In-Place Concrete Strength: New Pullout Methods


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Title: In-Place Concrete Strength: New Pullout Methods

Author(s): G. Mailhot, A. Bisaillon, G.G. Carette, and V.M. Malhotra

Publication: Journal Proceedings

Volume: 76

Issue: 12

Appears on pages(s): 1267-1282

Keywords: anchors(fasteners); blots; bond (concrete to reinforcement); compressive strength; concrete cores; field tests; nondestructive tests; pullout tests.

Date: 12/1/1979

A major drawback of existing pullout tests is that they have to be preplanned during the design and erection of formwork. To overcome these problems, investigations were undertaken to develop pullout tests that could be carried out on finished structures. Three possible approaches considered were: (A) pulling out of tapered anchors placed in drilled holes; (B) pulling out of bolts set in hardened concrete using epoxy; and (C) measuring the force required to cause shear failure of concrete using a split-sleeve assembly. The techniques were tried on 25 concrete slabs. The concrete covered a strength range from 17 to 42 Mpa. More than 1000 pullout tests using the three techniques were performed. Technique A gave relatively poor results in terms of reproduciblity. It also had some inherent difficulties, and was discontinued. Technique B appears promising. It is believed that this approach is viable but furthur research is needed. Technique C offers good possiblites and the simplicity of the test makes this method more attractive. However, within-test variations were higher than those obtained with Technique B. Modifications of procedures may reduce the variations.