The Impact of Expanded Glass Granulate on the Alkali-Silica Reaction

SCHLUSSELFELD, GERMANY–(Marketwired – September 28, 2015) – In Germany alone, damage to concrete or cement systems caused by an alkali-silica reaction results in annual repair costs in the millions. The aggregates react with the alkali of the cement or with externally supplied alkali. Absolutely inert aggregates do not exist, all aggregates react more or less with the hardened cement paste. Therefore, Poraver as a producer has dealt intensively with the topic of ASR to ensure the safe use of expanded glass in cement systems and concrete.

An alkali-silica reaction (or ASR, alkali reaction, alkali bustle or colloquially concrete cancer) is understood to be a chemical reaction between silicic acid from the concrete aggregates and the alkali hydroxide of the pore solution of the concrete. The resulting viscous alkali silicate gel is expansive and can cause damage to concrete. Water plays the role of a reactant. There is usually no damage in dry environmental conditions. Swelling pressures up to 20 N/mm² can develop that exceed the tensile strength of concrete significantly, leading to cracks and spalling. Expansion phenomena occur only in compact concrete. In pore-rich concrete on the other hand, the swelling pressures built up by the resulting gels are reduced through pores.

Scientific investigation of expanded glass in concrete

Experts requested scientific studies already several years ago, because it was known that glass in concrete can cause harmful ASR. Subsequently, Poraver has dealt intensively with the topic and commissioned studies at the University of Hanover and Bauhaus University Weimar.

In the studies, various dense-structure and porous lightweight test mixtures were prepared, on which measurements for strength, ultrasonic run time, carbonation, stretching and all obvious or microscopic studies were performed.

The test results

After an observation period of up to 3 years, there was no case with evident expansion phenomena, which are characteristic for the occurrence of harmful ASR. Furthermore, no hairline cracks, edge chipping, gel drops or other special peculiarities were observed. In contrast, significant expansion phenomena were observed in the prisms, which were prepared under the same conditions with Duran glass as aggregate. Furthermore, the properties of Poraver expanded glass granulate according to DIN 4226 were examined (from 2002 of DIN EN 13055) for lightweight aggregates.

No ASR damage from Poraver expanded glass granulate

Based on all conducted investigations, it has been scientifically established that Poraver expanded glass granulate is suitable as a lightweight aggregate for mortar and lightweight concrete and does not cause alkali-silica reaction damage.

Further information and photos are available here: http://www.poraver.com/us/influence-expanded-glass-granulate-alkali-silica-reaction-cementitious-systems-2/

Dennert Poraver GmbH, with production sites in Postbauer-Heng and Innisfil (Canada), has been the market leader in the production of expanded glass granulate for more than 30 years. Developed by Dennert Poraver GmbH, Poraver® is a lightweight aggregate made ¿from recycled glass, which has established itself in many different application areas because of its versatility and outstanding characteristics. With a planned annual production capacity of 500,000 m3, the company is the world’s largest manufacturer of expanded glass granulate.