Строительство и архитектура /4. Современные строительные материалы

A. Tertychny, O. Shynkevych, I. Mironenko

Odessa State Academy of Civil Engineering and Architecture

Assessment of the effectiveness of activation of fine grain mixtures and concretes modified with organic mineral fillers

The revealed experimentally-statistical regularities and the nature of changes in the rheological and physicomechanical properties are represented in the paper. One of the research tasks is to increase the efficiency of fine grain concrete due to the activation of solutions and concrete mixtures and using of mineral fillers of amorphous-crystalline or crystalline structure of various specific surfaces, as well as inorganic ultradispersed components such as: wollastonite, metakaolin and water-reducing additives – superplasticizer С-3 [1, 2].

Caused by the implementation of full-scale experiments, six-factor experimental-statistical models are calculated [3], they describe the change in the rheological and operational properties of the four kinds of mixtures (traditional preparation and in the activator mixer) under the influence of the above mentioned components and additives. On the basis of models, diagrams of the influence of all six factors and their mutual interference on the properties of the mixture and fine grained concrete were built. According to the obtained diagrams, general and particular trends in change of properties are established. It should be noted that the general and local trends for all studied mixtures are different.

Great importance in the use of raw materials of various genesis as components of composite astringents or mineral additives is acquired to issues related to the processes of its mechanoactivation by fine and superfine grinding. This is due to the fact that during the grinding process, the mineral raw material extends into a chemically active state, which contributes to give special properties to the copestones in the production of new modifiers, composite astringents and high-quality products based on them.

It is confirmed that, under the joint effect of activation and the test components, the properties of fine-grained mixtures and concretes can vary over a wide range [4]. The qualitative and quantitative content of additives-modifiers and fillers in the mixture affects on the properties of fine-grained concrete.

Thus, the possibility of reducing the W / C due to the plasticizing (diluting) action of the additive increases with increasing dosage of the plasticizer: for optimal dosages of cement and C-3, the decrease in water consumption is approximately the same in the majority of the studied compositions and is equal to 16-20% in average [4]. However, with a low W/C, the quantity of water, remaining in the early stages of hardening to other minerals may not be sufficient for their hydration and hydrolysis and for the processes of crystallization of emerging newgrowths. It should be concluded that decrease of W/C in a mortar or concrete mixture is not always appropriate from the point of view of the effect on structural stability and concrete strength. Such W/C decrease is advisable, which can occur due to excess water, not involved in the processes of water formation. According to the results of the experiments it can be concluded that this effect is achieved through the joint activation of all components of the mixture with using of water-reducing addives.

Local regularities of the effect of activation on the rheological properties of solution mixtures are established. It is shown that with increasing solids concentration the effect of dilution of mixtures increases; as a result of the W / C ratio can be reduced, that positively affects the properties of fine-grained concrete. Local regularities of the influence of the above mentioned mineral fillers and inorganic ultradisperse components on the physical and mechanical properties of fine-grained mixtures and concretes have been established.

Thus, the compressive strength and bending of solutions with fine-grained sand is above solutions with finely ground trepel, in 1,5-2 times. Activation of mixtures with fine-grained sand increases the strength of the solution by almost 20%. The bending strength of solutions with fine-grained sand is better than solutions with finely ground trefoil, 1.5-2 times. Addition of a wollastonite additive increases the compressive strength and tensile strength of all the above mentioned compositions up to 1.5 times.

Due to the addition of the IUD component and water-reducing additive C-3, the adhesion value can be increased by 2.5 times. More significant effect on adhesion has a specific surface of mountain meal. Due to a change in the specific surface area of mountain meal from 300-600 m²/kg, adhesion can be increased 3-4 times depending on the content of wollastonite.

For activated mixtures containing finely mountain meal, the thermal conductivity coefficient varies from 0.85 W / m C to 1 W / m C. For activated concrete mix with fine-grained sand, the coefficient of heat conductivity varies within 0.6 to 1.1 W/m C. It should be noted, that this value is significantly lower than value of the thermal conductivity of conventional sandy solutions, the thermal conductivity of which is 1.4 W/mC.

The general trends in water absorption of the activated and non-activated mixtures are different. Water absorption under the influence of the studied additives can vary within a wide range from 3 to 6 W/m C.

In the case of usage of fine-grained mixtures and solutions prepared in an activator mixer containing organo-mineral complexes, taking into account their close relationship with the composition of the mixture, it is necessary in each specific case to carry out a qualitative and quantitative adjustment of the compositions.

When choosing another type of mixture preparation (the traditional method), the ratio of components, including water / ratio, the type and content of additives, is also varied. The last one can be fulfilled on the basis of the obtained ES models.

The conducted researches show wide possibilities of modification of compositions of fine-grained concrete with organo-mineral ecologically harmless additives and testify to rationality of the complex development additives separately for the activated and not activated fine-grained concretes. During preparing activated fine-grained mixtures, the succession of charge sequence, the selection of the composition taking into account the granulometry, the type of mechanical action and the time of preparation are very important.

REFERENCES:
 
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2. Tolypin N.M. On the effectiveness of superplasticizers in fine-grained concretes, depending on the type of fine aggregate / N.M. Tolypin, Sh.M. Rakhimbayev, E.N. Karpachov // Bulletin of BSTU. V.G. Shukhov. - Belgorod, 2010. - №3. - P. 66-74.
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4. Shinkevich E.S. Effect of an organomineral complex on the properties of activated fine-grained concrete / E.S. Shinkevich, A.A. Tertychny, A.B. Tymnyak, A.I. Korchazhnikova // Bulletin of the Odessa State Academy of Construction. - Odessa, 2016. Issue. 62. - P. 194-200.