The Analysis of Secondary Raw Materials Usage in Self-Compacting Concrete Production

This work presents study of influence of thermo-electric fly ashes, dolomite siftings, quartz sand and granite fines on the properties of self-compacting concrete (SCC). During the research a part of cement was replaced by fly ashes (from 5 to 30 %), or quartz sand fines (from 2.5 to 10 %), or granite fines (from 2.5 to 10 %) and granulometrical composition of aggregates was modified by dolomite siftings fr. 0/2. It was established that fly ash and dolomite siftings did not increase water quantity necessary in order to make the same consistence of self-compacting concrete. It can be explained that small particles of fly ashes and dolomite siftings are contained among the particles of sand and coarse aggregates, and therefore the granulometrical composition is improved. There was observed no bleeding or segregation in self-compacting concrete with fly ashes, though the input of cement was less. If a part of cement is replaced with quartz sand fines (quartz-sand fines fineness are 1.28 time more than fineness of cement), the bleeding is observed, because their water absorption is lower. The data of the experiments demonstrates that fly ashes and dolomite siftings positively modify the consistence of self-compacting concrete, increase the compression strength of concrete up to 15 %, when fly ashes was used, and up to 9 %, when dolomite siftings was used. Therefore admixtures of fly ashes and dolomite siftings reduce the shrinkage strains (with fly ashes up to 25.4 % and with dolomite siftings up to 18 %). There was established, that is rationally to replace 2.5…5 % of cement by quartz sand or granite fines