White Cement Production

Introduction

Due to the large industrial, military and civilian construction in early 19b. work was underway to solve the problem of producing a hydraulic binder from an artificial raw material mixture consisting of limestone and clay. The new binding substance created was called Portland cement, since in a solidified form in color and strength it was very similar to the Portland stone mined near the city of Portland.

In 1825. In Moscow the book by Egor Cheliyev under the name "Full manual was published how to make the cheap and best marl or cement very strong for underwater buildings, kakto: canals, bridges, dams, basements, cellars and plaster of stone and wooden buildings". Egor Cheliev describes a method for producing binder from a mixture of lime or lime plaster with clay.

The inventor of modern Portland cement is often considered the Englishman Joseph Aspdin. In 1824, he received a patent for the manufacture of a binder from a mixture of lime and clay burning until its complete removal of carbon dioxide. Egor Cheliev has already described the method used to make hydraulic binder, which was more advanced than the method of Joseph Aspdin. Therefore, Chelieva is considered the founder of the production of Portland cement in our country. The capacity of the first plants was not large and amounted to tens of tons of cement per year.

Modern construction equipment is based mainly on the use of cement concrete and mortar. The wide variety of building structures, the peculiarities of their construction and the significant differences in service conditions under various types of aggressive influences caused the need to create cements with special technical properties, which could be used in the construction of hydroelectric power plants, in transport facilities, in the industrial production of prefabricated, conventional and prestressed reinforced concrete structures, in the construction of marine and oceanic structures, for highways and airfields, for drilling oil and gas wells, for the production of asbestos cement products, refractory concrete, etc. In 1962, on the production of cement, the USSR came out on top in the world, ahead of the United States.

Technological progress in the construction industry, the expansion of fundamental knowledge in the field of cement chemistry, the increased relevance of the problem of saving fuel and energy resources - all this caused the need to strengthen scientific work on special cements that differ in chemical composition.

Recently, white cement has become increasingly popular, with a number of advantages over gray, which makes it possible to safely call it the material of the 21st century.

White Portland cement is widely used for manufacturing:

* white concrete (including reinforced concrete );

* filling floors and terrasite floor tiles ;

* white plaster blends and masts ;

* cement-lime mortar ;

* different adhesive compositions ;

* artificial stone and brick ;

* products of small architectural forms and decor elements ;

* colored cements and concretes .

Since April 2005, Shchurovsky Cement OJSC has officially issued a new brand of white Portland cement - PC 500 D0 1 grade, the whiteness of which reaches 84-86%.

The main characteristics of the new white Portland cement are given below:

Physical and mechanical characteristics

Fineness of grinding:

• specific surface area, m2/kg............................................................................................................................................................................. 430 – 450

• balance on screen 0063,%..................................................................................................................................................... 1,0 – 1,5

• balance on the screen 0045,%............................................................................................................................................................................................................................................................................................................................................................................................................................................................ 2,0 – 3,0

• balance on screen 008,%..................................................................................................................................................................................................................................................................................................................... 0

Normal density,%.............................................................................................. 26,0 – 28,0

Water-cement ratio......................................................................................... 0,37 – 0,38

Setting time:

• start of setting, minutes..................................................................................................................... 90 – 120

• end of setting, minutes................................................................................ 150 – 180

Whiteness,%............................................................................................................. 81 – 83

Signs of false setting................................................................................. no

Steaming strength:

• 1 day: under compression, MPa................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 37 – 40

at normal hardening:

• 3 days: under compression, MPa............................................................................................................................................................................................................................................................................................................................................................................................. 36 – 39

• 28 days: under compression, MPa............................................................................................................................................................................................................................................................................................................................................. 52 – 55

• 28 days: in case of bending, MPa..................................................................................................................................................... 7,0 – 8,0

Gypsum content (as per SO3),%:.............................................................................. 2,8 – 2,9

Mineralogical composition of clinker,%

• C3S ................................................................................................................ 66,0 – 70,0

• C2S ................................................................................................................ 14,0 – 18,0

• CaOsv.................................................................................................................................................................................................................................................................................................................................. 0,80 – 1,70

• C3A ................................................................................................................ 12,0 – 14,0

• C4AF ................................................................................................................ 1,0 – 2,0

Product Characteristics

Technical requirements:

White Portland cement should be manufactured in accordance with the requirements of this standard according to the technological regulations approved in accordance with the established procedure.

