The Influence Of Air Content On The Performce Of Self-Compacting Concrete

With the rapid development of the construction industry, construction work onthe concrete demands of the increasing use of self-compacting concrete is also morecommon. Self-compacting concrete in the casting process without vibration, onlyunder its own weight and be able to fully fill the gap through the reinforced everycorner of the template, while mixture evenly dense, with enough cohesiveness,bleeding is not segregation, hardened has good mechanical properties and durability.Self-compacting concrete to solve some concrete problems should not be vibrated,reducing noise pollution during construction, to improve the construction efficiency,shorten the construction period. In addition, self-compacting concrete consumes a lotof fly ash, granulated blast furnace slag and silica fume and other industrial solidwaste conducive to the comprehensive utilization of resources and ecologicalenvironment protection.However, the strength of self-compacting concrete, discrete larger than ordinaryconcrete, to the engineering applications of the larger obstacles. The pilot study andtheoretical analysis, the strength of the discrete self-compacting concrete mainly bythe gas content of the uncertainty caused.Of the concrete mixture for foaming, entraining molding methods can adjust orchange the air content of concrete and hardened concrete pore structure. This byadjusting the air content of concrete mixture and shape to control the air content ofconcrete, a total of four series of self-compacting concrete-the benchmark series,anti-foaming series, air-entraining series and the "anti-foaming+air-entraining" series(each series of concrete divided into two groups, one group of vibration molding,forming another group of non-vibration), to study the gas content of theself-compacting concrete of various properties. Self-compacting concrete mixed withfly ash and slag two kinds of mineral admixtures general (Ratio between the two is1:1), the total cementitious material dosage were30%,40%and50%; plastic totalcondensate materials were450kg/m3,500kg/m3and550kg/m3. Focus on different topics in different mineral admixture dosage and total amount of cementitiousmaterials under the conditions of gas content on the mechanical properties ofself-compacting concrete and the durability of the effect, research shows that:1. Self-compacting concrete compressive strength of the discrete nature of the gascontent is mainly due to the uncertainty.2. Incorporation of defoaming agent or by vibration molding, self-compactingconcrete containing gas reduction, compressive strength, anti-carbonation propertiesand improved resistance to chloride ion permeability, frost resistance and early crackresistance decreased; incorporation of air-entraining agent, self-compacting concreteair content increased, the compressive strength, carbonation resistance and chloridepermeability were lower, frost resistance and early cracking performance; defoamermixed after the first air-entraining agent mixed, self-compacting concrete slightlyincrease air content, compressive strength, carbonation resistance and chloridepermeability were increased, early cracking performance.3. The main affecting factors of early concrete cracking of concrete within theirregular number of large bubbles, rather than the absolute value of the gas content.4. In addition to early cracking, the very premise of the gas content, the smaller thebubble spacing factor, self-compacting concrete, the better the performance of allkinds.