• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.833-840
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• 2004

Among non-destructive tests for compressive strength, rebound number test and pulse velocity test are the most widely used methods. However, the non-destructive tests mostly used in Korea was developed by foreign country. Therefore, it is unreasonable to directly apply them to concrete structures in Korea. In accordance with the suggestion of Institute of Architecture in Japan for rebound number test, a compressive strength is calculated by the mean value of 20 hit points without being considered standard deviation. Furthermore, there is no regulation on the number of measurements required for measuring compressive strength by pulse velocity test. This study, therefore, reviewed the rebound number test and pulse velocity test by chi-square, and suggested the minimum number of each test. As a result, the minimum number that falls within range of reliability for rebound number test and pulse velocity test are 11 and 7, respectively. If abnormal values are processed as missing and test groups are assumed to be arrayed in cross by considering changes in quality of actual concrete structures, 20 times and 9 times are appropriate for rebound number test and pulse velocity test, respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.2
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• pp.3749-3757
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• 1975

This study was conducted to investigate some effects of Cemesol on acidresistance and compressive strength of concrete. In mix design of concrete, the cemesol was used as an admixture of cement, and it was added to the mix in an amount equal to 0.1%, 0.2%, 0.3%, and 0.4% by weight of cement of the mix. Concrete specimens were made in accordance with the. Korean Standard Specification for concrete and they were tested for acid-resistance and compressive strength at 2 weeks intervals through 8 weeks. The tests were performed in two cases non-curing and curing for 28 days. The results obtained from the tests are summarized as follows. 1. Refering to acid-resistance test, the cemesol was comparatively effective at every cemesol content except 0.3% in case of non-curing and it was found that cemesol content of 0.4% was the optimum. On the other hand, the cemesol was ineffective in case of curing, but it was seen that cemesol content of 0.1% had some effect at 6 to 8 weeks curing only. 2. Refering to compressive strength test, the cemesol was remarkably effective at a content of 0.1% but it was also shown most inefiective at content of 0.3% in case of non-curing. On the other hand the cemesol was comparatively effective at every content of cemesol except a content of 0.2% in case of curing and it was determined that the cemesol content of 0.3% may be an optimum content. 3. Since optimum cemesol content varied according to acid-resistance, compressive strength and cases such as non-curing and curing, as indicated above may be desirable to choose an optimum cemesol content suitable for purposes and ciroumstances of construction works or conditions of location. 4. The corrosive rate was proportional to compressive strength in case of non-curing, but the relation was reversed in case of curing. It was found that corrosive rate for 8 weeks did not influence compressive strength in case of non-curing but compressive strength in case of curing begins to vary under the influence of corrosion. Thus, corrosion may be more serious to compressive strength in case of curing than that in case of non-curing.

• Journal of the Korea Institute of Building Construction
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• v.4 no.4
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• pp.63-70
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• 2004

The objective of this study is to evaluate the compressive strength of recycled aggregate concrete by the non-destructive testing. Main experimental variables were the replacement level of recycled aggregate and blast-furnace slag, which were divided into two series according to recycled aggregate maximum size. Test results showed that a recycled aggregate had a significant influence on the non-destructive testing results, such as rebound number, Ultrasonic pulse velocity, and frequency. A prediction model of compressive strength considering the replacement level of recycled aggregate was suggested by multi-regression analysis and was compared with test results.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.55-60
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• 2004

This study was performed to evaluate the early estimation of compressive strength of concrete using mineral admixture by refrigeration curing method. It was a method of early decision for the property of concrete after the curing age 28days through the refrigeration curing at $-18{\pm}3^{\circ}$ for five hours. The test result was fixed connection between the curing age 28days and 31hours by the compressive strength test through the standard curing and refrigeration curing. Accordingly, it can be reduced the mistake of construction work by forecasting the property of concrete through the refrigeration curing.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.125-128
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• 2006

As the ministry of construction and transportation established quality standards for recycled aggregate in August, 2005, the consumption of recycled aggregates is expected to be increased in construction fields in the future. Thus the relations between compressive strength of general concretes and that of recycled aggregate concretes which are applied to actual structures are attempted to investigate through non-destruction testing method. Presently Schmitt-Hammer test method is that concrete compressive strength is predicted by measuring surface hardness of concretes, and is well known as the most convenient and simply operated method among many non-destruction testing methods. In this study, cylinder specimen and mock-up were constructed using recycled aggregate concretes made by the first class recycled coarse aggregates and recycled fine aggregates specified in KS F 2573 (recycled aggregate for concrete), and compressive strength of hardened concrete of middle ages was evaluated.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.3
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• pp.183-190
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• 2006

Generally, application of steel pile as deep foundation member needs specials requirement for the connection method between steel pipe and concrete footing. To investigate real compressive behavior of connection member between steel pipe pile and concrete footing, three specimens were tested with carefully designed experimental system. Main test variable is the connection method between steel pipe pile and concrete footing. The bolted bonding method and hook bonding method was considered as the connection method in this study. From the test results gained from experiment, it was conformed that two types of connection method have the almost same compressive resistance capacity. Therefore, we can conclude that these two connection methods can be used as the strengthening method to verify the compressive composite action of concrete and steel pipe pile.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.473-479
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• 1996

Until now, we assumed in the time-dependent analysis of concrete structure that tensile creep has same characteristics as compressive creep has. But, in according to results of researches, it appears that tensile creep is different from compressive creep in quantity and in mechanics because tensile creep is affected significantly by micro cracking. The test results indicate that the creep behavior of concrete in compression and tension is rather different. The test data shows that the amount of creep under tensile loading is larger than that under compressive loading. In this paper, a realistic tensile creep model is suggested and incorporated in the formulation. In order to get more accurate results of time-dependent analysis. The present study indicates that the long-term deflection of concrete structures under realistic tensile creep model is somewhat larger than that under ordinary compressive creep model.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.163-168
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• 2002

The object of this study is to define the characteristics of high performance concrete with varing compressive strength of concrete and curing temperature. The major test variables are 1) high strength concrete(500kg/$cm^2$) and ordinary strength concrete(240kg/$cm^2$) compressive strength, 2) curing temperature and condition, 3) concrete curing age, 4) three types of cement. From the test results were shown that curing temperature and curing conditions were also very effective for high strength concrete and ordinary strength concrete, and concrete were largely effected by cement type and temperature during the hydration reaction process. This paper describes the effect of curing temperature for strength and characteristics of high performance concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.185-186
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• 2016

Four mortar mixes tested to evaluate the early-age compressive strength of magnesia-phosphate composite with phosphate type. Monopotassium phosphate, dipotassium phosphate, ammonium dihydrogen phosphate and diammonium phosphate used as phosphate. Test results show that the compressive strength of mortar used monopotassium phosphate as phosphate was highest, while compressive strength of mortars used dipotassium phosphate and diammonium phosphate as phosphate were not developed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.168-169
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• 2019

This study examined the effect of foam volume ratio and curing temperature the air dry density and compressive strength of lightweight concrete using bottom ash. Test results showed that the lightweight concrete possessed the compressive strength of 3.4~22.7 MPa at the air dry density of 1,041~1,583 kg/m3.