Recently, as the natural aggregates are exhausted, using the crashed stones bring the possibility of the alkali-aggregate reactivity. In this study, the samples are collected from the stony moutains chosen by using a geoligical survey map and analyzed in terms of the amount and the shape of the reaction minerals by a polarization microscope and X-ray diffraction which beling to the petrographic examination of aggregates for concrete. From this study, most samples of the sedimentary rocks and the granitte of the ignious rocks show the possibility of the alkali-aggregate reactivity.

Considerable efforts are still being made in the every part of the world to develop new construction materials. The polymer concrete is one of those promising new construction materials. The strength characteristics of fiber-reinforced polymer methods and filler contents on the properties of polymer concrete were explored. The effects of fiber addition are also discussed.

The purpose of this paper is to propose a method predetermining the 28-days strength of concrete. In this paper, it was predicted by regression analysis of the relation between 7-days and 28-days strength of fresh concrete and the strength of concrete early cured at $70^{\circ}C$ for rour hours after wet screening and addition of accelerating agent. It is concluded that the formula predeterming the 28-days strength of concrete using 25M/M rubbles from Sam-Cheok and sands from Yon-Gok, by the strength of concrete early cured for 4 hours is Y=-11.45 + 3.686X, where the coefficient of determination of regression-expression is r2=0.938, S=17.94(kg/$\textrm{cm}^2$).

The effect of superplasticizing agents on the sorkability performance in fresh concrete have been analyzed and investigated under various mix proportions of water cement ratio of 0.40, 0.50, 0.60 and 0.70, superplasticizing agents of NL-4000 and Rheobuild-716, and addition rate of sp. agents of 0.0, 0.5, 1.0, 1.5 and 2.0 in the practical range. It is the aim of this study to provide the fundamental data on the fluidity performance and workability improvement of superplasticized concrete such as time-dependent change of slump, flow value and compacting factor, air content, bleeding, mixing temperature and setting rate of fresh concrete comparing with base concrete and conventional concrete for the practical use and research data accumulation of superplasticized concrete in the side of development of concrete construction technology and management.

The effect of superplasticizing agents on the mechanical properties in hardened concrete have been analyzed and investigated under various mix proportions of water cement ratio of 0.40, 0.50, 0.60 and 0.70, Superplasticizing agents of NL-4000, and Rheobuild-716, and addition rate of sp. agents of 0.0, 0.5, 1.0, 1.5 and 2.0 in the practical range. It is the aim of this study to provide the fundamental data on the compressive strength, dynamic and static modulus of elasticity, stress and strain curve of hardened concrete comparing with base concrete and conventional concrete for the practical use and research data accumulation of superplasticized concrete in the side of development of concrete construction technology and management.

In this paper, morter and concrete specimens made with four cements were immersed in Mgcl2, MgSO4 Solution and artifical Seawater which was corresponded with Seawater. The hydration products of immersed cement pastes were looked over by using SEM, EDS and X-ray diffraction method. The results show that the concrete made with domestic flyash cement and blast-frrnace slag cement is superior to that of ordinary portland cement in resistance to chloride and sulphate solution. Especially, it is found that the attack of Cl-ion on the concrete plays an important role of the deterioration of concrete.

In order to discuss the engineering properties of carbon fiber reinforced cement composites with silica fume and silica powder, experimental studies in the CFRC were carried out. The types of fiber used which are in CFRC are PAN-based carbon fiber and Pitch-based carbon fiber. To examine the effects of types, lengths, contents of carbon fiber and matrices, their properties of fresh and fardened CFRC were tested. According to the test results, the process technology of light-weight CFRC is developed and their potimum mix proportions are successfully proposed. Also, it can be concluded that the reinforcement of carbon fiber is considerably effective in improving tensile strenghth, flexural strength, toughness and loss of shrinkage of CFRC compared with conventional mortar.

The purpose of this report is to investigate and analyze development and achievement of flowing and high-strength concrete by reacy mixed concrete companies in Korea. For this purpose, the investigation was divided into three parts, i.e., superplasticizers, flowing concrete, high-strength concrete. And, they were asked to quality control manager in ready mixed concrete companies. Many researches have been carried out. And, flowing concrete is applied to field in a few case. In order to improve practical applicability of high-strength concrete and make concrete strength higher, to begin with, profound research for concrete ingredients will be needed along with presentation of methods for obtaining workability and quality assurance.

