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

Izabela Hager,Agnieszka Baziak,Kinga Pławecka,Kinga Korniejenko,Arnaud Castel

doi:10.3390/ma14195741

Izabela Hager, Agnieszka Baziak + Show 3 more

Open Access

https://doi.org/10.3390/ma14195741

Copy DOI

Abstract

The aim of this paper is to analyze the influence of hybrid fiber reinforcement on the properties of a lightweight fly ash-based geopolymer. The matrix includes the ratio of fly ash and microspheres at 1:1. Carbon and steel fibers have been chosen due to their high mechanical properties as reinforcement. Short steel fibers (SFs) and/or carbon fibers (CFs) were used as reinforcement in the following proportions: 2.0% wt. CFs, 1.5% wt. CFs and 0.5% wt. SFs, 1.0% wt. CFs and 1.0% wt. SFs, 0.5% wt. CFs and 1.5% wt. SFs and 2.0% wt. SFs. Hybrid reinforcement of geopolymer composites was used to obtain optimal strength properties, i.e., compressive strength due to steel fiber and bending strength due to carbon fibers. Additionally, reference samples consisting of the geopolymer matrix material itself. After the production of geopolymer composites, their density was examined, and the structure (using scanning electron microscopy) and mechanical properties (i.e., bending and compressive strength) in relation to the type and amount of reinforcement. In addition, to determine the thermal insulation properties of the geopolymer matrix, its thermal conductivity coefficient was determined. The results show that the addition of fiber improved compressive and bending strength. The best compressive strength is obtained for a steel fiber-reinforced composite (2.0% wt.). The best bending strength is obtained for the hybrid reinforced composite: 1.5% wt. CFs and 0.5% wt. SFs. The geopolymer composite is characterized by low thermal conductivity (0.18–0.22 W/m ∙ K) at low density (0.89–0.93 g/cm3).

Highlights

Geopolymers are a class of synthetic inorganic aluminosilicate materials usually formed by the reaction of aluminosilicates with a silicate solution (e.g., Na2 SiO3, K2 SiO3 ) under strongly alkaline or acidic conditions (e.g., NaOH, KOH, H3 PO4 ) [1,2]
The results show that only the addition of steel fibers in an amount of 2 wt.% significantly increases the compressive strength of geopolymer composites
The4 results show that only the addition of steel fibers in an amount of 2 wt.% significantly increases the compressive strength of geopolymer composites

Summary

Introduction

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., Na2 SiO3 , K2 SiO3 ) under strongly alkaline or acidic conditions (e.g., NaOH, KOH, H3 PO4 ) [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]. The addition of fibers reduces the number of cracks and their dimensions in the material, which in turn minimizes the damage caused by cracking and keeps the material cohesive for longer periods of time under the given load [8,9] Such behavior is important, especially in emergency situations, such as fires or earthquakes, in which a person has more time to leave the endangered place. For this reason, reinforcing geopolymer matrices with fibers is a very interesting design solution that stands out from others currently available on the market [7,10,11]

Objectives

Methods

Findings

Discussion

Conclusion