No abstract

This work is devoted to development of optimum recipes of high-strength concretes based on filled binders with fine-milled anthropogenic mineral filler intended for earthquake resistant high-rise monolithic construction. The optimum recipes of concretes in this work have been developed on the basis of computations and experimental designing of cast concrete mixes with chemical additives and anthropogenic mineral fillers, as well as destructive inspection methods as the most precise for analysis of physicomechanical and deformation properties of concrete. The following raw materials have been used for production of high-strength concretes: natural quartz sands with the fineness modulus F.M. = 1.7-1.8; crushed limestone with the particles sizes of 5-20 mm; water reducing chemical additives and hardening retarder to control specifications of concrete mixes; plain Portland cement, grade PTs 500 D0; anthropogenic mineral additives (fillers) in the form of crushed concrete and ceramic bricks. Optimum recipes of monolithic concretes have been designed using anthropogenic raw materials including normal concrete grades with compressive strength of M30-M40 and high-strength concrete grades of M50-M80, characterized by high homogeneity of cement stone with significantly finer pores and lower shrinkage. Herewith, it has been established that fine-milled anthropogenic mineral filler in the form of crushed concrete and ceramic bricks at the ratio of 70:30, respectively, efficiently influences specifications of concrete mixes on their basis significantly increasing resistance of the mix against sedimentation and water gain. It has been established that the developed high-strength concretes based on filled binders with fine-milled anthropogenic mineral filler are characterized by high freeze–thaw resistance (from F400 to F600) and water tightness (W14 and higher), which is a solid base providing high lifecycle of such concretes.

No abstract

The method of introducing of finely ground granulated blast furnace slag (GBFS) in the composition of the cement as a result of dry mixing of the material with the additive is considered. The aim of the research was to study the effect of the addition of finely ground slag on the construction, technical, physical, mechanical, and structural characteristics of cement with mineral additives. The setting time was studied, the normal density of the cement paste with the addition of finely ground slag was determined. The dependences of the strength and porosity of the cement stone on the time of hydration of samples are built. The strength of the cement was determined by the national standard GOST 30744-2001. The porosity of the cement stone was determined by saturating the samples with an inert liquid. It has been established that the introduction of 3–5% of slag 1 and 1–3% of slag 2 provides an increase in the strength of cement stone during the first days of hardening on average by 37–44%; at the grade age - by 26–30%, decrease in porosity — by 17–28%. It is shown that the introduction of finely ground slag additives compacts and strengthens the structure of the cement stone. It has been established that grinding GBFS to a size of 1 μm (slag 1) is impractical because the obtained research results are comparable with the results when slag 2 is introduced into the cement composition.

No abstract