WO2010040325A1

WO2010040325A1 - A method of cement setting control

Info

Publication number: WO2010040325A1
Application number: PCT/CZ2009/000117
Authority: WO
Inventors: Karel Ling; Renata SZTANKOVÁ; Jaroslav Veverka; Libor SADÍLEK; Martin NOVOTNÝ
Original assignee: Elmos Trading Spol. S R.O.
Priority date: 2008-10-06
Filing date: 2009-10-06
Publication date: 2010-04-15
Also published as: CZ2008597A3

Abstract

Cement containing 5-99% of a finely ground inorganic substance having various specific surfaces, chemical compositions and physical properties, e.g. cement clinker and 1-95% of fine powder having hydraulic and/or pozzolana properties, with required specific surfaces, chemical composition and physical properties, e.g. natural pozzolana, industrial pozzolana, fly ashes, slags, tuffs, trasses, volcanic glass, calcined shale, limestone, etc., which is added to and mixed with the finely ground inorganic substance with various specific surfaces, chemical compositions and physical properties, creates a paste after mixing with water that sets and hardens due to hydration reactions and processes. The setting is controlled by means of a suitable adjustment of the ratios of water, the finely ground inorganic substance, e.g. cement clinker and the fine powder with hydraulic and/or pozzolana properties.

Description

A method of cement setting control

Technical Field

The invention relates to a method of cement setting control. The cement consists of a binder (finely ground inorganic substance) and a fine powder having hydraulic and/or pozzolana properties, which after mixing with water in a suitable ratio sets and hardens due to hydration reactions and processes.

Background Art

A large number of working procedures influencing the start of cement setting are known. The existing trend of influencing the hydration speed of cement consists in replacement of the universal gypsum with other control systems composed of more substances.

From the prior art represented by the documents (US patents US 3,959.004, US 4,306.912, US 4,306.912, US 4,168.985, US 4,551.176, US 5,076.851, UK patent GB 1 464 160, Czechoslovak patents CS 208 037, CS 208 038, CS 202 771, CS 225 063, CS 227 205, CS 274 936, CS 276 229 and Czech patents 280 609, CZ 283 298, CZ 294 810, CZ 293 322) gypsum-free cements are known that are based on ground cement clinker containing sulphonated polyphenolate or lignosulphonate, alkaline carbonate, hydrogen carbonate, hydroxide or silicate, or optionally other additives adjusting the start of setting, as e.g. boric acid, sodium potassium tartrate, etc., further optionally amorphous silicon dioxide, etc.

A shortcoming of solutions according to the state of the art is that during the subsequent setting control of cements (binders) is a higher viscosity and thus worse workability. The used admixtures that control setting very often reduce short-term strength, are economically inconvenient and do not meet standard requirements for the start of cement setting; therefore, their application is quite limited and another shortcoming is a relatively high quantity of the additive for setting-time control.

Another shortcoming of the existing methods for the production of cement, especially of the Portland cement type, which has been becoming important especially in the recent years, is a contribution to the production of "greenhouse gases", mainly CO₂. Approx. 5% of the global production of CO₂ comes from cement productions, out of which 50% results from chemical processes during firing in the cement furnace and 40% comes from the used fuel. During the production of 1 ton of clinker approx. 800 kg of CO₂ are generated.

Also, the consumption of energy during cement production represents a principal item influencing the economy of the production process. Approximate power consumption during the production of 1 ton of clinker varies, depending on the use fuel, in the range of 3 - 6 GJ per 1 ton of cement, i.e. approx. 833 - 1,666 kWh. A significant part of power consumption is also represented by the clinker grinding process.

Disclosure of Invention

The above mentioned shortcomings are removed by a cement in accordance with the invention containing 5-99% of a finely ground inorganic substance with various specific surfaces, chemical compositions and physical properties, e.g. a cement clinker and 1-95% of a fine powder having hydraulic and/or pozzolana properties, having required specific surfaces, chemical composition and physical properties, e.g. natural pozzolana, industrial pozzolana, fly ashes, slags, tuffs, trasses, volcanic glass, calcined shale, limestone, etc., which is added to and mixed with the finely ground inorganic substance having various specific surfaces, chemical compositions and physical properties to create a paste after mixing with water that sets and hardens due to hydration reactions and processes. The setting is controlled by means of a suitable adjustment of the ratios of water, the finely ground inorganic substance, e.g. cement clinker and the fine powder with hydraulic or pozzolana properties or both. Therefore, no setting-time control is necessary in this cement.

