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MATHEMATICAL MODEL OF KINETIC MODES OF CURING THE PORTLAND CONCRETE MIXES IN LIMY AND SULPHUR SOLUTE

MATHEMATICAL MODEL OF KINETIC MODES OF CURING THE PORTLAND CONCRETE MIXES IN LIMY AND SULPHUR SOLUTE
Михаил Елесин, доцент, кандидат технических наук, доцент

Анвар Низамутдинов, аспирант

Елизавета Зайцева, студент

Норильский индустриальный институт, Россия

Участник первенства: Национальное первенство по научной аналитике - "Россия";

In article the chemical method of modifying of concrete mixes by a saluting in limy and sulfur broth is considered. Mathematical models of characteristic areas of dynamics of a set of durability of concrete depending on concentration of sulfur are found in a solute, namely: - steady course of curing at small doses of a solute of an artificial satellite (concentration of Scommunal = 0,5-2,5 g/l); - obviously not a steady course of curing observed in the range of concentration of sulfur in a solute from 3 - 180 g/l;- steady a curing course at the high concentration corresponding to saturation broths (to 220 g/l).

Keywords: mathematical models, modifying, concrete mixes, limy and sulfur solute, curing, durability.

 

At the heart of receiving the quick-hardening Portland cement which are characterizing at hydration by a high thermal emission, catalyzing reaction as a whole, the high subtlety of crushing of clinker among which silicates prevails high-basic alite lies.

There is a basis to consider that braking of spontaneously begun hydration potentially active alite in usual cements is caused by the kinetic restrictions arising first of all at a hydrolytic stage of a full cycle of reaction of dissolution of a mineral. They are caused by an overstrain of crystallization of hydroxide of the calcium which is allocating for a surfaces of grain alite, owing to development of solid-phase nature of reaction. It is remarkable that the subtlety of crushing of clinker among which silicates prevails bleaches, isn't so effective regarding acceleration of curing of cement since in comparison with alitovy cements doesn't provide due level of a thermal emission that is caused by absence in structure of the last of the gentle atoms of calcium hydrating with a high thermal emission. Such distinction in structure of communications of molecules alite and belite caused high energy of activation of reaction of a protonization at the last the communication, causing destruction of a molecule and release of atoms of calcium, mixes up in the liquid phase which speed depends substantially on concentration of protons in it.

It is represented obvious that action of the majority of known additives accelerators of curing is explained by improvement of solubility of hydroxide of the calcium, hydroxide preventing passivation of a surface of grain in a stage initially its spontaneous allocation [1].

As properties and practice of puzzolanovy cements activation of the most part of the Portland  cement containing among silicates both high-basic, and the low-main compounds of silicates at the expense of the adjustable worker рН of a liquid phase towards reduction testify, can become effective only when ensuring under saturation of a liquid phase with calcium hydroxide. Otherwise at the same time with reaction activation belite, caused by decrease рН additional restrictions to hydrolysis alite will be caused by reduction of the worker рН and braking of reaction of hydration as a whole.

Considerable interest represents calcium polysulfide. Its water solutions receive by dissolution of powder sulfur in the water suspension of hydroxide of calcium [2] heated to boiling. Such limy and sulfur solut promotes increase of activity of a Portland cement. Its components have the small cost, and application it allows to utilize sulfur which in some cases represents withdrawal of industrial production. Thus efficiency of activation is higher on cements as a part of which the persistent prevails bleaches that is explained by limited solubility of reagent and the deficiency of the entered polysulfide which isn't providing in case of highly alitovy cements of involvement in reaction of all weight of hydroxide which was allocated in system of calcium. In it the experimental solution of a problem of receiving quick-hardening Portland cement by activation of the cheapest belite [3] is concluded.

For finding of influence of concentration of sulfur in a solute used a alyuminatny Portland  cement of M400, large filler – limy rubble, small filler – river sand (a ratio between large and small filler 4:1). Solute artificial satellites 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, answering to a stoichometry. The mass of sulfur was accepted at the rate of 220 g/l in a final suspension preparation. At such high extent of saturation of a limy and sulfur preparation the ratio of polysulfide of sulfur (Spoli) in it and tiosulfatny (Stio) is approximately equal 4. The polysulphidic component of lye is presented by a mix tetra-and pentasulfide calcium about prevalence of the last.

At a solute of dry part of a concrete mix at first when hashing entered settlement quantity of a preparation, and then an additive of water brought to normal density of dough, considering thus as total of shutting liquid and quantity in it actually waters.

The analysis of the obtained data 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 concentration of a solute of an artificial satellite (concentration of Scommunal = 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 saturation broths (215-220 g/l).

For definition of mathematical model of kinetic modes of curing of concrete mixes [4] were put 3 full factorial experiments covering three areas of dynamics of a set of durability. As factors in all three cases were accepted: X1 — concentration of sulfur in a solute, g/l; X2 — a consumption of cement in a concrete mix, %; X3 — time of curing of concrete (considering logarithmic dependence of curing in time under standard conditions, for our kinetic modes we simplified this dependence to linear intentionally setting as the receiving purpose the general described model).

Table 1

Variation of factors for the first complete factorial experiment

Factors

-1

0

+1

Х1, g\l

0

1,25

2,5

Х2, %

9

12

15

Х3, days

7

18

29

Table 2

Variation of factors for the second complete factorial experiment

Factors

-1

0

+1

Х1, g\l

20

40

60

Х2, %

9

12

15

Х3, days

7

18

29

5 samples for each experience were made, output indicators of Y1 are presented to MPa in table 4 – average values of the received durability for the first factorial experiment; Y2 – average values of the received durability for the second factorial experiment, MPa; Y3 – average values of the received durability for the third factorial experiment, MPa.

