Thaumasite Sulfate Attack And Preventive Methods

Paper ID : 1082-ISCH

Authors

Mahmoud Mohamed AlSayed * Helwan university

Abstract

It is generally accepted that conventional sulfate attack of cementitious materials involves the formation and the expansive properties of ettringite. However, another kind of sulfate attack, concerning cements and concretes containing limestone and attributed to the formation of Thaumasite (CaSiO3.CaCO3. CaSO4.15H2O), has been widely discussed during the last years. The formation of Thaumasite involves attack on the calcium silicate hydrate phase; resulting in a reduction in the binding strength and transformation of concrete or mortar into a mushy incohesive mass. The mechanism by which Thaumasite formation can be summarized into 2 stages ; the first stage is called carbonation process, whereas the second stage is called thaumasite formation .However there are many methods which can be used for either prevention or even decreasing its badly effect by using specific chemical reagents such as barium hydroxide . barium carbonate , and disodium hydrogen phosphate , or by addition of particular cement additives such as fly ash.

Keywords

Calcium silicate hydrate : is the main hydration product of the calcium silicates alite and belite in OPC, to which the material properties of concrete are primarily attributed. Ettringite : is a primary constituent of hydration of Portland cement concrete

Status: Abstract Accepted (Poster Presentation)