• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.207-214
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• 1997

Strength experimental on mortar which use Quenched Blast-Furnace Slag as aggregate was carried our for a fundamental study of application possibility of Quenched Blast-Furnace Slag as aggregate. It gives the following results. The strength of mortar use Quenched Blast-Furnace Slag is decrease as substitution rate is higher. As W/C rate increase, the strength decrease, but the strength decrease of fine aggregate rate 1:3 is lower than 1:2. The relation with fine aggregate is that the amount of fine aggregate is inversely proportional to strength. Th relation with age is proportional to strength and strength rate of going is lower than general mortar in 28 age the change of strength proportionately with W/C rate is that as W/C rate increases, th strength is drop ; it shows that it has same tendency as general mortar sand or crushed sand, but while W/C rate increase the strength is as high as general mortar. The reason can be assumed that water content per unit needed to Quenched Blast-Furance Slag is more than in case of sand. In addition, the relation with substitution rate is that the strength is the strongest at substitution rate 25% and 50% ; that is , sometimes it is higher than mortar which use sand 100%. In addition, long age strength of mortar which use Quenched Blast-Furnace Slag as aggregate is about to be studied in the last.

• Journal of the Korea Institute of Building Construction
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• v.4 no.2
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• pp.113-118
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• 2004

This study is a basic experiment on quality management of the compression strength of high strength concrete, aiming. at quality management of high strength mass concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Different from ordinary concrete, high strength concrete generally shows the temperature high rising caused by hydration heat inside the concrete. It is known that, in mass concrete, thermal stress occurs due to the difference in temperature between the inside and the outside, which causes a significant difference in compression strength between structure beams and managerial test pieces. It is also reported that there is a large difference between the compression strength of cylindrical managerial test pieces of standard underwater curing and the strength of structure beam concrete. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created thermal insulation curing box and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• 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.

• Structural Engineering and Mechanics
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• v.45 no.6
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• pp.837-851
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• 2013

In construction industry, strength is a primary criterion in selecting a concrete for a particular application. The concrete used for construction gains strength over a long period of time after pouring the concrete. The characteristic strength of concrete is defined as the compressive strength of a sample that has been aged for 28 days. Neither waiting for 28 days for such a test would serve the rapidity of construction, nor would neglecting it serve the quality control process on concrete in large construction sites. Therefore, rapid and reliable prediction of the strength of concrete would be of great significance. On this backdrop, the method is proposed to establish a predictive relationship between properties and proportions of ingredients of concrete, compaction factor, weight of concrete cubes and strength of concrete whereby the strength of concrete can be predicted at early age. Multiple regression analysis was carried out for predicting the compressive strength of concrete containing Portland Pozolana cement using statistical analysis for the concrete data obtained from the experimental work done in this study. The multiple linear regression models yielded fairly good correlation coefficient for the prediction of compressive strength for 7, 28 and 40 days curing. The results indicate that the proposed regression models are effectively capable of evaluating the compressive strength of the concrete containing Portaland Pozolana Cement. The derived formulas are very simple, straightforward and provide an effective analysis tool accessible to practicing engineers.

• Journal of Preventive Medicine and Public Health
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• v.45 no.6
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• pp.381-386
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• 2012

Objectives: To investigate the link between cigarette smoking and muscle strength in Japanese men. Methods: We used data on 4249 Japanese men, aged $43.3{\pm}13.9$ years, in this cross-sectional investigation study. Grip strength and leg strength were measured as indicators of overall muscle strength. Meanwhile, subjects' cigarette smoking habits were recorded by trained medical staff. The effect of cigarette smoking on muscle strength was evaluated. Results: A total of 1618 men (38.1%) were smokers and 1481 men (34.9%) exercised regularly. Significant differences in muscle strength were noted between men with and without a Brinkman index of 400 or greater, after adjusting for age. After adjusting for age, height, body weight and exercise habits, associations between the Brinkman index and leg strength and the ratio of leg strength to body weight were attenuated. Conclusions: Cigarette smoking might be negatively associated with muscle strength, especially grip strength in Japanese men.

• Advances in concrete construction
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• v.14 no.2
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• pp.115-130
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• 2022

This paper presents an application of the maturation effect on the strength of high-strength concrete which is produced with different origin aggregates. While investigating the maturation effect on HSC 384 specimens were prepared with 22 different origin aggregates. These prepared specimens were subjected to the standard compressive tests which were applied after curing for 2, 7, 28, and 56 days under appropriate conditions. The test results revealed that bright surface-low adherence behavior is valid in normal strength concretes, but is not as effective as expected in high-strength concretes. The application of artificial neural networks (ANNs) to predict 2, 7, 28, and 56 day compressive strength of HSC is also investigated in this paper. An ANN model is built, trained, and tested using the available test data gathered from experimental studies. The ANN model is found to predict 2, 7, 28, and 56 days of compressive strength of high-strength concrete well within the ranges of the input parameters considered. These comparisons show that ANNs have strong potential as a feasible tool for predicting the compressive strength of high-strength concrete within the range of the input parameters considered.

