Torpishev SH., Kuderin M.

Pavlodar Stadte University named after S.Toraygirov. Kazakhstan

CONCRETE DURABILITY MODIFYING ADMIXTURE

Periodically, many researchers have been focusing a great deal of attention on the issue of concrete strength development. Moreover the prevailing aim of this very sphere of investigations is considered to be the elaboration of various structure modifying methods, optimum in the way the void space arranged, if possible less expensive than the ones already known.

Authors present the complex chemical admixture due to which concretes of extra high water- and frost resistance, at relatively slump of 10 -12 cm, can be obtained.

The complex concrete-oriented admixture, contains sulfite-leavenous brew, natrium/sodium salt of non-organic acid, and additional emulsified mixture of mineral oils in terms of following masses ratio,%:

sulfite-leavenous brew ……………………… 13-24;

natrium salt of non-organic acid

(sodium nitrite, sodium nitrate, sodium sulphate) 19-29;

emulsified mixture of mineral oils …………… 47-68.

In this very suggested composition of complex admixture, the emulsified admixture of oil minerals is applied to be the plasticizing and air-entertaining agent containing by weight % synthetic residues of thermal polimerization 90-99, the post proceeding of an acetylation process 1-10.

The contribution of the emulsified oil minerals incorporation to the concrete mix can be explained in focus of various chemical reactions taking their place. Particularly indene, fulvene and stilbene forming the admixture and easily interacting with original portland cement (OPC) hydration products, on their hand form sparingly soluble doubled hydrate salts which excert gas-like H₂. Fluorene after being oxidized with atmospheric O₂, transfers to fluorenone or participating in similar displacement reactions, forms resistant compounds generating H₂ respectively. The very hydro-carbon molecules provide concrete mixture with entertaining of non-polar air vials, determine their dispersion and stabilization in the cement paste, for hydrocarbons plus H₂ plasticize the mixture. Having uniformly spread in the concrete mixture and being conventionally isolated ( actually air vials are not totally isolated, but less penetrative for water and solutions from without) pores act as peculiar absorbers and contribute the concrete frost-and water-resistance dramatically.

Since the prevailing distinguishing attribute of emulsified hydrocarbon compounds occurs to be their utter molecules’ asymmetry, which is balanced to provide their pronounced unwettability, thus chemical adsorption is the first stage only, and can be followed by chemisorptions or chemical reaction in the volume/medium of particles. There is a good reason to believe that admixture declines the interphase energy and facilitates disaggregation (deflocculation) of the particles. At the same time great amount of immobilized water is being disengaged and this very water is to provide the plasticizing effect. Moreover the adsorption layers themselves have capacity for flattening the surface roughness of particles thus declining the mutual friction coefficient. Due to this dramatically decreases the surface tension between mediums of liquid and air thus declining the effect of additional airentertaining.

The following components were used as constiuents/source materials for the complex admixture:

· sulfite-leavenous brew (SLV), meeting the requirements of Branch Standard -3-183-83, the by-product of sulfite waste liquor processing into nutrient or average yeast;

· natrium/sodium salt of non-organic acid represented by one of the following admixtures: sodium chloride [all-Union State standard 13830-84], sodium sulfate [all-Union State standard 4166-66], sodium nitrite [all-Union State standard 4197-74];

· emulsified mixture of mineral oils resulted via homogenization of gas-oil-kerosene fraction pyrolysis intermediates, synthesized at t^o 670 C^o over a superheated up to 610^oC steam.

To compare the effect of represented and yet known admixtures standard concrete mixes were made with slump of 10 cm. Specimens were tested in terms of/according to current standards/norms of durability [all-Union State standard 10180-78], frost resistance [all-Union State standard 10060-87], and water [non-]permeability [all-Union State standard 12730.0-78]

The emulsion is made in a certain amount of mixing water in electric mixers (2000 – 3000 rpm), providing its high dispersity and stability. Sulfite-levenous brew maintains the function of emulsifier/emulgator . (The) emulsion-mixing water ratio is incorporated to a dry mix of binding material and fillers during the process of concrete mixture elaboration on continuous/non-stoppable mixing for 1.5 -2 minutes.

The suggested issue is supposed to be solved via following solutions represented in Table 1.

Table 1

№	Complex admixture/agent content and admixture-incorporated concrete properties	Suggested contents(ratios)			Prototype
		1	2	3
1.	- sulfite-leavenous brew (SLV) - sodium salt of non-organic acid -sodium salt of oil-sulfite acids -emulsified mixture of oil products	13 19 - 68	19 24 - 57	24 29 - 47	61 15 24 -
2.	Compressive strength breaking point, MPa -at 28 days of moist curing -at 180 days of moist curing Flexture strength breaking point, MPa -at 28 days of moist curing -at 180 days of moist curing	37,3 40,5 3,8 4,3	38,6 41,6 3,98 4,54	35,5 39,8 3,76 3,99	34,3 35,5 3,55 3,69
3.	Water resistance, MPa	1,4	1,3	1,1	0,7
4.	Frost resistance, cycles	467	420	430	350

As it is seen from the Table 1 at 28 days of moist-curing, samples, made of concrete mixes and incorporated with the admixture of suggested content, as a fact reveal the compressive strength 21% higher than of the ones being planned for concretes of this class/type and 9% higher than the prototype. One can see the dynamics of compressive strength development further, at the age of 180 days. The compressive strength development at 180 days of moist curing was about 13%. The frost resistance of concrete incorporated with suggested complex admixture was 19% higher respectively and the water resistance was almost twice more then the ones of prototype.

Concretes incorporated with the suggested admixture can be successfully applied to industrial, civil, hydrotechnical and land-improvement engineering. Moreover they can be used in the following spheres of construction:

1) facing the canalization;

2) transport engineering;

3) establishing the bridge constructions and props;

4) monolith and prefabricated/combined tunnels.

Thus such incorporated concretes are to be of a great demand in constructions having high water- and frost-resistance requirements. The very admixture incorporated concrete mixes are of a great plasticity thus capable for being moved via pneumatic pavers and concrete pumps.