Cement.

Cement

Catalogue Basic Requirements 3.1 Introduction 3.2 Portland cement
3.3 Portland cement with mineral materials

Basic Requirements Class hour Contents 2 tests In this chapter we will
5 lectures 2 tests Contents In this chapter we will briefly introduce the classification, advantages and production of cement. mainly introduce Portland cement and Portland cement with mineral admixture, including: definition, composition, hydration, setting and hardening, technical properties and test, corrosion and prevention, characteristics and application.

Basic Requirement Emphasis Definitions of 6 kinds of Portland cement
Hydration properties of Portland cement composition Mechanism of hydration, setting and hardening Technical properties and test Corrosion and prevention Characteristics Applications

Basic Requirement Difficult points Notice
Mechanism of hydration, setting and hardening Relationship among cements Notice This chapter is one of the most important parts in the course. To connect the study of different cement To pay attention to the property differences and causes Back

Chapter 3 Cement §3.1 Introduction Advantages of cement Classification
Summary Back

Portland cement was developed in the nineteenth century.
It has become one of the most important building materials. It has complex chemical compositions, but the main cementing compound is calcium silicate hydrate. Ordinary Portland cement can be modified for high early strength, for sulfate resistance, for low heat production, or for use in masonry.

For architectural use, it can be formed white, black, or in various colors.
High-alumina cement and magnesium-oxy- chloride cement are different from Portland cement in chemical compositions. Property variety Low cost Plasticity Simple process Durability Bonding well with bar Hydraulicity Advantages of Cement Back

Classification Application General Cement Portland Cement
Ordinary Portland Cement Portland Blast-Furnance-Slag Cement Portland Pozzlana Cement Portland Fly-Ash Cement Composite Portland Cement

Characteristic Cement
Classification Special Cement Masonry cement Oil well cement Characteristic Cement Quick-hardening cement Expansive cement Sulfate resisting cement Modified cement

Sulfoaluminate Cement
Classification Back Chemical Component Portland Cement Common engineering Aluminous Cement Sulfoaluminate Cement Rush- repairing project, earlier strength project, engineering constructing in winter, anti-corrosion and freezing resistance Earlier strength/Antisulfate/Rush-repairing project/Anchor/ underground engineering

Summary Among many types of cement used in China, Portland Cement accounts for more than90% of the products of cement. We should stress the study of the compound, technical property, and application of Portland Cement in cement learning. Back

§3.2 Portland Cement Production and Composition of Portland Cement
Hydration, Setting and Hardening of Portland Cement Technical Properties of Portland Cement Corrosion and Prevention of Hardened Cement Characteristics and Application of Portland Cement Back

What is ‘Portland Cement’？
Mixing materials Gypsum Raw Clinker Portland Cement Portland cement is formed by grinding together clay-bearing and time-beating materials (usually clay and limestone) and is heated to about 1450℃. At 650℃ the limestone separates into CO2 and CaO. When the silica reaches the point of fusion, the atoms are able to move about and the CaO combines with SiO2 and a small amount of Al2O3 and Fe2O3, forming Portland cement clinker. The clinker is then ground to a fine powder, and a small amount of gypsum is added. Back

Production and Composition of Portland Cement
Limestone Bleeding 1450℃ Clay Grinding Raw material Clinker PⅠ Grinding Gypsum Iron ore powder PⅡ Mixing materials Fig Process to Produce Portland Cement

Mineral Compounds and Properties
Main Mineral Compounds of Portland Cement Clinker include (in tab.3.2.1): Tricalcium silicate Dicalcium silicate Tricalcium aluminate Tetracalcium aluminoferrite Properties of the compounds are in the tab3.2.2:

Tab.3.2.1 Mineral Compounds of Portland Cement
Chemical structural formula Abbreviation Tricalcium silicate 3CaO·SiO2 C3S Dicalcium silicate 2CaO·SiO2 C2S Tricalcium aluminate 3CaO·Al2O3 C3A Tetracalcium aluminoferrite 4CaO·Al2O3·Fe2O3 C4AF

