Title: Concrete Surface Void Ratio: Perspective from the Testing Laboratory

Author(s): Jacob L. Borgerson and Woodward L. Vogt

Publication: Symposium Paper

Volume: 338

Issue:

Appears on pages(s): 36-44

Keywords: aesthetics, bug holes, concrete, formed surfaces, surface void ratio, surface voids

DOI: 10.14359/51724725

Date: 3/1/2020

Abstract:
ACI 347.3R-13 provides guidance on the measurement and classification of surface voids (i.e., bug holes) in as-cast formed concrete surfaces. This paper will provide perspective from a testing laboratory on the challenges encountered when asked to perform surface void ratio measurements. Measurements were performed by field technicians and an engineer using the method as described in ACI 347.3R-13, in addition to a modified approach. Based on measurements performed on test areas of a cast-in-place shear wall for a high-rise condominium, it was determined that the between-operator variation and the selected test area significantly impact the classification of the surface. Because the test method does not specify methods for test area location selection or the number of test areas to sample, test results can vary greatly. Specifically, two 24 in. x 24 in. (610 mm x 610 mm) areas that are within 12 in. (300 mm) of each other may possess the highest and lowest classification. Based on field test results, an alternative method is proposed that provides better repeatability between operators and is more time efficient. In addition, based on measuring several different test areas on the same concrete surface, the number of test areas needed to accurately represent the void area of a surface was estimated.