Abstrakt
The alkali-silica reaction (ASR) originates under highly alkaline conditions in concrete, where reactive forms of SiO2 react with hydroxyl ions and alkalis, forming alkali-silica gels. Alkali-silica gels tend to absorb water molecules and expand causing deterioration of the concrete.
Quartz, a dominant component of aggregates used in concrete, exhibits variable potentials to cause ASR. This paper aims to quantify the ASR potential of quartzite aggregate sampled from the Těchobuz quarry (Moldanubian Zone, Bohemian Massif, Czech Republic).
Various macroscopic and microscopic techniques (image analysis, polarising and electron microscopy, cathodoluminescence) were employed and combined with the accelerated mortar bar test. Slight variations were found in the ASR potentials of aggregates crushed by different laboratory crushers.
Parameters such as particle shape and specific surface were suggested to be responsible for these variations in the ASR potential. A higher ASR potential was measured in the case of sample Nos.
A2 and B2, crushed employing a Retsch BB3A jaw crusher (1970). In contrast, sample Nos.
A1 and B1, crushed with a MEZ Mohelnice AP100L/4S/1 jaw crusher (1968), showed a lower ASR potential. Particle shape analysis did not indicate any differences when comparing aggregates crushed by different crushers.
The same conclusions were found when comparing the specific surface values. Some explanation could be seen in the different mineral compositions and microstructures of the samples investigated (quartz content, quartz deformation).