Statistical Methods for In-Place Strength Predictions by the Pullout Test


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Title: Statistical Methods for In-Place Strength Predictions by the Pullout Test

Author(s): William C. Stone, Nicholas J. Carino, Charles P. Reeve

Publication: Journal Proceedings

Volume: 83

Issue: 5

Appears on pages(s): 745-756

Keywords: aggregates; compressive strength; concrete construction; lightweight aggregates; pullout ests; regression analysis; statistical analysis.

Date: 9/1/1986

Pullout tests and comapnion cylinder tests were conducted to examine the variations in ultimate load with respect to concrete strength, and provide experimental data for the development of a new statistical procedure for predicting in-place compressive strengrth from the pullout test. The coeeficants of variation were found to be relatively constant with average values of 4 percent for cylinder tests and approximately 10 percent for pullout tests in concrete with hard coarse aggregates. Pullout test in lightweight concrete exhibited coefficants of variation of only 6 percent. Two test series were conducted with river gravel aggregate using apex angles of 54 and 70 deg. Both geometries produced coefficants of variation of 10 percent. A statistical procedure is developed for determining the correlation equation which accounts for: 1) the constant coefficants of variation in ultimate load, and 2) the X-variable (pullout load) error. Aprocedure is also developed to predict the in-place caracteristic strength to any desired confidence level. Amethod is presented to dtermine the appropriate number of in-place tests to be performed for a given concrete placement. A recommended minimum number of 8 to 12 pullout tests per 76 cubic meters (100 cubic yards) is proposed.