• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.61-72
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• 1991

This study was carried out to research the strength drop of concrete in dry environment. The mixing ratio of cement-fine aggregate was 1: 1, 1 : 2, 1: 3 and 1 : 4. The curing was compared standard curing with dry curing immediately after casting. It is analysis of strength change by water-proof mixing. The curing age of cement mortar was 3days, 7days, l4days and 28days. The result obtained from this study are summarized as follows. 1. The compressive and bending strength change by increasing the curing age, dry curing mortar the increasing rate of strength was decreased than standard curing mortar. 2. The compressive and bending strength change in early curing, strength difference between standard curing mortar and dry curing motar was gradually closed by increasing the W/C. 3. The dry curing mortar was decreased than standard curing mortar in decreasing rate of compressive and bending strength by increasing the W/C. 4. The compressive strength of water-proof mortar in early curing, liquid water-proof mortar was shown high strength in dry curing than standard curing. The powder and liquid water-proof mortar have a small effect in dry environment. The liquid water-proof mortar was high strength without relation change of curing age in dry environment than standard curing. 5. The compressive strength of liquid water-proof mortar in poverty mix, dry curing was shown high strength than standard curing. 6. The bending strength was increased than compressive strength by decreasing the volume of cement in early curing. The increasing rate of bending strength was decreased to compressive stength by increasing the curing age.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.83-88
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• 1998

II-anhydrite, slag, and fly ash produced as industrial by-product were reutilized for the manufacture of high strength admixtures for cement and concrete. The effects of these admixtures on the compressive strength of cement mortar and concrete were examined with those of domestic admixture. At the condition mortar and concrete. Especially, adding of II-anhydrite was very effective for the increasing of compressive strength. Therefore it is possible that these admixture as a high strength admixture apply to cement and concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.113-114
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• 2014

Though polymer cement mortar is widely used to repair or reinforce concrete as it has superior adhesion, dense internal structure, chemical resistance, and workability in comparison to those of general cement mortar, studies on its behaviors in high temperature environment such as fire is urgently required. Accordingly, in this experiment, the degrees of reduction in the compressive strength at different temperatures was grasped applying ISO834 Heating Curve, and the effect of polymer content and type on compressive strength could be determined. As a result of this experiment, it is found that polymer type and content have a big effect on reduction of compressive strength in high temperature range, and not only the dynamic characteristics but also the combustion characteristics in high temperature range are required to be studied considering occurrence of a fire in the future.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.377-378
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• 2023

This study examined the effect of curing conditions on the compressive strength of dry mortar for floor. The compressive strength according to the relative humidity during curing was compared, and the influence of expansive additives on compressive strength under water curing was reviewed. As a result, low relative humidity conditions during curing was not effective in improving the compressive strength of dry mortar for floor, and it was judged that the continuous hydration reaction insufficient due to lack of the moisture supply. In order to improve compressive strength, high relative humidity maintenance was found to be an important factor. However, under water curing conditions, the compressive strength has decreased as a result of continuous volume expansion due to the use of the expansive additives.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.3
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• pp.92-99
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• 1982

The objective of this study was to investigate the compressive and bending strength characteristics of epoxy resin mortar, which is still in an early stage of its use and study in Korea. The results obtained are summarized as follows; 1. The compressive strengths of epoxy resin mortar after 1 day, 2 days and 3 days were gained 87%, 91% and 95%, respectively, in view of that of mortar at the age of 7 days. This result showed that the initial compressive strength within 1 day was very high. 2. The highest compressive strength of epoxy resin mortar was 914 kg/cm2 at the point of having the mixing ratio of one to two. It reached up to 3.7 times that of the normal portland cement mortar at the age of 28 days. 3. The bending strengths of epoxy resin mortar after 1 day, 2 days and 3 days came up to 88%, 93% and 97%, respectively, in comparing that of mortar at the age of 7 days. It was expressed to be simielar to the tendency of compressive strength. 4. The highest bending strength of epoxy resin mortar was 384 kg/cm2 at mixing ratio of one to two. It came up to as much as 6.5 times in comparing with that of the normal portland cement mortar at the age of 28 days. Therefore, the epoxy resin mortar would be effective for promoting the bending strength of structural members. 5. The regression equation between compressive and bending strength was obtained as follows; oo~=0.391 oc+27.54 (r=0.99) And the estimated value of bending strength was corresponded to about 44 per cent in comparing with that of the compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.21-22
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• 2020