Tab.3.2.2 Properties of Mineral Compounds
Back Mineral types Tricalcium silicate Dicalcium silicate Tricalcium aluminates Tetracalcium aluminoferrite Abbreviation C3S C2S C3A C4AF Content (%) 37-60 15-37 7-15 10-18 Hydration speed fast slow fastest Hydration heat much little most more Strength high early low later high low Anti- corrosion good fine poor excellent Shrinkage middle better big small

Hydration, Setting and Hardening
of Portland Cement Hydration Mechanism Ways to avoid flash set Mechanism of modifying setting time by gypsum Not much gypsum Hydrate formed by clinker hydration Back

Hydration Mechanism When mixed with water, Portland cement hydrates and forms heat 3CaO·SiO2+H2O CaO·2SiO2·3H2O+Ca(OH)2 Triealcium silicate hydrates rapidly and forms earlier strength and earlier heat of hydration. Tricalcium silicate is formed in a kiln when the charge contains an abundance of lime, and hence the greater amount of CaO in the reaction.

Hydration Mechanism 2CaO·SiO2+H2O 3CaO·2SiO2·3H2O+Ca(OH)2
Dicalcium silicate hydrates slowly and is responsible for strength increase in concrete at later ages. The heat of hydration is liberated slowly. More dicalcium silicate is formed when the raw materials contain less lime.

3CaO·Al2O3+H2O 3CaO·Al2O3·6H2O
Hydration Mechanism Tricalcium aluminate hydrates rapidly and liberates a large amount of heat. If this reaction were not controlled, concrete would set so rapidly (flash set) that it could not be used in modern construction. 3CaO·Al2O3+H2O 3CaO·Al2O3·6H2O

Hydration Mechanism 4CaO·Al2O3·Fe2O3+H2O CaO·Al2O3·6H2O+CaO·Fe2O3·H2O The addition of iron or iron ore to the raw materials lowers the percentage of tricalcium aluminate. The iron reacts with the tricalcium aluminate, forming the tetra calcium aluminoferrite. This compound does not add significantly to the properties of concrete, but does cause the charge in the cement kiln to liquefy at lower temperature (lowers the point of fusion), thus reducing the energy required in cement manufacture.

Ways to avoid flash set A small amount of gypsum (CaSO4·2H2O) intergrounding with the cement clinker retards the hydration reaction of tricalcium aluminate so that the calcium silicates can set firstly.

Mechanism of Modifying Setting Time by Gypsum
The protecting layer is formed by wrapping up the clinker by Calcium sulfoaluminate hydrate needle crystal, hinders the entry of water, slows down hydration and stops flash setting. Thus the gypsum can modify the setting time. 3CaO·Al2O3·6H2O+ H2O+CaSO4·2H2O 3CaO·Al2O3·3CaSO4·31H2O Ettringite

Not Too Much of Gypsum Hardened cement corrosion
After hydration, tricalcium aluminate will react principally with sodium and magnesium sulfate, found in soil and water, which causes the concrete to disintegrate Moderate sulfate-resisting cement limits the percentage of tricalcium aluminate to 8 percent. This compound is limited to 5 percent in sulfate-resisting cement.

Hydrate formed by clinker hydration
In full hydration hydrate produced by clinker hydration is as following: Calcium silicate hydrate gel(70%) Calcium hydroxide (20%) Calcium aluminate hydrate Calcium ferrite hydrate Ettringite Fig Degree of hydration

Hydration, Setting and Hardening
of Portland Cement Setting and Hardening Definition Process of Setting and Hardening Factors Influencing Setting and Hardening of Portland Cement

Definition Setting Process Hardening Process
The process of losing plasticity and becoming dense of the paste, which is formed by mixing the cement and water. Hardening Process The process of forming hardening cement paste by the paste, which loses plasticity and its strength increases with time.

