The Bughole Problem


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Title: The Bughole Problem

Author(s): Thomas J. Reading

Publication: Journal Proceedings

Volume: 69

Issue: 3

Appears on pages(s): 165-171

Keywords: air entrainment;architectural concrete;bleeding (concrete);concrete construction;concrete finishes (hardened concrete);consolidation;formwork (construction);mix proportioning;placing;quality control;segregation;surface defects;vibration;voids;workablity.

Date: 3/1/1972

Specifications usally do not clearly spellout how many surface voids (bugholes) are accpetable. This leads to arguments between the contractor and the owner. We need a yardstick for rating concrete surfaces with respect to bugholes, and more know-how on how they can better be controlled. Most early attempts to develop a yardstick involved counting and measuring the surface voids. Other methods are now being investigated. Most bugholes are believed to consist of entrapped air resulting from incomplete consolidation of the concrete, but this point needs furthur investigation. The properties of the concrete mix affect our degree of success in expelling entrapped air. However, the characteristics of the vibrator and field procedures have an even greater effect. There are still differences of opinon as to the most effective combination. The ACI is doing everything possible to promote research to solve this difficult problem.