of the characteristics of aggregate and cement on the relationship between concrete compressive strength and Shear Wave velocity. It was experimented by the different types of cement and maximum coarse aggregate sizes. Type I cement and rapid setting cement was used. Aggregates from three different regions were used. Aggregate of 19mm and 13mm maximum coarse aggregate sizes was used for grading. The relationship between compressive strength and Shear Wave velocity was tested under the condition of same mixture. LA wear test was used to quantify the characteristics of aggregate. As a result, the relationship between concrete compressive strength and Shear Wave velocity was affected by the types of cement, but regular relationship was appeared regardless of types of aggregate, grading and abrasion ratio.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.559-566
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• 2010

Fifteen lightweight concrete mixes were tested to evaluate the effect of maximum size of coarse aggregate and the replacement level of natural sand on the various properties of fresh lightweight concrete. The different properties, such as water absorption against the elapsed time, pore size distribution and micro-structure of lightweight aggregates used, influencing on the workability of fresh concrete were also measured. Test results showed that the initial slump of lightweight concrete decreased with the increase of the replacement level of natural sand. The slump of all-lightweight concrete sharply decreased by around 80% of the initial slump after 30~60 minutes. The air content and bleeding rate of lightweight concrete were significantly affected by the replacement level of natural sand as well as the maximum size of coarse aggregates. Empirical equations recommended in ACI 211 and Korea concrete standard specifications underestimated the air content of the lightweight concrete, indicating that the underestimation increases with the decrease of the replacement level of natural sand. In addition, equations to predict the air content and bleeding rate of lightweight concrete were proposed based on the test results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.83-86
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• 2006

This study investigates engineering properties of concrete using recycled coarse aggregated manufactured by bar-crusher. Test showed that Bar-crusher(S) had more effective results at fresh state than cone-crusher(C) and impact-crusher(I). In case of specimens manufactured by S, increase of spindle velocity, incorporating ratio of recycled aggregate and maximum size of aggregate inclined fluidity. As for the hardened concrete, compressive strength of specimens by C or I exhibited lower value than that of S. In addition, specimens using recycled aggregate manufactured by 400rpm and 500rpm of spindle velocity showed less than 10% reduction rate of strength, which is not significant reducing value. It is found that 500rpm of the spindle velocity had the best strength performance, while 600rpm was the worst. Strength value of specimens decreased as incorporating ratio of recycled aggregate inclined, but the strength value of most specimens exhibited less than 10% of reducing rate, assuming favorable result, only at less than 25% incorporating ratio of recycled aggregate.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.477-484
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• 2013

In this study, eleven reinforced concrete beams, ground granulated blast furnace slag, replacing recycled coarse aggregate (BRS series) and recycled coarse aggregate with steel fiber (BSRS series), and standard specimen (BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the shear performance of such test specimens, such as the load-displacement, the failure mode and the maximum load carrying capacity. All the specimens were modeled in 1/2 scale-down size. Test results showed that test specimens (BSRS Series) was increased the compressive strength by 9%, the maximum load carrying capacity by 1~6% and the ductility capacity by 1.02~1.13 times in comparison with the standard specimen (BSS). And the specimens (BSRS Series) showed enough ductile behavior and stable flexural failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.1-10
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• 2014

In this study, thirteen reinforced concrete beams, ground granulated blast furnace slag, replacing recycled coarse aggregate with PVA fiber (BSPG series) and recycled coarse aggregate with hybrid fiber ($BSPGR_1$, $BSPGR_2$ series), and standard specimen (BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the Structural performance of such test specimens, such as the load-displacement, the failure mode, and the maximum load carrying capacity. All the specimens were modeled in 1/2 scale-down size. Test results showed that test specimens ($BSPGR_1$, $BSPGR_2$ series) was increased the compressive strength by 13%, the maximum load carrying capacity by 4~21% and the ductility capacity by 4~28% in comparison with the standard specimen (BSS). And the specimens ($BSPGR_1$, $BSPGR_2$ series) showed enough ductile behavior and stable flexural failure.