Cement_modified

Cement modified

Hydraulic cements and hydraulic cements mixed and cured by chemical reaction with water . They are also difficult and maintain stability underwater . Used in all aspects of concrete construction. During this reaction, called hydration , the cement combines with water to form a stone like mass

. When the paste ( cement and water ) in the aggregate ( sand and gravel , crushed stone or other granular material ) which acts as an adhesive is added and binds the aggregates together to form concrete

Hydration begins when the cement contacts water . Each particle of the fibrous cement forms a growth on the surface which gradually spreads until it is linked to the growth of other cement particles or adheres to adjacent substances . This development of the accumulation of fibrous strength leads to progressive rigidity , and curing .

Hydration is continued as long as the humidity and temperature favorable conditions ( curing agent) and space for the hydration products is available . Most of hydration and development of strength occurs in the first month , but continuous , albeit more slowly , over a long period with the appropriate temperature and humidity . Increases of more than 30 years there has been a continuous force

Portland Cement manufacturing materials used in the manufacture of Portland cement should contain sufficient amounts of calcium , silica , alumina and quantities of iron components . Raw materials are generally a mixture of lime ( calcium carbonate level ) , the material, such as limestone , and clay ( silica and alumina ) material such as clay , shale , fly ash , blast furnace slag or furnace . All of a process used wet or dry . In the dry process , grinding and mixing are carried out with dry materials . In the wet process , the

the grinding and mixing are carried out with the mixed with water in a form suspended materials .

The crude mixture was transferred to the prepared oven . Inside the furnace , the raw materials reach temperatures ( 14300C ) , a series of chemical reactions that make the molten material and create the cement clinker - ( gray - black granules ) , often of the size of the balls . The hot clinker is discharged from the lower end of the furnace and is transferred to various types of refrigerators . The clinker is ground fine so that substantially all thereof passes through a No. 200 sieve ( 75 microns ) sieve . Clinker tempered mixed with gypsum to produce a gray powder. This fine gray powder known as Portland cement .

Commodity career

rotary kiln

3CaO SiO2 Al2O3 SiO2 • • 2CaO 4CaO 3CaO • • • Al2O3 Fe2O3

CaCO3 (limestone) Al2O3 • 2SiO2 (clay, shale ) Fe2O3 ( iron oxide) SiO2 (silica sand )

clinker

interground Finished cement

A cement composition

• Plaster CaO + SO3 • 2H2O

oven

Processing these raw materials in the furnace

clinker

PORTLAND different types of cement types of Portland cement are manufactured to meet various normal physical and chemical requirements for specific purposes . Portland cement are manufactured to meet the specifications of ASTM C 150 , AASHTO M 85 or ASTM C 1157 . ASTM C 150 , Specification for Portland Cement offers eight types of Portland cement using Roman numerals designations as follows :

Type I Type II Type Normal moderate sulfate resistance of Type III high early strength low heat IV Type V high resistance sulfate Portland cement Type I Type I is the general purpose cement suitable for all uses where the special properties of other types are not required . Applications include concrete sidewalks , floors, reinforced concrete buildings , bridges, tanks, reservoirs , pipes, pieces of masonry and precast concrete products

Type II Type II Portland cement is used as a precautionary measure against the attacks of moderate sulfate is important. Used in structures or elements exposed to soil or normal plant

4

waters where sulfate concentrations are higher than normal but not unusually severe . Type II has properties moderate sulfate resistance , because it contains not more than 8% tricalcium aluminate ( C3A ) .

Type III Portland Cement Type III provides resistance to an early period , usually a week or less. It is chemically and physically similar to Type I cement except that the fine particles have been ground . It is used when the forms be removed as soon as possible or when the structure must be put into service quickly needed. When using in cold weather reduces the duration of the curing period using quick-setting cement in the following is recommended : ( a) In the construction of precast concrete , ( b) When the work is needed to be removed earlier reuse elsewhere, ( c) the repair of roads, ( d) especially in cold weather , where the rapid pace of development of force to reduce the vulnerability of concrete to freezing .

