• International Journal of Highway Engineering
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• v.15 no.5
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• pp.57-64
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• 2013

PURPOSES : It is to evaluate lightweight soil as a subgrade material based on mechanical tests and calculation of pavement performance. METHODS : In this research, various contents of cement and air foam are used to make lightweight soil using wasted dredged soil. Uniaxial compressive strength test is conducted to evaluate strength of 7 and 28 day cured specimens. Secant modulus was calculated based on the stress and strain relationship of uniaxial compressive strength test. Resilient modulus test was measured using by repeated triaxial compression test. The measured resilient modulus was used in layered elastic program to predict fatigue and rutting life at a given pavement structure. RESULTS : Uniaxial compressive strength increases as cement content increases but decrease as air foam content increases. Resilient modulus also increases as cement content increases and decrease as air foam content decrease. CONCLUSIONS : It is concluded that dredge clay soil can be used as subgrade layer material using by lightweight treated soil method.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.29-36
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• 2017

The purpose of this study is to investigate experimentally the effect of types of alkali-activators and curing conditions on the compressive and tensile behavior of fiber-reinforced cementless composites. Two types of alkali-activators and two curing conditions were determined and density test, compressive strength test, and uniaxial tension test were performed. Test results showed that the cementless composite with sodium silicate showed higher performance in terms of strength, tensile strain capacity, and toughness than that with calcium hydroxide and sodium carbonate. The effect of curing conditions depends on the types of alkali-activators.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.79-83
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• 2000

Interfacial and microfailure properties of carbon liber/bismaleimide (BMI) composites were evaluated using both tensile fragmentation and compressive Broutman tests with acoustic emission (AE). Since BMI is rather difficult matrix to apply for the conventional fragmentation test because of its too low elongation and too brittle and high modulus properties, dual matrix composite system was applied. After carbon fiber/BMI composite was prepared for rod shape by controlling differing curing stage, composites rod was embedded in toughened epoxy as outer matrix. The typical microfailure modes including fiber break, matrix cracking, and interlayer failure were observed during tensile testing, whereas the diagonal slippage in fiber ends was observed during compressive test. On the other hand, AE amplitudes of BMI matrix fracture were higher than carbon fiber tincture under tensile test because BMI matrix has very brittle and high modulus. The waveform of signals coming from BMI matrix fractures was consistent with AE amplitude result under tensile tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.159-167
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• 2004

The compressive strength of concrete is a criterion to produce concrete. However, the tests on the compressive strength are complicated and time-consuming. More importantly, it is too late to make improvement even if the test result does not satisfy the required strength, since the test is usually performed at the 28th day after the placement of concrete at the construction site. Therefore, strength prediction before the placement of concrete is highly desirable. This study presents the probabilistic technique for predicting the compressive strength of concrete on the basis of concrete mix proportions. The estimation of the strength is based on the probabilistic neural network which is an effective tool for pattern classification problem and gives a probabilistic result, not a deterministic value. In this study, verifications for the applicability of the probabilistic neural networks were performed using the test results of concrete compressive strength. The estimated strengths are also compared with the results of the actual compression tests. It has been found that the present methods are very efficient and reasonable in predicting the compressive strength of concrete probabilistically.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.215-225
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• 2008

In order to investigate the influence factors to compressive and tensile strength of basalt in Cheju Island, rock samples of Pyosenri basalt, trachy-basalt and scoria were taken from Seoguipo-Si Seongsan-Eup area, and a series of uniaxial compressive strength test and Brazilian test were carried out. Especially, these tests were performed in consideration of the loading speed, the moisture content in rock sample, and the anisotropy of rock strength. The uniaxial compressive strength was increased gradually as the loading speed rose. The increasing quantity of uniaxial compressive strength had a difference in each rock types. Also, the strength was decreased with increasing the moisture contents in rock sample by pore water. As the result of test considering the anisotropy of rock strength, the compressive strength in condition of failure occurred parallel to stratified layer is decreased about 12-26% more than that in condition of failure occurred inclined to stratified layer.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.49-52
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• 2009

