INFLUENCE OF A DISPERSED LIME ON TIGHTENING CEMENT STONE

The work is devoted to the actual direction of development of the construction industry - to increase the strength of concrete structures and products on the basis of portland cement due to the introduction of mixing with water in the composition of the raw mix of special applications. The promising addition is pre-vibroactivated lime.

The effect of the degree of dispersion of quenched lime and its quantitative content in cementitious sand and cement mixes on cement hardening processes is investigated in this work. The optimal parameters of vibration activation are established: amplitude of oscillations of blades of vibrator bunker 6-7 mm with a frequency of 50 Hz, consistency of quenched lime in the form of a paste like mass with an addition of 48% water, duration of vibration processing - not less than 20 to 45 minutes. The maximum increase in the strength of the cement stone provides the duration of vibration activation for 45 minutes. Introduction of the application of lime causes increased compressive strength at all stages of curing, especially effective its effect manifests itself from the 7th day. At the same time, the most effective is the introduction into the composition of mixtures of the application of vibration activated lime in the amount of 2% of the mass of cement, which provides a strength increase of up to 36% for 28 days of hardening.

Using methods of X-ray and electron-microscopic analysis, processes of forming the structure of a cement stone at different stages of curing have been studied. The data of X-ray analysis of cement stone with the application of vibroactivated lime showed that by phase composition on the 7th and 28th days of hardening, it is represented by the remains of unreacted clinker minerals C2S and C3S, and from the new forms, intense diffraction peaks of Portland and less intense reflexes of etringitis are recorded. Instead, the diffractograms do not show clearly expressed maxima of calcium hydrosilicates, which are difficult to identify at the specified curing stages due to their still weak crystallization stage.

With the help of an electron microscopic analysis, it was established that the total mass of cement stone consists of hydrophilic clinker minerals, which are largely hydrophilized and whose surface is coated with an amorphous gel-like substance, from which the needle-like clusters of calcium hydrosilicates appear in different directions. At the same time, the maximum degree of crystallinity of the products of hydration is fixed for specimens containing 2% of the application of vibroactivated lime.