Analysis of mortar coating with different types and proportions of chemical admixtures that have water retentivity properties

Alessandra Tolentino Souza,Catharina De Almeida Carvalhais,White José Dos Santos

doi:10.1590/s1983-41952021000600002

Alessandra Tolentino Souza, Catharina De Almeida Carvalhais + Show 1 more

Open Access

https://doi.org/10.1590/s1983-41952021000600002

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Abstract

abstract: Water retaining agents are the main admixtures used to retain water against evaporation and substrate suction, and there are several chemical compounds for this purpose. To deepen the knowledge of mortar admixtures, several concentrations (0%, 1.5%, 5%, 10% and 15%) of three different types of admixtures were studied: an acrylic polymer, a cellulosic and ethylene vinyl acetate. Fresh properties (consistency, water retention, density and incorporated air), physical indexes (density and porosity) and compressive strength at 28 days were analyzed. It has been found that admixtures can act in different ways on mortars depending on the type of chemical agent used and can significantly affect the mechanical and durability characteristics in the fresh and hardened state. With this work it was verified the importance of searching references about the influence of chemical compounds before using it.

Highlights

Water retaining agents are widely used on coating mortars, mainly, to retain water during the dehydration process caused by substrate suction or caused by evaporation into the atmosphere due to climate agents [1], [2]
It was impossible to carry out the experiment for 15% dosage of hydroxyethyl methyl cellulose (HEMC), as the mortar was extremely dry and had a stick aspect, the mechanical mixer used was unable to complete the mixing procedure proposed in item 2
- Consistency is reduced by HEMC, due to the association mechanism, where attraction forces between polymeric molecules may arise restricting the movement of water molecules, generating a gel and transforming the mortar on a dry material, making it impossible to conduct the experiment beyond 10% concentration. pAVE acted through the interlacing mechanism of the polymeric chains, which tends to increase viscosity, but in higher concentrations and the stresses of Flow table, fluidized the mixture

Summary

INTRODUCTION

Water retaining agents are widely used on coating mortars, mainly, to retain water during the dehydration process caused by substrate suction or caused by evaporation into the atmosphere due to climate agents [1], [2]. This study tended to establish a comparison between the admixtures, highlighting the differences and similarities between each one in properties in the fresh state: consistency, fresh state density and water retention; physical indexes: density in the hardened state, theoretical incorporated air and theoretical porosity; and compressive strength at 28 days. It was proposed, when it was possible, equations for approximating the behavior of each mortar

MATERIALS AND EXPERIMENTAL PROGRAM

RESULTS AND DISCUSSIONS

Water retention

Fresh state density and air entrained

Compressive strength

CONCLUSIONS