Abstract:

Cement?based wet?mixed plastering mortar was prepared by neutralizing and modifying dihydrate phosphogypsum with lime and adding cement，manufactured sand and plasticizer.The physical properties such as setting time，consistency and mechanical strength of the wet?mixed mortar with different dosages of phosphogypsum，cement and plasticizer were investigated，and the action mechanism of phosphogypsum in the wet?mixed mortar was analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）.The results showed that with the increase of phosphogypsum content，the setting time of the wet?mixed mortar was prolonged，and the 28-day compressive strength and the 14-day tensile adhesive strength of the wet?mixed mortar were decreased.With the increase of cement content，the setting time of wet?mixed mortar decreased，and the strength increased gradually.With the increase of plasticizer dosage，the bonding properties and lubrication of wet?mixed mortar became gradually excellent，and the setting time increased.When the controlling material proportion（mass fraction） was phosphogypsum of 35%，manufactured sand of 48%，cement of 17%，and external addition lime of 2%，plasticizer of 0.3%，the setting time of mortar was 25 h，28 d compressive strength was 6.2 MPa，14 d tensile bonding strength was 0.31 MPa，all of which met the requirements of WP M5 quality and technical indicators in the industrial standard JC/T 230—2007 Pre?mixed Mortar.Phosphogypsum in cement?based wet?mixed mortar played a cementing role by providing sulfate ions to react with calcium aluminate hydrate to generate mortar strength minerals ettringite.Unreacted phosphogypsum acted as fine aggregate filler.

Key words: phosphogypsum, cement, plastering mortar, properties