• Advances in concrete construction
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• v.2 no.2
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• pp.77-89
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• 2014

The properties of fresh and hardened concrete made using three types of artificial cold bonded aggregates are determined. The properties, namely, slump, water absorption, compressive strength and splitting tensile strength of concrete containing artificial aggregate are reported. The variables considered are aggregate type and water-to-cement ratio. Three types of cold bonded aggregates are prepared using fly ash and quarry dust. The water-to-cement ratio of 0.35, 0.45, 0.55 and 0.65 is used. The test result indicates that artificial aggregates can be recommended for making the concrete up to a strength grade of 38 MPa. The use of quarry dust in the production of artificial aggregate mitigates environmental concerns on disposal problems of the dust. Hence, the alternate material proposed in this study is a green technology in concrete production.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.37-40
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• 2006

In this paper, long term deflection of RC beam with variable substitution ratio of recycled aggregate is investigated. 6 RC beam specimens are designed using concrete made of coarse aggregate of 25mm size, mix strength of 21MPa, slump of 12cm and air content of $5.0{\pm}1.5%$. A few concrete blocks are made and used for long term loading. The loading and deflection instrumentation are conducted following the process codified in ACI 318-05 code. Test result shows that the deflection of specimens depends on the compressive strength of concrete. And it is concluded that the deflection of RC beam can be predicted like normal beam using ACI formula if certain level of compressive strength is acquired even recycled aggregate is used in making the beam.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.631-635
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• 2005

Aggregate gradation effects on cracking-related displacements of concrete are investigated in the laboratory using the German cracking frame. Concrete workability was assessed by use of the slump and drop tests for two different concrete mixtures consisting of gap-graded and dense-graded aggregates. Shrinkage strain, cracking frame strain, and concrete strain were measured and used to compare to strength gain and creep development. The measured and calculated strains of the different aggregate gradations were compared each other. Gradation effects on strength and stress development relative to tensile cracking at saw-cut tip were also investigated. Test results revealed that the gap-graded concrete has indicated larger shrinkage and creep strains than dense-grade concrete perhaps because of its higher volume concrete of cement mortars in the mixture.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.191-198
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• 1999

The purpose of this study is investigating characteristics of the concrete containing Fly-ash according to different 4 mix design, that is, the first mix design is partial replace Fly-ash of cement, second is partial replace Fly-ash of cement and fine aggregate, third is partial replace Fly-ash of fine aggregate, fourth partial replacement of fine and coarse aggregate. For this purpose, selected test variables were water-binder ratio with two levels of 45%, 50%, and Fly-ash contents with four levels 0%, 10%, 20%, 30%, As the result of this study are as follow. 1) The result of mix design of a partial replacement of cement, the slump-flow value was appeared a promotive effect of viscosity. But in case of the over with Fly-ash 10% and the other mix design was not changed slump value. 2) The unit weight of the mixing rate with Fly-ash 0% was $1.875{\sim}1.884t/m^3$, the other mix design 10% over with Fly-ash was $1.846{\sim}1.615t/m^3$, the difference was appeared less about 15% than that. 3) In design, partial replace Fly-ash of fine aggregate, this compressive strength was appeared that the concrete age after 7 days was higher than in partial replacement of cement, therefore, the default of a concrete with Fly-ash, that is the earlier compressive strength was to lessen, was improved. 4) The thermal conductivity of the all mix design was $0.447{\sim}1.144kcal/mh^{\circ}C$, this value was as good as a lightweight aggregate concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.19-21
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• 2012

This paper was to investigate the effect of incinerator ash on engineering properties of the high volume blast furnace slag concrete through Mock-up test. Test results revealed that the use of recycled aggregates resulted in increase of slump compared with the OPC concrete. But, the use of recycled aggregates did not affect the results of air contents and chloride contents. The use of recycled aggregates showed shortening of setting time of high volume blast furnace slag concrete. When the recycled aggregate was used, delay in strength development at early age happened with high volume blast furnace slag concrete compared with that of OPC concrete.

• Computers and Concrete
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• v.3 no.2_3
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• pp.163-175
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• 2006

This research was conducted to determine effect of pumice aggregate ratio, cement dosage and slumps on freeze-thaw resistance, density, water absorption and elasticity of concrete. In the first batch, $300kg/m^3$ cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for $3{\pm}1cm$, $5{\pm}1cm$ and $7{\pm}1cm$ slumps. Other batches were prepared with $200kg/m^3$, $250kg/m^3$, $350kg/m^3$, $400kg/m^3$ and $500kg/m^3$ cement dosages and 25% pumice aggregate +75% normal aggregate at a constant slump. Test results showed that when pumice-aggregate ratio decreased the density and freeze-thaw resistance of concretes increased. With increasing of cement dosage in the mixtures, density of the concretes increased, however, freeze-thaw resistance of concretes decreased. Water absorption of the concrete decreased with increasing cement dosage but increased with the pumice ratio. Water absorption of the concrete also decreased after freeze-thaw cycles. Freeze-thaw resistance of concretes was decreased with increasing the slumps.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.59-67
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• 2017