Process of Setting and Hardening
Initial period Initial dissolving and hydration; mobile and plastic lasting for 5-10min Incubation period The performance of gel layer surrounding cement is excellent; particle growth; lasts for 1h The cement particle expands , bonds and hydrates after the cracking gel layer; Lasts for 6h; Porous spatial net- coagulation structure;Losing plasticity Setting period Fillings of gel to capillaries; lasting for 6h~several years. Hardening period

Process of Setting and Hardening

Factors Influencing Setting and Hardening of Portland Cement
Factors such as: fineness and types of cement, blend of gypsum, age, temperature and humidity which influence setting and hardening of Portland cement. Age Blend of Gypsum Humidity Temperature Types Fineness Factors Fig3.2.3 Factors influencing Setting and Hardening of Portland Cement Back

Technical Properties of Portland Cement
Fineness Setting Time Soundness of the Portland Cement Strength Other properties Back

Fineness and Properties
Fineness related to the surface area touching with water, so it influences the setting/hardening speed and the properties of cement. Tab Fineness and Properties of Cement Small D < 40μ Great High Strength Too small Easily Cost High Large D >100μ Low

Fineness Requirements of Portland Cement
Specific Surface Area According to GB Specific Surface Area >300 m²/kg The distribution of particle size is measured by specific surface area instrument Measure the change of flow velocity when a little air gets across hardening cement paste Fig Specific Surface Area instrument

Setting Time Normal consistency Definition Testing methods
Engineering significance

Normal consistency and water requirement of normal consistency :P(%)
It refers to the consistency when the sinking distance of solid cone is 28±2mm. Water Requirement of Normal Consistency It refers to the water needed for forming normal consistency cement paste in a certain method.

Two test methods for water requirement of normal consistency
Fixed water quantity method Changed water quantity method We usually follow this when conflicting. Employed mostly by the green hands

Fixed water quantity method
Forming cement paste with normal consistency : 500gC+500×p%W Measure p%

Fixed water quantity method
Fig3.2.5 instruments for normal consistency

Testing Methods Test setting time of cement paste of normal consistency at stated temperature and humidity by cement paste setting time testing instrument. Fig3.2.6 setting time testing instrument

水泥凝结时间的测定

Setting Time Initial setting time
The time from watering cement to cement paste beginning to lose plasticity Standard require≮45min 1-3h for the domestic cement in use Test distance between testing needle and round container is 4±1mm Engineering significance For the purpose of mixing, transportation, placing, vibrating and masonry, the initial setting time should not be early.

Setting Time Final setting time
The time from watering cement to cement paste completely losing plasticity and beginning to have strength Standard require≯390min 5-8h for the domestic cement in use Test The sinking distance of the testing needle is 0.5 mm Engineering significance The final setting time should not be late so that the cement can be hardened quickly, have the fixed strength and continue to work.

Soundness of the Portland Cement
Definition Reasons for poor dimensional stability Evaluating dimensional stability

Soundness of the Portland Cement
Definition The process of reducing and averaging volume of the cement in the process of cement hardening. Poor dimensional stability Uneven volume change happened in the process of cement hardening, such as cracking, blending The opposite of soundness of the Portland cement causing the decrease of quality

Reasons for Poor Dimensional Stability
Three reasons too much disassociated f- CaO too much disassociated f-MgO too much gypsum Three reasons too much disassociated f- CaO f-MgO gypsum

Reasons for Poor Dimensional Stability
The hydrating speed of the overburnt f-CaO or f- MgO is slow, f-CaO or f-MgO begins to hydrate after cement hardening and causes the hardened cement to expand and crack. When added too much, gypsum continues to react with calcium aluminate hydrate to form calcium sulfoaluminate hydrate, whose volume increase 1.5 times as big as gypsum and causes the hardened cement paste to crack. At this time, sulfoaluminate hydrate is called cement bacillus.