Type IV Type IV Portland cement is used when the speed is to be minimized and the amount of heat generated by hydration. Develops strength at a slower rate than other types of cement pace pace. Type IV cement is intended to be used in mass concrete structures such as large gravity dams , where the temperature rise resulting from the heat generated during cooking should be minimized. Type IV cement is rarely available.

Type V Type V Portland cement is used particularly exposed to severe sulfate action - principally when the soil or ground water with high sulfate content . desire

strength more slowly than Type I cement. High sulfate resistance in cement type V is assigned to a low content of tricalcium aluminate , no more than 5 % . Using less than the proportion of cementitious material and a low water permeability are essential for the functioning of the entire concrete exposed to sulfates . Same type V cement concrete can not withstand severe sulfate exposure if the concrete is high. ratio of water to sulphate resistant cement materials using cement in the following recommended conditions . (A ) Concrete to be used in the foundation and basement, where the soil is infested with sulfates. (B) The concrete used for the manufacture of pipes can be buried in the ground or support sulfate marshes. ( C ) The concrete used in construction of wastewater treatment . (D) The foundation piles ( e) chemical , fertilizer and sugar ( f) the industries of food processing and petrochemical projects ( g ) Construction of building along the coastal areas.

White Portland cement is a Portland white cement Portland cement true gray cement differs mainly in color. It is made to comply with the specifications of Type I or Type III , the manufacturing process is controlled so that the final product will be white . White Portland cement is made from selected raw materials which contain negligible amounts of iron oxide and magnesium. White Portland cement is mainly used for architectural purposes in structural walls , concrete and prefabricated fiber glass, cement paint , grout and decorative concrete .

* Blended hydraulic cements (not important ) blended hydraulic cements are produced by intimately and uniformly grinding or mixing two or more types of fine materials . Cements compounds are used in all aspects of the construction concrete in the same manner as the Portland cements. The raw materials are Portland cement , ground granulated blast furnace slag , fly ash, silica fume , calcined clay , other pozzolan , hydrated lime , and combinations of these pre- mixed materials . ASTM C 595 recognizes five main types of blended cements as follows: Type Type ES Portland blast furnace slag cement IP pozzolanic Portland cement type P Type I ( PM) pozzolan modified - Portland slag cement type S cement type I ( SM ) Portland slag cement modified

Cement vast expansive cement is a hydraulic cement which increases slightly during the period of rapid hardening after dosing. Upon expansion , for example , is limited by the steel reinforcement , concrete expansive cement ( also called compensation of shrinkage of concrete ) can be used to ( 1 ) to compensate the decrease in volume due to drying shrinkage . ( 2 ) To induce tensile stress in reinforcement ( preload ) . (3) Stabilize the dimensions of post-tensioned concrete structures in the long term of the original design .

Cement waterproof waterproofing cement , sometimes called cements are generally impermeable by adding a small amount of a hydrophobic additive such as stearate ( sodium , aluminum , or other ) of cement clinker during the finish grinding .

Made by white or gray, waterproof cement to reduce the transmission of the capillary water when there is little or no pressure , but not stop the transmission of water vapor . Grout used in tiling and painting.

Ettringite cements are cements ettringite calcium sulfoaluminate cements are specially formulated for individuals, such as the stabilization of waste materials applications . They can be formulated so as to form large amounts of ettringite to stabilize the individual metal ions in the structure of ettringite . Ettringite cements have also been used in applications of fast curing , including use in coal mines.

Rapid hardening cement rapid hardening , high early strength , hydraulic cement used in construction applications , such as coating the fast track where the development of rapid force ( responsible for the design or strength in about four hours) is necessary . These cements commonly used for calcium sulfoaluminate initial resistance. They are classified into types VH ( very high initial resistance) , MR (medium quality - high early strength ) and GC ( general construction).

