• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.19 no.4
• /
• pp.208-213
• /
• 2009

Artificial lightweight aggregates were produced by using bottom ashes and dredged soils from coal power plant. The amount of glassy phases on the aggregate surfaces, specific gravities, absorption rates, and observations of cross-sectional surfaces were compared according to the compositions, sintering temperatures, and the amount of coating. It is concluded that surface modification by 10 % $CaCO_3$ coating on the aggregate surfaces enhances the properties of aggregates as follows: Specific gravities were controlled by depressing formation of large pores in the aggregates. Sticking phenomena among aggregates during the sintering process was drastically decreased by reducing glassy phases on the aggregate surfaces. Pumping problems during the application of ready-mix concretes containing lightweight aggregates having high value of absorption rates could be solved by reducing the absorption rate.

• Journal of the Korea Institute of Building Construction
• /
• v.15 no.6
• /
• pp.561-567
• /
• 2015

The research, in order to enhance the quality of recycled aggregate, was carried out the quality characteristics test of the recycled aggregates by applying the four kinds of surface treatment using a colloidal suspension of approximately 5nm~60nm particle size with the alkalinity of pH 10.2. The quality tests of recycled aggregate have been processed by specific gravity, water absorption, porosity, surface properties, and the compression and tensile tests. The colloidal suspension was coated effectively the surface of the old cement mortars of recycled aggregate with a constant thickness by colloidal suspension is being applied to the recycled aggregate surface under constant pressure of 100kpa and then it was dried in at $60^{\circ}C$. The surface treatment method by the Method C out of 4 kinds of surface treatment improved effectively the quality of the recycled aggregates, whereby it obtained the best compressive strength and tensile strength of the recycled aggregate concrete.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.3
• /
• pp.268-275
• /
• 2021

The three factors that determine the strength of concrete are the strength of cement paste, aggregate and ITZ(Interfacial Transition Zone) between aggregate and cement paste. Out of these, the strength of ITZ is the most vulnerable. ITZ is formed in 10~50㎛, the ratio of calcium hydroxide is high, and CSH appears low ratio. A high calcium hydroxide ratio causes a decrease in the bond strength of ITZ. ITZ is due to further weak area. The problem of ITZ appears as a more disadvantageous factor when it used lightweight aggregate. The previous study of ITZ properties have measured interfacial toughness, identified influencing factors ITZ, and it progressed SEM and XRD analysis on cement matrix without using coarse aggregates. also it was identified microstructure using EMPA-BSE equipment. However, in previous studies, it is difficult to understand the microstructure and mechanical properties. Therefore, in this study, a method of measuring electrical resistance using EIS(Electrochemical Impedance Spectroscopy) measuring equipment was adopted to identify the ITZ between natural aggregate and lightweight aggregate, and it was tested the change of ITZ by surface coating of lightweight aggregate with ground granulated blast furnace slag. As a result, the compressive strength of natural aggregate and lightweight aggregate appear high strength of natural aggregate with high density, surface coating lightweight aggregate appear strength higher than natural aggregate. The electrical resistivity of ITZ according to the aggregate appeared difference.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.4
• /
• pp.498-505
• /
• 2020

Aggregate occupies about 70-85% of the concrete volume and is an important factor in reducing the drying shrinkage of concrete. However, when constructing high-rise buildings, it acts as a problem due to the high load of natural aggregates. If the load becomes large during the construction of a high-rise building, creep may occur and the ground may be eroded. Material costs increase and there are financial problems. In order to reduce the load on concrete, we are working to reduce the weight of aggregates. However, artificial lightweight aggregates affect the interface between the aggregate and the paste due to its higher absorption rate and lower adhesion strength than natural aggregates, affecting the overall strength of concrete. Therefore, in this study, in order to grasp the interface between natural aggregate and lightweight aggregate by type, we adopted a method of measuring electrical resistance using an EIS measuring device, which is a non-destructive test, and lightweight bone. The change in the state of the interface was tested on the outside of the material through a blast furnace slag coating. As a result of the experiment, it was confirmed that the electric resistance was about 90% lower than that in the air-dried state through the electrolyte immersion, and the electric resistance differs depending on the type of aggregate and the presence or absence of coating. As a result of the experiment, the difference in compressive strength depending on the type of aggregate and the presence or absence of coating was shown, and the difference in impedance value and phase angle for each type of lightweight aggregate was shown.

