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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 40 Abstracts search results
Document:
SP82-20
Date:
September 1, 1984
Author(s):
John G.L. Munday and Ravindra K. Dhir
Publication:
Symposium Papers
Volume:
82
Abstract:
Cores are cut from structural members in order to establish the quality of in-situ concrete, particularly in terms of uniaxial compressive strength. Although the strength test itself is simple enough, the procedure used has to be carefully established and well understood as numerous factors can affect the measured value and hence the judgement on the quality of concrete. Some of the important factors have been considered in this paper, namely: the diameter of core; its slenderness ratio (R/d), direction in relation to placing of concrete and location in the structure; curing; cube/core strength relationship and soaking of cores prior to testing. The results obtained are discussed and recommendations put forward which could extend the role of core testing, as well as improve the reliability of the test and the interpretation of the results. The existing ASTM and BSI procedures for core testing are examined in the light of the results obtained. A procedure for the determination of in-situ concrete cube strength is described and it is suggested that the estimation from core strength values of the potential strength of concrete as measured by standard cube tests could give very misleading information and should be avoided.
DOI:
10.14359/6565
SP82-21
R.N. Swamy and A.H. Al-Hamed
This paper presents tests on 5Omm diameter cores to evaluate their use to determine in-situ concrete strength. The cores, with height to diameter ratios of 1 and 2, were drilled vertically from slabs which were cured in an uncontrolled internal environment to simulate conditions in practice. The variables investigated include concrete strength level, mix proportions, age, size and type of dense coarse aggregate and type of concrete, i.e. normal and lightweight. The core strength results are analysed to discuss the height to diameter correction factor and the relation between core strength and cube strength. The core strength results are related to core and cube pulse velocity and Windsor probe test results.
10.14359/6566
SP82-22
A.P. Keiller
Concrete is usually specified in terms of the strength of standard specimens (normally cylinders or cubes) which are cast from samples of the fresh concrete. If the concrete in a structure is to be investigated using core tests, an understanding of the factors which influence the measured strength of a core together with a knowledge of the relationship between the strength of standard specimens and the strength of concrete in structures are required. The paper presents results of both laboratory research and site investigations in which some of the relevant factors have been investigated.
10.14359/6567
SP82-23
A. Di Leo, G. Pascale, and E. Viola
In this paper a procedure aimed to assess the characteristic value of actual compressive strength of in-situ concrete is presented. It involves: an evaluation of the homogeneity, which may suggest a subdivision of the structure in parts characterized by different estimated strength levels; a calibration of estimated strength values on the basis of a sample of cores. The experimental values obtained from cores can be utilized to modify the characteristic value of estimated strength: a) by means of an appropriate correcting coefficient; b) statistically through the Bayesian approach, according to which the mean value of the actual strength is considered as a random variable. Consequently, its characteristic value also becomes a random variable. Within the context of the subjectivistic approach to the decision theory, the optimization of the core sampling size is also discussed. Two examples of application of the procedure are reported.
10.14359/6568
SP82-24
Ken Newman
This paper examines the influence of workmanship on the properties of concrete and the difference between the results obtained from standard specimen and in-situ tests. Few reinforced concrete engineers appear to understand the relevance and meaning of the results of in-situ/NDT tests. These methods measure concrete properties in the actual structure (i.e. "real-Crete") which engineers should be interested in, whereas they still place undue emphasis on the results from standard tests (i.e. "lab-Crete"). The respective responsibilities of the ready mixed concrete producer and contractor are defined. Recommendations are made for improving the reliability of compressive testing by means of standards for testing machines and their use, for differentiating between "lab-Crete" and "real-Crete" by providing guidance on the assessment of concrete strength in existing structures, and for specifying the required concrete properties in terms of the "lab-Crete" compressive strength.
10.14359/6569
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