SELECTION specifying Specification CEMENT cement for a project, be sure to check the availability of cement types as discussed below , the specifications must allow for flexibility in the choice of cement. The limitation of a project to a single type of cement, brand, or standard specification cement may cause project delays , and can not allow the best use of local materials. Cements with special properties that should not be necessary unless special features are needed.

When the share configuration Cement Portland cement is mixed with compounds of the chemicals in the water undergoes a series of chemical reactions that cause curing or setting . During the hydration process ( chemical reaction with water ) , a number of complex chemical compounds are formed. The formation of these compounds is not simultaneous . The setting of the cement action continues for a long period . Ordinary cement reached more than 90% of ultimate strength in 28 days. The following are the main

compounds formed during the action of cement in descending order of weight percentage .

Chemical Name Formula short notation

The percentages by weight

Tricalcium silicate 3CaO , C3S SiO2 50 2CaO dicalcium silicate , tricalcium aluminate SiO2 3CaO 25 C2S , C3A 12 tetra 4CaO Al2O3, Al2O3, Fe2O3 C4AF 8 gypsum CaSO4 , H2O CSH2 3.5

Tricalcium silicate ( C3S ) : Hydrates and hardens quickly and is largely responsible for the initial setup and initial resistance. Portland Cement high- exposure C3S higher strength to the top . After 28 days , the hydration of C3S is almost complete .

Dicalcium silicate ( C2S ) hydrates and hardens slowly and is largely responsible for the resistance increases beyond a week. C3S hydration practically begins when allowed to harden. In general, hydraulic systems , high cement blocks in C2S .

Tricalcium aluminate ( C3A ) : This compound and hydrates quickly hardens within about 24 hours after the addition of water to cement . A large amount of heat is released almost immediately and contributes little to the initial resistance . The gypsum is added to the Portland cement to slow the hydration of C3A . No plaster, Portland cement because C3A hydration to solve almost immediately after the addition of water ( the flash setting ) .

Tetra - calcium - aluminum ferrite (C 4 AF):

This compound hydrates rapidly , in about 24 hours after the addition of water to cement . But contributes little to the force. Most color effects are due to Portland cement C4AF .

Age, days

If water of greater than about 35 % in the mass of cement - water to cement ratio of 0.35 is used , while the porosity in the cured material remains , even after complete hydration . This is called capillary porosity . For full hydration of Portland cement is required only about 40 % water ( ratio of water to cement of 0.40 ) . If a higher ratio of water to cement to about 0.40 , the excess water is not necessary for the hydration of the cement remains in the pores or capillaries is used evaporates . If a cement of less than about 0.40 , water , a portion will remain non-hydrated cement is used .

Composites hydration reactions of Portland cement ( notation oxide )

Ingredients according to ordinary cement cement ingredients as mentioned above have the following functions . A . Lime ( CaO) : the force is applied to consolidate its deficiency causes cement to fix it quickly. Cal is unhealthy excess cement. Therefore, it is the rate at which the cement is carefully maintained. Two . Silica ( SiO2) : the strength of cement placement . Three . Alumina ( Al2O3) : This ingredient provides properties quick-setting cement . Weakens excess alumina cement

. April. Calcium sulfate (CaSO4 ) : This ingredient increases the time of initial setting of cement . May Iron oxide (Fe2O3 ) : This ingredient provides color, hardness and resistance to cement . 6 . Magnesia (MgO ) : This ingredient provides the hardness and color of the glue . If it is more than 5 percentage points then causes cracks after hardening mortar or concrete. 7 . Sulfur ( S ) : A small amount of sulfur is useful in the manufacture of a sound cement . The excess makes unhealthy cement.

Alkaline : The presence of which adversely affects the quality of the cement. and cause mold . If it exceeds 1 % in the cement , which leads to failure of the cement concrete . Efflorescence is a deposit of fine, white powder of soluble salts in water remaining on the surface of the masonry as the water evaporates . These salt deposits blooms tend to occur at the worst times , usually about a month after the building is constructed, and sometimes even a year after its completion.

