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Anwar Nizamutdinov, senior lecturer
Maria Kataeva, student
Norilsk State Industrial Institute, Russia
Championship participant: the National Research Analytics Championship - "Russia";
The way of modifying of low-branded concrete mixes in a highly mineralized limy and sulfur solute (ISS) Nature of dynamics of a set of durability of concrete can be various depending on concentration of sulfur in a solute. Final durability of the modified samples almost exceeds standard control samples of M100 and M170 twice. Thus the 3rd daily an indica-tor of Rcomp. of the modified samples are close to 28-days the control.
Keywords: modifying, concrete mixes, limy and sulfur solute, curing, durability.
Limy and sulfur broth became known in recent years as a solute ac-tivating hydration of a portlandtcement [1,2], and also as impregnating reagent for hardening of products from low-branded concrete [3,4].
For definition of complex influence of components of components of the highly mineralized limy and sulfur solute (ISS) on hydration processes depending on the weight of the full-turned polysulphidic sulfur and its concentration in a liquid phase us were carried out a series of ex-periences on samples of types of a concrete mix. Concentration of sulfur in a solute changed from the minimum 0,5 g/l to the maximum 220 g/l with fluctuation of standard durability from 10 to 20 MPa. Thus esti-mated dynamics of a set of durability both at early terms of curing, and at the subsequent to the final 28-days.
Materials and research methods
In experiment used a middle alyuminatny portlandtcement of M400 of Norilsk cement works (structure (%): C3S – 58,42%, C2S – 17,35%, C3A – 7,8%, C4AF – 13,25 %), large filler – limy rubble, small filler – river sand (a ratio between large and small filler 4:1). Preparation artificial satellite received dissolution of powder sulfur in the suspension of hydroxide of calcium heated to 90-95 °C. The weight structure of a dry mix was accepted in the ratio by S:Ca(OH)2 = 2:1. The mass of sulfur was accepted at the rate of 220 g/l in a final suspensions preparation.
At a disolutions of dry part of a concrete mix at first when hashing entered settlement quantity of a preparation, and then an additive of wa-ter brought to normal density of dough, considering thus as total of shut-ting liquid and quantity in it actually waters.
The received concrete mix filled in in forms of 10х10х10 cm in size. Durability of concrete samples determined by test of 4 samples of 10х10х10 cm in size for strength at compression on a laboratory press of 50 tons of force developing the maximum loading.
Results and discussion
Data of structures of samples and their tests are provided in tables 1,2. Their analysis shows that nature of dynamics of a set of durability can be various depending on concentration of sulfur in a solute, namely: steady course of curing without not filled dumping of durability observed at small doses of preparation artificial satellite (concentration of Sgeneral=0,5-2 g/l), are obvious not a steady course of curing observed in the range of concentration of sulfur in a solute from 2,5 g/l of the dissolved sulfur to rather high concentration of 150-180 g/l. And at last, we allocate area of the high concentration corresponding to saturated (215-220 g/l).
In effect each area of concentration the corresponding kinetic mode of process of the curing, differently influencing structure, structure and final durability of a cement stone is caused.
So, in the field of small concentration it is observed not only acce-leration of a set of early durability, but the increase in its final value in comparison with reference samples on water is noticeable.
Let's notice that efficiency of small additives depends also on con-centration of a portlandtcement in concrete. Additives on low-branded structures the maximum gain of final durability from three structures in which the content of cement changed from 12% in the smaller party are most effective is received on the structures containing 9,4% of cement, it made 118%.
The most part of the data provided in tables corresponding to wide area of concentration from 2,5 to 180 g/l, indicates rapid growth of dura-bility of samples of concrete in early terms and depressive character of a set of durability in the subsequent significantly worsening final indicator Rcomp.
The third mode of hydration curing of samples of concrete charac-terizing stability of a course of process, high early durability and its final 28-days the indicator caused by growth of concentration in a saturated solute up to 220 g/l of the general dissolved sulfur. In process of decrease in a mix of the content of cement grows and the hardening coefficient 28-days is model. So at the content of cement in a mix at the level of 12% the increase in an indicator of Rcomp. after 28-days curing made 112%, and at the content of cement of 9% made al-ready 193%, i.e. durability is almost twice higher, than at reference sam-ples. Nature of dynamics of a set of durability corresponds to basic pro-visions to earlier considered mechanism of hydration curing of cement in an artificial satellite at low for usual processes of hydration in water рН the liquid phase, being characterized negative redoks-potential .
Comparing kinetics of a set of durability of concrete at small doses of an artificial satellite (table 1) and that (figure 1) is its final durability with given roentgenograms, we come to a conclusion that at small doses of the artificial satellites which aren't influencing electrometric indicators of a liquid phase, the speed of a set of durability in early terms is caused by interaction of thiosulphate of calcium with hydrating aluminates of calcium and calcium sulfate with education by a new steady tiosul-fatkeeping phase hidrasulphataluminate C8Al8O12∙SO4∙S2O3∙24H2O, that (figure 1) is shown by the roentgenogram.
Results of test of the samples shut with a various consumption of sulfur
at the maintenance of a portlandtcement in a concrete mix of 9,4%
Contents, masses % in structures
Rcomp. 3-days, MPa (%)
Rcomp. 7-days, MPa (%)
Rcomp. 14-days, MPa (%)
Rcomp. 28-days, MPa (%)
Figure 1. Roentgenograms of products of hydration of knitting systems:
1 – portlandcement-water; 2 – portland cement-ISO (Sgeneral.=1 g/l);
3 - portlandcement-ISO (Sgeneral.=220 g/l)
At big doses the artificial satellite caused by sharp decrease рН process of hydration of silicates becomes depressive, and kinetics slow. In this case, owing to limited weight in a solute of the determined poly-sulfide capable potentially to provide restoration of Fe (III) to Fe(II), in-itiating hydration, this process proceeds quickly in early terms of curing.
In systems with the lowered concentration of these ions caused low as it is shown in table 1,2 and in figure 2 the tendency to Fe(III) restora-tion to Fe(II) is looked through only at the greatest possible concentration of sulfur when in a solute easily crystallizing hydrosilicate in the form of a macromolecular ampholyte is formed.
Thus, we will allocate the main technical advantage of preparation ISO, in technology of the concrete, shown by the data of tables reflecting dynamics of a set of durability during all standard term of curing in nor-mal conditions. First of all two modes of an strengthening with participa-tion of preparations artificial satellites providing the high speed of curing are allocated. In one of them the preparation is used as small additives in terms of the mass of the general dissolved sulfur, and in other as the sus-pension solute containing in solution and in suspensions part the most admissible mass of polysulfide and thiosulphate of calcium. Such dense limy and sulfur broth is considered as facilitating achievement effective a modifying threshold that in turn, facilitates realization of kinetic model of hydration transformation of the cement, providing both high early durability and final 28-days. So, the final durability of the modified samples almost exceeds standard control samples of M100 and M170 twice. Thus 3-days an indicator of Rcomp. of the modified samples are close to 28-days the control.