The transformation of concrete deformation characteristics and/or behavior affected by Alkali Silica Reaction, herein after ASR, has been reported and clarified by the specimen tests. The most report of research for the deform characteristics have been carried out by ASR accelerating test method due to the fact that deformation of the shape of the structure affected by ASR was thought to expand according to the development of ASR in a long term. The assumption for expansion rate of plain concrete could be determined by measurement of the remaining expansion rate with ASR accelerating test method. However, most structures in reality are reinforced concrete and so far no reports of the deformation characteristics for in-services reinforced concrete structure with long term aging available though reinforced concrete deformation characteristics affected by ASR have yet to be determined. The purpose of this paper is the confirmation of shrinkage after expansion by recording the maximum value of expansion of a 25 years old in-service reinforced concrete structure that was affected by ASR. In this regard, a numerical model of deformation characteristics of reinforced concrete affected by ASR due to the expansion was simulated, analyzed and the result was compared with the inspection record of the in-service structure.
This research attempts the improvement of frost-resistance-evaluation with using modified JIS A1148 freezing and thawing test. The major modifications of the test are ; 1) insertion of the dry or wet conditions of room temperature between freezing and thawing cycles in consideration of actual environment, 2) using salt water as well as the ordinary fresh water for the test liquid. This research also investigates the applicability of the scaling evaluation with the JIS freezing and thawing test comparing this with the result of RILEM CIF/CDF test which is the typical scaling test in Europe. From these results, frost damage was greatly influenced by the environmental condition and the test liquid. The insertion of the wet conditions of room temperature between freezing and thawing cycles caused severe frost damage. On the other hand, that of the dry condition improved the frost resistance. When the mass loss is less than 5%, test results showed clear relationship between the amount of scaling of JIS freezing and thawing test using salt water and RILEM CDF test. This indicates the applicability of the scaling evaluation by JIS freezing and thawing test.
In order to ensure the freezing and thawing resistance of extremely stiff consistency concrete such as roller compacted concrete pavement slab and instant stripping concrete blocks, the effect of air content and compaction void on durability factor were clarified in the case of increasing in water content and dosage of air entraining agent for a given unit cement content and increasing in sand percentage and compaction ratio for a given unit water content. And it was shown that the fine compaction voids were able to improve the freezing and thawing resistance and the void spacing factor including compaction void was larger than that of ordinary concrete with 60% of durability factor. Then, it was shown that the factor could be obtained safely by over 97% of compaction ratio on condition of over 2% of air content. Finally, the relationship between the freezing and thawing resistance index newly expressed by air content, water cement ratio and compaction ratio, and durability factor was shown as an experimental equation.
This paper reports results of verified strengths on the socket-type rigid joint. This type of joint could offer rapid and high-quality construction at the tunnel section in the underpass, combining the top slab with side wall. The former is a pre-cast prestressed concrete(PCaPC)member and the latter is a cast-in-place reinforced concrete(RC)member. In construction of the joint,the vertical section of the top slab is inserted into the socket section of the side wall, and mortar is filled in the opening space. The inserted length is approximately 1.5 times the width of the vertical section. Failure behavior and strength of the rigid joint model are verified by a monotonous loading test and a repeaded loading test of two million cycles.
Concrete structures are vulnerable to such acid environments as hot springs, sea origin soils and sewage plants. It is normally difficult for concrete to resist acid effects under the environment of pH less than 3 to 4; other measures as coating are necessary. It is rather important to understand durability of concrete under weak acid environment of pH 4 to 5 where concrete structures are normally exposed to the acid effects without protective measures. The durability of concrete under the environment, however, has not been sufficiently clarified yet. In particular, long term exposure test has been rarely carried out. In this study characteristics of neutralization of concrete were studied based on 15 years' exposure tests to soil of pH 4 to 5 and atmosphere of SO2 concentration of 5 to 40 ppm. It was shown that neutralization of concrete under the weak sulfuric acid environment is very different from ordinary carbonation; a dormant period of neutralization exists due to densified surface layer. The layer was shown to be formed by ettringite based on EPMA analysis, X-ray diffraction analysis and Vicker' s hardness measurement. Finally neutralization rate equations for concrete under weak sulfuric acid environment are proposed based on the above results.
This paper reports the RC piles with HIS (Hinge Isolated Structure System).At the Hinge region of pile head, main steel bars are un-bonded in order to mitigate damage of concrete, and supplementary main steel bars which are not anchored into pile cap are arranged to resist bending moment and shear. The main contents of the examination in this paper are the effect of shape of pile head(with or without taper processing) on structural performance, the effect of concrete strength particularly used at pile head on destruction property, and the effect of axial compression steel bars which are unevenly arranged in order to reduce axial stress acting on concrete. The results showed that the proposed piles with HIS have excellent structural performance.