The water transport of Na+ - ions in fly ash based alkali-activated cements stone

Abstract

The main distinction of fly ash and slags based alkali activated cements from OPC is that alkaline environment appears immediately after mixing with water and so because of high pH level it takes place more intensive destruction of covalent bonds, promoting formation of lower basic hydration products, which provide dense and homogenous structure of artificial stone. Fly ash based alkali activated cements are differ from slag alkali activated cements by lower speed of structure formation processes, that provide longer term of existence of N+ ions in unbounded state and needs more time to procuring conditions of hardening which are preventing of this ions transfer to the surface of specimen. In present study were investigated processes of Na+ ions mass transfer in artificial stone of fly ash based cements (up to 70% by mass) under influence of temperature and humidity gradients. It was shown possibility to use hydrophobic and redispersed admixtures, which provides slowing mass transfer processes of alkaline ions in the volume of concrete structure until their bonding into non-soluble compositions. This makes it possible to develop technology of concrete manufacture regardless hardening conditions