Evaluating Dimensional Stability
Boiling Method -accelerating test There are two methods to evaluating dimensional stability: Disc method Evaluating dimensional stability of boiled cement disc by observation Le chatelier soundness method Measuring expansion of hardened cement after boiling

水泥安定性的测定饼法

Evaluating Dimensional Stability
Fig Poor dimensional stability Fig Boiling testing instrument Fig Le chatelier soundness testing instrument

Restrict The accelerating test method can only test the over-use of f-CaO f-MgO and gypsum can not be tested by the above test So they must be controlled in the producing process to avoid over-use Standard defines MgO≯5%，gypsumSO3≯3.5%

Strength test Compressive strength and bending strength
can be tested by producing standard specimen （ 40×40×160） which is made by C:S:W=1:3:0.5 and cured in the standard condition C:S:W=1:3:0.5 test Standard specimen 40 × 40×160 Compressive strength Cured under the standard condition Bending strength

Fig.3.2.10 Strength testing instrument

Fig3.2.10 Strength testing instrument
Compressive strength instrument bending strength instrument Fig Strength testing instrument

抗压强度抗折强度

Strength Grades According to 3 days and 28 days compressive strength
3 days and 28 days bending strength Portland cement can be classified into 42.5，42.5R, 52.5，52.5R, 62.5, 62.5R grades. The strength of every age should not be lower than the required number in GB table. The cement of every grade can be classified into 2 types, high early- strength(R) ones and normal ones. 62.5R 62.5 52.5R 52.5 42.5R 42.5 Strength Grade

Technical Properties Analysis
The technical indexes of the cement before using are the 4 items: fineness, setting time， strength and soundness. Fineness, setting time， strength and soundness must be qualified. The cement can be used according to the requirement of the lower grade, if only the strength is unqualified. If only the strength is unqualified Cement of the lower grade

Other Properties Density Bulk Density
g/cm3, commonly 3.1g/cm3 Bulk Density kg/m3 Density of long-kept cement decreases a little. Free CaO combines with H2O, CO2 in the air to form Ca(OH)2 and CaCO3 with low density.

Alkali Content Alkali content which is donated by calculated value of Na2O+0.658K2O avoids alkali- aggregate reaction. Alkali content of low alkali cement≯0.6%， or treat between supply and requisitioning parties.

Hydration Heat Most hydration heat is given out at the initial period of hydration and its quantity depends on chemical compound and fineness of cement, mineral admixture and intrusion aid. The higher C3S, C3A, the finer the particle, the bigger hydration heat, the more advantageous to the construction in winter, but more harmful for mass concrete Back

Corrosion and Prevention of Hardened Cement
Introduction Representative Corrosion Types Denudation Corrosion Sulfate Corrosion Magnesia Corrosion Carbonate Corrosion Acid Corrosion Origin of Corrosion Prevention of Corrosion Back

Introduction The hardened cement paste can still be hardened and the strength can also increase in the normal condition (humid environment or in water). Corrosion of Hardened Cement The structure will be destroyed. Strength and durability will be decreased, or totally damaged in corrosive substance. Back

Representative Corrosion Types
Denudation Corrosion Sulfate Corrosion Magnesia Corrosion Carbonate Corrosion Acid Corrosion Alkali Corrosion Back

Denudation corrosion Denudation corrosion
It refers to the corrosion caused by dissolution of calcium hydroxide in soft water.

Denudation corrosion Preventive measure
In hard water, the following reaction happens On the surface, dense calcium carbonate layer will be formed to protect concrete Beforehand concrete should be carbonized in carbonizing apparatus-Artificial carbonation. Ca(OH)2 + Ca(HCO3) CaCO3 + H2O

Artificial carbonation
Denudation corrosion Preventive measure Ca(OH)2 + Ca(HCO3) 2 CaCO3 + H2O On the surface, dense Calcium carbonate layer will be formed to protect concrete Beforehand concrete should be carbonized in carbonizing apparatus Artificial carbonation

Sulfate Corrosion Characteristics
Sulfate medium-sea water, underground water and so on Sulfate reacts with ingredients in hardened cement to form dilatancy crystal and destroy the hardened cement Crystallization and expansion

