Maximum Percentage Of Which Species Is Present In Portland Cement?

Maximum Percentage Of Which Species Is Present In Portland Cement
The cement contains 35 to 40 percent lime, 40 to 50 percent alumina, up to 15 percent iron oxides, and preferably not more than about 6 percent silica.

Which species has highest percentage in Portland cement?

(B)- CaO: 50-60%, SiO2: 29-25%, Al2O3: 5-10%, MgO: 2-3%, Fe2O3: 1-2% and SO2: 1-2% (C)- SiO2: 40-50%, CaO: 30-40%, Al2O3: 10-20% (D)- CaO: 50%, SiO2: 50% Hint: Portland cement is a grayish coloured finely ground particles of calcareous and argillaceous material.

Which compound has maximum percentage proportion in cement C3A C4AF C3S C2S?

A typical example of cement contains 50–70% C3S, 15–30% C2S, 5–10% C3A, 5–15% C4AF, and 3–8% other additives or minerals (such as oxides of calcium and magnesium). It is the hydration of the calcium silicate, aluminate, and aluminoferrite minerals that causes the hardening, or setting, of cement.

What is the percentage of dicalcium silicate in Portland cement?

Calcium Orthosilicates – Dicalcium silicate is an important constituent of Portland cement clinker (comprising 10%–40% by weight of the phases present). It exhibits a number of polymorphs, classified by Bredig, 15 the hydraulically important polymorph in Portland cement being β-C 2 S.

  1. This also appears in slags, refractories and belite cements.
  2. On cooling from elevated temperatures, α -C 2 S passes through a number of closely related polymorphs α ′, α L ′ and α H ′ 16 (the latter two formerly were not distinguishable from α ′) before transforming to the β -form at 630°C.
  3. The transformation at lower temperature to the γ -modification is accompanied by a volume increase responsible for the well-known phenomenon of ‘dusting’.

These phase transformations are summarised in Fig.3.12, γ -C 2 S is non-hydraulic, but fortunately β -C 2 S can be stabilised to low temperature by quenching or by formation of solid solution with a large number of oxide impurities 17 which dissolve at high temperature in the α or α ′ phases.18 Iron, aluminium, sulfur, phosphorus and alkalis are all present with a combined concentration of about 5% on an oxide basis. Maximum Percentage Of Which Species Is Present In Portland Cement Fig.3.12, Relative free energies of C 2 S as a function of temperature. (Source: Nurse RW. The dicalcium silicate phase, In: Proceedings of the third international symposium on the chemistry of cement, London; 1952.p.56–90 (pub 1954).) The most abundant phase of Portland cement clinker is alite, an impure form of tricalcium silicate (C 3 S).

Although a ‘lower limit of stability’ exists for C 3 S at about 1200°C, the decomposition to CaO and C 2 S on cooling is kinetically restricted and the compound exhibits a number of metastable modifications in the temperature range between room temperature and 1100°C.28 Of these, the highest temperature, and only thermodynamically stable polymorph (metastable below 1200°C), designated R (for rhombohedral), melts incongruently at 2070°C to give CaO and liquid (see Fig.3.11 ) and, on cooling, undergoes reversible polymorphic transformation below 1100°C to monoclinic (and orthorhombic) and then triclinic modifications.

The monoclinic polymorph, M III, has a transient existence over a small range of temperature, 29 its stability being due to the impurity level, notably of MgO, in the structure. The cooling sequence is as follows: R → 1060 ° C M III → 1050 ° C M II → 990 ° C M I → 980 ° C T III → 920 ° C T II → 600 ° C T I All polymorphs have very similar structures mainly distinguished by small distortions as the C 3 S structure endeavours to accommodate crystallographic strain as it is cooled below its limit of stability ( Fig.3.11 ).

For this reason, the M and T polymorphs can be described in terms of pseudohexagonal unit cells. This is another case where the equilibrium phase diagram does not fully represent the situation for actual clinkers. In most clinkers, usually the M I or M II phases are present at room temperature 30 ; this is highly dependent on impurity content and heating and cooling history, for example, 0.8% MgO stabilises M III, whereas increasing SO 3 content favours M I,

Consequently, zoned M I –M III, crystals are often found in Portland cements. A relative free energy diagram 31 ( Fig.3.13 ) illustrates the differences between the equilibrium and non-equilibrium pathways. Fig.3.13, Relative free energies of C 3 S as a function of temperature. (Source: Adapted from Bigare M, Guinier A, Mazieres C, Regourd M, Yannaquis N, Eysel W, et al. Polymorphism of tricalcium silicate and its solid solutions. J Am Ceram Soc 1967; 50 :609–19.) Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780081007730000034

What is the main component of Portland cement?

2 Cementitious materials – Portland cement (OPC) consists of tri and dicalcium silicates, tricalcium aluminate, and tetracalcium alumino ferrite and calcium sulfate as gypsum. It has adhesive and cohesive properties and is capable of binding together mineral fragments in presence of water so as to produce a continuous compact mass of masonary. Maximum Percentage Of Which Species Is Present In Portland Cement Fig.2.1, Manufacturing process of Portland cement. Blended cements are mixtures of Portland cement and other hydraulic or non hydraulic materials (industrial and agricultural wastes such as fly ash, metakaoline, blast furnace slag, rice husk ash, etc.). Paste, mortar and Concretes are shown in Fig.2.2, Maximum Percentage Of Which Species Is Present In Portland Cement Fig.2.2, Representation of OPC paste, mortar and concrete. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780128178546000027

What is the percentage of gypsum added in Portland cement?

The cement manufacturing industry is the major consumer of gypsum, which is added to the clinker in a percentage of 3–5 wt%,.

Which cement has high percentage of C3S?

Detailed Solution. Rapid Hardening cement has a maximum percentage of C 3 S. Rapid Hardening Cement is also called high early strength cement.

