• Steel and Composite Structures
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• v.14 no.5
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• pp.473-491
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• 2013

The primary objectives of this paper are to describe the buckling patterns and to determine the squash load of steel plate-concrete (SC) walls. The major variables in this study were the width-thickness (B/t) ratio and yield strength of surface steel plates. Six SC walls were tested, and the results include the maximum strength, buckling pattern of steel plates, strength of headed studs, and behavior of headed studs. Based on the test results, the effects of the B/t ratio on the compressive strength are also discussed. The paper also presents recommended effective length coefficients and discusses the effects of varying the yield strength of the steel plate, and the effects of headed studs on the performance of SC structures based on the test results and analysis.

• Advances in concrete construction
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• v.4 no.4
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• pp.243-261
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• 2016

This research study focuses on utilizing sandstone which is overburden waste rock in coal mines to use in concrete as a replacement of fine aggregate. Physical properties of sandstone like water absorption, moisture content, fineness modulus etc., were found to be similar to conventional fine aggregate. Scanning Electron Microscope (SEM) analysis was carried out for analysing elemental composition of sandstone. There was no sulphur content in sandstone which is a good sign to carry the replacement. Fine aggregate was replaced with sandstone at 25%, 50%, 75% and 100% by volume and moulds of concrete cubes and cylinders were prepared. Compressive strength of concrete cubes was tested after 3, 7 and 28 days and split tensile & flexural strength was determined after 28 days. The strength was found to be increasing marginally with increase in sandstone content. Fine aggregate that was replaced by 100% sandstone gave highest strength among all the replacements for the compressive, split tensile and flexural strengths. Though increase in strength was marginal, still sandstone can be an effective replacement for sand in order to save the natural resource and utilize the waste sandstone.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.157-162
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• 2002

This study is intended to present a reference data for effective quality control of concrete through comparing the rebound value of P type schmidt hammer with the compressive strength with variation of mix proportion and curing condition. According to the results, the air-curing specimen shows the higher rebound value than standard specimen except high strength in the whole. Also the vertical stroke shows higher rebound value than horizontal stroke in standard specimen, however, the rebound value of the two does not show prominent difference in air-curing specimen. The estimation equation of compressive strength derived from this experiment estimates the compressive strength more largely than the estimation equation in P type schmidt hammer manual. Therefore it is thought that the new estimation equation that fits our condition will have to be presented.

• Advances in concrete construction
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• v.4 no.4
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• pp.283-303
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• 2016

Several types of industrial byproducts are generated. With increased environmental awareness and its potential hazardous effects, the utilization of industrial byproducts in concrete has become an attractive alternative to their disposal. One such by-product is ground granulated blast furnace slag (GGBS), which is a byproduct of the smelting process carried out in the iron and steel industry. The GGBS is very effective in the design and development of high-strength and high-performance concrete. This paper reviews the effect of GGBS on the workability, porosity, compressive strength, splitting tensile strength, and flexural strength of concrete.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.111-135
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• 2013

An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.143-150
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• 1994

To improve the qualities of high strength mortar and concrete with high range water reducing admixture, silica fume and gypsum is applied. The flow loss of mortar is reduced and the compressive strength of mortar and concrete is improved by silica fume. And the silica fume is effective for decreasing the temperature of high strength concrete. In addition to, the strength of high strength concrete is more improved by the gypsum.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.403-413
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• 2014

For the reliable design of the structural concrete by the strut-tie model approaches of current design codes, the effective strengths of concrete struts must be determined with sufficient accuracy. Many values and equations for the effective strengths have been suggested until now. As those are for the two-dimensional concrete struts, however, it is inappropriate to employ them in the strut-tie model designs of three-dimensional structural concretes. In this study, an approach, that determines the effective strengths of three-dimensional concrete struts consistently and accurately by reflecting the state of 3-dimensional stresses, the 3-dimensional failure criteria of concrete, the degree of cracks (or tensile strains of reinforcing bars crossing the struts), the strut's longitudinal length, the deviation angle between strut orientation and compressive principal stress flow, compressive strength of concrete, and the degree of concrete confinement by reinforcing bars, is proposed. To examine the validity of the proposed approach, the ultimate strength analyses of 115 reinforced concrete pile caps tested to failure by previous investigators were conducted by the ACI 318-11's strut-tie model approach with the existing and proposed effective strengths of concrete struts.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.2
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• pp.3018-3030
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• 1973

