• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.101-110
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• 2018

This study experimentally investigated the compressive and flexyral strength development characteristics of polymer concrete using four different type polymeric resins such as unsaturated polyester, vinyl ester, epoxy, and PMMA (polymethyl methacrylate) as binders. The test results show that the average compressive strength of those four different polymer concretes was 88.70 MPa, the average flexural strength was 20.30 MPa. Those test results show that compressive and flexural strengths of polymer concrete were much stronger than compressive and flexural strengths of ordinary Portland cement concrete. In addition, the relative gains of the compressive strength development at the age of 24 hrs compared to the age of 168 hrs were 68.6~88.3 %. Also, the relative gains of the flexural strength development at the age of 24 hrs compared to the age of 168 hrs were 73.8~93.4 %. These test results show that compressive and flexural strengths of each polymer concrete tested in this study were developed at the early age. Moreover, the prediction equations of compressive and flexural strength developments regarding the age were determined. The determined prediction equations could be applied to forecast the compressive and flexural strength developments of polymer concrete investigated in this study because those prediction equations have the high coefficients of correlation. Last, the relations between the compressive strength and the flexural strength of polymer concrete were determined and the flexural/compressive strength ratios were from 1/4 to 1/5. These results show that polymer concretes investigated in this study were appropriate as a flexural member of a concrete structure because the flexural/compressive strength ratios of polymer concrete were much higher than the flexural/compressive strength ratios of Portland cement concrete.

• Earthquakes and Structures
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• v.27 no.2
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• pp.113-126
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• 2024

In this study, the failure mechanisms of masonry-infilled frames, commonly employed in modern construction, are analyzed at the mesoscale. An equation has been formulated to predict various failure modes of masonry-infilled frames by examining 1392 frames. The equation takes into account variables such as the height-to-width ratio, compressive strength of the masonry prism, and plastic moment capacity of the frame section. The study reveals that the compressive strength of the masonry prism and the height-to-width ratio exert the most significant influence on the lateral strength of masonry-infilled frames with a height-to-width ratio ranging from 0.2 to 1.2. The developed equation demonstrates substantial agreement with previously reported relationships, indicating high accuracy. These findings provide valuable insights into the lateral strength of infill masonry frames, which can contribute to their improved evaluation and design.

• Smart Structures and Systems
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• v.31 no.1
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• pp.1-11
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• 2023

Assessment of the compressive strength of concrete plays a major role during formwork removal and in the prestressing process. In concrete, temperature changes occur due to hydration which is an influencing factor that decides the compressive strength of concrete. Many methods are available to find the compressive strength of concrete, but the maturity method has the advantage of prognosticating strength without destruction. The temperature-time factor is found using a LM35 temperature sensor through the IoT technique. An experimental investigation was carried out with 56 concrete cubes, where 35 cubes were for obtaining the compressive strength of concrete using a universal testing machine while 21 concrete cubes monitored concrete's temperature by embedding a temperature sensor in each grade of M25, M30, M35, and M40 concrete. The mathematical prediction model equation was developed based on the temperature-time factor during the early age compressive strength on the 1^st, 2^nd, 3^rd and 7^th days in the M25, M30, M35, and M40 grades of concrete with their temperature. The 14^th, 21^st and 28^th day's compressive strength was predicted with the mathematical predicted equation and compared with conventional results which fall within a 2% difference. The compressive strength of concrete at any desired age (day) before reaching 28 days results in the discovery of the prediction coefficient. Comparative analysis of the results found by the predicted mathematical model show that, it was very close to the results of the conventional method.

• Journal of the Korea Institute of Building Construction
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• v.7 no.1 s.23
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• pp.71-77
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• 2007

This paper is to investigate the effect of the curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of the compressive strength of the concrete was conducted using the equivalent age equation and the rate constant model proposed by Carino. Correction of Carino model was studied to secure the accuracy of strength development estimation by introducing correction factors regarding rate constant and age. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of BS has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.1
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• pp.113-120
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• 1999

Due to the heterogeneous nature of a concrete, periodic inspections are compulsory to maintenance of quality of concrete structures. The major object of this study is to analyze and investigate experimentally the experimental equation for the estimate of compressive strength of prestressed concrete. In this study, surface hardness method, ultrasonic method are investigated to evaluate strength of concrete specimens. Specimens are cast in laboratory and cores are cut from specimens in order to estimate the accurate strength. These values are used to compare with calculated values from test data. The result shows that the proposed equation can reproduce the results at prestressed concrete beam girders more appropriately than previous equations.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.259-264
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• 1999

The aim of this study of to compare the development of compressive strength of high-strength concrete with maturity and investigate the applicability the strength prediction models. An experiment was attempted on the high-strength concrete mixes using portland cement replaced by silica fume of 10% by weight of cement, the water-binder ratios of mixes being 0.30 and 0.35, the curing temperatures being 30, 20, 10, 5$^{\circ}C$. Test results of mixes are statistically analyzed to infer the correlation coefficient between the maturity and the compressive strength of high-strength concrete. The constant of strength prediction equation were determined from test results, and the equation was adopted to predict the strength of slab(W80$\times$D100$\times$H20cm). The slab was cast in the laboratory from the same batch water-binder ratio of 0.30, and cores were cut from slab in order to estimate the actual strength. These values are used to compare with predicted value. The present study allows more realistic determination of early age compressive strength of high-strength concrete and can be efficiently used to control the quality in actual construction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.75-78
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• 2005

This raper investigates the effect of curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of compressive strength of concrete was conducted using equivalent age equation and rate constant model. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of 35 has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.979-984
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• 2003

Quality control of ready-mixed concrete is most important in the production step because, the performance of hardened concrete is revealed due to ready-mixed concrete. Hardened concrete has several properties physically. Above all things compressive strength of concrete has a greate effect in the design of structures, analysis, and durability. Compressive strength is simple predicted by w/c up to date, but there are some limits because different compressive strengths can be revealed in the same w/c. Therefore this study contributes to the quality control of ready-mixed concrete through statistical analysis for the relation between mix factors in mix design and compressive strength, predictable equation for compressive strength.

• Geomechanics and Engineering
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• v.33 no.3
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• pp.261-269
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• 2023

In this study, the compressive strength of cement stabilized soil was predicted using the electrical resistivity measurement. The effects of the water to cement (w/c) ratio and recovered Carbon Black (rCB) contents were examined. A series of electrical resistivity and compressive strength tests were conducted on two types of stabilized soil after 28 days of curing. Multiple nonlinear regression (MNLR) analysis was used to evaluate the relationship between the compressive strength and the electrical resistivity in terms of the rCB, C_u (uniformity coefficient), and w/c ratio. The results showed that the w/c ratio and C_u have a strong influence on the compressive strength and electrical resistivity of the cement stabilized soil compared to the rCB content. The use of a small amount of rCB led to a decrease in the void space in the specimen and was attributed to the increase strength and decrease electrical resistivity. A high w/c ratio also induced a low electrical resistivity and compressive strength, whereas 3% rCB in the cemented soil provided the optimum strength for all w/c ratios. Finally, a prediction equation for the compressive strength using the electrical resistivity measurement was suggested based on its reliability, time effectiveness, non-destructiveness, and cost-effectiveness.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.537-540
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• 2006

In previous study, the effect of specimen sizes and shapes on the compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. In this study, the relationship between the cube compressive strength and the cylinder strength for representative specimen sizes was investigated by linear regression analyses. And, by reanalyzing the compressive strength prediction equations with specimen size and shape obtained in previous studies, the compressive strength prediction equations were generalized. In addition, its verification was investigated by comparing with the results obtained from other researchers.