Increase the Performances of Lime Finishing Mixes Due to Modification with Calcium Silicate Hydrates

Abstract

Lime plaster mixes are becoming more and more popular in the world’s building materials market every year. Therefore, the issue of increasing the efficiency of lime finishing coatings is relevant. The paper aim is the modification of lime binders with specially synthesized calcium silicate hydrates (CSHs). To obtain the CSH filler, liquid sodium glass was used with a silicate module of 1.53–2.9 and a density of 1130–1663 kg/m3. Using differential thermal analysis (DTA), X-ray diffraction (XRD) patterns, synthesized calcium silicate hydrates, as well as dry plaster mixes, and finishing coatings based on using them were studied. The regularities of the filler synthesis were established depending on the temperature, density, and silicate modulus of liquid glass, the amount of the precipitant additive, the rate of its introduction, and the drying mode. As a result of processing the obtained experimental data, a mathematical model was obtained for the composition “lime + CSH”. The phase composition of the filler was revealed, which is characterized by the presence of calcium silicate hydrates of the tobermorite group, a solid solution CSH (B) in the form of a weakly crystallized gel, a solid solution of C–S–H (II), hydrohalites, and calcites. It was found that the use of the fillers into the lime compositions, obtained with the rapid introduction of CaCl2 additive into water glass during the synthesis of the filler, promotes the acceleration of the plastic strength gain of lime compositions. It was revealed that the lime composites with the CSH filler are characterized by reduced shrinkage deformations up to 45%. The introduction of the CSH filler into the lime compositions increases the water resistance of the lime finishing layer by 36%. A technological scheme for the production of the lime dry plaster mixes has been developed; it can be introduced at existing factories of building materials without significant re-equipment of production.