Earthen plasters hygrothermal and mechanical performance: Effect of adding recycled gypsum from plasterboards and raw hemihydrate

The aim of the present study is to assess if recycled gypsum from plasterboard waste can be added to earth plastering mortars instead of raw calcium sulphate hemihydrate when a mineral binder addition is foreseen to improve durability. Earth mortars with additions of 0 %, 5 %, 10 % and 20 % vol. of raw hemihydrate, gypsum milled from plasterboards with and without thermal treatment were produced and tested. In general, the additions led to an overall improvement in mechanical strength and resistance to water and did not significantly influence the hygroscopicity of the earth plaster. In general, earth mortars with untreated gypsum waste achieved comparable to superior results compared to mortars with treated gypsum waste, indicating the viability of using recycled gypsum from plasterboard without thermal treatment as earthen plaster addition.