In the country, due to short comings of natural aggregates of good quality, it is common to use crushed stones. However, the investigation has not been done on the chemical reaction of crushed stones. This study tested and analyzed the aggregate chemical reaction by petrographic examination(ASTM C 295) for the test aggregates which had been tested by chemical method(ASTM C 289) in the first year. As a result, most of test aggregates didn't show any reaction but many have common deleterious mineral. Therefore, there exists the possibility of chemical reaction in petrogrphic point of view

Due to depleting reserves and environmental pressures, the availability of "good" aggregates, , particularly in many urban areas, has decreased in recent years and from the viewpoint of energy and resources saving, it may be very advantageous to use waste concrete as construction materials. Therefore, this paper, an experimental study on the application in the construction of recycled aggregate concrete, is the experimental program and properties of fresh concrete to investigate general performance and workability of concretef concrete

Critical shortage of natural aggregate for production of concrete is developing in many urban area. At the same time increasing quantities of demolished concrete form deteriorated and obsolete structures are generated as a waste material in the same areas. The reuse of a waste concrete may settle the problems of environmental pollution and shortage of adquate aggregate, Therefore, this study is to reuse a waste concrete as aggregate for concrete, It is the purpose of this present study to investigate and analyze how the addition rates of superplasticizer and curing condition affect the properties of fresh and hardened recycled aggregate concrete comparing with those of ordinary concrete and crushed stone concrete.

The study of recycled aggregate concrete in which demolition waste is utilized to produce aggregate for new concrete, can contribute to the solution of two problems. The first is the shortage of aggregate from river, and the second is the waste disposal problem. In comparison with natural aggregate concrete, recycled aggregate concrete shows reductions in compressive strength, tensile strength , vending strength, shear strength and increases in drying shrinkage and creep. Recycled aggregate concrete may also be less durable due to increase in porosity and permeability. Therefore, the purpose of this study is to analyze the applicability of recycled concrete in the influence of a substitute ratio of recycled sand gravel.

The study of recycled aggregate concrete in which demolition waste is utilized to produce aggregate for new concrete, can contribute to the solution of two problems, The first is the shortage of aggregate from river, and the second is the waste disposal problem. In comparison with natural aggregate concrete, recycled aggregate concrete shows reductions in compressive strength , tensile strength, vending strength , shear strength and increases in drying shrinkage and creep. Recycled aggregate concrete may also be less durable due to increase in porosity and permeability. The purpose of this study is to investigate and analyze the variation of engineering properties according to replacement proportion of recycled aggregates and applicability of non-destructive test in the gardened recycled concrete.

To analyze the using of recycled aggregate on concrete as the substitude aggregate is important problem for the reuse of waste matter and prevention of environmental pollution. Therefore, this study is designed for investigating and analyzing the mechanical properties and early estimational properties of strength on concrete using aggregate of the waste concrete. And is aimed to provide the fundamental data for recycled aggregate.

Recently inappropriate aggregates are used as a raw material for ready-mixed concretes, due to the shortage of natural aggregate resources and the prohibition of their extraction for the environmental protection. We, therefore, have conducted experiments to obtain some knowledge of properties of domestic aggregates and to investigate subsequent changes in the properties of the fresh and hardened concretes. To this end, aggregates currently used in 13 domestic ready-mixed concrete plants were collected. Most of aggregate used in this experiment satisfied the KS in density and unit weight. But some of the aggregates have the particle size distribution that can effect bad influence on concrete. In this experiment the aggregates are found to have a bad particle size distribution, resulting in high amount of a unit water content and a unit cement content in concrete.