What is C2S and C3S in cement?

For that, a series of experiments were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement) and their mixtures, in order to obtain different C-S-H gel structures during their hydration.

What is the percentage of clinker in Portland cement Mcq?

Concrete Technology Questions and Answers – Manufacture of Portland Cement This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Manufacture of Portland Cement”.1. _ is not use to make Portland Cement (PC). a) Calcareous Rocks b) Argillocalcareous Rocks c) Argillaceous Rocks d) Sand View Answer Answer: d Explanation: Sand is mixed with Cement to make concrete instead of making cement. Materials which we get from these 3 rocks are useful to make healty PC.2. Which one doesn’t comes under Calcareous Rocks? a) Limestone b) Cement rock c) Chalk d) Marine shell deposits View Answer Answer: b Explanation: Cement Rock comes in Argillocalcareous Rocks. And Calcareous Rocks have Limestone, Marl, Chalk, Marine Shell Deposits.3. What is the percentage of CLINKER in PC? a) 2-3% b) 4-6% c) 2-6% d) 3-5% View Answer Answer: c Explanation: Portland cement is made by mixing substances containing CaCO 3 with substances containing SiO 2, Al 2 O 3, Fe 2 O 3 and heating them to a clinker which is subsequently ground to powder and mixed with 2-6 % gypsum.4. As the materials pass through the kiln their temperature is rised upto _ a) 1300-1600 °C b) 1100-1500 °C c) 1300-1500 °C d) 1100-1600 °C View Answer Answer: a Explanation: 1300-1600 °C is the best range to melt the raw materials for a healty PC. Below 1300 °C the materials whcih we added to make PC won’t melt perfectly and the result will be unhealty PC.5. What is the diameter and length of the kiln respectively? a) 6m and 200m b) 200m and 6m c) 6m and 6m d) 200m and 200m View Answer Answer: a Explanation: They are produced in a range of sizes and units with diameters up to 6 m and lengths up to 200 m have been made. Check this: | 6. What is the range of CaCO 3 in Argillocalcareous Rocks? a) >75% b) 40-75% c) <45% d) 75% View Answer Answer: b Explanation: It is the standard value for in Argillocalcareous Rocks (40-75% CaCO 3 such as clayey limestone, clayey marl).7. Prepared raw mix is fed into the rotary kiln. a) True b) False View Answer Answer: a Explanation: Cement kilns are used for the pyroprocessing stage of manufacture of Portland and other types of hydraulic cement, in which calcium carbonate reacts with silica-bearing minerals to form a mixture of calcium silicates.8. What is the diameter of Clinker for making of Portland Cement? a),15-5 cm b),15-5 m c),3-4 cm d),3-4 m View Answer Answer: a Explanation: As the materials pass through the kiln their temperature is rised upto 1300-1600 °C. The process of heating is named as "burning". The output is known as "clinker" which is 0.15-5 cm in diameter.9. What is the composition of making the Mortar? a) P.C. + Water b) P.C. + Water + Sand c) P.C. + Water + Sand + Gravel d) Water + Sand + Gravel View Answer Answer: b Explanation: Mortar is a mixture of 3 materials i.e. cement, water and sand (P.C. + sand + water = Mortar), used in building for holding bricks or stones together.10. Cement is a material with adhesive and cohesive properties. a) True b) False View Answer Answer: a Explanation: Cement is a material with adhesive and cohesive properties which make it capable of bonding mineral fragments into a compact whole. Sanfoundry Global Education & Learning Series – Concrete Technology. To practice all areas of Concrete Technology,, » Next Steps:

Get Free Participate in Become a Take Chapterwise Practice Tests: Chapterwise Mock Tests:

, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry, He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at, Subscribe to his free Masterclasses at & technical discussions at, : Concrete Technology Questions and Answers – Manufacture of Portland Cement

What is the percentage of Sulphur dioxide in ordinary Portland cement?

The chief chemical constituents of Portland cement are as follows: –

Lime (CaO) 60 to 67%
Silica (SiO2) 17 to 25%
Alumina (Al2O3) 3 to 8%
Iron oxide (Fe2O3) 0.5 to 6%
Magnesia (MgO) 0.1 to 4%
Sulphur trioxide (SO3) 1 to 3%
Soda and/or Potash (Na2O+K2O) 0.5 to 1.3%

The above constituents forming the raw materials undergo chemical reactions during burning and fusion, and combine to form the following compounds called BOGUE COMPOUNDS,

Compound Abbreviated designation
Tricalcium silicate (3CaO.SiO2) C3S
Dicalcium silicate (2CaO.SiO2) C2S
Tricalcium aluminate (3CaO.Al2O3) C3A
Tetracalcium aluminoferrite (4CaO.Al2O3.Fe2O3) C4AF

The proportions of the above four compounds vary in the various Portland cements. Tricalcium silicate and dicalcium silicates contribute most to the eventual strength. Initial setting of Portland cement is due to tricalcium aluminate. Tricalcium silicate hydrates quickly and contributes more to the early strength.

The contribution of dicalcium silicate takes place after 7 days and may continue for up to 1 year. Tricalcium aluminate hydrates quickly, generates much heat and makes only a small contribution to the strength within the first 24 hours. Tetracalcium alumino-ferrite is comparatively inactive. All the four compounds generate heat when mixed with water, the aluminate generating the maximum heat and the dicalcium silicate generating the minimum.

Due to this, tricalcium aluminate is responsible for the most of the undesirable properties of concrete. Cement having less C3A will have higher ultimate strength, less generation of heat and less cracking. Table below gives the composition and percentage of found compounds for normal and rapid hardening and low heat Portland cement.

What is the maximum percentage of ingredient in cement?

