• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.577-583
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• 2022

In this study, the characteristics of self-healing mortars produced using an inorganic self-healing material consisting of ground granulated blast furnace slag, expansion agent, and anhydrite, were investigated. For three types of self-healing mortars with different amounts of the inorganic healing material, compressive strength was measured and the self-healing performance was evaluated through the constant water head permeability test. The healing rate and equivalent crack width according to crack-induced aging were used as indicies of healing performance evaluation. Considering the development of compressive strength of the self-healing mortars, the change in the healing rate with healing periods, and the economic feasibility, the optimal amount of inorganic self-healing materials was suggested as 20 % of the mass of cement.

• Journal of the Korean Wood Science and Technology
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• v.39 no.4
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• pp.333-343
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• 2011

The yellow poplar is an appropriate species for the age of low carbon green growth, because its absorption rates of ozone is greatly excellent, and also the absorption rates of carbon dioxide causing climate changes is very remarkable. The yellow poplar, which is a kind of rapid growth tree, shows a lack of performance as a structural member, however, it is suitable to use a variety of purposes like furniture materials, interior materials, plywood materials, and so on. In this study, the structural size skin-timbers were made by using the yellow poplar, and the compressive capacity was evaluated, also the numerical model was developed for the various uses. The rectangular shape skin-timber presented a good performance by showing 56.3% residual strength about the solid material. In case of the cylinder shape skin-timber showed a possibility to use diversely as a furniture material, as well as a structural uses, because almost 50% compressive capacity of material even though its residual area rates was 25%. Both rectangular shape and the cylinder shape represented that 'Brooming or end rolling' were the major failure mode, and partly splitting failure mode. The compressive capacity of the rectangular shape which residual area rates was large was higher than the cylinder shape, but it did not show statistical significance about the compressive capacity between them. Thus, it will be possible to use them mixed for a convenience of users. The result of the numerical analysis model was quite similar to actual test of the compressive capacity. Therefore, the yellow poplar can be utilized in the development of various uses by applying numerical analysis model about a variety of shapes and dimensions.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.263-266
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• 1999

This study aims to make high performance concrete for normal strength using crushed stone fines to control high strength of the high performance concrete. According to the experimental results, when crushed stone fines are increased every 10%, 15% of compressive strength is decreased, and 5% of drying shrinkage is increased, compared to normal high performance concrete. Also, high performance concrete has been evaluated to have good durability factor more than 100% in the 480cycle of freezing and thawing test, without regard to using AE and crushed stone fines.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.31-37
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• 2018

This study evaluates the dynamic tensile behavior of HPFRCC according to compressive strength levels of 100, 140 and 180 MPa. Firstly, the compressive stress-strain relationship of 100, 140 and 180 MPa class HPFRCC was analyzed. As a result, the compressive strengths were 112, 150 and 202 MPa, respectively, and the elastic modulus increased with increasing compressive strength. The static tensile strengths of HPFRCC of 100, 140 and 180 MPa were 10.7, 11.5 and 16.5 MPa, and tensile strength also increased with increasing compressive strength. On the other hand, static tensile strength and energy absorption capacity at 100 and 140 MPa class HPFRCC showed no significant difference according to the compressive strength level. It was influenced by the specification of specimen and the arrangement of steel fiber. As a result of evaluating the dynamic impact tensile strength of HPFRCC, tensile strength and dynamic impact factor of all HPFRCCs tended to increase with increasing strain rate from 10-1/s to 150/s. In the same strain rate range, the DIF of the tensile strength was measured higher as the compressive strength of HPFRCC was lower. It is considered that HPFRCC of 100 MPa is the best in terms of efficiency. Therefore, it is advantageous to use HPFRCC with high compressive strength when a high level of tensile performance is required, and it is preferable to use HPFRCC close to the target compressive strength for more efficient approach at a high strain rate such as explosion.

• Journal of electromagnetic engineering and science
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• v.17 no.3
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• pp.113-119
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• 2017

The application of compressive sensing (CS) to a radar imaging system based on a frequency-scanned microstrip leaky wave antenna is investigated. First, an analytical model of the system matrix is formulated as the basis for the inversion algorithm. Then, $L_1-norm$ minimization is applied to the inverse problem to generate a range-azimuth image of the scene. Because of the antenna length, the near-field effect is considered in the CS formulation to properly image close-in targets. The resolving capability of the combined frequency-scanned antenna and CS processing is examined and compared to results based on the short-time Fourier transform and the pseudo-inverse. Both simulation and measurement data are tested to show the system performance in terms of image resolution.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.1
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• pp.16-21
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• 2014

In the study, tensile, compression and in-plane tests about longitudinal direction of glass fiber were performed. Also, to obtain the material properties of GFRP fabric composite, tensile test was performed. All test were performed by the test method of ASTM. Maximum compressive strength was smaller than the maximum tensile strength at the longitudinal direction test results. Elastic modulus of the tensile and compressive was almost similar at the compression test results in the longitudinal direction. Based on the GFRP fabric composite test results, GF91 was showed good performance at maximum compressive, maximum strain and elastic modulus.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.282-283
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• 2014

An active study on UHPC, which has been recently used in high-rise building and bridges, is in progress. However, research on adhesion strength of normal concrete and UHPC is required to be studied due to the lack of information. In this study, experimental research progress for adhesion strength (shear strength of adhesive surface) evaluation of Bi-compressive strength concretes (UHPC, Normal concrete) is proceeded. First, specimens using glue are produced and surface treatment methods of concrete bonded section are considered. Second, Direct Shear test is applied on concrete bonded section of UHPC (80~180MPa) and Normal Concrete (NC). As a result of this study, it is confirmed that bond strength is deteriorated as the difference of intensity ration of NC and UHPC increases.

• Computers and Concrete
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• v.5 no.5
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• pp.475-490
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• 2008

The paper explores the potential of applicability of Genetic programming approach (GP), adopted in this investigation, to model the combined effects of five independent variables to predict the mini-slump, the plate cohesion meter, the induced bleeding test, the J-fiber penetration value, and the compressive strength at 7 and 28 days of self-compacting slurry infiltrated fiber concrete (SIFCON). The variables investigated were the proportions of limestone powder (LSP) and sand, the dosage rates of superplasticiser (SP) and viscosity modifying agent (VMA), and water-to-binder ratio (W/B). Twenty eight mixtures were made with 10-50% LSP as replacement of cement, 0.02-0.06% VMA by mass of cement, 0.6-1.2% SP and 50-150% sand (% mass of binder) and 0.42-0.48 W/B. The proposed genetic models of the self-compacting SIFCON offer useful modelling approach regarding the mix optimisation in predicting the fluidity, the cohesion, the bleeding, the penetration, and the compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.214-215
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• 2017

Extreme loads such as impact and explosion have higher strain rate than static loading condition. Therefore, it is necessary to evaluate mechanical properties at high strain rate in order to apply fiber reinforced cement composites to ensure safety performance against impact and explosion. In this study, the compressive properties of fiber reinforced cement composites by strain rate were evaluated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.152-153
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• 2016

In this research, we evaluate the performance for preventing frost damage at early age of mortar using variable cement and self-heating binder. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature without heat curing. We compare the compressive strength of mortar and concrete using variable cements and self-heating binder in low temperature.