Main parameters:

By material composition, white Portland cements are divided into the following species:

- Portland cement white (without mineral additives and filler additives);

-Portland cement white with additives (with active mineral additives and filler additives not more than 20%).

White Portland cements are divided into three varieties: 1, 2 and 3.

By compression strength at 28 days of age, white Portland cements are divided into grades: 400 and 500.

The white Portland cement symbol shall consist of:

cement names - white Portland cement (it is allowed to use the abbreviation of the name - PTB);

- cement grade - as per item 1.2.2;

- cement grades - as per item 1.2.3;

- values of maximum content of additives in cement (type of cement) - D0, D20;

- signs of cement plasticisation or hydrophobization - SM, GF;

-values of this standard.

Example of the symbol of white Portland cement with additives, 2nd grade, grade 400:

Portland cement white 2400D20GOST 965-89

Characteristics:

In the production of white Portland cements, the following are used:

- white Portland cement clinker, according to the chemical composition corresponding to the technological regulations;

-gypsum stone as per GOST 4013. Phosphogypsum, borogypsum, fluorogypsum can be used according to the relevant regulatory and technical documentation (NTD);

-Adding according to the corresponding NTD.

White Portland cement does not allow content of active mineral additives and additives, and white Portland cement with additives allows their total content up to 20% of cement weight, including active mineral additives of sedimentary origin not more than 10% and filler additives not more than 10%.

It is allowed to introduce special additives into white Portland cement not more than 2% of cement weight.

It is allowed to introduce process additives into white Portland cements that do not worsen their construction and technical properties, not more than 1%, including organic ones not more than 0.15% of cement weight.

By agreement of the manufacturer with the consumer, it is allowed to introduce plasticizing or hydrophobic additives into white Portland cements not more than 0.5% of the weight of cement in terms of dry substance of the additive.

The compression strength of white Portland cements at the age of 28 days should be at least:

39.2 MPa - for guaranteed grade 400;

49.0 MPa - "" "" "500.

The coefficient of variation of the ultimate strength of white Portland cements of each type and grade during compression at the age of 28 days, calculated by the results of tests for the quarter, should not be more than 7%.

The manufacturer shall determine the steaming activity of each batch of white Portland cement.

The light reflection factor in percentage of absolute scale shall be at least:

1) white Portland cements of varieties:

1st - 80,

2nd - 75th,

3rd - 70;

2) mineral additives:

fillers - 80,

active - 75;

3) gypsum - 70.

The content of sulfuric anhydride (SO (3)) in white Portland cements should be no more than 3.5% by weight.

The content of magnesium oxide (MgO) in the white Portland cement clinker should not be more than 4%, iron oxide (FeO) - more than 0.5%, insoluble residue - more than 1.5% by weight.

The beginning of the setting of white Portland cements should occur no earlier than 45 minutes, and the end - no later than 10 hours from the beginning of the closure.

White Portland cements should show a uniform change in volume when the samples are tested by boiling in water.

The grinding fineness of the white Portland cement should be such that the residue on the sieve with a cell size of 0.08 mm according to GOST 6613 is not more than 12% of the weight of the screened sample or that the specific surface area is not less than 250 sq.mXkg _ 1.

White Portland cements should not have signs of false setting.

Marking and packaging:

White Portland cements are marked and packed according to GOST 22237.

Process Part

3.3 WORKSHOP OPERATION MODE.

The operation mode of the workshop is the basis for calculating productivity, raw material flows, equipment. It determines the number of working days per year, the number of work shifts per day and working hours per shift.

Operation mode of main workshops and departments during the year:

quarry and crushing compartment - 307 days for 16 hours a day (4912);

raw material grinding unit - 307 days for 24 hours a day (7368);

cement grinding unit - 307 days for 24 hours a day (7368);

clinker firing shop - 337 days for 24 hours a day (8088);

silo-packing compartment - 365 days for 24 hours a day (8760);

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