Interconnection between Concrete Structure and Properties and Various Modifications

Abstract

In Russia it is promising to build high-speed networks of reinforced concretes with an increased resistance to various cyclic exposures. Such concretes must have an increased crack toughness achieved by modification of the structure of the concrete cement rock by the additives of superplasticizing agent, silica fume, etc. In the operated constructions concrete must preserve the structure and properties during the set service life. The ageing resistance of the cement rock structure is generally ensured by the phase composition and properties of hydrate phases obtained at application of the additives. The article contains the results of studying concretes modified by complex additives at different mechanical exposures. Cyclic tests were carried out at prismoidal specimens at the loading level of 0,9 of the load at failure by means of WAW-600kN test machine. Specimens of plain concrete and concrete modified by additives – plasticizers SP-1 and Glenium ACE 430, as well as complexes SP-1+silica fume and Glenium ACE 430+ silica fume were exposed to comparative studying of resistance to cyclic loadings. It has been determined that most durable in the cyclic loading conditions are concrete specimens with Glenium ACE 430+ silica fume complex additive. The tension tests at splitting, bending and compression confirmed the advantage of Glenium ACE 430+ silica fume complex. By means of the electron microscopy it has been determined that polycarboxylate superplasticizing agent contributes to amorphisation of the forming structure of calcium silicate hydrates. It is set that cyclic loadings cause crystallization of amorphized calcium silicate hydrates with recovery of Portlandite or recrystallization of primary hydrates.