Magnesia Corrosion MgCl2+Ca(OH)2 = Mg(OH)2+CaCl2
Characteristics Magnesia medium-sea water, underground water and so on Magnesia reacts with ingredients in hardened cement to form freely soluble and dilatancy crystal , and destroy the hardened cement. MgCl2+Ca(OH)2 = Mg(OH)2+CaCl2 MgSO4+ Ca(OH)2+H2O = Mg(OH)2+CaSO4·2H2O Crystallization and expansion Freely soluble

Carbonate Corrosion Ca(OH)2+CO2+H2O CaCO3+2H2O CaCO3+H2O+CO2 Ca(HCO3)2
Characteristics Carbonate medium-sea water, underground water and so on. Carbonate reacts with ingredients in hardened cement to form freely soluble and destroy the hardened cement. Ca(OH)2+CO2+H2O CaCO3+2H2O CaCO3+H2O+CO Ca(HCO3)2 Freely soluble

Acid Corrosion O H CaSO OH Ca SO CaCl HCl ) (   Characteristics
Acid medium-industry environment and so on Acid reacts with ingredients in hardened cement to form freely soluble crystallization, expansion and destroy the hardened cement. Freely soluble Crystallization and expansion O H CaSO OH Ca SO CaCl HCl 2 4 ) (  

Alkali Corrosion Dry air Freely soluble Characteristics
Alkali reacts with ingredients in hardened cement to form freely soluble crystallization, expansion and destroy the hardened cement Freely soluble Dry air Crystallization and expansion Back

Origin of Corrosion Hydrates such as CH, C-A-H are liable to react with some corrosion substance. The inner structure of hardened cement is not perfectly compact. Influence from environment. Back

Prevention of Corrosion
Selection of cement varied with environment features. Improving denseness of cement. Prevented coating should be covered on the surface of concrete. Impregnated concrete should be employed for the special concrete project. Back

Characteristics and Application of Portland Cement
High Strength high strength concrete and prestressed reinforced concrete Fast hardening fast setting and high early-strength, construction in winter, prefabrication, site cast and so on. Excellent freezing resistance the winter construction and project suffering from circles of freezing and thawing in cold area Back

Characteristics and Application
of Portland Cement Poor corrosion resistance the project with erosion substance, such as fresh water and sea water. Poor heat resistance the project with the requirement for heat resistance Large heat of hydration disadvantage to mass concrete, but advantageous to thermal storage construction in low temperature season

Characteristics and Application
of Portland Cement Excellent abrasion resistance road and field. Carbonation resistance strong protecting effect and applicable to the environment with high consecration of CO2 Back

§3.3 Portland Cement With Mineral Materials
Chapter 3 Cement §3.3 Portland Cement With Mineral Materials Mineral Admixture Ordinary Portland Cement (P.O) Portland granulated Blast-furnance-slag Cement (P.S) Portland-Pozzlana Cement (P.P) Portland fly-ash cement (P.F) Composite Portland Cement (P.C) Back

Mineral Admixture Definition Classification Active admixture
Introduction Secondary Hydration Reaction Function of Active Admixture Inactive admixture

Mineral Admixture Definition Improving Property
processed or raw mineral materials when grinding Adjusting Strength Grade Lowering Costs Mineral Admixture is the processed or raw with the purpose of improving cement property, adjusting cement grade and lowering costs.

Classification by performance
active admixture (Pozzolan Admixture) and inactive admixture（filling admixture） Classification by performance Inactive admixture （filling admixture） Active admixture (Pozzolan Admixture)

Active Admixture Introduction
It is not hardened after grinding and watering. But after mixed with lime and water A secondary hydration activity happens To form hydraulic cementing material activity Volcanic ash activity

Hydraulic cementing forms
Secondary Hydration Reaction SiO2 +mH2O + xCa(OH) xCaO·SiO2·nH2O Hydraulic cementing forms Consumption Ca(OH)2 Active admixture Al2O3 +aH2O + yCa(OH) yCaO·Al2O3·bH2O

Active Admixture Although active admixture is not a compound of Portland cement. The replacement of a portion of cement with active admixture changes the properties of the various types of cement.