This paper aims to evaluate hydration and intensity property of different kind of members and intensity in order to evaluate compressive strength of structural concrete using Joint Separation Test Body(JSTB). In fact it is difficult to test and evaluate already have constructed member. In this case, common method used by construction engineer is that ; Schmidt rebound hammer test, Ultrasonic pulse test, Method of using test specimen previously cast. However, these method to control the structural intensity involve many problem and impossibility to adapt construction. 80, this paper proposes advance an opinion which have proper to examine intensity. has also aims to examine its validity and the plan to make similar environment with structural concrete and joint separation test body in order to verify efficiency assessment and on-site application.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.5-11
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• 2015

The development of Controlled Low Strength Material (CLSM), which is a highly flowable material, has been performed for the application of backfill. The objective of this study is to compare the compressive strength and compressive wave velocity of CLSM according to the curing time. To investigate the characteristics of the CLSM consisting of sand, silt, water, flyash, and CSA cement, uniaxial compression test and flow test were carried out. For the measurement of compressional waves, a cell and a couple of transducers were used. The test results show that the compressive strength increases with the curing time, while the increment of compressive strength decreases with the curing time. In addition, the compressive wave velocity increases with the curing time, and the correlation between the compressive wave velocity and compressive strength is similar to exponential function. This study suggests that the correlation between the compressive wave velocity and compressive strength may be effectively used for the estimation of compressive strength of the CLSM at early curing time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.103-111
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• 2015

To evaluate the compressive strength of concrete, rebound test and ultra pulse velocity methods as well as core test were widely used. The predicted strength effected by age, maturity and degradation of concrete, is a slight difference between in-situ concrete strength. The compressive strength of standard cylinder specimens and core samples by obtained from drilling will have a difference since the concrete is disturbed during the drilling by machinery. And the rebound number and ultra pulse velocity are also changed according to the age and maturity of concrete that effected to the surface hardness and microscpic minuteness. The authors performed the experimental work to reflect the age and core effect to the results from NDE test. The test results considering on the core and age of concrete were compaired with the proposed equation to predict the compressive strength.

• Advances in concrete construction
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• v.11 no.4
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• pp.335-345
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• 2021

It is known from the literature that there are relatively few studies on the engineering properties of ultra-high performance concrete (UHPC) in early age. In fact, in order to ensure the safety of UHPC during construction and sufficient durability and long-term performance, it is necessary to explore the early behavior of UHPC. The test parameters (test control factors) investigated included the percentage of cement replaced by silica fume (SF), the percentage of cement replaced by ultra-fine silica powder (SFP), the amount of steel fiber (volume percent), and the amount of polypropylene fiber (volume percentage). The engineering properties of UHPC in the fresh mixing stage and at the age of 7 days were investigated. These properties include freshly mixed properties (slump, slump flow, and unit weight) and hardened mechanical properties (compressive strength, elastic modulus, flexural strength, and splitting tensile strength). Moreover, the effects of the experimental factors on the performance of the tested UHPC were evaluated by range analysis and variance analysis. The experiment results showed that the compressive strength of the C8 mix at the age of 7 days was highest of 111.5 MPa, and the compressive strength of the C1 mix at the age of 28 days was the highest of 128.1 MPa. In addition, the 28-day compressive strength in each experimental group increased by 13%-34% compared to the 7-day compressive strength. In terms of hardened mechanical properties, the performance of each experimental group was superior to that of the control group (without fiber and without additional binder materials), with considerable improvement, and the experimental group did not produce explosive or brittle damage after the test. Further, the flexural test process found that all test specimens exhibited deflection-hardening behavior, resulting in continued to increase carrying capacity after the first crack.

• Advances in concrete construction
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• v.9 no.3
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• pp.249-256
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• 2020

This paper aims at investigating the effect of crumb rubber size and content on compressive behaviors of concrete under axial compression. Concrete specimens are designed and produced by replacing natural aggregate with crumb rubber content of 0%, 5%, 10%, 15% and three different sized crumb rubbers (No. 20, No. 40, No. 80 crumb rubber). And the failure mode, compressive strength, elastic modulus, stress-strain curves, peak strain and ultimate strain are experimentally studied. Based on the test results, formulas have been presented to determine the compressive strength, elastic modulus, the relationship between prism compressive strength and cube compressive strength, stress-strain curves and peak strain of crumb rubber concrete (CRC). It is found that the proposed formulas agree well with the test result on the whole, which may be used to practical applications.