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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP112-09

Date: 

January 1, 1989

Author(s):

C. J. Turkstra, P. Zoltanetzky, Jr., H. P. Lim, and C. Gordon

Publication:

Symposium Papers

Volume:

112

Abstract:

Presents a comparison of 28 day concrete strength as measured by field probe penetration tests and standard laboratory cylinders. Over a period of 11 months, 318 matched sets of tests were performed on 4000-psi concrete at four major projects. Primary field variables include the project location, operators, test guns, and the element type on which the field tests were made. Corrections to account for temperature variations are considered. Results include statistical analysis of the effects of test parameters and the correlation between field and laboratory results. Based on standard statistical tests, it is concluded that the variability of field probe results is similar to that of the corresponding laboratory cylinder tests. Results did not depend significantly on operators or the particular equipment used. However, results did depend significantly on the type of structural element tested and on the range setting of the firing gun. It is concluded that the calibration charts provided with the equipment should be reviewed.

DOI:

10.14359/3736

Document: 

SP112-08

Date: 

January 1, 1989

Author(s):

T. R. Harrell

Publication:

Symposium Papers

Volume:

112

Abstract:

A case history of methods used to evaluate the allowable form removal time for a large diameter tunnel concrete lining is presented. To meet schedule requirements, a concrete placement was to be made every alternate day. A triad of testing was done to evaluate the time at which the reusable, self-propelled, steel-skinned form could be stripped from an existing placement. This testing consisted of field-cured cylinders and nondestructive testing that included embedded thermocouples in the concrete placements and penetration-resistance testing. Reference curves and tables were developed for use in the form removal evaluation. Statistical methods were used on test data obtained from results of testing done with the actual concrete mix to be used in the placements. Control curves were then developed. Target values were selected to be used in determining when the concrete was of sufficient strength to allow for the form removal.

DOI:

10.14359/3726

Document: 

SP112-07

Date: 

January 1, 1989

Author(s):

G. V. Teodoru

Publication:

Symposium Papers

Volume:

112

Abstract:

Aim is to analyze the correlations between several nondestructive measured values (ultrasonic velocity and attenuation, rebound number) and the compressive strength of concrete. A computational program performs a step-by-step analysis. First, isolated linear correlations are established for each one of the three nondestructive tests. Then the results are compared with each other in the sense of a general multiple correlation of the values. Since the results obtained from the nondestructive tests are equally scattered, the program determines interactively, in a second step, the multiple coefficients of correlation and restarts the analysis several times by tentatively disregarding the presumably bad experimental results. Since the measured values also comprise a large spectrum of magnitude, limits of validity of the assumed correlations are investigated concomitantly with the process of analysis. A last step is performed to identify a tendency of deviation of the single and multiple correlations from the basic linear ones.

DOI:

10.14359/3715

Document: 

SP112-10

Date: 

January 1, 1989

Author(s):

T. J. Parson

Publication:

Symposium Papers

Volume:

112

Abstract:

Reports results of an investigation into the use of maturity for predicting early-age concrete strengths. Prediction models were developed from cylinder-test results obtained from twelve concrete mixtures cured under three constant curing conditions. A datum temperature of 25 F (-4 C) was used as it appeared to produce the best results. A prediction model based on estimated ultimate concrete strength was used and found to be independent of curing temperature. However, the estimated ultimate concrete strength value appeared to be dependent on curing temperature. The model was verified by using it to predict concrete strengths obtained from cylinders and slabs cured outdoors.

DOI:

10.14359/2372

Document: 

SP112-03

Date: 

January 1, 1989

Author(s):

M. A. Taylor

Publication:

Symposium Papers

Volume:

112

Abstract:

Gamma-ray absorption techniques were used to determine the amounts of each component in a system of mixtures (such as concrete). The technique uses photons of several energies in contrast to previous applications where only one energy was employed. The use of multiple energies provides more information than the single-beam system, and thus more properties can be determined. Several possible models for cementitious materials are discussed and compared. The paper presents the experimental determination of the initial data set needed prior to prediction experiments. One predictive technique is evaluated by comparison with blind tests.

DOI:

10.14359/2362

123

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