Jaspreet Singh said: (Mar 23, 2015)
Lime: 63%. Silica: 22%. Alumina: 6%. Iron oxide: 3%.
You might be interested:  Who Is Responsible For Health And Safety On Construction Sites?

Which chemical has highest content in OPC?

Concrete Technology Questions and Answers – Types of Cement This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Types of Cement”.1. Which chemical compostion has highest content in OPC? a) Alumina b) Silica c) Lime d) Iron Oxide View Answer Answer: c Explanation: Lime forms nearly two-third (2/3) of the cement.

2. Excess in lime causes _ a) The cement to shrink and integrate b) The cement to shrink and disintegrate c) The cement to expand and integrate d) The cement to expand and disintegrate View Answer

Answer: d Explanation: Sufficient quantity of lime forms di-calcium silicate (C2SiO2) and tri-calcium silicate in the manufacturing of cement.3. Silica in excess causes _ a) The cement to set slowly b) The cement to set quickly c) The cement to expand d) The cement to disintegrate View Answer Answer: a Explanation: Silica gives strength to the cement.

  1. Silica in excess causes the cement to set slowly.4.
  2. Alumina in excess causes _ a) Reduces the strength of the cement b) Inceases the strength of the cement c) No change d) Sometimes increase or decrease the strength of the cement View Answer Answer: a Explanation: Alumina supports to set quickly to the cement.

It also lowers the clinkering temperature. Alumina in excess reduces the strength of the cement.5. Which compound gives the colour to the cement? a) Lime b) Silica c) Iron Oxide d) Alumina View Answer Answer: c Explanation: Iron oxide pigments are in the form of particles ranging approximately from 0.1 to 1.0 micron.

The difference in color between one pigment and another is due to the shape and surface structure of the particle. Check this: | 6. Which cement contains high percentage of C 3 S and less percentage of C 2 S? a) Rapid Hardening Cement b) Ordinary Portland Cement c) Quick Setting Cement d) Low Heat Cement View Answer Answer: a Explanation: This cement contains high percentage of C 3 S and less percentage of C 3 S.

This is infact high early strength cement.7. When concrete is to be laid under water _ is to used. a) Rapid Hardening Cement b) Ordinary Portland Cement c) Quick Setting Cement d) Low Heat Cement View Answer Answer: c Explanation: When concrete is to be laid under water, quick setting cement is to used.

This cement is manufactured by adding small percentage of aluminum sulphate (Al 2 SO 4 ) which accelerates the setting action.8. Which of the following is correct for Low Heat Cement? a) Suitable for use in cold weather areas b) Heat of hydration is reduced by tri calcium aluminate content c) This cement requires longer period of curing d) This cement contains high aluminate %age usually between 35-55%.

View Answer Answer: b Explanation: In this cement the heat of hydration is reduced by tri calcium aluminate content. It contains less percentage of lime than ordinary port land cement. It is used for mass concrete works such as dams etc. Sanfoundry Global Education & Learning Series – Concrete Technology.

Get Free Participate in Become a Take Chapterwise Practice Tests: Chapterwise Mock Tests:

, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry, He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at, Subscribe to his free Masterclasses at & technical discussions at, : Concrete Technology Questions and Answers – Types of Cement

Which of the following is not present in Portland cement?

Hint: We must know that the portland cement is a common material and is the basic ingredient of concrete. Portland cement forms a paste with water that hardens on binding with sand and rock. Complete step by step answer: We can use portland cement popularly as a binding material in the form of a finely ground powder that is prepared by burning and grinding a mixture of limestone and clay or limestone and shell.

When it is mixed with water, the Constituents of Portland cement reacts chemically with the water that leads to the process of hydration and decomposition or hydrolysis. These processes make the mixture harden and thus it develops strength. Portland cement is composed of following chemicals, namely, \​ ( tricalcium aluminate), \​ ( tricalcium silicate), \ ( Dicalcium silicate), \ (Sodium oxide), \ (Potassium oxide), \ (Calcium sulfate dihydrate ) and \​ (Tetracalcium- aluminatferrite) The Portland cement is composed of 60% calcium oxide, 25% silica, 7% of alumina, 2 to 2.5% magnesia and 2 to 2.5% ferric oxide.

We know calcium silicates and calcium aluminates are forms of Calcium oxide. So, Portland cement does not contain calcium phosphate. $\therefore $The correct option is the option D. Additional information: We must know that Joseph Aspdin from England is the inventor of the basic process of Portland cement manufacturing.

  • Portland cement has been named so for the resemblance of the cement when set to portland stone from the Isle of Portland.
  • There are five types of Portland cement available in the world market depending upon their content, properties and usage.
  • Percentage of above mentioned contents of Portland cement varies from type to type.

Note: Calcium phosphate has nutritive value; we can use it as an antacid and also as a dietary supplement in veterinary medicines. It is used in medicine as a calcium supplement dose.

Why Portland cement is called Portland?

Definition of portland cement – Q. What is portland cement? A. Portland cement is the product obtained by pulverizing clinker, consisting of hydraulic calcium silicates to which some calcium sulfate has usually been provided as an interground addition.

  1. When first made and used in the early 19th century in England, it was termed portland cement because its hydration product resembled a building stone from the Isle of Portland off the British coast.
  2. The first patent for portland cement was obtained in 1824 by Joseph Aspdin, an English mason.
  3. The specific gravity of portland cement particles is about 3.15.

There are four primary phases in portland cement: tricalcium silicate (C 3 S), dicalcium silicate (C 2 S), tricalcium aluminate (C 3 A), and tetracalcium aluminoferrite (C 4 AF). The strength and other properties of concrete are mainly derived from the hydration of tricalcium and dicalcium silicates.

Why is Portland cement is used mostly?

