The Influence of Lime Solution in Kneading Water Substitution on Cement Roughcast and Mortar Coating.

André M Santos,Ângelo J Costa E Silva,João M P Q Delgado,António C Azevedo,João M F Mota,Fernando A N Silva

doi:10.3390/ma14154174

Abstract

The understanding of the mechanical fixation behavior of coatings is crucial for a better comprehension of the bonding systems, especially at the interface between the mortar and the substrate. Physical adherence is related, among other things, to the contents of the materials used in the roughcast and mortar coatings, due to the colloidal water penetration into the pores of the substrate. This work evaluated the influence of different lime solution additions replacing the kneading water in the preparation of roughcast and mortar coatings. Two types of substrates were investigated:ceramic bricks and concrete blocks. Three wall masonry panels were constructed, with dimensions of 220 × 180 cm2, one of concrete block and two of ceramic bricks, followed by the application of roughcast and mortar coating with an average thickness of 5 mm and 20 mm, respectively. Direct tensile bond strength tests were performed and the results, with a 95% confidence level, showed that substrate ceramic and treatment in the roughcast exhibited a better behavior regarding the distribution of the tensile bond strength of the tested specimens. However, no significant differences of the amount of addition used (0%, 5%, 10% and 15%) on the tensile bond strength were observed.

Highlights

A primary step to obtain an adequate behavior of mortar coating systems is the preparation of the base to assure an appropriate and efficient tensile strength of the system
This work aims to evaluate the influence of different lime solution additions in the kneading water of roughcast and plaster mortar, namely on the tensile bond strengths of mortar with ceramic brick and concrete blocks substrates
This research work evaluated the influence of different lime solution contents (0%reference, 5%, 10% and 15% in relation to the amount of water used) replacing the kneading water in the preparation of roughcast and plaster mortar, for two types of substrates and two type of treatments, on the tensile bond strength of tested specimens

Summary

Introduction

A primary step to obtain an adequate behavior of mortar coating systems is the preparation of the base to assure an appropriate and efficient tensile strength of the system. The execution of a roughcast layer is one of the most used strategies used to ensure such a base because it standardizes the characteristics of the base, increases the contact area and, mainly, increases the roughness of the surface. High absorption substrates can result in insufficient water for the complete hydration of cement near the interface area between the substrate and the roughcast, which weakens this region (approximately 20 μm). Substrates with low absorption can lead to water accumulation in the interface zone, increasing the porosity and contributing to the increase of the water/cement ratio, compromising its performance [3]

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