Secondary cementing reaction
Hydration Reaction First reaction Portland cement hydrates Takes place when portland-pozzolan cement is used or when a pozzolan is added to concrete with portland cement Secondary cementing reaction

Characteristics of Secondary Hydration Reaction
Sensitivity to temperature Low reaction speed at common temperature High reaction speed at high temperature Consumption Ca(OH)2 Improving the structure of pores

Consumption Ca(OH)2 When the calcium silicates hydrate, hydrated lime is one of the products of hydration This leaves a reactive soluble salt in the concrete mass and is responsible for the white encrustations and efflorescence which appears in hydraulic structures where the lime has leached to the surface and reacted with CO2.

Function of Active Admixture
Improving products. Lower costs. Better the property of cement. Adjusting strength grade of cement. Expanding application range. Benefiting to prevention of environment. Making full use of industry rubbish. Protecting the environment.

Better the property of cement
Reducing temperature rise Pozzolanic action occurs very slowly. Consequently the temperature rise is much smaller

Better the property of cement
Reducing alkali-aggregate expansion A pozzolan is an active, amorphous silica. Reacting readily with any alkali in the presence of moisture. The pozzolan, as a very finely divided silica. Readily consuming the Na2O and K2O from the cement. Completely dispersing the expansive silica. Consequently, the alkalis are not available to react with reactive aggregates.

To Reduce Harmful Effects of C3A
The harmful effects of tricalcium aluminates can be reduced by use of a pozzolan. If the pozzolan is used to replace 30 percent of the Portland cement, the percentage of tricalcium aluminates in the total cementing material will also be reduced by 30 percent.

Types of Active Admixture
Fly ash Granulated blast furnace slag Other active admixture

Fly ash is the flu dust that is precipitated in the smokestacks of coal-burning power plants Granulated blast furnace slag composed of the fine particles of shale in the coal which form tiny spheroids of glass when exposed to the hot flame of the furnace

Other active admixture such as silica fume diatomite ground pumice other volcanic rocks

Inactive Admixture Characteristics
It can’t form hydraulic cementing material with gelatification after grinding and mixing with lime in water. Quartz Clay Slow cooling slag Back

Ordinary Portland Cement
Introduction Technical Properties Strength demand Application Back

What is Ordinary Portland Cement
Mixing materials P.O Grinding Hydraulic cementing material Clinker Ordinary Portland Cement is the hydraulic cementing material. It is made by grinding a few mixing materials and proper gypsum. The maximum quantity of mixing materials should be no less than 15%. Gypsum

Technical Properties Sieve residue ≯10%
Measure the screening rate of the square mesh sieve with 0.08mm Screening Method Negative pressure Sieving method Water pressure sieving method Dry sieving method

Technical Properties Strength grades
It can be classified into 6 strength grades :32.5, 32.5R , 42.5R , 42.5, 52.5, 52.5R Requirements of strength are in the following table. Final setting time can not exceed 10h

Same to Portland cement
Technical Properties Same to Portland cement Other requirements of technical properties and range of applications are same with Portland cement. The mineral compound is in the range of Portland cement for a few quantity of mixing materials.

Tab.3.3.1 Strength Demand of Ordinary Portland Cement
Strength grade Compression strength (MPa) Fracture strength（MPa） 3d 28d 32.5 32.5R 42.5 42.5R 52.5 52.5R 11.0 16.0 21.0 22.0 26.0 2.5 3.5 4.0 5.0 5.5 6.5 7.0

Application of P. O It is the main type of common cement and mainly used in the project of concrete and reinforced concrete. The application range is the same with Portland cement. Back

What is Portland granulated blast-furnance slag Cement
Hydraulic cementing material Clinker granulated blast-furnance slag Gypsum Grinding P.S It refers to the cement which is formed by Cement clinker, granulated blast- furnance slag and a little gypsum Quantities of granulated blast-furnance slag is 20%～70%

