The development of a prototype surface airflow device for concrete is described. the method is based on measurement of the rate of airflow through a vacuum plate placed on a concrete surface under a vacuum of approximately 25 in. of hg. effective depth of measurement is demonstrated to be approximately 0.5 in. below the surface. for calibration of the method, concretes were cast using a variety of water-to-cement ratios as well as admixtures such as latex and silica fume. results were found to correlate well with chloride diffusion constants derived from 90-day ponding tests, as well as with true air permeabilities measured using a pulse decay technique. design of a field prototype based on the surface airflow technique is also presented. the field instrument is designed to obtain readings at the rateof approximately one per minute, and be powered by rechargeable battery packs. although surface moisture has an influence on test results, simple techniques for rapid drying of small test areas have beendeveloped. plans for future testing are presented. this paper appears in transportation research record no. 1304, highway maintenance operations and research 1991.
Samenvatting