• Structural Engineering and Mechanics
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• v.74 no.5
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• pp.671-678
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• 2020

In this work, the dynamic properties of a high performance concrete containing glass powder (GP) was studied. The GP is a new cementitious material obtained by recycling waste glass presenting pozzolanic activity. This eco-friendly material was incorporated in concrete mixes by replacing 20 and 30% of cement. The mechanical properties of building materials highly affect the response of the structure under dynamic actions. First, the resonant vibration frequencies were measured on concrete plate with free boundary conditions after 14, 28 and 90 curing days by using an alternative vibration monitoring technique. This technique measures the average frequencies of several excitations done at different points of the plate. This approach takes into account the heterogeneity of a material like concrete. So, the results should be more precise and reliable. For measuring the bending and torsion resonant frequencies, as well as the damping ratio. The dynamic properties of material such as dynamic elastic modulus and dynamic shear modulus were determined by modelling the plate on the finite element software ANSYS. Also, the instantaneous aroused frequency method and ultrasound method were used to determine the dynamic elastic modulus for comparison purpose, with the results obtained from vibration monitoring technique.

• Advances in concrete construction
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• v.5 no.6
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• pp.671-683
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• 2017

Commonly used concrete in general, consists of cement, fine aggregate, coarse aggregate and water. Natural river sand is the most commonly used material as fine aggregate in concrete. One of the important requirements of concrete is that it should be durable under certain conditions of exposure. The durability of concrete is defined as its ability to resist weathering action, chemical attack or any other process of deterioration. Durable concrete will retain its original form, quality and serviceability when exposed to its environment. Deterioration can occur in various forms such as alkali aggregate expansion, freeze-thaw expansion, salt scaling by de-icing salts, shrinkage, attack on the reinforcement due to carbonation, sulphate attack on exposure to ground water, sea water attack and corrosion caused by salts. Addition of admixtures may control these effects. In this paper, an attempt has been made to replace part of fine aggregate by tailing material and part of cement by fly ash to improve the durability of concrete. The various durability tests performed were chemical attack tests such as sulphate attack, chloride attack and acid attack test and water absorption test. The concrete blend with 35% Tailing Material (TM) in place of river sand and 20% Fly Ash (FA) in place of OPC, has exhibited higher durability characteristics.

• Advances in concrete construction
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• v.15 no.6
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• pp.431-444
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• 2023

This study investigated the use of latex-modified sand concrete reinforced with sisal fibers (LMSC) as a repair material. Notably, no prior research has explored the application of LMSC for this purpose. This paper examines the interface bond strength and the type of failure between LMSC as a repair material and the normal concrete (NC) substrate utilising four different surfaces: without surface preparation as a reference (SR), hand hammer (HA), sandblasted (SB), and grooved (GR). The bond strength was measured by bi-surface shear, splitting tensile, and pull-off strength tests at 7, 28, and 90 days. Scanning electron microscopy analysis was also performed to study the microstructure of the interface between the normal concrete substrate and the latex-modified sand concrete reinforced with sisal fibers. The results of this study indicate that LMSC has bonding strength with NC, especially for HR and SB surfaces with high roughness. Therefore, substrate NC surface roughness is essential in increasing the bonding strength and adhesion. Eventually, The LMSC has the potential to repair and rehabilitate concrete structures.

• Computers and Concrete
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• v.26 no.3
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• pp.227-237
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• 2020

Strain rate investigations are needed to calibrate strain-rate-dependent material models and numerical codes. An appropriate material model, which considers the rate effects, need to be used for proper numerical modeling. The plastic concrete cut-off wall is a special underground structure that acts as a barrier to stop or reduce the groundwater flow. These structures might be subjected to different dynamic loads, especially earthquake. Deformability of a structure subjected to dynamic loads is a principal issue which need to be undertaken during the design phase of these structures. The characterization of plastic concrete behavior under different strain rates is essential for proper designing of cut-off walls subjected to dynamic loads. The Cowper-Symonds model, as one of the most commonly applied material models, complies well with the behavior of a plastic concretes in low to moderate strain rates and will be useful in explicit dynamics simulations. This paper aims to present the results of an experimental study on mechanical responses of one of the most useful types of plastic concrete and Cowper-Symonds constant determination procedures in a wide range of strain rate from 0.0005 to 107 (1/s). For this purpose, SHPB, uniaxial, and triaxial compression tests were done on plastic concrete samples. Based on the results of quasi-static and dynamic tests, the dynamic increase factors (DIF) of this material in different strain rates and stress state conditions were determined for calibration of the Cowper - Symonds material models.