Table 3

Variation of factors for the third complete factorial experiment

Factors

-1

0

+1

Х1, g\l

200

210

220

Х2, %

9

12

15

Х3, days

7

18

29

Table 4

The plan of the made complete factorial experiments

Experience number

Major factors

Intercoupling

Durability, MPa

Х1

Х2

Х3

Х1·Х2

Х2·Х3

Х1·Х3

Х1Х2Х3

Y1

Y2

Y3

1

+

+

+

+

+

+

+

30,5

21,0

30,0

2

-

+

+

-

+

-

-

30,7

9,9

29,5

3

+

-

+

-

-

+

-

11,1

14,7

19,3

4

-

-

+

+

-

-

+

10,1

9,4

18,0

5

+

+

-

+

-

-

-

24,5

30,0

24,9

6

-

+

-

-

-

+

+

25,3

11,9

30,5

7

+

-

-

-

+

-

+

8,77

10,2

11,8

8

-

-

-

+

+

+

-

6,3

4,2

11,6

The received initial equations of regressions, checked on the importance of coefficients and adequacy of model. Check of coefficients of the equations on the importance with coefficient use Styyudenta showed that in all equations there are not significant coefficients, that is the received models can be used for the general description of process, but not for concrete decision-making. After rejection not significant coefficients model checked on adequacy with use of criterion of Fischer. As a result to data processing the following equations three kinetic modes of curing of concrete mixes describing all in an artificial satellite were received:

y1= 18,41 + 9,34х2 + 2,19х3 - 0,56х1х2 + 0,66х2х3;
y2= 13,91 + 5,06х1 + 4,28х2 + 2,23х1х2 - 2,59х2х3 - 0,96х1х3;
y3= 21,95 + 6,77х2+ 2,25х3- 0,825х1х2– 1,23х2х3+ 0,9х1х3.

Analyzing the received models it is possible to draw a conclusion:

1) values а0 testify to initial considerable excess of durability of samples in areas small (to 2,5 g/l) and over big concentration (220 g/l) solute under equal other conditions;

2) in the first and in the third equation concentration of a Portland  cement (or concrete brand), in the second equation concentration of sulfur in a solute has the greatest influence;

3) joint influence of concentration of sulfur with the maintenance of a Portland cement in the first and in the third modes of curing slow down process that positively affects the initial stage of formation of a rigid framework of a material while in the second mode they accelerate process that brings to further to self-damage of samples and negative joint influence of these factors in time, that is with the third factor;

4) due to the lack of the third factor and its negative joint influence with other factors in the second equation, it is possible to decide with confidence that the kinetic mode of curing of concrete images in average area of concentration of sulfur (from 2,5 to 180 g/l) is not stable in time;

5) Additional factor of increase of durability in the third mode of curing is the joint strengthened action of high concentration of sulfur in time, that isthe first and third factor.

 

References:

  1. Elesin M. A. Polysulphurous connections in technology of construction materials: scientific edition. - Novosibirsk: NGASU, 2002. - 250с.
  2. Elesin M. A. Studying of kinetics of dissolution of sulfur in calcium hydroxide//the Magazine of applied chemistry, St. Petersburg, 1996, T.69, Vyp. 7, page 1069-1072.
  3. Nizamutdinov A.R. New way of hydrochemical modifying of Portland  cementny structures in a limy and sulfur solute//Nizamutdinov A.R. Umnova E.V. Botvinyeva I.P., Elesin M. And / Global scientific potential, Tambov, 2012, No. 10 (19), page 69-72.
  4. Elesin M.A. Pilot studies in construction: manual. - Norilsk: Scientific research institute, 2010,110 pages.
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Ваша оценка: Нет Средняя: 5 (1 голос)
Комментарии: 2

Пименова Галина

Вопросы корректирования свойств строительных материалов всегда были в центре внимания всех участников строительного комплекса. В настоящее время даже терминология в нашей области претерпевает существенное обновление - мы начинаем мыслить категориями "умный дом", "зеленое строительство". С учетом этого актуальность представленной здесь работы безусловна, проблема только в прочтении содержания статьи - отсутствует возможность оценки адекватного перевода. Однако культура представления материала очевидна. Спасибо.

mahmoud

Уважаемый Михаил Анатольевич! Привлекло название Вашей статьи. Актуальность этой тематики велика. К сожалению, прочитать статью не удалось, т.к. представлен некорректный перевод . Очень сожалею. С уваж., Загороднюк Л.Х.
Комментарии: 2

Пименова Галина

Вопросы корректирования свойств строительных материалов всегда были в центре внимания всех участников строительного комплекса. В настоящее время даже терминология в нашей области претерпевает существенное обновление - мы начинаем мыслить категориями "умный дом", "зеленое строительство". С учетом этого актуальность представленной здесь работы безусловна, проблема только в прочтении содержания статьи - отсутствует возможность оценки адекватного перевода. Однако культура представления материала очевидна. Спасибо.

mahmoud

Уважаемый Михаил Анатольевич! Привлекло название Вашей статьи. Актуальность этой тематики велика. К сожалению, прочитать статью не удалось, т.к. представлен некорректный перевод . Очень сожалею. С уваж., Загороднюк Л.Х.
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