Hydrophobisation of mortars containing waste polyurethane foam

Abstract

This paper investigates the physical and mechanical properties of mortars modified with waste polyurethane foam (WPF) and the influence of hydrophobising agents on the physical characteristics. The sand was substituted with WPF (2-4 mm grain size) in the mortars which consisted of 5, 10 and 15% of foam, respectively. The contact angle of lightweight mortars was determined (θw) in the function of time, prior to and after the frost resistance test. The surface free energy characterizing the wettability and adhesion of mortars under normal conditions and following frost erosion was calculated with Neumann’s method based on the obtained data. The structure of mortars, adhesion of lightweight aggregate to cement paste and the structure of thin hydrophobic film were demonstrated by means of scanning electron microscopy. The mortars subjected to hydrophobisation process revealed a slight mass change caused by freezing and thawing processes: 0.1% for methyl silicone resin, 2.1% for alkyl-alkoxy-silane, and 9.2% for the samples which were not hydrophobized. On average, the contact angle of the standard mortars was 3 times lower than the one of hydrophobic material. The best results illustrating the efficiency of hydrophobisation were obtained for methyl silicone resin.

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

“…Similar conclusions were reported by different authors, especially for cases in which particles of polysiloxane resign were too large to penetrate the tiny porous structure of concrete [ 32 , 35 ]. Łukowski [ 36 ] and other researchers [ 28 , 34 , 35 ] confirmed that the geometry and composition of the polymer particle, not the chemical nature of polymer compound, had significant relevance during the formation of the polymer coating. As a result of water penetration thorough the pervious coating and frost activity, stratification at the joint of the concrete base and the polymer coating is possible.…”

“…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 ].…”

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

“…The contact angle was 157.3 • and the water absorption was reduced by about 92.51%. Hydrophobisation of lightweight mortars containing waste polyurethane foam carried out in work [36] increased frost resistance up to 84% compared to the model samples. The work of Barnat-Hunek et al [37] is another example confirming the effectiveness of hydrophobisation which has helped to protect the mortar with expanded cork from the destructive effects of frost.…”

“…Therefore, in recent years the use of various hydrophobic agents, to minimize the decomposition rate of porous materials, has been widely discussed [36][37][38]. Furthermore, the concentration and type of the active substance in the agent constitute a very crucial factor.…”

“…Furthermore, the concentration and type of the active substance in the agent constitute a very crucial factor. In the literature, there can be noted examples of different additives and admixtures that can be used for hydrophobisation, such as superhydrophobic nano-silica [29], particle-siloxane [31], silica particles in rice husk ash modified using fluoroalkyl silane [30], methyl-silicon resin [36], alkyl-alkoxy-siloxane [36], SiO 2 -CH 3 submicron-sized [38], alkyl-alkoxy-siloxane oligomer and methyl silicone resin in an organic solvent [37], cyanoacrylates [39], polydimethylsiloxane [35], ammonium polyphosphate [40], SiO 2 / polymethyl-hydro siloxane synthesized by sol-gel [41], Nano-SiO 2 within organic films [42].…”