• Magazine of the Korea Concrete Institute
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• v.2 no.4
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• pp.61-68
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• 1990

This experimental study is aimed to investigate the coating method of scoria lightweight aggregate for reo duction of water absorption and the physical dynamic characteristics of coated-scoria jightweight aggregate con¬crete. The coating methods are as follows: I) Non-coating method. II) Coating method of only cement paste. rn) Coating mehtod of surface-coating agent after coating by cement paste. IV) Coating method of only surfaee-coating agent. V) Coating method of cement pasted after coating by surface-coating agent. The summerized conclusion are as fallows ; 1) Specific gravity and the rate of water absorption were lowest when aggregate was covered by only surface-coating agent, especially, rate of absorption was about 10% of non-coating aggregate. 2) Coated-aggregate were about 0.87~0.97t/m3 and lightweight concrete made of coated-aggre¬gates were 1.80~ 1.94 t/m3 in unit weight. 3) Compressive strength of the lightweight concrete made of cement pasted-coating aggregate was about 200~215kg/crrl. 4) The higher the rate of water absorption of coarse aggregate, the higher the rate of deterioration of compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.21-28
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• 2014

The purpose of this study is to investigate the mechanical properties and carbonation resistance of concretes using lightweight aggregate coated surface finishing materials. To evaluate the mechanical properties and carbonation resistance of concrete, slump, air amount, air-dried unit volume weight, compressive strength, and carbonation depth are tested. In terms of the unit volume weight of concrete, air-dried unit volume weight of concrete using coating lightweight aggregate was measured as $1,739{\sim}1,806kg/m^3$. When using coating aggregate, compressive strength of concrete at 28 days was measured as much as 82.7~95.9% of the compressive strength using non-coating aggregate. It is found that compressive strength tends to decrease with coating lightweight aggregate. However, all concretes using coating lightweight aggregate except O-LWAC satisfied the criteria for 28-day compressive strength suggested in KS. The measurement of carbonation depth when the water-repellent agent was used found that carbonation depth was reduced by as much as 2.6~6.1%. On the other hand, when using polymer waterproof agent, carbonation depth was reduced by as much as 8.6~12.0%. Consequently, to improve carbonation resistance, polymer waterproof agent was more effective than water-repellent agent. In particular, epoxy showed the most outstanding performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.107-108
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• 2022

In recent years, the construction industry has a tendency to increase of high-rise builidngs. High rise buildings can use limited space efficiently. But High rise buildings have problem that have extremely heavy weight. Various studies are being conducted to reduce the weight of buildings. Although lightweight aggregate is a meterial that can effectively reduce the weight of buildings, the strength of the aggregate itself is weak and the absorption rate is high, so the strength of the ITZ(Interfacial Transition Zone) area is weak. Therefore, it is essential to improve the interfacial area when using lightweight aggregates. In this study, an experiment was conducted to improve the adhesion between the aggregate and cement paste and to strengthen the interfacial area by coating the surface of the lighteight aggregate with Blast Furnace Slag. To confirm the improvement, compressive strength and EIS(Electrochemical Impedance Spectroscopy) measurements were perfromed. Using EIS, the change in electrical resistance of the cement hardened body was confirmed. As a result, it was confirmed that the lightweight aggregate coated on the surface showed highter compressive strength and electrical resistance than the non-coated lightweight aggregate, and that the coating material was filled in the interfacial area and inside the aggregate that helped to strengthen the compresssive strength and higher electrical resistance.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.727-738
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• 2023

In concrete, the interface between the aggregate and cement paste is often the most critical factor in determining strength, representing the weakest zone. Lightweight aggregate, produced through expansion and firing of raw materials, features numerous surface pores and benefits from low density; however, its overall aggregate strength is compromised. Within concrete, diminished aggregate strength can lead to aggregate fracture. When applying lightweight aggregate to concrete, the interface strength becomes critical due to the potential for aggregate fracture. This study involved coating the surface of the aggregate with blast furnace slag fine powder to enhance the interfacial strength of lightweight aggregate. The impedance of test specimens was measured to analyze interface changes resulting from this surface modification. Experimental results revealed a 4% increase in compressive strength following the coating of the lightweight aggregate surface, accompanied by an increase in resistance values within the impedance measurements corresponding with strength enhancement.

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

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

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.223-228
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• 1997

In this study, bottom ash, lightweight aggregate, and Expanded Polystyrene was used to lighten the mortar. In order to compensate the reduction of strength caused by lightening, the waste foundry sand produced as solid waste was substituted for fine aggregate. As the device of reducing the ratio of absorption, the procedure of mixture was altered to check the effectiveness of surface coating of porous lightweight aggregate. It was observed over 170kg/$\textrm{cm}^2$ compressive strength at gravity about 1.3, an over 380kg/$\textrm{cm}^2$ at gravity about 1.7. the maximum strength was occurred when 30% of fine aggregate was replaced was replaced with waste foundry sand, and the ratio of absorption was decreased over 10% by changing the procedure of mixture.

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

• Computers and Concrete
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• v.19 no.5
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• pp.451-455
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• 2017

Technological advancements in the field of building materials are achieved day by day. In this study, a new lightweight concrete aggregate is produced by mixing certain rates of colemanite (0%, 7.5%, 12.5%, 17.5%), cement and coating the surface of pumice aggregate with this mixture. Thin aggregate sections are analyzed with specific gravity, unit weight, water absorption, impact, and crushing experiments. In this way, the production of cement and cement+colemanite coated lightweight concrete aggregates is investigated and an opinion on the likely behavior of these concrete types is provided.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.111-116
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• 2022

Recently, building structures tend to be super high-rise and large-scale with the development of concrete technology. When high-rise building is constructed of reinforced concrete structure, it has a disadvantage that its own weight increases. Light weight aggregate(LWA) was developed to compensate for these shortcomings. Manufacturing concrete using these light weight aggregates has the advantage of reducing the self weight of the reinforced concrete structure, but has a disadvantage in that the strength of the concrete is reduced. In this study, an experimental study was conducted to investigate the strength characteristics of hardened cement according to the presence or absence of surface coating of lightweight aggregates. As a result, in terms of compressive strength, the surface-coated lightweight aggregate exhibited higher strength than the uncoated lightweight aggregate. Also, it was considered that this is because the interfacial voids of the surface coated lightweight aggregate mixed cement hardened body were filled with blast furnace slag fine powder particles.