Due to the recent shortage of river sand resulting from a rapid growth of concrete construction, sea sand and pit sand are increasingly used in stead. It is , however, well noted that non-washed sea sand used in reinforced concrete causes to corrode reinforcing steel and to incur cracks in concrete, and thus eventually result in damage to concrete. Moreover, many sources of pit sand in our country are randomly used without experimental research for its applicability to concrete construction. The purpose of this research to activate the usage of pit sand and sea sand for concrete construction to solve the recent shortage of river sand. Followings have been experimentally investigated : 1)Physical properties of pit sand and sea sand, 2)Compressive strength of mortar on the weight of pit sand passing through No.200 sieve, 3) Compressive strength of mortar on the chloride content of sea sand, 4) Compressive strengths of concrete using pit sand and sea sand, respectively, 5)Corrosion propagatio in reinforcing steel on the chloride concent, of sea sand, and 6)etc.

Admixtures for concrete placed underwater have been developed to the stage that they are now widely used. The use of this type of product allows concrete to be placed underwater with far less risk than was previously possible. One of the problems facing users of underwater concreting admixtures is how does one test such products in order to access their performance initially while minimizing the expense of carrying out site trials. This paper will introduce three categories of laboratory test for underwater concrete listed next : fluidity test, non-segregation test, strength test. Trial underwater concretes were ordinary Portland cement. Strength and workability development and segregation resistance properties of the concrete under the coexistence of some kinds of superplasticizer were studied for this laboratory tests.

The flexural and horizontal shear behavior of overlaid concrete slabs is investigated in the present study. An experimental program was set up and several series of overlaid concrete slabs have been tested to study the effect of different surface preparation ; and dowels between old slab and overlay under service load. The present study indicates that the overlaid concrete slabs behave integrally with existing bottom slabs up to yield range for rough and doweled joints.

Steel fiber reinforced concrete(SFRC) which is made by short, randomly distributed steel fibers in concrete is superior in its tensile mechanical properties to plain concrete in enhancement of tensile strength and tensile ductility. These improvements are attributed to crack arresting mechanism and formation of longer crack paths due to fibers , which as a consequence lead to increase in energy absorption capacity of SFRC. In the post-peak region under tensile stresses, major macrocrack forms at critical section. The opening of this macrocrack is mainly resisted by both of the fiber pull-out bridging the cracked surfaces and the resistance by matrix softening. In this study, micromechaincal approach has been made in order to simulate tensile behavior of SFRC and based on which the theoretical model is presented. This model reflects the features of both the composite material concept and the spacing concept in predicting tensile strength of SFRC. The model also takes into account for the effects of matrix tensile softening and fiber bridging by pull-out on the resistance for the post-peak behavior of SFRC. It has been shown that the developed model satisfactory predicts the experimental results.

This study was performed for the purposes of estimating steel corrosion of concrete structures under the environment of seawater. The corrosion of steel was accelerated in artificial seawater with seven kinds of specimen which was embedded in mortar. By measuring choride content in mortar, half cell potential and corrosion area ratio, the degree of steel corrosion can be assumed.

The purpose of this study is to provide a firm base for the quality improvement of high strength concrete and the development of ultra high strength concrete as well as enviromental con-servation and utilization of byproducts from industrial processing such as Fly ash and Silica fume. A comprehensive experimental study was performed to investigate the effects on the quality improvement of high strength concrete using mineral admixtures. As results, 400~500kg/$\textrm{cm}^2$ compressive strength and excellent flowability can be obtained if fly ash is replaced with cement in the range of 305. In case of using powder type silica fume, 600~700 kg/$\textrm{cm}^2$ compressive strength is showed and 600~800kg/$\textrm{cm}^2$ compressive strength cam be obtained with liquid type silica fume. But it is necessary to increase dosage of high range water reducer for flowability using powder type silica fume. Especially, higher strength concrete cam be obtained when maximum size of coarse aggregate is lower than 25mm.

This paper deals with the effect of siliceous slurry coatings on mortar microstructure under a damp environment. For estimation on effect of siliceous slurry coating, microstructure of coated mortar was observed through SEM. Crystal production in mivrosturcture of coated mortar was periodically increased, and more produced in mortar of high water-cement ratios. And they were generated mainly in mortar ranging from the surface to the inside about 2.5 or 3mm deep.