This study is about high strength self-leveling mortar according to the mixing ratio of polymer. The self-leveling mortar currently released in Korea maintains a compressive strength of 40 Mpa as of 28 days. In addition, the level of bonding strength and flexural strength are kept the same. However, through this study, it is confirmed how the self-leveling mortar with a compressive strength of 60Mpa as of the 28th is shown according to the amount of polymer mixed. Experimental factors were configured according to the amount of polymer mixed, and the types of experiments were to confirm compressive strength, flexural strength, adhesion strength and flow. In addition, by confirming the early strength, a study was conducted to improve the quick workability compared to the self-horizontal mortar in the market.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.103-105
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• 2012

With blast-furnace slag is a by-product generated when pig iron is produced. It has been used as the concrete admixture due to high reactivity. However, It causes low strength development during early age. In order to make up for this drawback, in this study, we evaluated compressive strength of mortar replaced with high volume blast-furnace slag. Experimental results, Compressive strength of mortar based on blast-furnace slag is affected by cement type, substitution rate of blast-furnace slag and pH after mixing.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.875-881
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• 2004

The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60. 1MPa, B:41.7MPa, C:25.5MPa). Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over $15\%$, but increased rapidly in the porosity of new mortar fewer than $15\%$.

• Advances in materials Research
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• v.11 no.2
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• pp.121-146
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• 2022

In the recent years, the use of agricultural waste in green cement mortar and concrete production has attracted considerable attention because of potential saving in the large areas of landfills and potential enhancement on the performance of mortar. In this research, microparticles of palm oil fuel ash (POFA) obtained from a multistage thermal and mechanical treatment processes of raw POFA originating from palm oil mill was utilized as a pozzolanic material to produce high-performance cement mortar (HPCM). POFA was used as a partial replacement material to ordinary Portland cement (OPC) at replacement levels of 0, 5, 10, 15, 20, 25, 30, 35, 40% by volume. Sand with particle size smaller than 300 ㎛ was used to enhance the performance of the HPCM. The HPCM mixes were tested for workability, compressive strength, ultrasonic pulse velocity (UPV), porosity and absorption. The results portray that the incorporation of micro POFA in HPCMs led to a slight reduction in the compressive strength. At 40% replacement level, the compressive strength was 87.4 MPa at 28 days which is suitable for many high strength applications. Although adding POFA to the cement mixtures harmed the absorption and porosity, those properties were very low at 3.4% and 11.5% respectively at a 40% POFA replacement ratio and after 28 days of curing. The HPCM mixtures containing POFA exhibited greater increase in strength and UPV as well as greater reduction in absorption and porosity than the control OPC mortar from 7 to 28 days of curing age, as a result of the pozzolanic reaction of POFA. Micro POFA with finely graded sand resulted in a dense and high strength cement mortar due to the pozzolanic reaction and increased packing effect. Therefore, it is demonstrated that the POFA could be used with high replacement ratios as a pozzolanic material to produce HPCM.

• Computers and Concrete
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• v.19 no.2
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• pp.121-126
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• 2017

This paper presents the effect of aggregate type on high temperature resistance of self-compacting mortars (SCM) produced with normal and lightweight aggregates like expanded perlite and pumice. Silica fume (SF) and fly ash (FA) were used as mineral additives. Totally 13 different mixtures were designed according to the aggregate rates. Mini slump flow, mini V-funnel and viscometer tests were carried out on the fresh mortar. On the other hand, bulk density, porosity, water absorption and high temperature tests were made on the hardened SCM. After being heated to temperatures of 300, 600 and $900^{\circ}C$, respectively, the tensile strength in bending and compressive strength of mortars determined. As a result of the experiments, the increase in the use of lightweight aggregate increased total water absorption and porosity of mortars. It is observed that, the increment in the usage of lightweight aggregate decreased tensile strength in bending and compressive strengths of mortar specimens exposed to high temperatures but the usage of up to 10% expanded perlite in mortar increased the compressive strength of specimens exposed to $300^{\circ}C$.