The Influence of Short Coir, Glass and Carbon Fibers on the Properties of Composites with Geopolymer Matrix

Abstract

The aim of the article is to analyze the influence of short coir, glass and carbon fiber admixture on the mechanical properties of fly ash-based geopolymer, such as: flexural and compressive strength. Glass fiber and carbon fibers have been chosen due to their high mechanical properties. Natural fibers have been chosen because of their mechanical properties as well as for the sake of comparison between their properties and the properties of the artificial ones. Fourth series of fly ash-based geopolymers for each fiber was cast: 1, 2, and 5% by weight of fly ash and one control series without any fibers. Each series of samples were tested on flexural and compressive strength after 7, 14, and 28 days. Additionally, microstructural analysis was carried out after 28 days. The results have shown an increase in compressive strength for composites with fibers—an improvement in properties between 25.0% and 56.5% depending on the type and amount of fiber added. For bending strength, a clear increase in the strength value is visible for composites with 1 and 2% carbon fibers (62.4% and 115.6%). A slight increase in flexural strength also occurred for 1% addition of glass fiber (4.5%) and 2% addition of coconut fibers (5.4%). For the 2% addition of glass fibers, the flexural strength value did not change compared to the value obtained for the matrix material. For the remaining fiber additions, i.e., 5% glass fiber as well as 1 and 5% coconut fibers, the flexural strength values deteriorated. The results of the research are discussed in a comparative context and the properties of the obtained composites are juxtaposed with the properties of the standard materials used in the construction industry.

Development and Characterization of Lightweight Geopolymer Composite Reinforced with Hybrid Carbon and Steel Fibers

“…Geopolymers are a class of synthetic inorganic aluminosilicate materials usually formed by the reaction of aluminosilicates (e.g., fly ash, metakaolin) with a silicate solution (e.g., Na 2 SiO 3 , K 2 SiO 3 ) under strongly alkaline or acidic conditions (e.g., NaOH, KOH, H 3 PO 4 ) [ 1 , 2 ]. Products based on geopolymers are characterized by very good properties such as compressive strength, thermal stability, acid resistance, and fire resistance or dimensional stability [ 2 , 3 ]. This gives the opportunity to use them in construction, to immobilize toxic waste and heavy metals (e.g., waste from asbestos, radioactive waste), or as refractory coatings in the aerospace industry [ 3 , 4 ].…”

“…Products based on geopolymers are characterized by very good properties such as compressive strength, thermal stability, acid resistance, and fire resistance or dimensional stability [ 2 , 3 ]. This gives the opportunity to use them in construction, to immobilize toxic waste and heavy metals (e.g., waste from asbestos, radioactive waste), or as refractory coatings in the aerospace industry [ 3 , 4 ]. However, the relatively low resistance to brittle cracking is a limitation for the use of these materials in many areas.…”

Effect of Fiber Reinforcement on the Compression and Flexural Strength of Fiber-Reinforced Geopolymers

“…However, the problem is the cementitious environment, which leads to rapid corrosion of the popular types of S and E glass fibers, contributing to the disintegration of reinforced concrete structures [45,46]. Many studies and scientific papers have been devoted to glass fibers as reinforcement in geopolymers [47][48][49][50][51][52].…”

“…Alkaline environments protect the fibers against oxidation, making carbon fiber-reinforced geopolymers suitable for use at elevated temperatures [53][54][55]. For the reinforcement of geopolymers, carbon fibers are most commonly used in the form of fabrics, long fibers, chopped fibers, dispersed particles, and also in the form of graphite, graphene, or waste left over from the manufacture of aerospace components [49,[56][57][58]. The main obstacle to the large-scale use of carbon fibers is their high production cost.…”

Geopolymers Reinforced with Natural Fibers: A Comparison among Different Sources

“…While they possess promising mechanical properties, i.e., compressive strength, they suffer from extreme brittleness and from limited dimensional stability. These features, as well as the absence of a well-established standardization, presently limit the application of these materials in civil engineering, although some commercial applications have already been reported [1]. In order to overcome this problem, a common strategy is to modify the material through the addition of fibers [2][3][4][5].…”