AIR BUBBLE STABILITY MECHANISM OF AIR-ENTRAINING ADMIXTURES AND AIR VOID ANALYSIS OF HARDENED CONCRETE

Monolayer of two kinds of air-entraining agent GYQ and modified rosin R are formed in KSV 2000 Langmuir min-trough at air-water interface, respectively. The surface pressure of each monolayer is measured using the wilhelmy plate technique. The static surface elasticity of monolayer at air-water interface are discussed by analyzing the pi-A isotherm. The air void characteristics of hardened concrete are determined by automated linear traverse method with image processing system based on ASTM C 457. It's found that the performance of air bubble stability of air-entraining admixtures is determined directly by the strength of monolayer at air-water interface. Comparing with the air void characteristics of hardened concrete produced by air-entraining admixtures, higher strength of GYQ monolayer resulted in the smaller spacing factors and more excellent air void characteristics. It's indicated that durability of harden concrete produced by GYQ is better than modified rosin R.