Development of Alkali Activated Pervious Cementless Concrete
Pervious concrete is a topic of recent interest and finds vivid applications such as for discharging rain water, filtration of waste water etc. Pervious concrete made with cement as a binder poses serious threats to the environment due to the large amount of green house gases released, especially carbon dioxide, owing to the production of cement. Therefore, it is imperative to find a suitable substitute for cement in the production of concrete. This study presents about the production of pervious concrete, completely replacing cement with fly ash geopolymer binder system. Pervious geopolymer concretes were prepared from Class F fly ash, sodium silicate, sodium hydroxide solution, coarse aggregate and a little quantity of fine aggregate. The alkali to binder ratio of 0.50 by mass and sodium silicate to sodium hydroxide ratio of 2.50 were used. In order to improve the workability of mixture, a super plasticizer Conplast SP 430 (2-3% by weight of binder) was added. Temperature curing at 50 ºC for 24 hours was done. Compression, permeability and water absorption tests were conducted on the specimen at 7 days. The compressive strength of the mixture was found to be 11.66 MPa which is more than that of a brick and water absorption was nearly 2%. The permeability of water through the specimen was found to be 24.63 ml/sec for a pervious cubical specimen of size 10 cm. The pervious concretes produced in this work were not only environment friendly but also achieved better mechanical properties and water permeability. It is inferred that the fly ash geopolymer system could be used to produce pervious concrete.
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