This study investigates the effects of compressive strengths on mechanical properties of concrete with compressive strengths of 40 and 80 MPa. In this study, The steel fiber an aspect ratio of 64 and a tensile strength of 1,600 MPa used. As the result, There are no significant effect of fiber tensile strength on mechanical properties of normal strength SFRC. For high strength SFRC, Specimen with high strength fiber have superior performance then that with normal strength fiber.

The purpose of this study is to compare the compression strength of gypsum substituted mortar with that of mortar. After replacing the cement with the loess, a portion of the remaining cement was replaced with gypsum to make specimens. When the gypsum is replaced, the strength of all the specimens is lower than that of the standard specimen. It is necessary to use a long-term strength mixed material to replace this.

The heavyweight industrial waste was used as concrete ingredient instead of natural aggregate, however, design standard did not consider effects of heavyweight aggregate on flexural strength. Therefore, in this paper, correlation between compressive and flexural strength of concrete using industrial was compared. From the results, compressive strength and flexural strength decreased with industrial waste increasing. And, it was shown that the test results of flexural strength were higher than the predicted value from design standard.

The purpose of this experimental study is to increase the strength of mortar mixed with activated Hwang-Toh (AHT) and granulated blast furnace slag (GGBS) as a compound for the development of eco-friendly concrete. The compressive strength test was carried out by making mortar specimens with a certain ratio of AHT and GGBS. The percentage of AHT were at 30% and 50% and the GGBS were a 40% and 50% as Major variables. The results of this study showed that for specimens with percentage of AHT at 30% with GGBS increased above the strength of the mortar without the binding. However, the compressive strength of experimentation with percentage of AHT at 50% with partially replace GGBS has decreased by more than the mortar without the binding. Therefore, further study is deemed necessary.

The purpose of this study is to compare the strength according as variables of Hwang-Toe activation temperature based on existing references. Compressive strength tests were carried out when the activation temperature was set to 450℃, 600℃, 850℃ and the replacement ration was set to 30%, 50%. As a result, it showed that strengths of specimens overall increased to 850℃. However, strengths of specimens with 50% replacement of Hwang-Toe were significantly reduced at 450℃ and 600℃. In this regard, it is necessary to study the proper quality of activated Hwang-Toe for mortar application in the future.

Concrete has recently been modified to have various performance and properties. However, the conventional method for predicting the compressive strength of concrete has been suggested by considering only a few influential factors. so, In this study, nine influential factors (W/B ratio, Water, Cement, Aggregate(Coarse, Fine), Fly ash, Blast furnace slag, Curing temperature, and humidity) of papers opened for 10 years were collected at 4 conferences in order to know the various correlations among data and the tendency of data. The selected mixture and compressive strength data were used for learning the Deep Learning Algorithm to derive a prediction model. The purpose of this study is to suggest a method of constructing a prediction model that predicts the compression strength with high accuracy based on Deep Learning Algorithms.

Prediction of compressive strength of concrete by Maturity Method is applied in construction site. However, due to the use of wired type high-priced equipment, economic efficiency and workability are falling. In this study, a newly developed concrete embedded wireless sensor is used to perform a mock-up test. Next, the concrete compressive strength of the Maturity Method is predicted using Saul and Plowman's function as measured temperature data. The predicted concrete strength at the beginning of the age was the actual strength and stiffness, but the error rate was less than 1% at 28th day.

이 논문은 압축강도 수준(100, 140, 180 MPa급)에 따른 HPFRCC의 동적충격 인장강도를 평가하였다. 먼저 100, 140, 180 MPa급 HPFRCC의 압축응력-변형률 관계를 분석한 결과 압축강도는 각각 112, 150, 202 MPa로 나타났으며, 압축강도가 높아짐에 따라 탄성계수도 증가하는 경향을 나타내었다. 100, 140, 180 MPa급 HPFRCC의 정적 인장강도는 각각 10.7, 11.5, 16.5 MPa로 나타났으며, 압축강도가 높아질 수록 인장강도도 증가하는 경향을 나타내었다. 반면 100 및 140 MPa급 HPFRCC에서의 인장강도 및 에너지 흡수능력은 압축강도 수준에 따라 큰 차이를 보이지 않았다. 이는 시험체의 규격 및 강섬유의 배열에 영향을 받은 것으로 판단된다. HPFRCC의 동적충격 인장강도를 평가한 결과, 변형률 속도가 10-1/s에서 150/s로 증가할수록 모든 HPFRCC의 인장강도와 동적증가계수는 증가하는 경향을 보였다. 한편 동일한 범위의 변형률 속도에서 HPFRCC의 압축강도가 낮을수록 인장강도에 대한 DIF가 높게 측정되어 효율적인 측면에서는 100 MPa급 HPFRCC가 가장 우수한 것으로 나타났다. 따라서 높은 수준의 인장성능이 요구되는 경우 높은 압축강도를 가지는 HPFRCC를 사용하는 것이 유리하며, 폭발과 같은 고속변형률 속도에서 보다 효율적인 접근을 위해서는 목표 압축강도에 근접한 HPFRCC를 사용하는 것이 바람직한 것으로 판단된다.

