37º IAHS World Congress on Housing: - Universidad de Cantabria

XXXVII <strong>IAHS</strong><strong>World</strong> <strong>Congress</strong> on HousingOctober 26 – 29, 2010, Santander, SpainCODE: 102NEW GYPSUM PLASTER WITH HIGH FIRE RESISTANCESuesta C. a , López-Buendía A.M. a , Moliner V. ba Materials Technical Unit, AIDICObFire resistance Laboratory, AIDICOAIDICO, Benjamín Franklin, 17, 46980 Paterna, Valencia, Spaina e-mail: cristina.suesta@aidico.esKey words: gypsum plaster, fire resistance, ettringiteAbstractThe objective is to obtain a new material of high fire performance based in gypsum plaster. Theimprovement under fire conditions of the new material is based on the addition of ettringite to gypsumplaster matrix. The good behaviour of ettringite under fire conditions in the new material is due itshigh water amount that produces several effects, as follows: heat absorption for mineral transformationavoiding temperature increase, water release, low thermal conductivity .Stable phase of ettringite has between 26 and 32 water molecules (Ca 6 [Al(OH) 6 ] 2 (SO4) 3·32H 2 O, withthe empirical formula 3CaO·Al 2 O 3·3CaSO 4·32H 2 O) and it can be obtained from reagents:Al 2 (SO 4 ) 3 .18H 2 O and Ca(OH) 2 .in N 2 atmosphere. Since this way is too expensive, another method isproposed to synthesize ettringite. In this case, ettringite is formed together with little amounts ofgypsum or calcium sulphate dihydrate. Samples of ettringite formed by this way are cured at 20ºC at98% of moisture during 7 days to assure water content. New material looks like conventional gypsumplaster but X-ray diffraction show strong peaks of ettringite and weaker peaks of gypsum.This new material can be used as a new matrix or as an addition for conventional gypsum plastermaterials after drying and sieving. The little amount of gypsum (dihydrate) acts as an hydrationaccelerator and growing crystal nucleus so setting time is reduced. Consistence of gypsum plaster isnot affected when adding ettringite-gypsum mix up to 7%.Industrial pilot plant was used to fabricate gypsum plaster at industrial size to validate dosage andevaluate the feasibility of the developed product.Medium scale normalized fire resistance tests were made to assess the effect of new materialunder fire conditions. These test reveals that ettringite-gypsum matrix shows a very goodperformance under fire conditions delaying the increase of temperature in the sample. Time toreach 140ºC is up to 70 minutes more than for conventional gypsum plasters. Fire behaviourof ettringite-gypsum mix is very good too when it is added to gypsum plaster matrix.37º <strong>IAHS</strong> <strong>World</strong> <strong>Congress</strong> On Housing Science 58