In order to discuss the mechanical properties of fiber reinforced composites with fly ash, lime, gypsum and polymer emulsion-Stylene Butadiene Rubber Latex (SBR) , experimental studies on FRC were carried out. The kinds of fiber used in FRC are PAN-dervied and Pitch-derived carbon fiver, alkali-resistance glass fiber. As a test results, the flexural strength and tougthness of fiber reinforced fly ash. lime.gypsum cement composites are remarkably increased by fiber contents ,but compressive strength of the composites are influenced by kinds of fiber more than by fiber contents. Also, addition of a polymer emulsion (SBR) to the composites decreased the bulk specific gravity, but compressive and flexural strengths, toughness of the composites are not influenced by it, are considerably improved by increasing fiber contents.

The purpose of this fundamental study is to investigate the mechanism of high strength concrete using the high calcium sulfate cement from a point of view in cement hydration and micro structure. As a results, it was found that the internal pores of concrete are decreased by using the high calcium sulfate cement, because the hydrates of Ettringite which is densified in structure is much formed in early ages at steam curing. In addition to the ettringite needs the 32 times of free water formed mixing water for hydration. This effect are not only decreased the water to cement ratio and also increase to comp, strength of concrete. It was conclude that these above the two facts are the main mechanism of high strength concrete using high calcium sulfate cement.

The objective of this experimental investigation is to examine the feasibility and the usefulness of the complementary crosstie in the current ACI 318-89 code for rienforced concrete columns subjected to constant axial load and lateral load reversals. Tests were conducted on1/3 scaled four columns with the length of 1.9m and the cross section of 20$\times$20 cm. The main parameters of specimens were the magnitude of axial load applied and the configuration of transverse reinforcements . From the experimental results, it can be seen that while the column subjected to lower axial load represented considerable ductility behaviors, the column subjected to higher axial load showed the brittle failure

A method for approximating the failure surfaces for columns in compression and biaxial bending was proposed by using the moments along the line of a diagonal of the section. This method showed the better approximations for the failure surfaces of columns than the method of ACI. To calculate the moments along the line of a diagonal of the section, an approximate method which is not influenced by the number of steel s and the location of inner steels was proposed This method gave satisfactory approximations for practical sections of columns.

Axial load-strain relationships of confined concrete with spiral reinforcement were investigated. The main variables were compressive strength of concrete, spacing of hoop reinforcement, and specimen height of plain concrete. The program included tests of eleven confined specimens, and twelve plain specimens, but for all specimens no longitudinal reinforcement was provided. Load-strain curves of confined and plain concrete specimens are reporeted.

In this study, a simple and accurate model equation for prediction of shear strength of reinforce concrete beams without web, reinforcement is proposed based on basic shear transfer mechanism and modified Bazant's size effect law. The proposed equation includes the effects of concrete strength, longitudinal steel ratio, shear span to depth ratio and effective depth. Comparisons with published experimental data indicate that the proposed equation estimates properly the effects of these factors. Among many equations, ACI code equation, Zsutty's equation and Bazant's equation are selected for comparison. As the result, the accuracy of the proposed equation is better than that of any other equations.

Twelve 1/2 scale modeled wall specimens were tested statically up to failure to investigate she shear behavior of concrete walls reinforced with welded wire fabric. major variables were spacing of reinforcing bars, type of reinforcing bar(rebar, welded sire fabric, knurling wire) and the existence of tied column type reinforcement

8 Wall specimens (1/2 scaled) used welded wire fabric (Ф=6mm) and ordinary deformed reinforcement(D6) of which their ultimate tensile strength were almost same were tested to investigate the inplane-flexural behavior. Test results show that : 1. The wall strength with welded wire fabric was 20% less than that with deformed bar. 2. The wall ductility ratio of welded wire fabric was 1/3 times than that of deformed bar, approximately. 3. It is recommened that lap splice of welded sire fabric should be avoided in critical fracture zone.