D. Uses of CEM IV Portland Cement –

It is used for the production of low and medium-class concrete.It is used for the production of construction mortars and different types of concrete products.It develops a stable strength of the structure.It has good physical and mechanical characteristics.

Where is the most Portland cement made?

China produces the most cement globally by a large margin, at an estimated 2.5 billion metric tons in 2021. China’s cement production share equates to over half of the world’s cement. India was the world’s second-largest cement producer, with production amounting to a distant 330 million metric tons in 2021.

What is most abundant phase in Portland cement?

5.2.3.1 Silicate phases – The silicate phases are the most abundant in Portland cement, often comprising more than 75% of the cement, with the concentration of tricalcium silicate (C 3 S) typically being at least twice that of dicalcium silicate (C 2 S).

  • Hydration of the calcium silicate phases is responsible for the development of the compressive strength of the cement.
  • The hydration reactions are given in the following equations (using the cement chemical notation): (5.1) C 3 S + 5,3H → C 1.7 SH 4 + 1,3CH (5.2) C 2 S + 4,3H → C 1.7 SH 4 + 0,3CH The composition of the calcium silicate hydrate (C–S–H), written as C 1.7 SH 4 in this example, includes the observation that C 3 S will not fully hydrate unless there is sufficient water present to form Portlandite (CH) and a C–S–H composition close to C 1.7 SH 4,

This water content includes chemically bound water, which requires significant heating to remove it and evaporable or weakly bound water. The amount of bound water in C–S–H is equivalent to water-to-cement (H/S) ratios of 1.3–1.5, Calcium silicate hydrate is written as C–S–H to indicate that there is not just one fixed ratio of oxides.

  • The ratio of CaO to SiO 2 (C/S) can vary from around 1.2 to 2.3.
  • The hydration mechanisms of C 3 S and C 2 S are similar, although the reaction rate of C 2 S is much slower than that of C 3 S,
  • Thus the hydration of C 3 S is responsible for the start of the set and early strength development.
  • The hydration of C 2 S is significant only for the final compressive strength of the set cement.

The hydration of cement phases is an exothermic process and can be followed by isothermal calorimetry. The process can be broken down into four stages, with the typical time scales of each stage shown in Fig.5.1 for C 3 S. For well-cementing applications, stages 1 and 2 are key to controlling the mixing and placement of the cement slurry, and stage 3 controls the initial development of compressive strength. Maximum Percentage Of Which Species Is Present In Portland Cement Figure 5.1, Rate of heat generation during the hydration of C 3 S. Reproduced with modifications from J.W. Bullard et al., Mechanisms of cement hydration, Cement and Concrete Research, 41 (12), 2011, 1208–1223. In stage 1, there is a rapid wetting and congruent dissolution of the C 3 S as soon as it is mixed with water giving a high exothermic signal.

What type of cement is Portland cement?

Portland cement, binding material in the form of a finely ground powder, usually gray, that is manufactured by burning and grinding a mixture of limestone and clay or limestone and shale.

Which has maximum percentage in cement clinker?

Clinker Substitution – Cembureau

Clinker can be blended with a range of alternative materials, including pozzolans, finely ground limestone and waste materials or industrial by-products. The clinker-to-cement ratio (percentage of clinker compared to other non-clinker components) has an impact on the properties of cement so standards determine the type and proportion of alternative main constituents that can be used. To ensure the future use of other constituents, the cement industry is dependent on the local supply of these materials.

The use of other constituents in cement and the reduction of the clinker-to-cement ratio means lower emissions and lower energy use. Ordinary Portland cement can contain up to 95% clinker (the other 5% being gypsum). The current average clinker-to-cement ratio over all cement types in the EU27 is 73.7%.

  1. Different cement types have different properties, including hardening time, early and late strength, resistance to salty conditions and chemically aggressive environments, heat release during curing, colour, viscosity and workability.
  2. The importance and relevance of these qualities depend on the desired application of the cement and concrete.

There is a need to ensure that all the cement manufactured is safe and durable as it will be used in structures that are made to last at least 50 years or more. Thus, high durability of the final product concrete is a key property for sustainable construction.

Natural pozzolans, such as clays, shale and certain types of sedimentary rocks. Limestone (finely ground), which can be added to clinker (without being heated and transformed into lime). Silica fume, a pozzolanic material and a by-product in the production of silicon or ferrosilicon alloys. Granulated blastfurnace slag (GBFS), a by-product of the pig-iron/steel production process. Fly ash, dust-like particles from flue gases of coal-fired power stations.

The availability of alternative materials that can be used as other constituents varies considerably. For example, granulated blastfurnace slag availability depends on the location and output of blastfurnaces for pig-iron production equipped with slag granulation facilities, whilst fly ash use is dependent on supply from sufficiently close coal-fired power plants.

The availability of pozzolans depends on the local situation and only a limited number of regions have access to this material for cement production. Limestone is abundant worldwide and is easily accessible to most cement plants. Cement standards serve to guarantee the performance of each cement type.

The use of other constituents has an impact on the way the cement will perform in both the short and long term. The success of cements with a low clinker-to-cement ratio will also depend on market acceptance. Quality is crucial for building stability and, as such, a matter of public safety, e.g.

  • Bridges, sky scrapers as well as for the sustainability of investments into infrastructures and buildings.
  • A global clinker-to-cement ratio of 78% in 2006 meant that about 550-600 million tonnes of constituents other than clinker were used.
  • The International Energy Agency (IEA) estimated that in 2005, there were around 1,215 million tonnes of material suitable for clinker substitution globally (excluding pozzolan and limestone).
You might be interested:  Which Dr Fixit Is Best For Roof?

On this basis, it seems that the use of other constituents could be doubled. However, this scenario is only hypothetical because it does not take into account that these quantities do not necessarily reflect the required quality or local market situation.