This study was carried out to investigate the effects of various mix designs of concrete on the compressive strengths and corrosive rates when the concretes were immersed in sea water of the West Sea, as the part of study related to durated to durability of concrete by action of the sea water. Concrete mix designs used in this study were ordinary Concrete mix, Concrete mixes with different admixtures such as fly ash, pozzolith and vinsol resin, and pozzolan concrete mix. The concrete specimens were made and cured for 7 days and 28 days in the fresh water in accordance with the Korean Standard specification for concrete. Compressive strengths of the specimens were measured after immersing the specimens for one year in fresh water and sea water which were placed indoors. The sea water used in this test was taken from the Bay of Ahsan. Corrosive rate was also tested after immersing the specimens in the same sea water and placed indoors for one year. The results obtained from the tests are summarized as follows; 1. Compressive strength of an ordinary concrete was the lowest of the various mix desings of concrete immersed both in the fresh water and the sea water. Therefore, the uses of pozzolan cement, fly ash, pozoolith and vinsol resin in mix design of concrete had and effect on increasing compressive strength. 2. Pozzolan concrete was the most effective on compressive strength in the fresh water, but it had less effect than concrete with fly ash admixture immersed in the sea water. 3. The use of fly ash admixture in mix design of concrete showed higher strength as the immersing age is longer both in fresh water and sea water than the other concretes besides pozzolan concrete, but the concretewith fly ash admixture had lower strength than pozzolan concrete in the sea water. Therefore, concrete with fly ash admixture might be better than the pozzolan concrete as far as durability of concrete to sea water was concerned. 4. The use of pozzolith admixture in mix design of concrete had less compressive strength than the use of pozzolan cement for fly ash admixture both in fresh water and sea water. However, the concrete with pozzolith admixture was much stronger than one with vinsol resin admixture in fresh water, but somewhat stronger in the sea water. 5. Though the use of vinsol resin admixture was more effective than ordinary concrete on compressive strength both in fresh water and sea water, it was the least compressive strength among the other concretes. 6. Relation between compressive strengths and absorption rates of every kind of concrete besides concrete with fly ash admixture showed a linear regression line and the compressive strength is highee as the absorption rate is lower. Concrete with fly ash admixture had extremely high strength in comparison with corresponding adsorption rates of the other concretes. 7. Corrosive appearance on the surface of concretes was not occured significantly when exposed to the sea water for one year, However, the specimens of concretes besides ordinary concrete were a little heavier than those cured in fresh water for 28 days.

• Computers and Concrete
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• v.13 no.4
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• pp.423-436
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• 2014

Ground Granulated Blast Furnace Slag (GGBFS) is widely used as an effective partial cement replacement material. GGBFS inclusion has already been proven to improve several performance characteristics of concrete. GGBFS provides enhanced durability, including high resistance to chloride penetration and protection against alkali silica reaction. In this paper results of an experimental research work on influence of low-reactivity GGBFS (which is largely available in Iran) on the properties of mortars and concretes are reported. In the first stage, influence of GGBFS replacement level and fineness on the compressive strength of mortars was investigated using Taguchi method. The analysis of mean (ANOM) statistical approach was also adopted to develop the optimal conditions. Next, based on the obtained results, concrete mixtures were designed and water penetration, capillary absorption, surface resistivity, and compressive strength tests were carried out on highstrength concrete specimens at different ages up to 90 days. The results indicated that 7-day compressive strength is adversely affected by GGBFS inclusion, while the negative effect is less evident at later ages. Also, it was inferred that use of low-reactivity GGBFS (at moderate levels such as 20% and 30%) can enhance the impermeability of high-strength concrete since 28 days age.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.241-244
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• 2004

The evaluation of Single or multi-degregation of concrete coated by high performance surface penetration agency was examined through various tests, i.e., carbonation, absorption, carbonation + chloride ion and carbonation + chemical solution according to various high performance surface penetration agencies and various compressive strengths of base concrete. The 2 types of high performance surface penetration agencies were used i.e., inorganic and alcohol soluble. And 2 types of compressive strength of base concrete were used such as 21 30. MPa. The characteristics of concrete coated high performance surface penetration agency was more improved than that of non-coated concrete, and especially, water soluble inorganic agency was most effective. And if compressive strength of base concrete was low, the improved effects would be larger.