Metakaoline blended cements improve GRC durability and ductility

Abstract

Even using A.R. glass, long term properties of GRC are affected by physical attack of the fibres. This phenomenon is due to lime formation resulting from O.P.C. hydration. Using highly reaction pozzolana in the cement can lead to a lime free hydrated matrix, and thus may solve the basic problem. For this study metakaoline has been used since it is a fairly cheap, widely available mineral product and can be very reactive provided heating parameters are well fitted. Flexural tests carried out on air spray cast plates with various curing conditions point out that early age strengths are slightly reduced but ductility is already improved. Long term tests show that mechanical properties are significantly improved and that strength and ductility go on increasing with time. Furthermore, application to facing panels would lead to interesting architectural qualities because of the light aspect of metakaoline and of the suppression of carbonation phenomena. It is concluded that using metakaoline blended cement associated with A.R. glass can lead to a new GRC with much improved mechanical properties and aspect qualities, not affected by long term embrittlement or strength loss.