This combination can also be applied to cement types having specific properties, e.g. barium and strontium cement, quick-setting cement, aluminate cement, etc.

The cement in accordance with the invention achieves criteria of cement conformity for general as well as special use.

The cement in accordance with the invention is beneficial from the economic as well as environmental point of view as high quantities of fine powder having hydraulic or pozzolana properties are processed while at present this powder is deposited in dumping sites to a greater extent. The cement according to the invention exhibits very high chemical resistance both to a sulphurous water not containing any minerals and to a sulphate water as well as an aggressive carbon dioxide.

The cement in accordance with the invention is compatible with common plasticizers and super plasticizers.

The cement according to the invention makes it conveniently possible to use for the preparation of a concrete mixture, besides standard mixing water, also sea water or brackish water. These types of water can also be used for concrete treatment.

Best Mode for Carrying Out of the Invention:

Example 1

To finely ground cement clinker with the specific surface of 370 m².kg^"1 30% of siliceous- aluminous fly ash from electrostatic precipitators is admixed, based on the weight of the clinker. From the obtained cement a paste with W = 0.49 is prepared that starts to set after 180 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1:3 with continuous grain size (standard sand), which is stored in the form of bodies having the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 2O⁰C. After 48 hours the bodies exhibit the compressive strength of 10.2 MPa, bending strength of 2.2 MPa, after 7 days the compressive strength of 25 MPa, bending strength of 4.5 MPa and after 28 days the compressive strength of 34.8 MPa and bending strength of 5.6 MPa.

Example 2

To finely ground cement clinker with the specific surface of 370 m².kg^"' 10% of blast-furnace granulated slag, based on the weight of the clinker, and 25% of siliceous-aluminous fly ash from electrostatic precipitators, based on the weight of the clinker, are admixed. From the obtained cement a paste with W = 0.47 is prepared that starts to set after 80 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 2O⁰C. After 48 hours the bodies exhibit the compressive strength of 9 MPa, bending strength of 2 MPa, after 7 days the compressive strength of 26.3 MPa, bending strength of 4.9 MPa and after 28 days the compressive strength of 42.6 MPa and bending strength of 7.9 MPa.

Example 3

To finely ground cement clinker with the specific surface of 300 m².kg^'1 25% of siliceous- aluminous fly ash from electrostatic precipitators, based on the weight of the clinker, and 10% of limestone, based on the weight of the clinker, are admixed. From the obtained cement a paste with W = 0.6 is prepared that starts to set after 70 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 2O⁰C. After 48 hours the bodies exhibit the compressive strength of 16.4 MPa, bending strength of 3.2 MPa, after 7 days the compressive strength of 23 MPa, bending strength of 4.7 MPa and after 28 days the compressive strength of 38 MPa and bending strength of 5.6 MPa.

Example 4

To finely ground cement clinker with the specific surface of 450 m².kg^'' 55% of siliceous- aluminous fly ash from electrostatic precipitators, based on the weight of the clinker, is admixed. From the obtained cement a paste with W = 0.5 is prepared that starts to set after 120 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 2O⁰C. After 48 hours the bodies exhibit the compressive strength of 10.1 MPa, bending strength of 2.2 MPa, after 7 days the compressive strength of 23.7 MPa, bending strength of 4.4 MPa and after 28 days the compressive strength of 33.7 MPa and bending strength of 5.7 MPa.

Example 5

To finely ground cement clinker with the specific surface of 450 m².kg^"1 50% of siliceous- aluminous fly ash from electrostatic precipitators, based on the weight of the clinker, and 30% of blast-furnace granulated slag, based on the weight of the clinker, are admixed. From the obtained cement a paste with W = 0.48 is prepared that starts to set after 285 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 20⁰C. After 48 hours the bodies exhibit the compressive strength of 8 MPa, bending strength of 1.8 MPa, after 7 days the compressive strength of 20.8 MPa, bending strength of 4.1 MPa and after 28 days the compressive strength of 33.2 MPa and bending strength of 5.5 MPa.