Technical Properties Its property is different from Portland cement and ordinary cement Reasons: In cement, Portland cement and ordinary cement is more and the clinker is little Technical performance: It can be divided into 6 types:32.5, 32.5R, 42.5, 42.5R, 52.5, 52. 5R Its early hardening is low Other technical requirements are the same with Portland cement

Tab.3.3.2 Strength Demands of P.S,P.P,P.F
Strength grade Compression strength (MPa) Fracture strength（MPa） 3d 28d 32.5 32.5R 42.5 42.5R 52.5 52.5R 10.0 15.0 19.0 21.0 23.0 2.5 3.5 4.0 4.5 5.5 6.5 7.0

Comparing to Portland Cement and Ordinary Cement
Characteristics of P.S Comparing to Portland Cement and Ordinary Cement Strength is low in the early days and high in the later days The hydration of slag cement takes 2 steps: hydration of cement clinker; secondary hydration reaction. In the early days of a secondary hydration, the strength is low with low speed and little hydration. But it is contrary to the later days. It is applicable to the prefabricated member cured in the middle days and projects with bearing slowly. But it is not applicable to the projects with the requirement for higher early hardening.

Characteristics of P.S Strong anti-corrosion and poor carbonation resistance It is applicable to the water concrete and marine concrete Not used in house with high concentration of CO2 Because of the low content of calcium hydroxide. Low hydration heat It is applicable to the project with mass concrete

Characteristics of P.S Temperature sensitivity
It is applicable to the high temperature cuing because of temperature sensitivity. Low anti-freezing The early hardening is low . Water requirement of volcanic ash is big. Heat resistance It is applicable to the project with requirement of heat resistance concrete.

Characteristics of P.S Poor permeability
The large quality of mixing materials result in sharp arris of blast-furance slag and low water requirement and retentivity; therefore it can form bleeding channels easily. Note: the latter 2 items are the features of P.S. and other properties same with PP、 PF cement. Back

What is Portland-Pozzlana Cement
Pozzlana mixing materials P.P Grinding Hydraulic cementing material Clinker It refers to the cement which is formed by cement clinker, Portland-Pozzlana mixing materials and a little gypsum Quantities of Pozzlana mixing materials are 20%～50% Gypsum

Characteristics comparing to P.S Similar points
Strength is low in the early days and high in the later days. Strong anti-erosion and poor carbonation resistance Low anti-freezing Low hydration heat Temperature sensitivity

Characteristics comparing to P.S Different points
Impermeability is excellent when cured in humid condition or in water. Volcanic ash reacts with lime to have the effect of expension and forms calcium silicate hydrate, which densifies the structure of hardening cement paste. It can easily shrink/powdery when it is in the dry condition. Because hydration cannot happen in the dry condition and strength keeps stable, calcium silicate hydrate gel can also make cement shrink and form crack. It is not available to the construction in dry area Back

What is Portland fly-ash cement
P.F Grinding Hydraulic cementing material Clinker It refers to the Fly ash and a little gypsum Quantities of Fly ash is 20%～40% Gypsum

Characteristics comparing to P.S Similar points
Strength is low in the early days and high in the later days Strong anti-erosion and poor carbonation resistance Low anti-freezing Low hydration heat Temperature sensitivity

Characteristics comparing to P.S Different points Low early-strength
The fly ash form a double cementing action after 1~3 months because the fly ash surface structure is dense. It is available to the slow construction. Small shrinking, excellent crack resistance, because of dense surface structure and little water absorption. Excellent workability of blended concrete. Back

Composite Portland Cement P.C
It refers to Portland cement which is formed by Portland cement clinker and two or more kinds of mixing materials. Characteristics 32.5～52.5R 6 strength grades Others are the same with P.O. Requirements of strength（GB ）

Tab.3.3.3 Strength Demand of P.C
Strength grade Compression strength (MPa) Fracture strength（MPa） 3d 28d 32.5 32.5R 42.5 42.5R 5.25 52.5R 11.0 16.0 21.0 22.0 26.0 52.5 2.5 3.5 4.0 5.0 5.5 6.5 7.0

Chapter 3 THE END

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