• Advances in materials Research
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• v.11 no.1
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• pp.75-90
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• 2022

In this paper, functionality of soft computing algorithms such as Group method of data handling (GMDH), Random forest (RF), Random tree (RT), Linear regression (LR), M5P, and artificial neural network (ANN) have been looked out to predict the compressive strength of concrete mixed with marble powder. Assessment of result suggests that, the overall performance of ANN based model gives preferable results over the different applied algorithms for the estimate of compressive strength of concrete. The results of coefficient of correlation were maximum in ANN model (0.9139) accompanied through RT with coefficient of correlation (CC) value 0.8241 and minimum root mean square error (RMSE) value of ANN (4.5611) followed by RT with RMSE (5.4246). Similarly, other evaluating parameters like, Willmott's index and Nash-sutcliffe coefficient value of ANN was 0.9458 and 0.7502 followed by RT model (0.8763 and 0.6628). The end result showed that, for both subsets i.e., training and testing subset, ANN has the potential to estimate the compressive strength of concrete. Also, the results of sensitivity suggest that the water-cement ratio has a massive impact in estimating the compressive strength of concrete with marble powder with ANN based model in evaluation with the different parameters for this data set.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.4
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• pp.3137-3146
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• 1973

This study was to investigate the effects of compaction, compressive strength and Atterberg limits in accordance with the temperatures changes. It was conducted on four soils-KJ, JJ, MH, SS-at temperatures of -1, 1, 3, 5, 7, 10, 15, 19, $22^{\circ}C$. These tests were obtained the maximum dry density and the optimum moisture content of four soils in accordance with temperature changes by using distilled water and $CaCl_2$ 10% solution, and were put to the compressive strength tests on remolded specimens of soils compacted at the optimum moisture content. The result of the study can be summarized as follows; The maximum dry density increased with an increase in temperature, and the use of $CaCl_2$ 10% solution had higher maximum dry density than distilled water. The optimum moisture content decreased with an increase in temperature, and the use of $CaCl_2$ 10% solution had lower optimum moisture content than distilled water. The maximum compressive strength was shown high peak from $7^{\circ}C\;to\;15^{\circ}C$, and the use of $CaCl_2$ 10% solution had higher maximum compressive strength than distilled water. The liquid limit and plasticity index decreased with an increased in temperature. It is estimated that the use of $CaCl_2$ 10% solution can lower the minimum compacted temperature from $2^{\circ}C\;to\;4^{\circ}C$ in low temperature.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.161-167
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• 2008

Optimization of concrete mixing system is very important for the production of quality mixture of concrete and requires very complicated, specialized knowledge as there are a variety of variables that influence the result. One of the methods of optimizing the concrete mixing system is to minimize the volume of cement paste which, in turn, means maximizing the volume of aggregate. The purpose of this study is to determine the minimum volume of cement paste used in the design of concrete mixture and to design the optimum concrete mixing system based on the fluidity of mortar and concrete. In determining the minimum volume of cement paste, experiments of mortar and concrete were performed based on their workability, material segregation and bleeding. Type of aggregate, granularity distribution and sand percentage were used as test parameters and measurements were taken of the distribution of granularity, usage of HRWRA, minimum volume of paste and drying shrinkage and compressive strength of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.253-258
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• 2002

An evaluation equation of the minimum shear reinforcement content for reinforced concrete beams was theoretically proposed. The proposed equation takes into account the effects of compressive strength of concrete, longitudinal reinforcement content and shear span ratio. The proposed equation was compared with the current ACI 318-99 and CSA A23.3-94 codes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.53-54
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• 2015

As the result of uniaxial compression strength test on the CLMS mixing BFS and SS with BFS 4000, it required to determine the desired strength through increasing unit quantity of cement in mixing process because of dramatic strength deterioration of strength according to increasing replacing rate. In this study's result, regardless of differences in fine aggregates used, in order to get uniaxial compression strength in the scope exceeding criteria of minimum strength for applying to the field, the most reasonable combination was to mix replacing BFS with fineness of 6000 in 30%. For the CLMS mixing BFS and SS, in order to improve flow ability by securing quantity of minimum unit and to repress bleeding rate with securing uniaxial compress strength considering the field applicability, regardless of differences in fine aggregates used, to mix BFS over 6000 in 30% was most effective.

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.97-103
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• 2014

To ensure durability and light weight of bridges, high-strength concrete is required for long-span deck slabs. Such a technology eventually extends the life of bridges and improves the economic efficiency. The results of this study suggests a formula for calculating the minimum thickness of long-span deck slabs built with high strength concrete. The minimum thickness is proposed based on the limit states indicated in the CEB-FIP Model Code and the Korean Highway Bridge Design Code(limit state design). The design compressive strength of concrete used for the study is 80MPa. Moreover, the required thickness for satisfying the flexural capacity and limiting deflection is estimated considering the limit state load combination. The formula for minimum thickness of deck slabs is proposed considering the ultimate limit state(ULS) and the serviceability limit state(SLS) of bridges, and by comparing the Korean Highway Bridge Design Code and similar previous studies. According to the research finding, the minimum thickness of long-span deck slab is more influenced by deflection limit than flexural capacity.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.52-59
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• 2015

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specified strength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of core test data.

• Geomechanics and Engineering
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• v.23 no.3
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• pp.227-244
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• 2020

Earthen structures have an excellent bioclimatic performance, but they are vulnerable against earthquakes. In order to investigate the edification process and costs, a full-scale rammed soil house was constructed in 2004. In 2016-2019, it was studied its seismic damage, durability and degradation process. During 2004-2016, the house presented a relatively good seismic performance (M_w=5.6-6.4). The damaged cover contributed in the fast deterioration of walls. In 2018 it was observed a partial collapse of one wall due to recent seismicity (M_w=5.6-6.1). The 15-year-old samples presented a reduced compressive strength (0.040 MPa) and a minimum moisture (1.38%). It is estimated that the existing house has approximately a remaining 20% of compressive strength with a degradation of about 5.4% (0.0109 MPa) per year (considering a time frame of 15 years) if compared to the new soil samples (0.2028 MPa, 3.52% of moisture). This correlation between moisture and compressive strength degradation was compared with the study of new soil samples at the same construction site and compared against the extracted samples from the 15-year-old house. At 7-14-days, the specimens presented a similar compressive strength as the degraded ones, but different moisture. Conversely, the 60-days specimens shown almost five times more strength as the existing samples for a similar moisture. It was observed in new rammed soil that the lower the water content, the higher the compressive/shear strength.

• Computers and Concrete
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• v.7 no.3
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• pp.221-237
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• 2010

In this study 72 different high strength concrete (HSC) mixes were produced according to the Taguchi design of experiment method. The specimens were divided into four groups based on the range of their compressive strengths 40-60, 60-80, 80-100 and 100-125 MPa. Each group included 18 different concrete mixes. The slump and air-content values of each mix were measured at the production time. The compressive strength, splitting tensile strength and water absorption properties were obtained at 28 days. Using this data the Genetic Programming technique was used to construct models to predict mechanical properties of HSC based on its constituients. These models, together with the cost data, were then used with a Genetic Algorithm to obtain an HSC mix that has minimum cost and at the same time meets all the strength and workability requirements. The paper describes details of the experimental results, model development, and optimization results.

• 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.