Analysis of Three Types of Quartzite as Coarse Aggregate Material and their Impact on Compressive Strength on Concrete

Abstract

Aggregates are the most important constituents of concrete. They give body to the concrete, reduce shrinkage, enhance strength and effect economy. The quartzite rock available in Delhi is a prominent geological material available in the entire Aravali range. Most of the manufacturing of concrete is going on using quartzite as aggregate material. However, three different categories of quartzite have been classified on the basis of its colour composition namely greyish quartzite, reddish quartzite and yellowish quartzite. An experiment was carried out to study the impact of these quartzites on the compressive strength of concrete. The greyish quartzite was taken as coarse aggregate material with size ranging from 16 to 20 mm and of uniform density, specific gravity and sorting coefficient. The concrete was manufactured for three different grades of M10, M15 and M20 and compressive strength of the cubes casted were monitored for a period of 3, 7, 14 and 28 day curing. Similarly, the reddish quartzite and yellowish quartzite material with identical properties of density, specific gravity and sorting coefficient was also tested. It was found that the greyish quartzite being metamorphosed directly from the granite, inherited the strength of granite to some extent. However, due to weathering impact on reddish quartzite and yellowish quartzite, it lost its strength. Also, the presence of ferrous and ferric material in them violated its non-active reaction and became chemically active; hence, disturbed the workability of concrete. It was also observed that the greyish quartzite aggregate does not disturb the water/cement ratio and no segregation or bleeding was recorded during its manufacture. However, the reddish quartzite and yellowish quartzite disturbed w/c ratio as a result bleeding and segregation was recorded. In all, it is found that the greyish quartzite may be taken as a reliable coarse aggregate and the required compressive strength of all the said grades of concrete was achieved; whereas in reddish and yellowish quartzite concrete, the strength parameters were affected due to disturbance in w/c ratio and workability; by the virtue of which the required compressive strength was not achieved. Since, most of the builders and developers are using these quartzites as aggregates, without its proper segregation, the design of the building was affected which is a very important finding of the paper and needs required attention by the concerned engineers and structural designers.
Keywords: Quartzite, Coarse aggregate, Compressive strength, Aravalli range