Influence of Alkali Activator Type on the Hydrolytic Stability and Intumescence of Inorganic Polymers Based on Waste Glass.

Adrian Ionut Nicoara,Alina Ioana Badanoiu

doi:10.3390/ma15010147

Adrian Ionut Nicoara, Alina Ioana Badanoiu

Open Access

https://doi.org/10.3390/ma15010147

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Abstract

The main objective of this study is the synthesis and characterization of low cost alkali-activated inorganic polymers based on waste glass (G-AAIPs) using a mixture of NaOH and Ca(OH)2 as alkali activators, in order to improve their hydrolytic stability. This paper also presents detailed information about the influence of composition determined by X Ray Diffraction (XRD), microstructure determined by Scanning Electronic Microscopy (SEM) and processing parameters on the main properties of G-AAIP pastes. The main factors analyzed were the glass fineness and the composition of the alkaline activators. The influence on intumescent behavior was also studied by heat treating of specimens at 600 °C and 800 °C. The use of Ca(OH)2 in the composition of the alkaline activator determines the increase of the hydrolytic stability (evaluated by underwater evolution index) of the G-AAIP materials compared to those obtained by NaOH activation. In this case, along with sodium silicate hydrates, calcium silicates hydrates (C-S-H), with good stability in a humid environment, were also formed in the hardened pastes. The highest intumescence and an improvement of hydrolytic stability (evaluated by underwater evolution index and mass loss) was achieved for the waste glass powder activated with a solution containing 70% NaOH and 30% Ca(OH)2. The increase of the waste glass fineness and initial curing temperature of G-AAIPs have a positive effect on the intumescence of resulted materials but have a reduced influence on their mechanical properties and hydrolytic stability.

Highlights

Fire is a serious threat to people’s lives and property, frequently leading to the destruction of buildings with economic and architectural importance
The main objective of this study is the synthesis and characterization of low cost alkali-activated inorganic polymers based on glass waste (G-AAIPs) using a mixture of NaOH and Ca(OH)2 as alkali activators, in order to improve their hydrolytic stability evaluated by underwater evolution index (u.e.i.) This paper presents information about the influence of composition determined by X ray diffraction (XRD), microstructure determined by Scanning Electronic Microscopy (SEM) and processing parameters on the main properties of AAIP pastes
The mineralogic compositions of glass alkali-activated inorganic polymers (G-AAIP) samples after 7 days of hardening were assessed by X-ray diffraction (XRD)

Summary

Introduction

Fire is a serious threat to people’s lives and property, frequently leading to the destruction of buildings with economic and architectural importance (for example, Grenfell Tower, UK 2017 or Notre Dame de Paris, FR, 2019). Protecting the infrastructure against fires is a necessity. For this purpose, different methods of protection against fire (active or passive) have been developed [1,2,3,4]. Fire protection is necessary for buildings with metal structures [3,4,5]. The existing methods for passive fire protection of steel rely on the use of materials that reduce the heat transfer to the protected metal structure. Intumescent materials swell when subjected to fire and can be used as passive fire protection in buildings; these materials can provide thermal protection to the underlying structure or can seal the penetrations in walls/floors preventing fire and smoke spreading in adjacent rooms [6]

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