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Narov R. A., candidate of technical sciences Tashkent Institute of Architecture and Construction E-mail: allanazar86@mail.ru
CONCRETE WITH FILLING AGENT AND ACETONE-FORMALDEHYDE RESIN ADDITIVE
Abstract: The relevance of the use of mineral fillers, such as gliege and electrothermophosphoric slag is discussed in the paper. It was established that mineral additives should be used in conjunction with acetone-formaldehyde resin (AFR) additives to prepare concrete mixtures with high workability at reduced cement consumption. It is proved that the use of mineral fillers increases the strength properties of concrete by reducing the water-cement ratio and by increasing the proportion of cement hydration products. It is established that the most promising direction of the use of the developed concrete is the structures with high rates in frost resistance and water impermeability.
Keywords: ACF - acetone-formaldehyde resin, electrothermophosphoric slag, adsorption, structure formation, water demand, mobility, coarse-dispersed fillers, water impermeability, frost resistance.
Introduction and 450 kg/m3 decreases by 15-20 (10-15); 17-25 (11-16);
One of the most important problems in concrete and re- 19-28 (17-20)%, respectively. inforced concrete production is the problem of total economy Water demand of concrete mix on the mixed binding
of material, energy and labor resources while ensuring its high quality. Concrete technology currently has a wide range of tools to reduce resource intensity without compromising its technical properties. One of these tools is the use of active mineral fillers in concrete mixes in combination with effective plasticizing agent. There is a large amount of experimental and theoretical studies in this direction, and considerable practical experience has been gained in the use of fillers and additives such as gliege and electrothermophosphoric slag. As a result, significant economy of cement, increase in strength and durability, improvement of a number of other properties of concrete has been observed [1].
Complex application of AFR additive [2] and fillers from gliege and electrothermophosphorous slag provides significant economy in cement while improving technological, technical and operational properties of concrete. It was established that with rational dispersion of 0.15 m2/g of fillers and 0.15% of AFR additive, economy in cement in the mixed binder amounts to 28-35%. At the same time, the strength of the filled cement stone is comparable to the strength of ordinary Portland cement of the brand 400. Consider in more detail the effect of gliege and electrothermophosphoric slag fillers on concrete properties.
Concrete mix with mineral fillers and AFR additives in a wide range of workability have less water demand at sand-rubble ratio r = 0.33. Plasticizing effect of the combined use ofAFR additive and coarse-dispersed fillers is manifested due to decrease in total surface of contact, depending on initial mobility of concrete mix. So, as one would expect, water demand of concrete mixes with mobility of concrete mixes equal to 2.6, 10 and 20 cm with slag (gliege) fillers in the amount of 25 and 50% at the consumption of binding agent 290, 370
agent substantially depends on the adsorption activity of the filler. For example, water demand of a mix with slag is 5-10% less than with gliege, which is explained by the greater activity of the latter. The influence of quantitative content of coarse-dispersed fillers on water demand is manifested depending on the flow rate of binding agent in concrete mix. So, at a binder consumption of 370 and 450 kg/m3, an increase in fillers content from 25 to 50% contributes to a reduction in water demand of concrete mix, regardless of initial workability. At a consumption rate of binding agent 290 kg/m3, water demand of concrete mix with 50% of filling agent is slightly higher than at 25%. This increase in water demand is explained by the fact that in a mix with such content of binding agent the proportion of sand (its wetting ability is significantly higher than that of gliege or slag) increases.
Contribution of coarse-dispersed fillers to the change in concrete strength is determined by the particle size, their adsorption activity with respect to water and AFR resins. Reduction in water demand of ordinary concrete mixes, provided they have the same workability, leads to an increase in concrete strength. As a result of structure-forming effect up to a certain limiting filler content and reduction in water demand due to decrease in total contact surface, the strength of concrete increases. The increase in concrete strength significantly depends on AFR additive [3]. Further increase in filler amount despite the reduction in water demand and in hardening effect of AFR additive leads to a decrease in concrete strength, due to diluting effect and the decrease in active clinker part of cement.
The above is confirmed by the example of a concrete mix of workability 2, 6, 10 and 20 cm, obtained with standard fill-
Section 7. Materials Science
ers of Portland cement of brand 400 and coarse-dispersed fillers - gliege and slag.
Water content of concrete mix is favorably affected by relative increase in the strength of concrete with mineral filler. The greater the amount of water in initial composition of the mix, the higher the increase in strength. It. This can probably be explained by the fact that when the active clinker part of cement is replaced by mineral fillers, conditions are created for greater hydration of the binding agent and as a result less un-responded particles of the binder remain in the cement stone. On the other hand, the presence of a large amount of water in concrete provides favorable conditions for the hardening of the mixed binder in a moist environment. So, if the increase in the strength of concrete with gliege (slag) at the consumption of a binder of 290, 370 and 450 kg/m3 and sand-rubble ratio 0.5 and the mobility of concrete mix 2 cm is 15-35, respectively, then the increase in cast concrete is 35-43%. At an increase in fillers up to 50%, the strength of concrete with 0.15% ofAFR obtained from concrete mixes with mobility of 2-20 cm and binder consumption of290-450 kg/m3 reaches the values of reference concrete [4; 5].