• Computers and Concrete
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• v.21 no.1
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• pp.11-20
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• 2018

The possibilities of non-linear analysis of reinforced-concrete structures are under development. In particular, current research areas include structural analysis with the application of advanced computational and material models. The submitted article aims to evaluate the possibilities of the determination of material properties, involving the tensile strength of concrete, fracture energy and the modulus of elasticity. To evaluate the recommendations for concrete, volume computational models are employed on a comprehensive series of tests. The article particularly deals with the issue of the specific properties of fracture-plastic material models. This information is often unavailable. The determination of material properties is based on the recommendations of Model Code 1990, Model Code 2010 and specialized literature. For numerical modelling, the experiments with the so called "classic" concrete beams executed by Bresler and Scordelis were selected. It is also based on the series of experiments executed by Vecchio. The experiments involve a large number of reinforcement, cross-section and span variants, which subsequently enabled a wider verification and discussion of the usability of the non-linear analysis and constitutive concrete model selected.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.99-102
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• 2002

This paper discusses the estimation of construction cost of high fluidity concrete using segregation reducing type superplasicizer with 350kgf/cm2 of design strength and 60$\pm$5cm of slump flow in order to verify the cost down effect of high fluidity concrete compared with that of plain concrete with 350kgf/cm2 of design strength and 18cm of slump and with 210kgf/cm2 of design strength and 15cm of slump. According to research, under same strength levels, although material cost of high fluidity concrete is somewhat higher than that of plain concrete due to segregation reducing type superplasticizer, labor cost and equipment cost of high fluidity concrete is cheaper than that of plain concrete. However, based on the strength differences, high fluidity concrete shows lower material cost, labor cost and equipment cost than that of plain concrete due to decreasing in size of member and re-bar caused by high strength development of concrete.

• Computers and Concrete
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• v.14 no.5
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• pp.503-526
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• 2014

Concrete is a versatile construction material used in many engineering structures. The design of concrete structures requires a thorough understanding of their material properties under various loading conditions. Several experimental investigations have been carried out to examine the behavior of concrete. This paper is an attempt to summarize the behavioral aspects of concrete under different loading conditions. Failure models developed out of these experimental investigations are reported in this paper with their merits and demerits.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.8-13
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• 1995

High flowing concrete has been made using a combination of different cementitious material. The use of supplementary cementitious material like ground granulated slag is not only interesting from an economical point of view but also from a mechanical and rheological point of view. In the case of high strength concrete, relation between the maturity and compressive strength development of high strength concrete is aproximated by appling gompertz curve and suggested new estimating method. It is the aim of this study to analysis the effect of different types of mineral fine power on the setting and compressive strength development of high flowing concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.450-455
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• 1997

In recent years the research and development about the new material proceeds rapidly and actively in building industry. We are concerned with high-strength concrete as a new material. As the building structure becomes bigger, higher and more specialized, so does the demand of material and member with high strength for building expands greatly. In the future, we will quite need to research repair and rehabilitation to make high strength concrete structural building for our safe. So, I did an study on carbon fiber sheet rehabilitation(CFSR) of reinforced high strength concrete beams. The carbon fiber reinforced plastic(CFRP) bonding method is widely used for reinforcing the existing concrete structure among the various methods. The test results indicate that CFS is very effective for strengthening the damaged beams and controlling deflections of the repaired beams. When carbon fiber sheet rehabilitation of reinforced high strength concrete beams happened diagonal crack, the increase in the number of CFS layer didn't effect the increase in strength of beams. Also, by changing the CFS stick position gave diversified ultimate load in CFSR beams.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.202-203
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• 2017

In this study, the concept of exposed concrete is basically considered and various expressions of concrete surface texture are verified variously. Based on this comparison, the characteristics of exposed surface of concrete according to the change of coating material applicable to formwork are compared and analyzed. I am trying to find a way to apply exposed concrete in a convenient way, In order to observe the characteristics of concrete exposed surface according to the form material, As the surface is smooth and tight, the surface condition of the concrete is smooth and the pore is small.