Aditivos para concreto leve | Agentes espumantes de alto desempenho para concreto celular
Concreto leve celular, que também conhecido como CLC, é um método de espuma pré-formada que utiliza cinzas volantes para substituir o cimento. A espuma retém ar no agregado, making the material light and stiff but strong enough for high load bearing applications. This paper presents the effects of replacing the portland cement by various levels of fly ash in a typical cellular lightweight concrete mix and compares its compressive strength at curing age 3, 14, 28 e 60 days to conventional portland cement. The results of this study indicate that replacing the cement by 10 e 20 percent by weight of the binder significantly improves the compressive strength of cellular lightweight concrete without affecting its water absorption or porosity.
The stability of the foamed concrete is dependent on the ability to retain the air bubbles during production, construction and in service. This can be achieved by maintaining a low Water-cement ratio during the forming process. The foam can then be mixed and pumped with the help of specialised foam generating, mixing and pumping equipment.
The optimum proportion of foaming agent is 0.6 para 0.8% em peso do cimento. Foam agents containing more than this amount are unstable and collapse easily. This is due to the reactions of the foaming agent with other products in the mix which can cause segregation and increase drying shrinkage. Além disso, mixing the foam for longer than required destroys the bubbles. This affects the quality of the finished product.