The purpose of this study is to compare the ultrasonic pulse velocity before and after core compression test of steel fiber reinforced concrete using the ultrasonic pulse velocity method. The correlation between the column member ultrasonic pulse velocity before core test, the column member ultrasonic pulse velocity after core test, and the compressive strength of the core specimen were analyzed by fabricating a steel fiber reinforced concrete hollow column member.

This study was performed an experimental study on mortar containing phytoncide solution. The compressive strength properties with various phytoncide containing ratios were evaluated. The phytoncide solution containing ratios adopted in this study were 0, 2, 4, 6, 8 and 10%. The compressive strength was measured at 3, 7 and 28 days for the hardened mortar specimens. According to the experimental results, the phytoncide has not affect the compressive strength and flow.

This paper presents the findings of the study conducted to evaluate workability and compressive strength characteristics of rapid-setting concrete containing metakaolin. The experimental variable selected was the rate of cement replacement with metakaolin at 0, 5, 10, and 15 percent. The findings are summarized as follows: compared with the control specimens with no replacement rate, the workability and compressive strength of the concrete with 5% of cement replaced with metakaolin were comparable to those of control specimens at 4hours; however, at 72 hours, the compressive strength of the concrete with the same replacement rate was larger than the strength of the control specimens by 4.1%, while no increase in strength was observed at higher replacement rates, implying that the optimum replacement rate of cement with metakaolin is 5%.

Prediction of the compressive strength of the maturity method has been studied by several researchers and has been applied to the construction of concrete structures. In order to apply the maturity method, which is a function related to temperature and time, it is important to measure the accurate temperature inside the concrete during the curing period. The purpose of this study is to verify the performance by analyzing sensitivity, measurement and transmission accuracy by exposing wireless embedded sensor to various curing environment.

Effect of confining pressure on the shear strength of ultra-high-performance fiber-reinforced concrete (UHPFRCs) was investigated using a new shear test setup. Different confining pressures were applied and maintained to the specimens prior to shear testing. The shear strength of UHPFRCs was obviously sensitive to the confining pressure: the higher confining pressure produced higher shear strength. The confined shear strength could be expressed as a function of unconfined shear strength, confining pressure, and tensile strength.

Filler material (concrete or mortar) has been used for shielding radioactive waste, however, it is proceeded out evaluation for radiation shielding performance. So, it is needed to check the property in the shielding performance. Therefore, in this paper, mechanical properties of concrete was evaluated for the applicability using heavyweight waste glass as fine aggregate of filler material. From the test results, compressive and elasticity modulus were significantly affected by substitution of heavyweight waste glass, however, it could be improved the performance by using mineral admixture as binder.

The purpose of this study is to investigate the effects of reinforcement arrangements on the high strength of concrete and to present the quantitative values. To complete this research, two types of concrete strengths (40 MPa and 60 MPa), two types of reinforcing bar diameters (10 ㎜ and 13 ㎜), and seven types of specimens with or without reinforcement arrangements were prepared and tested for compressive strength. As a result, the strength of the cores containing the reinforcement can be predicted to have 82% - 94% of the strength of the cores without reinforcement.

Domestic facilities are managed in accordance with the "Special Law on the Safety and Maintenance of Facilities", and are managed through periodical inspection and safety diagnosis. In the inspection and diagnosis of such facilities, Comprehensive analysis results from exterior and non-destructive survey, and the five grade of the facility is managed. Most of the non-destructive tests are carried out in consideration of operation. In this paper, the purpose of this study is to investigate the change of compressive strength and the characteristics of the core strength in the ○○ tunnel.