There is also uncertainty regarding the future availability of clinker substitutes as well as the impact of environmental policy and regulation. For example, the future decarbonisation of the power sector could limit the availability of fly ash, or the application of Nitrogen Oxide(s) abatement techniques in coal-fired power stations could mean that the fly ash may be unusable as a constituent in cement due to higher NH3 (ammonia) concentrations.

Furthermore, some of these materials are already used in concrete, rather than cement, production. Finally, a life cycle cost analysis needs to be done to ensure that policies are based on the entire life cycle in order to avoid focusing solely on intermediate material impact.

Low-clinker cements can offer both environmental benefits as well as favourable product characteristics. Nevertheless, it is important that a whole life cycle approach is applied to public procurement rather than simply focusing on product footprinting or intermediate product impacts. Facilitate access to raw materials and enhancing waste and by-products recycling policies. Provide support for and access to R&D funding. In addition, a strong industry focus on innovative cements and concretes has the potential to respond to the requirements of sustainable and resource-efficient production and construction.

F or the purposes of meaningful reporting, the definition of cement used in the GNR database differs slightly from that in common use. In this document, cement and cementitious products are considered equivalent, Source: Source: Development of State of the Art Techniques in Cement Manufacturing: Trying to Look Ahead (CSI/ECRA- Technology Papers), State of the Art Paper No 4: Reduction of clinker content in cement: long-term perspective : Clinker Substitution – Cembureau

Why 2% gypsum is added in the cement?

Why Gypsum is Added to Cement? Published: October 31, 2015 Portland cement is hydraulic cement. This means that it sets and hardens faster due to a chemical reaction with water. As a result, it will also harden under water. Whenever water is mixed with cement, a smooth paste is formed that remains plastic for a short time.

During this period, the paste can be disturbed and remixed without injury. As the reaction between water and cement continues, the plasticity of the cement paste is lost. This early period in the hardening of cement is known as `Setting of Cement’. Why Gypsum is added to Cement? When cement is mixed with water, it becomes hard over a period of time.

This is called setting of cement. Gypsum is often added to Portland cement to prevent early hardening or “flash setting”, allowing a longer working time. Gypsum slows down the setting of cement so that cement is adequately hardened.

What are the four primary compounds that make up 90% of Portland cement by mass?

Background – Concrete is made by the combination of cement, water, and aggregate of various sizes to make a workable slurry that has the consistency of a thick milk shake.

Name Percent by Weight Chemical Formula
Tricalcium silicate 50% 3Ca0 SiO2
Dicalcium silicate 25% 2Ca0 SiO2
Tricalcium aluminate 10% 3Ca0 Al2 O3
Tetracalcium aluminoferrite 10% 4Ca0 Al2 Fe2 O3
Gypsum 5% CaSO4 H2O

The binding quality of portland cement paste is due to the chemical reaction between the cement and water, called hydration. Portland cement is not a simple chemical compound, it is a mixture of many compounds. Four of these make up 90% or more of the weight of portland cement: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.

In addition to these major compounds, several other play important roles in the hydration process. Different types of cement contain the same four major compounds, but in different proportions. The cement in concrete needs water to hydrate and harden. Even though the chemical reactions may be complete at the surface of the concrete, the chemical reactions at the interior of the concrete take much longer to complete.

The strength of the concrete keeps growing as long as the chemical reactions continue. When water is added to cement, the chemical reaction called hydration takes place and contributes to the final concrete product. The calcium silicates contribute most to the strength of concrete.

  1. Tricalcium silicates are responsible for most of the early strength (first seven days).
  2. The original dicalcium silicate hydrates, which form more slowly, contribute to the strength of concrete at later stages.
  3. The following word equations describe the production of concrete.
  4. Tricalcium silicate + Water (yields) Calcium silicate hydrate + Calcium hydroxide + heat Dicalcium silicate + Water (yields) Calcium silicate hydrate + Calcium hydroxide + heat Of the five chemical reactions important for providing the strength for concrete the above reactions are the most important.

The two calcium silicates, which constitute about 75 percent of the weight of portland cement, react with water to form two new compounds: calcium hydroxide and calcium silicate hydrate. The latter is by far the most important cementing component in concrete.

The engineering properties of concrete—setting and hardening, strength and dimensional stability—depend primarily on calcium silicate hydrate gel. It is the heart of concrete. When concrete sets, its gross volume remains almost unchanged, but hardened concrete contains pores filled with water and air that have no strength.

The strength is in the solid part of the paste, mostly in the calcium silicate hydrate and crystalline phases. The less porous the cement paste, the stronger the concrete. When mixing concrete, therefore, use no more water than is absolutely necessary to make the concrete plastic and workable.

Who is the largest producer of Portland cement?

China produces the most cement globally by a large margin, at an estimated 2.5 billion metric tons in 2021. China’s cement production share equates to over half of the world’s cement.

Which chemical composition has highest content in ordinary Portland cement?

The chief chemical constituents of Portland cement are as follows: –

Lime (CaO) 60 to 67%
Silica (SiO2) 17 to 25%
Alumina (Al2O3) 3 to 8%
Iron oxide (Fe2O3) 0.5 to 6%
Magnesia (MgO) 0.1 to 4%
Sulphur trioxide (SO3) 1 to 3%
Soda and/or Potash (Na2O+K2O) 0.5 to 1.3%

The above constituents forming the raw materials undergo chemical reactions during burning and fusion, and combine to form the following compounds called BOGUE COMPOUNDS,

Compound Abbreviated designation
Tricalcium silicate (3CaO.SiO2) C3S
Dicalcium silicate (2CaO.SiO2) C2S
Tricalcium aluminate (3CaO.Al2O3) C3A
Tetracalcium aluminoferrite (4CaO.Al2O3.Fe2O3) C4AF

The proportions of the above four compounds vary in the various Portland cements. Tricalcium silicate and dicalcium silicates contribute most to the eventual strength. Initial setting of Portland cement is due to tricalcium aluminate. Tricalcium silicate hydrates quickly and contributes more to the early strength.