In the reinforced concrete structure, as the height of building structure increases, the accurate estimation of differential column shortening is important factor in the structural design. In this study, the analysis of column shortening is applied to 36-story building structure to be built in time. As a result, it may found that, as the difference of compressive stress become larger, differential shortening effect due to creep and shrinkage are more signicant factor to structural designer.

The paper presents the results of shaking table test conducted on the 1/3.3 scaled large concrete panel model. The behaviors of large concrete panel structures subjected to seismic excitations are controlled by capacity of horizontal and vertical joints. To Study the seismic capacity of the large concrete panel structures, experimental researches for joints and structural assemblage are needed. Especially, since the magnitude of seismic loads are depended on the variation of time, period and accelerations, dynamic test is needed for estimating the seismic resistance of large concrete panel structures. The objective of this paper is to study the behaviors of large concrete panel structures on seismic excitations and to estimate the safety. Test results are as follows : 1) Test model was critically damaged in the first floor horizontal joint by rocking. 2) Elastic limit(0.12kg) of test model was 5times higher than that of korean seismic design code. 3) Maxium base shear of test model at the ground acceleration of 0.12g was 3.5 times higher than the result of equivalent static analysis. 4) Damping ratio of test model turned out 3.9~5.3% and the period at 0.12g was 0.065sec.

To develop the detailing methods at the ends of flexural shear walls. which are satisfying the ductility requirement corresponding to R = 3.5 and capable of improving the consturctibility, tests of ten isolated cantilever shear walls were carried out under the load condition comprising the cyclic lateral and constant vertical loads. major test parameters include the way of detailing and arrangement of transverse reinforcement in the boundary elements at the ends of walls, and placement of vertical reinforcement. From tests, comparable ductile behavior in test specimens incorporating the channel type of open hoops, compared with those incorporating the regular type of closed hoops, was observed.

In earthquake structural engineering towards a better understanding of both the earthquake ground motion and structural response, the design of concrete structures to resist strong ground input motions is not a simple matter, and analytical models for such structures must be developed from a design perspective that accounts for the complexities of the structural responses. The primary objective earthquake structural engineering research is to ensure the safety of structures by understanding and improving a design menthodology. Ideally, this would require the development of an analytical model related to a design methodology that ensures a dectile performance. For the accurate assessment of the adequacy of analytically developed model, experiments conducted to study the inplane inelastic cyclic behavior of structures should verify the analytical approach. The paper is to demonstrate experimentally verified analytical method that provide the adequate degree of safety and confidience in the behavior of R.C. structural components and further attempts to extend the developed modeling technique for use by practicing structural engineers.

Possibility of fatigue failure in punching shear of reinforced concrete decks of highway bridges is analytically investigated by applying Matsui et al.'s experimental finding to models of 2-meter span decks designed in compliance with previous and current codes. Decks made of concrete of compressive strength of 240㎏/㎠ showed longer fatigue life than decks made of 210㎏/㎠ concrete at the same Md/U rations ; higher Md/U ratio resulted in linger fatigue life but its effect is insignificant in decks having effective depths of 14 and 15cm. Decks designed to higher load factors as specified by current codes showed longer fatigue life than decks designed to lower load factors specified by previous codes ; yet fatigue failure appeared to occur in both decks within their normal life span, thus indicating need for redefining the minimum deck thickness.

Recent increasing traffic volumes have made many bridges on highway be widened. Depending on the construction method of bridge widening, several undesirable problems have been arisen with the additional stresses resulting from de-staging of new bridge and the difference of the amount of creep and shrinkage between new and existing bridge. The main focus of this paper is given to investigate the variation of the adhesive strength of steel bar and construction joints of new and old concrete slab. The result shows that repeated vibration loadings was caused some bad effects on the construction joints between new and existing bridges.