• Proceedings of the Korean Society of Disaster Information Conference
• /
• 2016.11a
• /
• pp.349-352
• /
• 2016

기존의 가열식 일반아스팔트 공법은 동결 등에 원인으로 포장재의 수명이 짧아져 잦은 유지보수가 필요한 문제점을 갖고 있으며, 이로 인해 내구성이 뛰어난 포장공법의 필요성이 대두되고 있다. 불투수성 방수아스팔트는 이러한 문제를 해결하기 위한 방안의 하나로 아스팔트 혼합물이 골재와 골재 사이를 강력하게 부착하며, 골재간의 공간을 메우고, 골재표면을 두껍게 코팅하여 골재 상호간의 강한 접착을 유지시켜주는 열가소성 폴리머를 사용한 포장공법이다. 본 연구는 불투수성 방수아스팔트 혼합물 개발을 위한 연구의 일환으로 석회석함유량, 유제함유량, 다짐강도, 실험온도 차이에 따른 불투수성 방수아스팔트 혼합물의 압축강도 특성을 실험을 통해 비교 검토하였다. 결과 분석을 통해 각각의 변수에 따른 압축강도 특성을 파악하였으며, 불투수성 방수아스팔트 혼합물 배합설계에 기초자료로 활용하고자 한다.

• Proceedings of the Korean Society of Disaster Information Conference
• /
• 2016.11a
• /
• pp.353-356
• /
• 2016

불투수성 방수아스팔트는 아스팔트 혼합물이 골재와 골재 사이를 강력하게 부착하며, 골재간의 공간을 메우고, 골재표면을 두껍게 코팅하여 골재 상호간의 강한 접착을 유지시켜주는 열가소성 폴리머를 사용한 포장공법이다. 이러한 불투수성 아스팔트는 기존의 가열식 일반아스팔트 공법에서 문제시 되고 있는 내구성 저하와 잦은 유지보수로 인한 문제점을 해결할 수 있는 공법으로 차세대 고내구성 포장공법으로 주목을 받고 있다. 본 연구는 불투수성 방수아스팔트 혼합물 개발을 위한 연구의 일환으로 상온과 영하 $10^{\circ}C$의 조건하에서 기존 아스팔트수지와 새로운 개념의 불투수성 고분자계 수지의 부착성능 비교 검토하였으며, 아스팔트혼합물의 부착성능도 실험을 통해 비교 하였다. 실험결과 불투수성 아스팔트의 부착성능이 기존 아스팔트에 비해 상온은 물론 저온에서도 뛰어난 성능을 발휘하는 것을 확인 하였다.

• International Journal of Highway Engineering
• /
• v.14 no.1
• /
• pp.45-53
• /
• 2012

This study was performed to analyze test results on drying shrinkage for concrete specimens mixed with various constituents in concrete mixes. Test variables are coarse aggregate types(Limestone, Sandstone, Granite, Andesite, Gneiss), fine aggregate types(natural sand, crushed sand) and cement amounts(normal strength, high strength). Epoxy coating of(U&V-H(A,B)) was applied onto the specimen surface to simulate diverse volume surface ratios(22.2, 40, 85.7, 150, 200, 300) with different specimen sizes. The experiments had been executed during 1,014 days at a condition of $20^{\circ}C$ and relative humidity of 60% in environmental chambers. Test results showed that shrinkage strain from the specimen equivalent to real pavement decreased to 39% compared to the standard specimen recommended by KS. Test results also showed that shrinkage strain of the specimen mixed with Limestone was 56~76% of that with Sandstone, thus Limestone mix seems to be suitable to the concrete pavement.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.389-392
• /
• 2008

Ultra-high strength concrete becomes one of the main research areas because recently concrete structure is larger. The quality of aggregate (ultra-high strength and uniformity) as well as chemical admixture and mineral additives is a key factor for ultra-high strength concrete development. However, natural aggregate including crushed aggregate is inappropriate for ultra-high strength concrete because ultra-high strength quality cannot be maintained uniformly over whole natural aggregate lot. In this study ceramic aggregate was applied for ultra-high strength concrete in order to assure uniform quality of ultra-high strength aggregate. Ultra-high strength concrete was achieved by applying coated ultra-high strength ceramic aggregate to enhance the bonding strength between aggregate and cement paste. Also for actual application light weight ceramic aggregate(density 2.2 $g/cm^3$) with zero water absorption was tested.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.5
• /
• 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.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.109-110
• /
• 2022

Recently, it tend to increase the high-rise and large-scale of buildings and the developtment of construction technology can to be applied reinforced concrete structures to high-rise buildings. However, when a high-rise buildings is constructed with reinforced concrete, it has a disadvantage that buildings weight increases. In order to resolve the weight of reinforced concrete structures, various types of lightweight aggregates become development and research. Although lightweight aggregates can be reduced the weight of concrete, the strength of ITZ(Interfacial Transition Zone) is lowered due to its less strength than natural aggregates. In this study, an experimental study was conducted to coat the surface of lightweight aggregates with GGBFS(ground granulated blast furnace slag) to improve the strength of cement matrix mixed with lightweight aggregates. Result of this experimental study shows that the compressive strnegth of the surface coating lightweight aggregates was higher than general lightweight aggregates. Also, it was considered that this is because the pore at the ITZ of the surface-coated lightweight aggregates mixed cement matrix are filled with GGBFS fine particle.