Gliege Portland cement and slag Portland cement with electrothermophosphoric slag are most widely used for the construction of hydro-technical structures. Pozzolatic Portland cement with 30% of gliege in its mix hardens more slowly than ordinary Portland cement and at the age of 28 days it gains 80-85% of the brand strength. The same refers to Portland cement with slag. Therefore, for the concrete to be used in hydro-technical engineering the brand age is extended to 180 days. Thus, the long-term increase in strength is a characteristic feature of concrete with pozzolatic cement and slag Portland cement. The greater the value of concrete
Pozzolatic Portland cement with 25-27% of gliege, along with its use in hydro-technical engineering, is also recommended for the manufacture of products of ground parts of buildings and structures [5]. In this regard, it should be emphasized that the coarse-dispersed fillers in combination with AFR additives contribute in a greater extent to improving the weather resistance of concrete. Concrete with Portland
strength increase the lower the strength of 28 day old concrete, and concrete with pozzolatic Portland cement at decrease in binder consumption has a higher strength for a longer time
The effect of plasticizing agents on the growth of concrete strength over time depends on the mechanism of surface-active substance effect on the processes of hydration and hardening. Additives like SDV and SNV do not accelerate the strength of concrete. It follows that reducing the duration of a set of brand strength for concrete with pozzolatic and slag Portland cement is an important task. In this sense, it is preferable to use the additives of plasticizing action which accelerate cement hardening in concrete. AFR refers to these additives. The use of coarse-dispersed gliege fillers and electrothermophosphoric slag in combination with AFR additives can contribute to the successful solution of this problem. The nature of change in strength of concrete with coarse-dispersed fillers and AFR additives is similar to cement stone. Portland cement with coarse-dispersed gliege and slag with 0.15% of AFR differs by accelerated structure-formation and short duration of strength increase.
The increase in the strength of concrete with coarse-dispersed fillers and AFR additives depends on the amount of gliege and slag, as well as on water content in concrete mix. Relative increase in the strength of concrete with 25% of filling agent is significantly higher than that of conventional pozzolatic cement. In addition, the increase in the strength of concrete with 25% of filling agent is significantly higher after 3 months of hardening, comparing with the same indicator of concrete of factory-manufactured pozzolatic cement. As one would expect, the higher the growth of the strength of concrete with fillers, the higher the water content in concrete mix; see (Table 1).
cement and mineral fillers is characterized by good weather resistance and monotonous increase in strength at hardening. So, if compare 12 months of age concrete on ordinary Portland cement to 1 month of age, it has 48-53% increase in strength; while concrete with Portland cement and 25% of gliege (slag) are characterized by 66-75 (57-64), 68-77 (58-65%) increase, respectively.
Table 1. - Calculation of the strength of concrete at hardening in wet conditions
Composition of the binder in concrete Cone settlement, cm Compressive strength, MPa, in months
Brand of cement and its consumption, m3 Type of a filler and its consumption, kg/m3 1 3 6
Gliege Portland cement -320 - 2 17.2 22.4 27
Portland cement ordinary-240 Gliege -80 2 21.6 27.5 30.0
Portland cement ordinary -290 Gliege -100 2 19.5 31.8 32.4
Portland cement ordinary -240 Slag-80 2 20.2 29.3 31.7
Portland cement ordinary -290 Slag-80 2 18.6 31.2 32.2
Thus, the enlargement of the filler particles and the use of AFR additives have a positive effect on the increase in concrete strength in both wet and natural atmospheric conditions; this expands the fields of application of concrete with fillers. For the production of precast concrete products, slag Portland cement is effective along with ordinary Portland cement, and pozzolatic one is recommended for products and structures, which are subject to increased requirements in water and frost resistance [6].
Under standard modes of heat-moisture treatment of products, the strength of steamed concrete depends on the type and amount of filler and consumption of mixed binder. At 25% filling of concrete with 0.15% of AFR additive after steaming it gains 85-93% of design strength. Increase in amount of fillers up to 40-45% results in 70-75% growth in the strength of filled concrete after steaming. Thus, concrete with coarse-dispersed fillers - gliege and slag in combination with AFR additive can be effectively used in manufacture of precast concrete products.
Conclusion
So, based on the above one may conclude that the use of coarse-dispersed fillers, such as gliege and electrothermo-
phosphoric slag in combination with AFR plasticizing additive has a positive effect on water demand of concrete mix and on strength gain of concrete, improves its technological and operational properties. The studies have shown that with 25% introduction of coarse-dispersed gliege or slag and 0.15% of AFR additive into concrete mix, there is a decrease in water demand of concrete mix with gliege down to 17-25%, with slag - 19-28% depending on the binder consumption.
The results obtained by experimental method have shown that concrete with 25% of filler (gliege or slag) and 0.15% of AFR additives after standard modes of heat-moisture treatment gained 85-90% of design strength.
A positive effect of coarse-dispersed fillers (gliege and slag) on strength characteristics of concrete has been revealed. Concrete with coarse-dispersed fillers on average increases the strength by 20% per month more than concrete with ordinary Portland cement.
It is stated that with optimal dispersion of used fillers -0.15 m2/g and optimal filling - 25% of gliege and 50% of slag in combination with 0.15% of AFR additive the economy in cement in the mixed binder is respectively: 28-33% with gliege and 25-29% with slag.
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