Research into the Long-Time Strength of Cement Stone with a Modified Structure

Abstract

The problem of a time-dependent gain of a cement dispersed system’s strength remains the focus of both domestic and foreign researchers in terms of its practical significance. To study the above problem, we used non-additive sulfate-resistant Portland cement grade 400 made by Volsk city plant with a normal density of 24 %. 9 series of samples were made from fresh Portland cement. The kinetics of changes in the cement stone’s physical and mechanical properties was observed on series’ samples for 9.5 and 18 years. The paper imparts the values of the cement, water, superplasticizer consumption and compaction ration derived from compacted cement paste after forming test pieces, numerical values of properties in check dates as a result of natural moisture exchange with the environment and drying of test samples to a constant mass at 105°C, as well as the degree of its hydration at the age of 18 years, which was determined by calculation from non-evaporable, that is, chemically bound, water, taking into account that its amount in fully hydrated cement comprises 23% of the cement mass. Changing of the superplasticizer introduction procedure, even with a minimum consumption of S-3, led to a change in the yield value of the cement stone. The experiments targeting to reveal the long-time behavior of a superplasticized cement stone allow us to speak of a clear trend in the influence of SP and its introduction procedure on changes in long-time strength values. However, this is only a trend, since there are many other factors of influence than those discussed in this paper, which testifies to the necessity for a more detailed study of this problem due to its complexity considering the development and application of a new generation superplasticizer and composite binders to construction practice.