In Korea, inspection and precise safety diagnosis is regularly carried out to maintain and manage the main tunnel(NATM) which has been passed ten years after completion. In this study, we collected the laboratory test results of the concrete lining in the existing road and railway tunnels, and analyzed the correlation between compressive strength and unit mass of concrete. It is hoped that it will be used for efficient maintenance and management work of tunnels in the future.

이 연구는 CRC기둥강도곡선의 비탄성영역에 대한 해석적 고찰이다. CRC기둥강도곡선의 비탄성영역은 최대 잔류응력 크기 0.5σy 와 Bleich이론을 기초로 하고 있다. 이는 실제로 알려진 최대 압축 잔류응력의 크기가 0.3σy 인 경우 보다 다소 보수적이다. 본 연구는 열압연강재의 최대 압축 잔류응력의 크기를 0.3σy 으로 고려하여 그에 따른 기둥강도곡선과 접선탄성계수 Et를 제안하고 이를 CRC에서 제안하고 있는 값들과 각각 비교 고찰한다. 축 압축력을 받는 비탄성 기둥의 응력은 기둥에 작용하는 하중이 좌굴을 일으키기 전에 재료의 비례한도를 넘어 항복점에 도달할 것이다. 따라서 점차적인 단면의 항복 상태에 따른 기둥강도곡선을 검토할 필요가 있다. 본 연구는 최대 압축 잔류응력 σr = 0.5σy 을 사용하여 재료의 항복에 따른 임계하중 곡선식을 유도하고 이를 CRC기둥강도곡선과 비교 고찰한다.

본 연구는 콘크리트 산업에 있어 자원 고갈, 환경 문제 등을 대처할 수 있는 순환골재의 활용을 촉진하며 순환골재콘크리트의 레미콘 실생산을 위한 기초적 연구로서, 순환골재 사용량에 따른 슬럼프 고정 순환골재콘크리트의 물시멘트비 변화 및 물리적 특성을 실험하고 그 결과를 회귀분석하여 순환골재콘크리트의 압축강도 추정을 위한 단위시멘트량, 순환골재의 사용량, 물시멘트비 등 레미콘 생산 조건을 검토하여 다음과 같은 결론을 얻었다. 순환골재를 사용한 콘크리트는 목표 슬럼프를 유지하기 위해서는 단위수량 증가가 요구되며, 순환굵은골재 보다 순환잔골재의 치환에 더 많은 단위수량의 증가가 필요하였다. 순환잔골재의 치환율은 60%이하는 레미콘 품질기준에 벗어나지 않는 공기량 확보가 가능하였다. 순환골재를 사용한 콘크리트의 압축강도는 순환골재의 치환율이 증가할수록 감소하는 것으로 나타났으며, 특히 순환잔골재를 100% 치환한 경우 압축강도는 25%정도 저하하였다. 순환골재를 사용한 콘크리트의 배합인자에 따른 압축강도의 상관관계를 분석한 결과, 순환잔골재>물시멘트비>공기량 순으로 영향을 미치는 것으로 나타났다.

In this study, alkali-activated slag (AAS) concrete made with blast furnace slag (BFS) was investigated as a replacement for ordinary Portland cement (OPC) concrete for changes in the compressive strength before and after CO2 exposure and chemical reactions with CO2. Before CO2 exposure, the compressive strength of AAS concrete was found to be up to 21 MPa, which was higher than that of OPC concrete. Exposing AAS concrete to CO2 at 5,000 ppm for 28 days did not significantly change the compressive strength. In contrast, the compressive strength of OPC concrete decreased by 13% in the same conditions. In addition, AAS concrete had the highest CO2 capture capacity of greater than 50 g CO2/kg, while the CO2 capture capacity of OPC concrete was only 2.5 g CO2/kg. Rietveld analyses using XRD results showed that fractions of main calcium-silicate-hydration (C-S-H) gels on the surface of AAS concrete did not significantly drop after CO2 exposure; the C-S-H gel on the AAS concrete was continuously produced by reacting with the SiO2 produced after the reaction with CO2 and Ca(OH)2 inside the concrete, with the result that the compressive strength of AAS concrete did not change after CO2 exposure. Thus, AAS concrete can be applied to CO2-rich environments as both a stable construction material and a CO2 sequestrate agent.