  • The contribution of dicalcium silicate takes place after 7 days and may continue for up to 1 year.
  • Tricalcium aluminate hydrates quickly, generates much heat and makes only a small contribution to the strength within the first 24 hours.
  • Tetracalcium alumino-ferrite is comparatively inactive.
  • All the four compounds generate heat when mixed with water, the aluminate generating the maximum heat and the dicalcium silicate generating the minimum.

Due to this, tricalcium aluminate is responsible for the most of the undesirable properties of concrete. Cement having less C3A will have higher ultimate strength, less generation of heat and less cracking. Table below gives the composition and percentage of found compounds for normal and rapid hardening and low heat Portland cement.

Which cement contains high percentage?

Rapid Hardening cement has a maximum percentage of C 3 S. Rapid Hardening Cement is also called high early strength cement.

What percentage of concrete is Portland cement?

User Guidelines for Waste and Byproduct Materials in Pavement Construction

PORTLAND CEMENT CONCRETE PAVEMENT Application Description

INTRODUCTION Portland cement concrete (PCC) pavements (or rigid pavements) consist of a PCC slab that is usually supported by a granular or stabilized base, and a subbase. In some cases the PCC slab may be overlaid with a layer of asphalt concrete. Portland cement concrete is produced at a central plant and transported to the job site in transit mixers or batched into truck mixers directly and then mixed at the project site.

  1. In either case, the PCC is then dumped, spread, leveled, and consolidated, generally using concrete slip-form paving equipment.
  2. MATERIALS Basic components of PCC include coarse aggregate (crushed stone or gravel), fine aggregate (usually natural sand), Portland cement, and water.
  3. The aggregate functions as a filler material, which is bound together by hardened Portland cement paste formed by chemical reactions (hydration) between the Portland cement and water.

In addition to these basic components, supplementary cementitious materials and chemical admixtures are often used to enhance or modify properties of the fresh or hardened concrete. Concrete Aggregate The coarse and fine aggregates used in PCC comprise about 80 to 85 percent of the mix by mass (60 to 75 percent of the mix by volume).

Proper aggregate grading, strength, durability, toughness, shape, and chemical properties are needed for concrete mixture strength and performance. Portland Cement and Supplementary Cementitious Materials Portland cements are hydraulic cements that set and harden by reacting with water, through hydration, to form a stonelike mass.

Portland cement typically makes up about 15 percent of the PCC mixture by weight. Portland cement is manufactured by crushing, milling, and blending selected raw materials containing appropriate proportions of lime, iron, silica, and alumina. Most Portland cement particles are less than 0.045 mm (No.325 sieve) in diameter.

Portland cement combined with water forms the cement paste component of the concrete mixture. The paste normally constitutes about 25 to 40 percent of the total volume of the concrete. Air is also a component of the cement paste, occupying from 1 to 3 percent of the total concrete volume, up to 8 percent (5 to 8 percent typical) in air entrained concrete.

In terms of absolute volume, the cementing materials make up between about 7 and 15 percent of the mix, and water makes up 14 to 21 percent. Supplementary cementitious materials are sometimes used to modify or enhance cement or concrete properties. They typically include pozzolanic or self-cementing materials.

Pozzolanic materials are materials comprised of amorphous siliceous or siliceous and aluminous material in a finely divided (powdery) form, similar in size to Portland cement particles, that will, in the presence of water, react with an activator, typically calcium hydroxide and alkalis, to form compounds possessing cementitious properties.

Descriptions of various kinds of pozzolans and their specifications are provided in ASTM C618. Self-cementing materials are materials that react with water to form hydration products without any activator. Supplementary cementitious materials can affect the workability, heat released during hydration, the rate of strength gain, the pore structure, and the permeability of the hardened cement paste.

Coal fly ash that is produced during the combustion of bituminous coals exhibits pozzolanic properties. Silica fume is also a pozzolanic material consisting almost entirely (85 percent or more) of very fine particles (100 times smaller than Portland cement) that are highly reactive. Coal fly ash produced during the combustion of subbituminous coal exhibits self-cementing properties (no additional activators, such as calcium hydroxide, are needed).

Similarly, ground granulated blast furnace slag reacts with water to form hydration products that provide the slag with cementitious properties. Coal fly ash and ground granulated blast furnace slag can be blended with Portland cement prior to concrete production or added separately to a concrete mix (admixture).

  1. Silica fume is used exclusively as an admixture.
  2. Chemical and Mineral Admixtures An admixture is a material, other than Portland cement, water and aggregate, that is used in concrete as it is mixed to modify the fresh or hardened concrete properties.
  3. Chemical admixtures fall into three basic categories.

They include water-reducing agents, air-entraining agents, and setting agents. Chemical admixtures for concrete are described in ASTM C494. Water-reducing agents are chemicals that are used to reduce the quantity of water that needs to be added to the mix, at the same time producing equivalent or improved workability and strength.

  1. Air entrainment increases the resistance of concrete to disintegration when exposed to freezing and thawing, increases resistance to scaling (surface disintegration) that results from deicing chemicals, increases resistance to sulfate attack, and reduces permeability.
  2. Air entrainment can be accomplished by adding an air-entraining admixture during mixing.
You might be interested:  How To Complaint In Mcd For Illegal Construction?

There are numerous commercial air entraining admixtures manufactured. Descriptions and specifications are described in ASTM C260. Setting agents can be used to either retard or accelerate the rate of setting of the concrete. Retarders are sometimes used to offset the accelerating effect of hot weather or to delay the set when placing of the concrete may be difficult.

