Dry pack mortars for self-levelling floor compounds based on β-hemihydrate and modified phosphogypsum binder

Abstract

The paper considers the influence of β-hemihydrate and phosphogypsum binder on the properties of dry pack mortars for self-levelling floors. As preliminary research demonstrated that adding to phosphogypsum (PG) admixtures of lime and PA or PC superplasticizer permits to obtain binder with high compressive (up to 24 MPa) and bending strength (up to 12 MPa). The manufacturing of dry pack mortars for self-levelling floor underlayment was determined as one of the areas of PG application. There has been investigated composite binder consisted of PG, Portland cement and metakaolin. There have been determined linear deformations of PG/ based binder comparing to β-hemihydrate calcium sulphate binder and bending to compressive strength ratio. The method of planned experiment was applied for determination the optimal proportion of the components of the mortar. There were considered the sand / binder ratio, cement and metakaolin portions in binder, water-binder ratio and content of Tylose (water-retaining admixture). There was tested composite binder consisted of PG (or β-hemihydrate), PC and metakaolin. There were tested flow spread on Suttard's viscometer, time of application, and compressive strength at the age of 1, 3 and 28 days. The flow spread diameter of the mixtures was within the range of 180-200 mm, and time of application was between 30 and 45 min. The compressive strength of mortar specimens is up to 4 MPa, at the age of 3 days is 10 MPa and at the age of 28 days reaches 17 MPa. The increasing of Portland cement dosage and metakaolin makes the most positive effect on strength parameters. The mortar based on PG is applicable for underlayment of different flooring compounds types.