• Journal of the Korea institute for structural maintenance and inspection
• /
• 제23권5호
• /
• pp.23-29
• /
• 2019

This study applies to the surface modification technique by coating the surface of aggregates using the modified paste such as cementitious materials in order to develop completely recycling technology of coarse aggregate. In this case, coating thickness of modified aggregate can be considered that the decision is dependent on the viscosity and tenacity of modified paste. In this study identify the flow properties of the fresh modified paste, and examined for the coating thickness of modified aggregate. As a result, it was possible to design a quantitative coating thickness of modified paste assuming that a modified paste to a Bingham Fluid and consider by excess paste theory and rheology constant (yield value). Accordingly, it is considered that the quantitative mix design of concrete using by surface modified aggregates will be possible.

• International Journal of Highway Engineering
• /
• 제9권4호
• /
• pp.227-236
• /
• 2007

The design number of gyration is required in the process of asphalt mix design using gyratory compactor. The purpose of this study is to select the design number of gyration for asphalt mix design in the laboratory. Three types of methods were used to select the design number of gyration. The first method is to select the gyration number which gives the same density with the mixtures compacted with 75 blows of Marshall Compaction. The second method is to select the gyration number which gives the same deformation strength with the mixtures compacted with 75 blows of Marshall Compactor. The third method is to select the gyration number which meet the 4% air voids. Ten mixtures, one type of aggregate(granite), one type of asphalt binder(pen. 60-80), and 10 types of gradation, were prepared for the laboratory tests. As a result, 100 number of gyration was selected for the design number of gyration of the asphalt mix design. This result shows a similar trend with the design number of gyration used in the foreign countries. Thus, the design number of gyration selected in this study can be used for the asphalt mix design using the gyratory compactors.

• Magazine of the Korea Concrete Institute
• /
• 제7권2호
• /
• pp.136-145
• /
• 1995

A method for lmprovlng strengths of recycled concrete was studied to make use of it in nolmal concrete structures. Recycled conc~ete was prepared by replacing 50% by weight of coarse aggregate with recycled aggregate. Mix design rnet hod for crushed aggregates was used and specirriens were cured by normal moisture curing method. A plastlciser and a fly ash were added to the mix to improve performance of recycled concrete. Compressive strength, flexural strength, tensile strength, elastic modulus, stress-strain relationship, long-term compressive strength and fracture toughness were evaluated and compared with those of rlormal concretes. Recycled concrete showed, in general, lower compressive strength than normal concreks. It also showed lower elastic modulus, lower tensile and flexural strengths, and higher strain under the same stress level. However, by reducing w /c ratio down to 35% using the plasticiser. average compressive strength(${\alpha}_{28}$) of recycled concrete was reached. with slump of $16{\pm}2$cm, to $225kg/cm^2$ or hlgher, which is an acceptable strmgth level for normal structural concrete. I-Iowevei., elastic modulus and strain should be improved further for practical use of recycled concrctc: in normal structure. Fly ash addition in both concretes showed an effect of irnprovilig long term compressive strength and reducing strengths.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 한국농공학회 2000년도 학술발표회 발표논문집
• /
• pp.259-265
• /
• 2000

This study is a fundamental research for recycling waste vinyl in asphalt concrete mixture for roadway pavement. The mixing method and proper content of waste polyethylene(PE) film were determined through preliminary mix design. This study was performed mix designs using 2 type graduations of aggregate and used two types waste PE film. The asphalt concrete mixture was satisfied with the specification of the Ministry of Construction and Transportation. Its showed that dense grade asphalt concrete mixture containing waste vinyl were higher performance in comparision to other mixtures(common dense grade mixture and gap grade mixtures). From results of this study, it was confirmed that addition of waste vinyl improved on quality of asphalt concrete mixture.

• Proceedings of the Korea Concrete Institute Conference
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.641-646
• /
• 2001

Generally, when Fly-Ash was used as replacement material of cement in concrete, it might occur retardation of setting and hardening. So, it is unable to use a large amount of Fly-Ash as replacement for cement. However, if it is used as replacement material of fine aggregate in concrete, we can use a large amount of Fly-Ash and settle a problem of natural-aggregate exhaustion. Furthermore, engineering properties of High Volume Fly-Ash Concrete Is better than that of plain concrete But, the larger Fly-Ash is replaced, the more fluidity of High Volume Fly-Ash Concrete decrease, because porous organization of Fly-Ash adsorb water and Superplasticizer. In this study, after appending additional water to High Volume Fly-Ash Concrete in proportion to weight of Fly-Ash, we intend to find proper ratio which doesn't affect strength and satisfy fluidity As a result of this study, it was found that fluidity of mortar with 25~28 percentage of additional water was satisfied with fluidity of plain mortar, and compressive strength of that was similar to plain mortar's

