Thesis is aimed at developing a technology for producing high-strength fine-grained concretes using granite siftings containing a significant amount of ≤ 0.16 mm particles as the main aggregate.
The results of the sedimentation analysis indicate that particles of the granite siftings less than 0.16 mm consist mainly of large particles, which can act as an inert filler of cement concrete. The content of dispersed particles, which may have a significant number of active centers, and contribute to the acceleration of nucleation of crystals (more than 40 ... 45%).
As the results showed, the degree of hydration of cement was in the range of 45 to 76%. The introduction of granite filler increases the homogeneous homogeneity of pores (α). This is especially noticeable in the initial terms of hardening of a cement stone. The composition containing the polycarboxylate superplasticizer hydrates more slowly, due to the lower water content of the cement paste due to the high water-reducing effect of the additive. The adsorption membrane, formed by a superplasticizer, is very permeable to water molecules and does not create significant obstacles for the hydration of cement and the formation of a solid structure of cement stone.
The performed experimental studies have shown that if the polycarboxylate superplasticizer is introduced into the concrete mixture, the negative effect of the dusty fraction of withdrawal is compensated, which positively affects the basic properties of the concrete mixture and the strength of the concrete during compression, while acting microfiller. The established technological parameters allow to obtain with application of granite releases with an optimized granulometric composition and when introducing an additive of superplasticizer concrete with a strength of 60...65 MPa.
An additional introduction of the aluminosilicate additive - metakacolin can increase the compressive strength at the age of 28 days to 70...75 MPa. The analysis of the corresponding quantitative dependences suggests that metakacolin, due to high dispersion and pozzolan activity, provides greater efficiency than granite dust. The increase of the strength of fine-grained concrete at the expense of metakaolin is (35-38)%, which is consistent with known data. As for the dusty fraction of withdrawal, the effectiveness of metakolin injection significantly increases with superplasticizer administration, although an increase in strength to (8...10%) is observed for unplasticized mixtures.
It is proved that reduction of pore sizes and increase of their homogeneity due to an increase in the number of dust particles in the presence of superplasticizer content of 0,5...1% contributes to increasing the frost resistance to 500...550 cycles. The investigated concrete can be classified as elevated (F100 ... F200) and high (F400 ... F500) frost resistance classes. The increase of the fraction less than 0.16 mm in the offsets without the superplasticizer due to increased water consumption of the concrete mixture and, accordingly, the open porosity and pore size causes a decrease in water proof from W6 to W2. In the presence of an amount of 0.5-1% additive, water proof increases to W8-W10.
The method of designing the composition of high-strength fine-grained concrete on granite siftings is developed, which allows determining the relationship between the components and the required content of additives, taking into account the required compressive strength, the fraction content is less than 0.16 mm in the compartments.
The nomograms of frost resistance and waterproofness of high-strength fine-grained concrete on granite siftings have been constructed, allowing additionally to take into account these parameters when designing the composition of concrete.
The proposed technological parameters for obtaining high-strength fine-grained concrete with the use of granite siftings with an increased content of particles ≤0.16 mm are confirmed by the release of a experimental-industrial party.
