Surface tension of cementitious pore solutions at low atmospheric pressure: An experimental exploration

Abstract

Currently, it is believed that surface tension increases with the reduction of atmospheric pressure, and the increased surface tension is considered as the primary cause of the decreased bubble stability in cement-based materials at low atmospheric pressure. However, this viewpoint lacks experimental verification due to the difficulty in measuring surface tension at low atmospheric pressure. This study systematically explores the effect of low atmospheric pressure (0∼0.1 MPa) on the surface tension of pore solutions of fresh cement pastes. The surface tension of pore solutions was measured at different atmospheric pressures by using the high-accuracy automatic interface tension meter. Results show that the impact of low atmospheric pressure on the surface tension of deionized water, cement and fly ash pore solutions is insignificant. Therefore, the decrease in bubble stability and air content of concrete at low atmospheric pressure cannot be attributed to the change of surface tension. The effect of low atmospheric pressure on the surface tension of air-liquid interface is explained from the perspective of intermolecular force and density. This research helps to better understand the impact of low atmospheric pressure on surface tension and lays the essential groundwork for improving bubble stability of cement-based materials in high-altitude regions.