1 Associate Professor, Brigham Young University, Dept. of Civil and Environmental Engineering, ffonseca@et.byu.edu
2 Graduate Student, BYU, Dept. of Civil and Environmental Engineering
ABSTRACT
The air content of mortar and that of concrete are determined using the procedures outlined in ASTM C 185 and ASTM C231, respectively. The mortar testing employs a gravimetric method relying on batch proportions, specific gravities, and other laboratory measurements. The level of accuracy of the mortar method is heavily reliant on the accuracy of the technician in both proportioning the batch and performing the test. The procedure outlined in ASTM C 231 is intended to be used solely with concrete, but a literature review has indicated that researchers and industry professionals also employ ASTM C 231 to determine the air content of mortar. The reason appears to be the ease and speed of the pressure method.
This article describes a simple study to evaluate the relationship between the results from testing employing the gravimetric and the pressure methods. The pressure method used for concrete can be performed much more quickly and easily and is universally applicable to any mix design. The gravimetric method used for mortar, on the other hand, is more labor intensive and requires more accuracy on the part of the technician. The conclusion from this research is that the pressure method can be successfully used to determine the air content of mortars. Even though a standard air meter requires more mortar to perform the testing, smaller air meters are available which can mitigate this concern. The obtained positive correlation between the test results from both methods and comparable mean and variances demonstrate an acceptable level of accuracy. Thus, the use of the pressure method is recommended due to time savings and ease of operation.
KEYWORDS: air content, air meter, flow table method, air entrained, masonry air content
171.pdf
