• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.739-742
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• 2005

In this study, we predicted the service life against the freezing and thawing. as a result, we found that in the case of using the low quality crushed sand with high water-cement ratio, there is the possibility of deterioration. but in any other case, we concluded that there is no chance to deteriorate if we have the required air contents by using AE agent. we are going to improve the method to evaluate more exactly the durability of the concrete with crushed sand by acquiring data from the specimen which are exposed to field for long time.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.227-230
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• 1998

The void ratio, continuous void ratio, coefficient of permeability, compressive strength and tensile strength were considered according to the EAF(Electric Arc Furnace) slag replacement and sand percentage in permeable concrete used with EAF slag as aggregate. The sand percentage was directly proportional to the permeable coefficient, but inversely proportional to the compressive strength. When the compressive strength and coefficient of permeability were 230 kg/$\textrm{cm}^2$ and 1$\times$$10^{-1}$ cm/sec, the useful sand percentage was 8%. When the EAF slag replacement was 25%, the coefficient of permeability was the most low and compressive strength was the most high.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.285-292
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• 2001

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented for mixture of high strength concrete using crushed sands. Mixing design of concretes are various water-cement ratios(w/c) such as 25%, 40%, 55% and different replacement ratio of crushed sands to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strength of concretes with w/c lower than 40% and 25% is higher than $400kgf/cm^2$ and $600kgf/cm^2$ respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.429-432
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• 2005

An investigation for long-term strength characteristics of crushed sand concrete using crushed sands produced in Yang-san, Kim-hae and Jin-hae that can assume to respectively represent eastern, middle and western suburb of Busan was carried out. Cases were divided as variation of blend ratio of crushed sand (50, 60, 70, 80, 90, 100$\%$) and area. Compressive strength, unit weight and strain in age of 28, 60, 90, 180, 356 days were measured in each case. Compressive strength, unit weight and modulus of elasticity were increased as time goes by and they are expected to keep on increasing in long-term age as well.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.53-60
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• 2012

The main object of this paper is to investigate the effects of high temperatures on the physical and mechanical properties of natural sand concrete(NSC) and crushed sand concrete(CSC). Test samples were exposed to high temperature ranging from $200^{\circ}C$ to $800^{\circ}C$. After exposure, various tests were conducted. Color image analysis and weight losses were determined and compressive strength test and splitting tensile strength test were conducted. The results indicated that weight losses increased as exposure temperature increased with comparable decreasing rate. The results also showed that compressive strength and splitting tensile strength and modulus of elasticity decreased as exposure temperature increased. The results also showed that residual compressive strength of NSC decreased more drastically than that of CSC at $200^{\circ}C$ and $400^{\circ}C$. Residual splitting tensile strength of NSC decreased more than that of CSC at $200^{\circ}C$, while NSC and CSC showed comparable residual strength ratio at $800^{\circ}C$.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.277-289
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• 2011

This study proposes a new testing method for shear bearing capacity of FRP-concrete interface, which could well consider a loading condition corresponding to a tunnel lining undergoing axial compression and could be easily carried out with a simply specified specimen. A parametric study is carried out for capturing an optimized condition of coarse-sand coating of FRP, which governs shear bearing capacity of FRP-concrete interface, by using the proposed testing manner in this study. From the parametric study, it is shown that the proposed testing method is reasonably feasible in comparison with the existing testing methods. An optimum condition of coated sand size and sand density is given for the shearing capacity of FRP-concrete interface.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.17-20
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• 2005

