• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.609-615
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• 2011

MgO concrete containing lightly burnt MgO powder at $850{\sim}1,000^{\circ}C$ may have a long-term expansibility characteristic. Such expansibility of MgO concrete can compensate the shrinkage at later ages since the hydration of the MgO is very slow. However, the addition of MgO delays the initial hydration of cement and increases the setting time of cement. Also, the porosity and pore-size distribution of the MgO concrete are different from OPC concrete. Therefore, in order to use MgO in practice, both mechanical and durability properties of MgO concrete should be carefully examined. In this study, durability tests on carbonation, freezing-thawing, and diffusion of chloride were carried out after 56 days of underwater curing at $20^{\circ}C$ to compare durability characteristics of 5% MgO-mixed concrete with those of OPC concrete. The results showed that MgO concrete shows a greater durability than the concrete with no MgO, because the micro structure in the MgO concrete is much denser due to its expansibility characteristic.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.541-550
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• 2011

Many researches have been performed on concrete with fly ash and bottom ash. However researches on concrete with pond ash (PA) and its application to RC (Reinforced Concrete) structure are limitedly carried out. This paper presents an applicability of PA concrete in construction of real size structure. Referring to the previous study, 2 domestic PA samples with normal performance are selected and 2 replacement ratios (25% and 50%) to fine aggregate are considered for 5 PA concrete structures consisting of column, slab, and wall. In order to evaluate the property of fresh concrete, several tests including air content, slump, and setting time are performed. Using cored out samples from hardened PA concrete structure, tests for strength, resistance to carbonation and chloride penetration are carried out and compared with control samples. Additionally, tests for rebound hardness, drying shrinkage, and hydration heat are performed for PA concrete structure. The test results showed that PA concrete has reasonable strength and durability performances compared to those of normal concrete. Therefore, its potential application to RC structure is promising. The PA aggregate can be more actively used for RC structures with better quality control for content of fly ash, bottom ash, and unburned carbon.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.62-69
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• 2012

This study investigates the engineering properties of the high strength concrete depending on dosages and types of shrinkage reduction agent. Test results showed that for the properties of fresh concrete, the addition of the conventional shrinkage reduction agent (SR) of 0.25% decreased slump flow up to 40% as compared with control concrete, whereas the addition of the emulsified waste cooking oil (EWCO) decreased slump flow of only 5% to 10%. Other properties of fresh concrete with the agents, namely air content, unit weight and setting time, were similar to the results of the control concrete. For the properties of hardened concrete, the compressive strength of the concrete with SR decreased at both early and later stage. However, the compressive strength of the concrete with EWCO was similar to the control concrete at early age, but decreased at later stage (up to 10% reduction at 28 days). For the effect of the agents on autogenous shrinkage of the concretes, the addition of EWCO decreased up to 33%, whereas that of SR decreased up to 29%. Hence, it can be said that the addition of EWCO in high strength concrete has an effect on reducing the autogenous shrinkage as compared with a conventional agent and only slight influence on the slump flow and air content of concrete. By taking all aspects of using EWCO, it is concluded that the optimum content of EWCO will be in the range of between 0.5% and 0.75%.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.113-120
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• 2007

In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Also, as little pore volume and closed structure of antimicrobial concrete were observed, watertightness of it was verified. Finally artificial accelerating test for biochemical corrosion was proposed, and its suitability was experimentally proved.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.3-10
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• 2017

In case of Korea highways, about 60% of highways are paved by concrete and more than 50% of them were repaired due to reduction in required performance such as damage in pave or joint and delamination of cover pavement. However, repairing old material in such structure generally costs a lot of money and induces difficulty in maintenance. Thus, enhanced material for ensuring economic efficiency should be developed. The present study designed concrete mixtures with 3 levels of replacement using OPC (0, 10, 20%) in calcium aluminate cement and to evaluate material performance for load pavement, experimental works for setting time, compressive strength and flexural strength were carried out on those materials. As a result, 20% replacement for OPC was determined as an optimized material in terms of required physical performance and its unit price. Moreover, to determine cost in load pavement economy analysis using a program (CA4PRS) was conducted with widely used paving materials. Result showed that application for 20% replacement for OPC was the most efficient in economical aspect, arising from 4.052 and 1.577 billion won for total construction and user cost, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content arc satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When, AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When. AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.133-140
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• 2004

This study is intended to investigate the properties of bleeding reduction of concrete using AE water reducing agent for the type of bleeding reduction with the replacement admixture. According to the results, when the adding ratio of AE water reducing agent for the type of bleeding reduction increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 50 min. When AE oater reducing agent for the type of bleeding reduction is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for the type of bleeding reduction. Synthetically, it proves that AE water reducing agent for the type of bleeding reduction satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• International Journal of Concrete Structures and Materials
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• v.10 no.1
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• pp.15-28
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• 2016

With the aim to reduce the atmospheric $CO_2$, utilization of the carbonated lime produced from the aqueous carbonation reaction for the synthesis of a cementitious material would be a promising approach. The present investigation deals with the aqueous carbonation of slaked lime, followed by hydrothermal synthesis of a cementitious material utilizing the carbonated lime, silica fume, and hydrated alumina. In this study, the aqueous carbonation reaction was performed under four different conditions. The TGA, FESEM, and XRD analysis of the carbonated product obtained from the four different reaction conditions was performed to evaluate the efficacy of the reaction conditions used for the production of the carbonated lime. Additionally, the performance of the cementitious material was verified analyzing the physical characteristics, mechanical property and setting time. Based on the results, it is demonstrated that the material produced by the hydrothermal method possesses the cementing ability. Additionally, it is revealed that the mortar prepared using the alternative cementitious material yields $33.8{\pm}1.3MPa$ compressive strength. Finally, a plausible reaction scheme has been proposed to explain the overall performances of the aqueous carbonation as well as the hydrothermal synthesis of the cementitious material.

• 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.