• Proceedings of the Korea Concrete Institute Conference
• /
• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
• /
• pp.148-153
• /
• 1995

In this report, the physical and chemical properties of Che-ju aggregates were stedued, and the properties of concrete using 5 types combinations of Che-ju aggreagtes were compared with those of concrete using Dag-jeon area aggreagtes. As a result of the properties of Che-ju aggregates are very different with Dae-jeon area aggregates in many aspects. Especially, entrained air content of aggregate is over 1.5% so that the freezing & thawing resistance of concrete was caused in decrease. And the texture properties of Che-ju aggregates and a little content of the entrained air in mortar increase bonding stress between mortar and aggregate, as a result in improving the compressive strength of concrete. Meanwhile, the relationship between cement water ratio(C/W) and 28days compressive strength of concrete(F28) is derived from the stastical regression using experimental data as $F_{28} = -99 + 276 *($(C/W), so this eqation is useful for mix-design of concrete in Che-ju area.

• Journal of The Korean Society of Agricultural Engineers
• /
• 제56권5호
• /
• pp.45-54
• /
• 2014

This study was performed to evaluate compressive strength, flexural strength, static modulus of elasticity, stress-strain ratio and durability of abrasion on EVA concrete reinforced steel fiber (SF) in order to use hydraulic structures, underground utilities, offshore structures and structures being applied soil contaminated area. It is used ordinary portland cement, crushed coarse aggregate, nature fine aggregate, EVA redispersible polymer powder, superplasticizer and deforming agent to find optimum mix design of EVA concrete reinforced steel fiber. EVA concrete reinforced SF was effected on the improvement of mechanical properties and durability of abrasion.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제3권2호
• /
• pp.155-160
• /
• 1999

Recently, the study on mix design of lightweight concrete using the polystyrene foam balls is put into practice from the viewpoint to grade up the quality of concrete and recyclable usage of industrial by products. Polystyrene aggregate concrete, PAC, can be used as structural concrete in low strength application. For instance, PAC could be used in the middle part of sandwich panel where stresses are generally low and in the case of grid-type reinforcement where it does not need high bond strength but little compressive strength to resist the pressure of transverse reinforcement. From this point of view, the authors discussed the influence of fluidity and compressive strength of concrete by the difference of the volume percentage of polystyrene foam balls and water cement ratio.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 한국건축시공학회 2021년도 봄 학술논문 발표대회
• /
• pp.327-328
• /
• 2021

In the manufacturing process of ready-mixed concrete, quantity management directly affects the workability and strength of concrete. Therefore, water quantity is the most important management factor for water quality control of ready-mixed concrete. It can be said that the number of unit water in the mix design, the water quantity due to the surface water contained in the aggregate used, and the water quantity taking into account the concentration of sludge contained in the recycling water when using the recycling water are factors that affect the quantity management of ready-mixed concrete. In this study, as a stable quality control method of ready-mixed concrete, a quantity management method by aggregate surface water and a sludge concentration management method according to the use of recycling water were proposed. Thus, we tried to suggest an efficient quantity management method for stabilizing the quality of ready-mixed concrete.

• International Journal of Highway Engineering
• /
• 제8권1호
• /
• pp.15-23
• /
• 2006

Criteria of the current asphalt mix design, Marshall method, includes the stability and flow which are not related with field performance of HMA mixture, together with the air void, Void filled with asphalt (VFA) and/or Void of mineral Aggregate(VMA). In addition, the limits of stability and flow are satisfied in most cases, the Optimum asphalt content (OAC) is determined based on volumetric properties, such as the air void and/or VFA and/of VMA. Therefore, many researchers have sought mechanistic properties which can replace the stability and flow, making the designed mixture having potential for better field performance. This study initiated to develope a mix design by introducing two performance-related mechanistic properties, the deformation strengh and fracture energy, in place of the stability and flow of the Marshall method. The deformation strength $(S_D)$ from the Kim Test has a high correlation with rutting property and the fracture energy(FE) from the indirect tensile test represents the fatigue cracking property of asphalt mixture. Four types of asphalt mixture were prepared for examining possibility of using the suggested mix design method in comparison with current methods. The results showed that mechanical properties were reflected in determination of OAC with this suggested mix design, unlike the existing Marshall method.