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. • Earth mortars workability is influenced by the addition of gypsum-based binders, especially hemihydrate. • Linear shrinkage of the mortars increases with the content of gypsum and hemihydrate. • Raw and recycled gypsum-based binders additions improve the mortars mechanical performance. • Earthen plasters hygroscopic capacity is not significantly influenced by the additions. • Recycled gypsum without thermal treatment is an eco-efficient addition for earth plasters.