Petrographic characteristic

Micropetrographic aggregate analyses of studied highway concretes proved differences in their rock composition as shown in Fig. 1.

Basic differences were in amount of black clay shales, granitoids and silicites in aggregate composition. It was unambiguously proved that the lowest degraded concretes were with the highest amount of granitoids. On the contrary the highest degraded were concretes with prevailing portion of black clay shales and silicites in aggregate composition. Percentage composition of aggregate in the highest degraded part of drill core is shown in Fig. 2.

Concurrently with micropetrographic analyses of highway concrete aggregates we focused on assessment of two different aggregate deposits. The first of one is opened in old submarine volcanic rocks. The second one is in granitoid rocks.

In comparison between drill cores 1, 3 and 7 are samples 1 and 7 very similar in aggregate composition. Variability in aggregate composition for concrete production probably reflects original rock heterogeneity in the rock massif in the quarry.

The drill core No.: 2 is in good quality, without significant cracks, without alteration in material composition and without formation of secondary minerals. Granitoid rocks predominate over metabasalts, shales and cemented detrital sediments. Studied rock composition leads to assumption about ASR, which was not anticipated in concretes in the Czech Republic up to the 1999.
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