This paper suggests a systematic procedure for maintenance of reinforced concrete (R/C) structures. In this paper the deteriorations of R/C structures are classified by eleven causes and diagonistic techniques are devided into six major steps. The suggested diagonisis steps are summarized in the flow chart and it would be helpful to develop the expert system for maintenance of R/C structures.

In recent years, it has been found that one of the most significant factors in the reduction of the life of concrete pavements is the presence of voids beneath the slab. In the design of pavement, it is assumed that there is a full support through the length of the pavement. When a void develops, this assumption is no longer vaild. With increasing void size, traffic loads have a very a significant increase in stress. Thus, the combination of existing voids and increasing traffic loads results in significant pavement life reduction. Basea on the results of an experimental deflection using Dynaflect device and a theoretical one on the pavement model, this study presents a rational evaluation technique for detecting voids beneath the plain reinforced concrete pavement.

This report introduces the large scale prefabricated apartment project in Saudi Arabia designed and built by Hyundai Engineering and construction Co. as turn-key basis from ministry of Public works and ltousing of Saudi Arabia. This project using precast large panel system is 7,600 dwelling unit, total building area 1.8 mil sguare meters. Large panel system is a kind of industrialized building method which classified as monolithic system, total system and structural system. Hyundai Engineering and Construction Co. develop his own prefabricated large panel system for this project and named "HYUNDAI SYSTEM". The key point of this system is vertical and horizontal joints between panels. Also stability of whole building structure is especially important for this kind of prefabricated building. building.

Thicknesses of the base concrete blocks for large machines were estimated by analyzing the resonance modes of mechanical vibrations. The vibration was produced by the mechanical impact and detected by a wideband conical transcuder. There signals were analyzed by FET and thicknesses were obtained by the peaks of frequency spectrum. The estimated thickness upto 100cm are in good agreement with the real ones. For the layered concrete block, the estimated thickness is dependent on the acoustic reflective index at the boundary of the two layers.

Construction of high-rise precast concrete apartment is an atractive alternative solution for severe shortage of residential facilities, especially in metropolitan areas in Korea. New building regulations enforced since 1988 requires all buildings higher than 6 storeys to be designed for earthquake. However, we hardly have any experience on seismic design of precast concrete buildings. This paper deals with methodology of seismic design and design considerations of connections for the large panel structures. Also addressed in this paper are studies needed to develop proper seismic design procedures of precast concrete buildings.

Various studies have been done to investigate the effectiveness of lateral confinement of lower strength concrete(below 420kg/$\textrm{cm}^2$). But little research its effectiveness for high strength concrete. A certain concern has been arised that the beneficial effect of lateral confinement in high strength concrete may be different from that in lower strength. This study aimed to investigate that concern with different confinement spacing(D/2 : D/4). The results show that beneficial effects of spiral confinement are more pronounced for lower strength concrete as compared to higher strength concrete.

It is widely recognized that the strength of reinforced concrete members has characteristics of random variations due to the variability of the mechanical properties of concrete and steel, the dimensional error as well as incorrect placement of reinforcing bars. In those sources of randomness, variations in concrete strength may be the one affecting the strength of R.C. members most. The concrete strength is usually assumed to have large uncertainty due to the variations in many factors, such as material properties, proportions of the concrete mix, methods of mixing, transporting, placing and curing, etc. In this study, the random characteristics inherent in the strength of field-cast concrete have been examined based on the data collected by testing standard cylinders made of field-cast concrete and cured under in-situ condition.

A numerical procedure is developed to analyze the time-dependent behavior of prestressed concrete bridges constructed by the segmental cantilever method. The developed computer program accounts for the time-dependent properties of prestressed concrete materials due to the varing modulus of elasticity, creep and shrinkage of concrete and the stress relaxation of prestressing steel. It also accounts for the stiffness increase due to the presence of the steel reinforcements and the effects of the shear deformation of the prestressed concrete bridge girders. The program is applied to a multi-span continuous segmental prestressed concrete bridge to demonstrate its capabilities.

In this paper an experimental approach of the relocation plastic hinging zones of nine reinforced concrete exterior beam-column subassemblages under cyclic loads was tried. The main parameters of the testing program were location of the plastic hinge, difference of the special reinforcement, inclined or intermediate layers of longitudinal reinforcement, applied maximum shear stress. The conclusions presented herein are based on the limited texts conducted. Inclined or intermediate layers of longitudinal reinforcement and extra top and bottom steel in the beam over a specific legnth can be used to move the beam plastic hinging zone away from the column face. But, for the use of intermediate layers of longitudinal reinforcement, sheat reinforcement detail need further investigation.