PHYSICAL specifications of cement for cement to set limits on both their physical properties and chemical composition often PROPERTIES . An understanding of the importance of certain physical properties is useful for interpreting the results of tests of cement. Approximately 95 % of the cement particles have a size less than 45 microns . With average size of about 15 microns overall size distribution of the particles is called cement - cement ‖ finesse finesse affects the heat and the rate of hydration. A greater fineness of cement ( lower particle size ) increases the rate at which the cement hydrates faster and thus the development of force. The effects of increasing fineness on the strength of the dough is mainly present during the first seven days . Today, the fine is usually measured by testing air permeability which can indirectly measure Blaine surface of cement particles per unit mass . Cementos with finer particles have a larger surface area in square meters per kilogram of cement .

The force resistance refers to the ability of a hardened paste to maintain its volume . Lack of strength or the delayed destructive expansion can be caused by an excessive amount of free lime or magnesia hard burned.

In the strength test , 25 - mm square bars are exposed to high temperature and pressure in the autoclave to determine the stability of the volume of the cement paste . Consistency refers to the relative mobility of a suspension of cement mortar or to freshly mixed flow . During testing of cement pastes are mixed with normal consistency as defined by a penetration of 10 ± 1 mm Vicat plunger . The normal consistency of the method is used to regulate the water content of the dough. Adjusting the length of the initial setting time is the time water is added time until the dough is no longer time to fluid and plastic and fine-tuning is the time needed for the dough to acquire a degree hardness. The trials were conducted with the Vicat apparatus . The curing time is also affected by the fineness of the cement , the water-cement ratio and additives that can be used. Curing of the concrete are not directly correlated with the curing time of the pulp due to the loss of air or water on the substrate , the presence of aggregates , and because the temperature differences in the field ( versus temperature controlled laboratory tests) .

Vicat

Curing early (False Set and Flash Set) early cure is the rapid development of the stiffness of the work or the plasticity of the cement paste, mortar or concrete. This includes both the game and false flash game . FALSE is set evidenced by a significant loss of plasticity without changing the amount of heat shortly after mixing. From the point of view of implementation and management , false trends established in the cement cause any difficulty if the concrete is mixed for a longer than normal or remixed without additional water before being transported and placed time . False set occurs when a substantial amount of gypsum ( waste water ) in the dehydrated cement mill to form gypsum . Flash game or fast manifested by rapid and early loss of the ability to work as a paste , mortar or concrete. It is usually accompanied by the release of heat due mainly to the rapid reaction of aluminates.

Compressive strength compressive strength as specified by ASTM standards cement is obtained from tests of 50 mm (2 in.) . Mortar cubes tested in accordance with ASTM C 109 standard norm. These cubes are made and cured in the manner prescribed by a standard arena . Compressive strength is influenced by the type of cement , or more precisely, the composite composition and fineness of cement, in general , the intensities of cement ( mortar on the basis of evidence - kind) can not be used to predict strength concrete with a high degree of accuracy because of the many variables in the general, concrete mixtures , construction methods and environmental conditions in the field

The heat of the heat of hydration ( Joule / gr ) of cement is the heat released when cement and water react . The amount of heat generated is a function primarily of the chemistry

cement composition , with C3a and C3S compounds are primarily responsible for the evolution of high heat . The water - cement , the cement fineness , and the curing temperature are also factors related . An increase in the fineness , the cement content , and the curing temperature increases the heat of hydration . Although the Portland cement can generate heat for many years , the rate of heat production is higher at an early age .

Loss on ignition loss on ignition (LOI ) of Portland cement is determined by heating a sample of known weight of cement of between 900 ° C and 1000 ° C until a constant weight is obtained. The weight loss of the sample is then determined. Normally, a high fire loss is an indication of pre- hydration and carbonation , which can be caused by prolonged ACT values ​​ranging from 0 to 3% or improper storage .

