Effect of Atmospheric Pressure on Performance of AEA and Air Entraining Concrete

Yan Shi,Huaquan Yang,Aiguo Wang,Shihua Zhou,Xingdong Lv

doi:10.1155/2018/6528412

Abstract

The effect of atmospheric pressure on performance of air entraining agent (AEA) and air entraining concrete was studied in Tibet and Hubei, China. The result shows that the reduced atmospheric pressure increased surface tension and lowered foaming property of solution. The AEA with excellent foaming ability and stability is preferred in low atmospheric pressure. The freeze-thaw deterioration process of hardened pastes is relatively faster under low atmospheric pressure. The effect of air pressure on concrete frost resistance performance is more sensitive than the mechanical property. The bigger pores and poor uniformity of internal pore size distribution led to the deterioration of concrete macroscopic properties. Therefore, the AEA varieties should be preferred, the dosage of AEA should be increased, and pore structure of pastes should be optimized to ensure the durability of concrete frost resistance for construction in low-pressure areas.

Highlights

Introduction e altitude ofChina’s Tibet region is higher than 3000 m. e significant climatic environment of high-altitude area is low pressure, large temperature difference between day and night, dry and windy due to high and complex terrain, highaltitude atmospheric circulation, and solar and other strong radiation along with various other factors
E air entraining agent (AEA) can introduce a large number of homogeneously distributed air micropores and, improve the mixing workability, antipermeability of concrete performance, and frost resistance [2, 3]. e factors of ambient temperature, humidity, and air pressure affect the air entraining concrete performance besides the factors of raw materials, proportion of mixture, and construction method
Solution Characteristics of AEA. e surface tension of the same batch of liquid AEA was tested by the platinum ring surface tension apparatus in three different places (Hubei Wuhan, 101.1 kPa, Tibet Shannan, 65.9 kPa, and Tibet Naqu, 57.2 kPa). e foaming capacity and foam stability of the AEA were tested by the shaking method

Summary

Introduction

Introduction e altitude ofChina’s Tibet region is higher than 3000 m. e significant climatic environment of high-altitude area is low pressure, large temperature difference between day and night, dry and windy due to high and complex terrain, highaltitude atmospheric circulation, and solar and other strong radiation along with various other factors. E factors of ambient temperature, humidity, and air pressure affect the air entraining concrete performance besides the factors of raw materials, proportion of mixture, and construction method. E mechanism of atmospheric pressure affects relatively the concrete performance. According to Zhu et al [6], the air content of the concrete shows decreasing tendency with the decreasing atmosphere pressure. Li and Fu suggested that the air content of concrete shows linear decrease with the decreasing atmosphere pressure. E higher the initial air content, the greater the decreasing rate of the air content with the ambient air pressure is found. E greater the slump of concrete is, the stronger the ability to resist reduction in the air content due to lower air pressure is [7] Li and Fu suggested that the air content of concrete shows linear decrease with the decreasing atmosphere pressure. e higher the initial air content, the greater the decreasing rate of the air content with the ambient air pressure is found. e greater the slump of concrete is, the stronger the ability to resist reduction in the air content due to lower air pressure is [7]

Methods

Results

Conclusion