The objective of this paper is to investigate experimentally the effect of replacement of recycled coarse aggregates with 5~13mm in size on a field applicability of concretes through Mock-up test. Seven different mock-up specimens were prepared with the size of $1200{\times}800{\times}800mm$ simulating column and wall. For the concrete mixtures, 24MPa, 27MPa and 40MPa of nominal strength were adopted with 30% and 70%(only for 24MPa) of 5~13mm recycled coarse aggregate (RCA) replacement and without 5~13mm RCA(Plain). For test items, slump, slump flow, compressive strength with different curing conditions, core drilling, rebound numbers and drying shrinkage were measured. Test results indicated that 30% of 5~13 mm RCA replacement resulted in increase in slump, slump flow and resistance against segregation, while air contents decreased compared to those of plain mixture. Compressive strength of concrete with 30% of 5~13mm RCA was shown to be higher than that of plain mixture due to optimum packing effect associated with presence of well graded aggregates. Rebound number of the mock-up specimen with 30% of 5~13mm RCA had lower fluctuation according to hitting location than that of plain mock-up specimen. It is believed from the results of the study that replacement of 30% of 5~13mm RCA brings desirable improvement in various aspect of concrete performance due to associated dense packing effect.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.751-754
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• 2004

There are many factors that affect on the flowing properties of high flowing concrete(HFC), which are fluidity, compactibility, non-segregation ability and fillingability. And because the aggregate which is one of the factors occupies high volume in concrete, it has a much effect on the properties of high flowing concrete according to its size, quality and quantity etc. This is an experimental study to analyze the effect of admixture and volume of coarse aggregate in concrete on the flowing properties of high flowing concrete. For this purpose, the kinds of admixture are fly-ash and blast furnace slag. Also volume of coarse aggregate in concrete are 280, 290, 300, 310, 320 $(\ell/m^3)$. The test of flowablity properties is slump-flow, Air content, V-lot, L-Flow. According to test results, it was found that the compactibility of HFC is more superior to use blast furnace slag than other, and according .to kind of admixture, most compatible volume of coarse are different. Also when used blast furnace slag, the volume of coarse are increased than used fly-ash.

• Advances in concrete construction
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• v.15 no.3
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• pp.179-190
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• 2023

The effect of glass fibres (GF) and polypropylene fibres (PPF) on the fresh properties and mechanical properties of lightweight concrete (LWC) exposed to high temperatures is investigated in this study. In this study, fifteen LWC mixtures were carried out in three different groups reinforced with PPF or GF fibers by 0%, 0.2%, and 0.4% by volume of concrete. The first group included aluminum powder (AP) as an air agent at 0.03% with the normal weight coarse aggregate (NWCA) by 100% of the weight of coarse aggregate. In the second group, 33% of the NWCA weight was replaced by lightweight coarse aggregate (LWCA). In the third group, 67% of the NWCA weight was replaced by LWCA. The slump, unit weight, Compressive strength (CS), tensile strength (TS), and flexural strength (FS) were examined. For two hours, the CS and FS were subjected to elevated temperatures of 200℃, 400℃, and 600℃, in addition to microstructure analysis of concrete. In comparison to the reference mixture, the fresh properties and bulk density of LWC decreased with the use of the air agent or the replacement of 67% of the NWCA with LWCA. As a result of the fiber addition, both the slump test and the bulk density decreased. The addition of fibers increased the CS; the highest CS was 38.5 MPa when 0.4% GF was added, compared to 28.9 MPa for the reference mixture at the test age of 28 days. In addition, flexural and TS increased by 53% and 38%, respectively, for 0.4% GF mixes. As well as, adding 0.4% GF to LWC maintained a higher CS than other mixtures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.78-87
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• 2009

When the steel slag is utilized to the concrete as the alternative fine aggregate, its use is limited as the concrete aggregate because of expansibility caused by much quantity of free CaO. So, this study is intended to examine the characteristics of the concrete which uses the rapidly cooled steel slag whose content of free CaO is sharply reduced by rapidly cooling the steel slag as the fine aggregate. Accordingly, by comparing and considering the results of the concrete slump loss test with the different substitution ratio and fine aggregate ratio of rapidly cooled steel slag, hydration by XRD and SEM analysis, compressive test by age, a length variation test and rapid chloride ion penetration test, the rapidly cooled steel slag's proper substitution ratio and the fine aggregate ratio was derived.