This study investigates mock-up test of the concrete containing crushed sands with improved quality and following could be draws as conclusions. The slump satisfies the target value. The air content reaches the goal, however, it decreases by the occurrence of loss with elagse of age. In normal strength region, the setting time of CS24 member is shorter than that of SS24 member. In high strength region, the setting time of SS50 member is make only slower than that of CS5O because of the use of retarding AE agent. The compressive strength of the concrete using crushed sands is little higher than the concrete using washed sea sands, and the compressive strength of core sample increases at lower part. Drying shrinkage of the concrete using crushed sands is larger than that using washed sea sands. At water caring condition, both the concrete using crushed sands and using washed sands expand at first, exhibit to be swelled and with elagse of age, they remain relatirely constant. Also, the drying shrinkage occurred greatly when the width and thickness of a member are small because it is easy to evaporate the inner part vapor in the small width and thickness of a member. there can be little different according to the location of a contact gauge, however it is similar to the change of specimen's length change. The concrete using crushed sands, of which grading, grain shape and fine particle is improved, are comparable to the quality of the concrete using washed sea sand.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.85-91
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• 2008

Prepacked concrete has recently been used in the special constructions fields such as underwater concrete work, heavy-weight concrete work, underground structure work, partial repair works for damaged reinforced concrete structures. and polymer-modified mortars have been employed as grouting mortars for the prepacked concrete. The purpose of this study is to recommend the optimum mix design of polymer-modified grouting mortars for prepacked concrete. Polymer-modified mortars using SBR and EVA emulsions as admixture of grouting mortars for prepacked concrete are prepared with various mix proportions such as sand-binder ratio, fly ash replacement ratio, polymer-binder ratio. and tested for flowability, viscosity of grouting mortars, bleeding ratio, expansion ratio, flexural and compressive strengths of grouting mortars and compressive and tensile strengths of prepacked concretes. From the test results, it is apparent that polymer-modified mortars can be produced as grouting mortars when proper mix design is chosen. We can design the mix proportions of high strength mortars for prepacked concrete according to the control of mix design factors such as type of polymer, polymer-binder ratio, sand-binder ratio and fly ash replacement ratio. Water-binder ratio of plain mortars for a constant flowability value are in the ranges of 43% to 50%. SBR-modified mortar has a little water-binder ratios compared to those of plain mortar, however, EVA-modified mortar needs a high water-binder ratio due to a high viscosity of polymer dispersion. The expansion and bleeding ratios of grouting mortars are also controlled in the proper value ranges. Polymer-modified grouting mortars have good flexural. compressive and tensile strengths, are not affected with various properties with increasing fly ash replacement to cement and binder-sand ratio. In this study, SBR-modified grouting mortar with a polymer-binder ratio of 10% or less, a fly ash replacement of 10% to cement and a sand-binder ratio of 1.5 is recommended as a grouting mortar for prepacked concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.392-397
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• 1998

In this paper, the properties of cement mortar used recycled aggregate are analyzed and compared with river and crushed sand mortar. Recycled aggregates are made by crushing wasted concrete had various compressive strength, and test items are the properties of fresh mortar, hardened mortar and durability. According to the experimental results, flow, unitweight, strength and durability of cement mortar used recycled aggregates decrease compared with those of river and crushed sand mortar.

• Computers and Concrete
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• v.5 no.5
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• pp.491-501
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• 2008

The present study verifies compressive strength, ultrasonic pulse velocity, electrical resistance,permeable ratio, and shrinkage from waste glass controlled low strength materials (WGCLSM) and early-high-strength WGCSLM specimens, by replacing the sand with waste glass percentages of 0%, 10%,20%, and 30%. This study reveals that increasing amounts of waste LCD glass incorporated into concrete increases WGCLSM fluidity and reduces the setting time, resulting in good working properties. By increasing the glass to sand replacement ratio, the compressive strength decreases to achieve low-strength effects. Furthermore, the electrical resistance also rises as a result of increasing the glass to sand replacement ratio. Early-high-strength WGCSLM aged 28 days has twice the electrical resistance compared to general WGCSLM. Early-high-strength WGCSLM aged 7 days has a higher ultrasonic pulse velocity similar to WGCSLM aged 28 days. The variation of length with age of different compositions is all within the tolerance range of 0.025%. This study demonstrates that the proper composition ratio of waste LCD glass to sand in early-high-strength WGCSLM can be determined by using different amounts of glass-sand. A mechanism for LCD optical waste glass usage can be established to achieve industrial waste minimization, resource recycling, and economic security.