• Korean Journal of Agricultural Science
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• v.3 no.2
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• pp.214-224
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• 1976

This research was attempted as one of studies on the strength of mortar added admixtures at different curing temperatures. Variations of curing temperature to. test compressive strength, tensil strength and bending strength were $20^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$ and these results were summarized as follow : In strength of mortar added briquette ash, the compressive strength was increased: 1.58 percent, the tensile strength 0.96 percent, and the bending strength 1.26 percent compared with standard strength, by increasing one degree of celsius temperature. Also in strength of mortar added fly ash, the compressive strength increased on the average 1.3 percent, the tensile strength 0.99 percent, and the bending strength 1.18 percent at the above conditions. In case of using fly ash as admixture, maximum compressive strengths was attained at the level of 25 percent of fly ash, maximum tensile strength at the level of 20 percent of fly ash, and maximum bending strength at the level of 20 percent of fly ash. In case of using briquette ash, maximum compressive strength was attained maximum strength at 20 percent of the admixture, maximum tensile strength at the level of 15 to 20 percent of admixture and maximum bending strength at the level of 20 percent of admixture. Although addition of briquette ash was less effective in increasing the strength compared with the addition of fly ash, briquette ash might be used as one of admixtures because the control of curing temperature might affect in getting the required practical strength.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.261-268
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• 2004

The main objectives of this study are to investigate the anisotropic characteristics of rocks and to evaluate the relationships between physical properties. A series of experiments were performed in three mutually perpendicular directions for three rock types, which are granite, granitic gneiss and limestone. The relationships of measured physical properties were evaluated. The results of ultrasonic wave velocity measurement show that granite of three rock types gives the largest directional difference, and that the wave velocity in a plane parallel to a transversely isotropic one is dominantly faster than that in a subvertical or vertical plane. It implies that ultrasonic wave velocity for rock could be used as a useful tool for estimating the degree of anisotropy. The ratio of uniaxial compressive strength to Brazilian tensile strength ranges approximately from 13 to 16 for granite. from 8 to 9 for granite gneiss, and from 9 to 18 for limestone. The directional differences for granite and granitic gneiss are very small, and on the other hand, is relatively large for limestone. It is suggested that strength of rock makes quite difference depending on the rock types and loading directions, especially for the anisotropic rocks such as transversely isotropic or orthotropic rocks. The ratio of uniaxial compressive strength to point load strength index ranges from 18 to 20 for granite, from 17 to 19 for granitic gneiss, and from 21 to 24 for limestone. These results show that point load strength index makes also a difference depending on rock types and directions. Therefore. it should be noted that the ratio of uniaxial compressive strength to point load strength index could be applied to all rock types. Uniaxial compressive strength shows relatively good relationship with point load strength index, Schmidt hammer rebound value, and tensile strength. In particulat, point load strength index is shown to be the best comparative relationship. It is indicated that point load test is the most useful tool to estimate an uniaxial compressive strength indirectly.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.61-72
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• 1991

This study was carried out to research the strength drop of concrete in dry environment. The mixing ratio of cement-fine aggregate was 1: 1, 1 : 2, 1: 3 and 1 : 4. The curing was compared standard curing with dry curing immediately after casting. It is analysis of strength change by water-proof mixing. The curing age of cement mortar was 3days, 7days, l4days and 28days. The result obtained from this study are summarized as follows. 1. The compressive and bending strength change by increasing the curing age, dry curing mortar the increasing rate of strength was decreased than standard curing mortar. 2. The compressive and bending strength change in early curing, strength difference between standard curing mortar and dry curing motar was gradually closed by increasing the W/C. 3. The dry curing mortar was decreased than standard curing mortar in decreasing rate of compressive and bending strength by increasing the W/C. 4. The compressive strength of water-proof mortar in early curing, liquid water-proof mortar was shown high strength in dry curing than standard curing. The powder and liquid water-proof mortar have a small effect in dry environment. The liquid water-proof mortar was high strength without relation change of curing age in dry environment than standard curing. 5. The compressive strength of liquid water-proof mortar in poverty mix, dry curing was shown high strength than standard curing. 6. The bending strength was increased than compressive strength by decreasing the volume of cement in early curing. The increasing rate of bending strength was decreased to compressive stength by increasing the curing age.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.32-38
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• 1998

This paper is to investigate of microhardness, adhesive strength, tensile strength, and fatigue strength of ceramic sprayed steel. Rotary bending fatigue tests have been conducted at room temperature in air and 3% NaCl solution using specimens of carbon steel(S45C) with sprayed coating layers of Ni-4.5% Al(under coating) and $TiO_2$ (top coating). The microhardness has been improved at $800^{\circ}C$ heat treatment and 150mm spraying distance. Tensile strength of the sprayed steel is dependent on the substrate strength. The fatigue strength of the sprayed steel is larger than that of substrate due to blasting and constraint surface of plastic deformation effect. In low stress level, the corrosion fatigue strength of the sprayed steel were lower than that of fatigue strength in air by corrosion.