Example 6

To finely ground cement clinker with the specific surface of 370 m².kg^"1 5% of siliceous- aluminous fly ash from electrostatic precipitators, based on the weight of the clinker, is admixed. From the obtained cement a paste with W = 0.55 is prepared that starts to set after 120 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 20⁰C. After 48 hours the bodies exhibit the compressive strength of 34 MPa, bending strength of 4.9 MPa, after 7 days the compressive strength of 45.5 MPa, bending strength of 8.1 MPa and after 28 days the compressive strength of 57 MPa and bending strength of 9.9 MPa.

Example 7 To finely ground cement clinker with the specific surface of 450 m².kg^"' 95% of blast-furnace granulated slag, based on the weight of the clinker, is admixed. From the obtained cement a paste with W = 0.46 is prepared that starts to set after 290 minutes. A mortar prepared from this cement, at the ratio of the cement to sand of 1 :3 with continuous grain size (standard sand), which is stored in the form of bodies with the dimensions of 4x4x16 for 24 hours in a saturated water steam medium, is left in water for 28 days at the temperature of 2O⁰C. After 48 hours the bodies exhibit the compressive strength of 7.4 MPa, bending strength of 1.8 MPa, after 7 days the compressive strength of 16.5 MPa, bending strength of 3.6 MPa and after 28 days the compressive strength of 34.7 MPa and bending strength of 4.7 MPa.

Examples 1 - 7 were performed in accordance with the CSN EN 196-1, CSN EN 196-2, CSN EN 196-3, CSN EN 196-6 and CSN 72 2113 standards.

Industrial Applicability The cement in accordance with the invention can be used for the production of high-strength concrete, for the production of reinforced and pre-stressed monolithic as well as precast structures exposed to high stress, for the production of complex concrete products, for the production of common concrete, especially transport concrete and massive concrete structures, supporting walls, etc. Further, it can be used for the production of concrete that is permanently exposed to damp or wet medium (waterworks), production of less demanding concrete and concrete products, production of cement road surfaces, concrete for airport surfaces, concrete for foundation and other structures in an aggressive soil medium, concrete for structures exposed to aggressive water, vapours and gases, for the production of concrete structures exposed to influences of sea water, or for the production of concrete treated by and produced with the use of sea water. Gypsum-free cement in accordance with the invention can also be used for the production of concrete with resistance to media with an increased content of sulphates (sulphate- proof) or for the production of concrete structures with increased resistance to ionizing radiation.

The production of cement in accordance with the invention can preferably reduce emissions of CO₂ generated during cement production, namely up to approx. 50%, depending on the produced type of cement. Also, the power consumption can be significantly reduced, all while maintaining the required properties of the produced cement type.

Claims

1. A method of cement setting control, characterized in that it is carried out by means of a suitable adjustment of mutual ratios of water, a finely ground inorganic substance and a fine powder having hydraulic and/or pozzolana properties.

2. The method of cement setting control in accordance with claim ^characterized in t h a t the fine powder having hydraulic and/or pozzolana properties, having required specific surfaces, chemical composition and physical properties, e.g. natural pozzolana, industrial pozzolana, fly ashes, slags, tuffs, trasses, volcanic glass, calcined shale, limestone, etc., which is ground together with the fine inorganic substance, or the fine powder is added to it after grinding because it has sufficiently fine surfaces while the content of the fine powder is from 1 to 95%.

3. The method of cement setting control in accordance with claims 1 and 2, characterized in that the finely ground inorganic substance having various specific surfaces, chemical compositions and physical properties, e.g. Portland clinker, aluminate clinker, barium clinker, strontium clinker, etc. is ground together with the fine powder having hydraulic and/or pozzolana properties or is added to it after grinding while its content is from 5 to 99 %.

4. The method of cement setting control in accordance with claims 1 to 3, c h a ra c t e riz e d i n t h a t the specific surface of the finely ground inorganic substance is from 200 m².kg^"1 to 700 mlkg^"1.

5. The method of cement setting control in accordance with claims 1 to 4, characterized in that the suitable content of water is achieved at the water coefficient W = 0.25 to 1.5, based on the weight of cement.