MATERIAL PROPERTIES AND TESTING METHODS Concrete Aggregate Since aggregates used in concrete mixtures comprise approximately 80 to 85 percent of the concrete mixture by mass (60 to 75 percent of the concrete mixture by volume), the aggregate materials used have a profound influence on the properties and performance of the mixture in both the plastic and hardened states. The following is a listing and brief comment on some of the more important properties for aggregates that are used in concrete paving mixtures:

Gradation – the size distribution of the aggregate particles affects the relative proportions, cementing materials and water requirements, workability, pumpability, economy, porosity, shrinkage, and durability. The size distribution of the aggregate particles should be a combination of sizes that results in a minimum of void spaces. Absorption – the absorption and surface moisture condition of aggregates must be determined so that the net water content of the concrete can be controlled. Particle Shape and Surface Texture – the particle shape and surface texture of both coarse and fine aggregates have a significant influence on the properties of the plastic concrete. Rough textured, angular, or elongated particles require more water to produce workable concrete than smooth, rounded, compact aggregates, and as a result, these aggregates require more cementing materials to maintain the same water-cement ratio. Angular or poorly graded aggregates may result in the production of concrete that is more difficult to pump and also may be more difficult to finish. The hardened concrete strength will generally increase with increasing coarse aggregate angularity, and flat or elongated coarse aggregate particles should be avoided Rounded fine aggregate particles are more desirable because of their positive effect on plastic concrete workability. Abrasion Resistance – the abrasion resistance of an aggregate is often used as a general index of its quality. Durability – resistance to freezing and thawing is necessary for concrete aggregates, and is related to the aggregate porosity, absorption, permeability, and pore structure. Deleterious Materials – aggregates should be free of potentially deleterious materials such as clay lumps, shales, or other friable particles, and other materials that could affect its chemical stability, weathering resistance, or volumetric stability. Particle Strength – for normal concrete pavements, aggregate strength is rarely tested. It is usually much greater than and therefore not as critical a parameter as the paste strength or the paste-aggregate bond. Particle strength is an important factor in high-strength concrete mixtures.

Table 24-5 provides a list of standard test methods that are used to assess the suitability of conventional mineral aggregates in Portland cement concrete paving applications. Table 24-5. Concrete aggregate test procedures.

Property Test Method Reference
General Specifications Concrete Aggregates ASTM C33
Ready Mixed Concrete ASTM C94/ AASHTO M157M
Concrete Made by Volumetric Batching and Continuous Mixing ASTM C685/AASHTO M241
Terminology Related to Concrete and Concrete Aggregates ASTM C125
Gradation Sizes of Aggregate for Road and Bridge Construction ASTM D448/AASHTO M43
Sieve Analysis of Fine and Coarse Aggregate ASTM C136/AASHTO T27
Absorption Specific Gravity and Absorption of Coarse Aggregate ASTM C127/AASHTO T85
Specific Gravity and Absorption of Fine Aggregate ASTM C128/AASHTO T84
Particle Shape and Surface Texture Flat and Elongated Particles in Coarse Aggregate ASTM D4791
Uncompacted Voids Content of Fine Aggregate (As Influenced by Particle Shape, Surface Texture, and Grading) ASTM C1252/AASHTO TP33
Index of Aggregate Particle Shape and Texture ASTM D3398
Abrasion Resistance Resistance to Degradation of Large-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine ASTM C535
Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine ASTM C131/AASHTO T96
Durability Aggregate Durability Index ASTM D3744/AASHTO T210
Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate ASTM C88/AASHTO T104
Soundness of Aggregates by Freezing and Thawing AASHTO T103
Deleterious Components Petrographic Examination of Aggregates for Concrete ASTM C295
Organic Impurities in Fine Aggregate for Concrete ASTM C40
Clay Lumps and Friable Particles in Aggregates ASTM C142
Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test ASTM D2419
Volume Stability Potential Volume Change of Cement-Aggregate Combinations ASTM C342
Accelerated Detection of Potentially Deleterious Expansion of Mortar Bars Due to Alkali-Silica Reaction ASTM C227

Portland Cement and Supplementary Cementitious Materials Although it comprises between only 7 to 15 percent of the absolute volume of concrete mixture, it is the hardened paste that is formed by hydration of the cement upon the addition of water that binds the aggregate particles together to form a stonelike mass.

Chemical Composition – differences in chemical composition, particularly with supplementary cementitious materials that could be less uniform than Portland cement, could affect early and ultimate strengths, heat released, setting time, and resistance to deleterious materials. Fineness – the fineness of the cement or supplementary cementitious materials affects heat release and rate of hydration. Finer materials react faster, with a corresponding increase in early strength development, primarily during the first 7 days. Fineness also influences workability, since the finer the material, the greater the surface area and frictional resistance of the plastic concrete. Soundness – refers to the ability of the cement paste to retain its volume after setting, and is related to the presence of excessive amounts of free lime or magnesia in the cement or supplementary cementitious material. Setting Time – the setting time for the cement paste is an indication of the rate at which hydration reactions are occurring and strength is developing and can be used as an indicator as to whether or not the paste is undergoing normal hydration reactions. False Set – false set or early stiffening of the cement paste is indicated by a significant loss of plasticity without the evolution of heat shortly after the concrete is mixed. Compressive Strength – compressive strength is influenced by cement composition and fineness. Compressive strengths for different cements or cement blends are established by compressive strength testing of mortar cubes prepared using a standard graded sand. Specific Gravity – specific gravity is not an indication of the quality of the cement, but is required for concrete mix design calculations. The specific gravity of Portland cement is approximately 3.15.

Table 24-6 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of Portland cement and supplementary cementitious materials for use in concrete paving mixtures. Table 24-6. Portland cement and supplementary cementitious materials test procedures.

