Glass - Back to the Future!

Presenting Author:
Ales Helebrant

article posted 22 March 2016

Ales Helebrant is head of the Department of Glass and Ceramics at University of Chemistry and Technology in Prague. He is interested in the description of interaction between inorganic non-metallic materials and environment, especially in kinetics and mechanisms of glass corrosion and in interaction of bioactive materials and layers with simulated body fluids. His research group also develops the bioactive and antibacterial layers on biomaterials.

Corrosion of Glass Fibres in Concrete

Helena Hradecka, Barbora Holubova, Lukas Brazda1, Zuzana Zlamalova Cilova & Ales Helebrant*
University of Chemistry and Technology Prague, Dept. of Glass and Ceramics, Technicka 5, CZ 16628 Prague 6

The composite materials made of ultra-high performance concrete and alkali resistant glass fibres are often used among advanced building materials. The glass fibres should increase the mechanical strength of material by avoiding the cracks propagation. The aim of the project was to study and describe the kinetics and mechanisms of glass fibers in solutions simulating the concrete environment. Two types of alkali resistant fibres were used: Anti-crackTM HD (SiO2 56.84, ZrO2 19.96, Na2O 16.18, CaO 6.18, Al2O3 0.28, TiO2 0.10, Fe2O3 0.07, HfO2 0.32 and P2O5 0.02 in wt. %, measured by XRF) and Anti-crackTM HP ((SiO2 56.92, ZrO2 19.90, Na2O 16.04, CaO 6.31, Al2O3 0.27, TiO2 0.09, Fe2O3 0.07, HfO2 0.34 and P2O5 0.02in wt. %). These fibres differ in system of lubrication. As corrosive solution, simulating the environment in concrete, the saturated Ca(OH)2 solution was used, with pH 12.7. In order to differentiate the influence of pH value itself and the chemical composition of compare the influence of pH and chemical composition of solution on the corrosion mechanism also KOH solutions with pH 12.7 and 14.0 were also used. The corrosion was studied at 80C up to 42 days under static conditions. Both lubricated fibres and fibres without lubrication (fired at 560C for 3 hours) were corroded.

Fig.1. HD glass fibers after 28 days in KOH solution (pH 12.7)
Fig.2. HD glass fibers after 28 days in Ca(OH)2 solution (pH 12.7)

From the analysis of solution (AAS), glass surface (SEM/EDS, XRD) we can conclude, that: 1) The fibres corrosion in the strong alkaline solutions are not significantly influenced by the type of lubrication. 2) The glass dissolution is incongruent. 3) In Ca(OH)2 solution, secondary precipitated layers of calcium hydroxide, calcium carbonate and in the case of fired fibres of calcium silicate are formed. Under this precipitated layer, the lubricated fibres shows the pit corrosion, on the fibres without lubrication the corrosion of glass surface is visible. 4) In KOH solutions, the corrosion lead to the surface layer with decreased amount of Na2O and increased amount of ZrO2 and CaO. The amount of SiO2 in this layer was slightly decreased in comparison with original glass. Acknoledgement This study was accomplished with the financial support from the Grant Agency of the Czech Republic, reg. number 14-20856S The kinetics of corrosion processes and corrosion media transport in advanced ultra-high performance concretes (UHPC) 1Present address JV Group, Re u Prahy