Influence of consistency and air content in fresh concrete on characteristics of air bubbles in hardened concrete

摘要

Increased frost resistance of concrete can be achieved by adding air-entraining agent to the fresh concrete mix. Adequate air entrainment is in practice usually checked by measuring total air content of fresh concrete. However, characteristics of air pore system, above all their number and distribution by size, rather than total air content are responsible for adequate frost resistance of concrete. Therefore aim of tests carried out in framework of my diploma was to analyze characteristics of air bubbles in hardened concrete with help of linear microscopical analyses (LMA) in accordance with SIST EN 480-11:2005. Main influencing parameters that were studied were consistency and total air content of fresh concrete. Also the comparison between spacing factor of air bubbles and amount of materials scaled from surface at salt-frost scaling test according to SIST 1026 have been made for particular concrete mix.