Property Test Method Reference
General Specifications Portland Cement ASTM C150
Blended Hydraulic Cement ASTM C595
Expansive Hydraulic Cement ASTM C845
Pozzolan Use as a Mineral Admixture ASTM C618
Ground Blast Furnace Slag Specifications ASTM C989
Silica Fume Specifications ASTM C1240
Chemical Composition Chemical Analysis of Hydraulic Cements ASTM C114
Fineness Fineness of Hydraulic Cement by the 150 µm (No.100) and 75 µm (No.200) Sieves ASTM C184/AASHTO 128
Fineness of Hydraulic Cement and Raw Materials by the 300 µm (No.50), 150 µm (No.100) and 75 µm (No.200) Sieves by Wet Methods ASTM C786
Fineness of Hydraulic Cement by the 45 µm (No.325) Sieve ASTM C430/AASHTO T192
Fineness of Portland Cement by Air Permeability Apparatus ASTM C204/AASHTO T153
Fineness of Portland Cement by the Turbidimeter ASTM C115/AASHTO T98
Cement Soundness Autoclave Expansion of Portland Cement ASTM C151/AASHTO T107
Setting Time Time of Setting of Hydraulic Cement by Vicat Needle ASTM C191/AASHTO T131
Time of Setting of Hydraulic Cement by Gillmore Needles ASTM C266/AASHTO T154
Time of Setting of Hydraulic Cement Mortar by Modified Vicat Needle ASTM C807
False Set Early Stiffening of Portland Cement (Mortar Method) ASTM C359/AASHTO T185
Early Stiffening of Portland Cement (Paste Method) ASTM C451/AASHTO T186

CONCRETE PAVING MATERIAL The mix proportions for concrete paving mixtures are determined in the laboratory during mix design testing. This involves determination of the optimum characteristics of the mix in both the plastic and hardened states to ensure that the mix can be properly placed and consolidated, finished to the required texture and smoothness, and will have the desired properties necessary for pavement performance.

Slump – slump is an indication of the relative consistency of the plastic concrete. Concrete of plastic consistency does not crumble but flows sluggishly without segregation. Workability – workability is a measure of the ease of placing, consolidating, and finishing freshly mixed concrete. Concrete should be workable but not segregate or bleed excessively. Setting Time – knowledge of the rate of reaction between cementing materials and water (hydration) is important to determine setting time and hardening. The setting times of concrete mixtures do not correlate directly with the setting times of the cement paste because of water loss and temperature differences. Air Content – the amount of entrapped or entrained air in the plastic concrete can influence the workability of the concrete mixture and reduce its propensity for bleeding.

Hardened Concrete

Strength – concrete pavements must have adequate flexural strength to support the design traffic loads (repetitions of loaded axles) that will be applied over the service life of the facility. While compressive strength can also be measured, flexural strength is more relevant to the design and performance of concrete pavements. Density – the density of concrete paving mixes varies depending on the amount and relative density of the aggregate, the amount of air that is entrained or entrapped, and the water and cementing materials content of the concrete. Durability – the hardened concrete pavement must be able to resist damage from freezing and thawing, wetting and drying, and chemical attack (e.g., from chlorides or sulfates in deicing salts). Air Content – the finished and cured concrete should have adequate entrained air in the hardened cement paste to be able to withstand cycles of freezing and thawing. Frictional Resistance – for user safety, the surface of an exposed concrete pavement must provide adequate frictional resistance and resist polishing under traffic. Frictional resistance is a function of the aggregates used and the compressive strength of the concrete. Volume Stability – concrete paving mixtures must be volumetrically stable and must not expand due to alkali aggregate reactivity. Concrete paving mixtures should not shrink excessively upon drying.

Table 24-7 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of concrete paving mixtures. Table 24-7. Concrete paving materials test procedures.

Property Test Method Reference
General Specifications Ready Mixed Concrete ASTM C94/AASHTO M157
Concrete Made by Volumetric Batching and Continuous Mixing ASTM C685/AASHTO M241
Concrete Aggregates ASTM C33
Terminology Related to Concrete and Concrete Aggregates ASTM C125
Pozzolan Use as a Mineral Admixture ASTM C618
Ground Blast Furnace Slag Specifications ASTM C989
Chemical Admixtures for Concrete ASTM C494
Air Entraining Agents ASTM C260
Silica Fume Specifications ASTM C1240
Slump Slump of Hydraulic Cement Concrete ASTM C143/AASHTO T119
Workability Bleeding of Concrete ASTM C232/AASHTO T158
Hydration and Setting Time of Setting of Concrete Mixtures by Penetration Resistance ASTM C403
Strength Compressive Strength of Cylindrical Concrete Specimens ASTM C39/ASHTO T22
Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) ASTM C78/ AASHTO T96
Splitting Tensile Strength of Cylindrical Concrete Specimens ASTM C496/AASHTO T198
Air Content Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete ASTM C457
Air Content of Freshly Mixed Concrete by the Pressure Method ASTM C231/AASHTO T152
Air Content of Freshly Mixed Concrete by the Volumetric Method ASTM C173/AASHTO T196
Unit Weight, Yield, and Air Content of Concrete ASTM C138
Density Specific Gravity, Absorption, and Voids in Hardened Concrete ASTM C642
Durability Resistance of Concrete to Rapid Freezing and Thawing ASTM C666
Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals ASTM C131/AASHTO T96
Volume Stability Length Change of Hardened Hydraulic-Cement Mortar and Concrete ASTM C157
Length Change of Concrete Due to Alkali-Carbonate Rock Reaction ASTM C1105

REFERENCES FOR ADDITIONAL INFORMATION ACI Manual of Concrete Practice, Part 1 – Materials and General Properties of Concrete, American Concrete Institute, Detroit, Michigan, 1994. Kosmatka, S.H. and W.C. Panarese. Design and Control of Concrete Mixtures,