Surface Modification of Lightweight Mortars by Nanopolymers to Improve Their Water-Repellency and Durability

Abstract

The paper explores the possibility of covering the mortar with the lightweight aggregate by the nanopolymer silane and siloxane as surface hydrophobisation. The investigation involved the mortars with two types of hydrophobic agents diluted with water in a ratio of 1:4 and 1:8. Mortar wetting properties were determined by measuring the absorbability, water vapor diffusion, contact angle (CA) and surface free energy (SFE) of their structure. Surface micro-roughness and 2D topography were evaluated. Scanning electron microscopy (SEM) has shown the microstructure and distribution of pores in mortars. The reduction in absorbency after the first day of testing by 87% was shown. An improvement in frost resistance after 25 cycles by 97% and an 18-fold decrease in weight loss after the sulphate crystallization test were observed. The hydrophobic coating reduces the SFE of mortars and increases the CA. In the case of using silanes, a 9-fold increase CA was observed.

Durability of Hydrophobic/Icephobic Coatings in Protection of Lightweight Concrete with Waste Aggregate

“…It was also noted that hydrophobization was weaker (less durable) in the case of impervious concrete, because the hydrophobization formulation was unable to penetrate the composite structure, in contrast to materials of higher porosity. Numerous studies have reported the positive influence of hydrophobization on the absorptivity and permeability of cement materials [ 8 , 21 , 24 , 26 , 29 , 30 , 31 , 32 , 33 , 34 ].…”

“…The basis of organosilicon polymers is siloxane Si-O-Si and silica-carbon Si-C-Si bonds [28]. Very good efficiency of mortars and LC was reported by Ramachandran et al [29], Szafraniec et al [30], Suchorab et al [8], Liu et al [31], and Barnat-Hunek et al [32], or Sadowski and Stefaniuk [33].…”

“…Figure 7 presents the microstructure and adhesion of the cement paste to EPS and sand. Studies performed by Szafraniec et al [30] showed that hydrophobization of mortar containing perlite with water emulsion based on silanes caused a decrease in sample mass loss by up to 18 times. Additionally, an increase in the concentration of hydrophobic agents caused a reduction in mass loss after the test of resistance against salt crystallization.…”

“…It was showed that the hydrophobization of LC composites containing recycled polyurethane foam increased frost resistance by over 80%, compared to the reference samples [ 34 ]. However, surface hydrophobization is not always efficient in the improvement of concrete characteristics, especially when the concrete contains industrial waste [ 24 , 30 , 35 ]. Studies performed by Liu et al [ 31 ] proved that surface hydrophobization of concrete by silane reduces damage caused by cycles of freezing and thawing, but is unable to prevent damage inside insufficiently aerated concrete.…”

Evaluation of the contact angle and wettability of hydrophobised lightweight concrete with sawdust

“…This is because it reaches deeper parts of the material. Szafraniec et al in [59] showed the effectiveness of surface hydrophilisation of porous mortars with perlite. Samples surfacetreated with aqueous emulsion based on organofunctional silanes diluted in demineralised water in the ratio of 1:4 proved to be the most resistant to water absorption.…”