Recent increasing traffic volumes have made many bridges on highway be widened. In widening of existing bridges, construction joints between old and new parts of concrete slabs are subjected to repeated traffic loads during placing and during of concrete. Therefore, the main goal of this paper is given to investigate the variation of the shear strength of widening deck. As a result, the occurrence of cracks in vibrating specimen is faster than that of non-vibrating one, and most of cracks are occurred at new concrete. And the difference of shear strength in vibrating specimen is larger than non-vibrating one, but the difference is negligible. Also, it shows the same result about direct and non-shrinkage joint specimen test.

In widening of existing bridges, construction joints between old new parts of concrete slabs are subjected to repeated traffic loads during placing and curing of concrete. Therefore, the main focus of this paper is given to examine several construction methods of bridge widening. As a result, the occurrence of cracks in vibrating specimen is faster than non-vibrating one, but the difference between flexural strength and ultimate moment was negligible. Also, it shows the same result in other construction method, say direct and non-shrinkage joint specimen.

The objective of this study is to clarify analytically the pullout behavior of axial bars from a footing. The bond stress-slip model obtained from the results by the finite element method as well as the pullout tests in massive concrete was used in order to evaluate the slip of bars from the footing. Also, the process of bond mechanism was taken into consideration on order to express the deterioration of bond stress along bars, The shape and magnitude of bond stress distribution depends upon each loading steps. Using equilibrium equation of axial force, $\tau$-S relationship and $\sigma$s-$\varepsilon$s relationship, the differential equations of each loading steps are derived. Applying both boundary and equilibrium conditions to the equations, the amount of slip could be determined. Calculated values on the basis of proposed method evaluation of the slip of bars have a good agreement with the experimental results.

As the vibration loads are variable and the design criteria are more strict, in this study, the dynamic characteristics of the slab is analyzed and the and the vibration is controlled for the special peculiarity of structures. First, the procedure of dynamic analysis is developed by the finite element method and then examined by using the slab model tests. Second, in order to improve the dynamic characteristics, the effects of the number of supports, material properties, position of exciting force, added mass and dynamic balance on the dynamic behavior of reinforced concrete slabs are analysed. It is concluded that the vibration can be controlled by the change in the natural frequency of system and the use of the high-strength concrete or polymer impregnated concrete (PIC), and the dynamic characteristics can be considerably affected by the arrangement of equipments, added mass, and dynamic balance, etc.

Rail carrying structures in international routes as well as domestic ones shall be designed to carry HL(High Speed Railway live Load) loads, The loads shall be placed in the most unfavourable position for the part of the structure in question. In general, influence lines may be used to determine the maximum bending moments and maximum shear forces in the reinforced concrete rahmen bridge structures. In this study, based on the finite element analysis, equivalent distributed loads of HL loading for design of the rahmen bridges are deterimined.

F.E.M formulation is carried out in order to determine temperature distribution in the concrete structure. According to this formulation an F.E.M. code is developed, which is capable of silmulating time varying boundary conditions and nonlinear thermal properties.

본 연구는 철근콘크리트 격납구조물에서 가상의 냉각제 유출사고에 의한 온도하중과 압력에 따른 거동을 알아보기 위한 비선형 해석을 수행하였다. 시간에 따른 온도하중을 결정하기 위하여 과도온도해석을 통해 격납구조물 단면내의 온도분포를 구하였다. 구조물은 기하학적 비선형성과 재료비선형성을 고려한 판 및 쉘요소로 이상화되며, 쉘요소는 두께방향에 따라 변하는 응력을 고려하기 위해 몇 개의 층으로 이루어진 모델을 사용하였다. 열응력은 인접한 두시간 단계에서의 온도차를 하나의 하중증가로 고려하여 초기변형 문제로 변환하여 결정되었다. 본연구에서의 수치실험에 의하여 과도온도해석에 근거한 비선형온도경사를 고려할 때의 변위가 고려하지 않을 때의 변위에 비해 크게 나타남을 알 수 있다.