Bulk density The bulk density of the cement is defined as the mass of the cement particles , in addition between the particles per unit volume . The apparent density of the concrete may vary greatly depending on how it is handled and stored . Portland cement pile that can weigh only 830 kg/m3 , whereas when it was consolidated by vibration , the same cement can weigh up to 1650 kg/m3. For this reason, the best practice is that the cement must be evaluated for each batch of concrete produced , rather than using a volumetric measurement

Transport and packaging Portland cements most are shipped in bulk by rail, truck, barge or bags. Pneumatic (compressed air) the loading and unloading of the transport vehicle is the most popular way of handling bulk cement . The bags of cement are also used for various construction purposes . In Jordan , a bag of Portland cement has a mass of 50 kg , and other countries , a bag of cement can have a mass of 25 kg or 50 kg.

Storage of cement concrete is a material sensitive to humidity if kept dry and retain its quality indefinitely. Cement stored in contact with moist air or moisture sets slower and weaker than the cement is dry. In the cement plant , and ready mixed concrete facilities , bulk cement is stored in silos. The relative humidity in a store or warehouse used to store cement bag should be as low as possible. All cracks and openings in the walls and ceilings must be closed. Cement bags should not be stored in moist soils, but must be based on platforms. Bags should be stacked to reduce air circulation

At the time of use, the cement should be free flowing and free of lumps. If pieces do not break easily , cement should be tested before being used in a lot of work . Standard stress tests should be performed when the cement quality is doubtful . Calculating the composition of clinker compounds four levels of clinker minerals can be estimated using a first draft in 1929 by the method of Bogue calculation. The method is based on the following assumptions: The process can be expressed mathematically ( in mass% ) as follows: Bogue equations C3S = 4.07C - 7.60S - 6.72A - 1.43f - C2S = 2.87S 2.85S - 0.75C3S C3A = 2.65A - C4AF = 3.04F 1.69F (Only valid when A / F  0.64)

Bogue potential composition : Oxide Analysis Example

Oxide 20.6 % SiO2 Al2O3 Fe 2O3 5.07 2.9 63.9 1.53 0.15 CaO 2.53 MgO 0.73 K2O Na2O SO3 15.8 LI

Calculating the phase composition of the sample of above cement

C3S = 4.07 ( 63.9 ) - 7.60 (20.6 ) - 6.72 (5.07 ) - 1.43 ( 2.90) - 2.85 (2.53) = 58.1 C2S = 2.87 (20.6 ) - 0.754 (58.1) = 15.632.65 (5.07) - 1.69 (2.90) = 8.5 C3A = 2.65 (5.07 ) - 1 69 (2.90) = 8.5 C4AF = 3.04 (2.90) = 8.8

Content equivalent alkali Na2Oe Na2Oe = Na2O + ( 0.658 x K2O ) = 0.73 0.15 = 0.85 ( should not be > 0.7) If > 0.7 , high concrete - cement is alkaline considered . However, give a good guide to the properties of cement in terms of strength development , heat of hydration and sulfate resistance . When the calculation of the composite cement composition ( instead of clinker ) to the normal convention is assumed that all of the SO3 is combined with Ca present ( ie , is present as calcium sulfate ) .

Relations control controls the composition of the clinker and plant performance optimization is greatly assisted by the use of three relations :

The critical factor is the ratio of the saturation control of the lime , which is determined by the ratio of lime , silica , alumina and iron oxide , and adjusts the relative proportions of C3S and C2S . Formula LSF ( Lime saturation ratio ) derived from studies of phase equilibrium high temperature. When RSA is greater than 100 % , there is an excess of lime , which can not be combined regardless of the time for which the slag is raised , and this remainder of the free lime in the clinker . As the level of uncombined low lime must be obtained ( ~ 3 % or less and preferably less than 2 % ) , the clinker LSF generally in the range of 95-98 % .

final