Hydration of cement

Hydration of Cement and Some special types of Cement

1. HYDRATION OF CEMENT Presented By, D.SARATHKUMAR ., B.E., (710015813007) II-Year- M.E-Structural Engineering(Part Time) Anna University Regional Campus, Coimbatore-641 046 & Special Types of Cement

2. Content The discussion is divided into following sections. Hydration-Introduction Hydration Process or Mechanism Heat of Hydration Factors Affecting Hydration Special Types of Cement References

3. Hydration- Introduction Chemical reaction take place between cement and water is referred as hydration. Hydration is the reaction( Series of chemical reactions ) of cement with water to form the binding material (C-S-H Gel).

4. Structure of 1.4 nm tobermorite , a sheet like silicate composed of octahedral layers and silicate chains. The silica tetrahedra can be replaced by hydroxil ions. If part the bridging tetrahedra (B) are replaced only paired groups remain explaining the dimer signal in NMR studies. Structure of C-S-H gel

5. Structure of C-S-H gel x c Structural water Adsorbed water Capillary pore C-S-H layer C-S-H particle C-S-H gel models

6. Hydration- Introduction Name of the Compound Formula Abbreviated Formula Percentage Tri-calcium Silicate 3CaO.SiO 2 C 3 S 25-50 Di-calcium Silicate 2CaO.SiO 2 C 2 S 20-45 Tri-Calcium Aluminate 3CaO.Al 2 O 3 C 3 A 5-12 Tetra Calcium Aluminoferrite 4CaO.Al 2 O 3 .Fe 2 O 3 C 4 AF 6-12 Bogue’s Compounds

7. Hydration- Introduction In presence of water, the silicates(C 3 S and C 2 S) and Aluminates(C 3 A and C 4 AF) form products of hydration which in time produce a firm(Solid) and hard mass - the hydrated cement paste

8. Hydration Process - Calcium Silicate (C 3 S & C 2 S)

9. Hydration Process- C 3 S 2(3CaO.SiO 2 )+6H 2 O 3 CaO.2SiO.3H 2 O + 3Ca(OH) 2 OR 2C 3 S+6H C 3 S 2 H 3 + 3Ca(OH) 2 Tri-calcium Silicate hydrates rapidly and forms earlier strength of the concrete . C 3 S produce more amount heat during hydration process. Cement with more content of C 3 S is better cold weather concreting . Calcium Silicate Hydrates

10. SEM micrographs of fractured C 3 S pastes (w/c = 0.4) in pure water at (A) 7 days, (B) 13 days, (C) 1 month of hydration HYDRATION PRODUCTS

11. HYDRATION PRODUCTS Early Porous C-S-H gel (Eternite shingle, 2100x) Late dense C-S-H gel (Eternite shingle, 800x)

12. Hydration Process- C 2 S 2(2CaO.SiO 2 )+4H 2 O 3CaO.2SiO.3H 2 O + 3Ca(OH) 2 OR 2C 2 S+4H C 3 S 2 H 3 + Ca(OH) 2 Di-calcium Silicate hydrates slowly and it is responsible for progressive strength of the concrete . C 3 S produce less amount heat during hydration process. Responsible for major strength of concrete. Calcium Silicate Hydrates

13. The other products of hydration of C 3 S and C 2 S is Calcium Hydroxide . Lack of durability of concrete, is on account of the presence of calcium Hydroxide. Ca(OH) 2 reacts with sulphates presents in soil or water to form Calcium Sulphate which further reacts with C3A and causes the deterioration of concrete. This reaction is known as the sulphate attack. Hydration Process- Ca(oh) 2

14. Hydration Process- Ca(oh) 2 The use of blending materials such as fly ash ,silica fume& other pozzolanic materials are steps to over come the sulphate attack. Pozzolan + Calcium hydroxide+ water C-S-H (Gel) Only advantage is that Ca(OH)2 ,being alkaline in nature maintain pH value around 13 in the concrete which resists the corrosion of reinforcements .

15. Hydration Process- Calcium Aluminate Hydrates (C3A&C4AF)

16. Hydration Process- C 3 A 3CaO.Al 2 O 3 +H 2 O 3CaO.Al 2 O 3 .6H 2 O OR C 3 A + H C 3 AH 6 Tri-calcium Aluminate hydrates rapidly about 225 o C. C 3 A produce large amount heat during hydration process. Hydrated aluminates do not contributes anything to the strength of concrete, but it will be give durability of concrete. Calcium Aluminate Hydrates

17. Hydration Process- C 4 AF 4CaO.Al 2 O 3. Fe 2 O 3 +H 2 O 3CaO.Al 2 O 3 .6H 2 O +CaO.Fe 2 O 3 .H 2 O C 4 AF + H OR C 3 AH 6 The hydrates of C4AF show a comparatively higher resistance to the attack of sulphates.

18. HYDRATION PRODUCTS Lathshaped AFm (sulfatefree) crystals (3900x) Ettringite (sulfatefree) crystals (1500x) Hydrogarnets (1500x) All images are from fiber concrete samples.

19. w/c is 0.5 for (a) a is 1.0 for (b) Volume relationships

20. Hydration mechanisms in Portland cement

21. Hydration mechanisms in Portland cement

22. Heat Hydration The Hydration of cement with water is exothermic . Exothermic -An exothermic reaction is a chemical reaction that release s by light or heat. The liberation of heat is called heat of hydration .

23. Heat Hydration Study and control of hydration becomes important in mass construction(like dams.etc.,) Heat evolution due to the reaction of solution of aluminates(C 3 S) and sulphates.(C 3 A) Initial heat evolution ceases quickly when the solubility of aluminates is depressed by gypsum. The next heat evolution is on account of formation of ettringite and reaction of C 3 S. Ettringite -Calcium Aluminate tri-sulphate Hydrates (C 6 AS 3 H 32 ).

24. HEAT EVOLUTION DURING PORTLAND CEMENT HYDRATION I II III time (hours) heat evolution rate W/kg Induction (dormant) period 10 20 30 preinduction period acceleration period

25. TEMPORAL EVOLUTION OF THE PRODUCTS Temporal evolution of the hydration hydration products (Kurtis, )

26. HEAT EVOLUTION AND HYDRATION REACTIONS I C 3 A hydration Formation of ettringite Ettringite coating retards further aluminate hydration Ettringite to monosulfate transformation and further aluminate hydration Relationship between reactions and heat evolution

27. Factors affecting Hydration Chemical Composition of Cement Cement Type Sulfate Content Fineness of Cement Water Cement Ratio Curing Temperature Effect of Admixtures

28. Special Types of Cement Acid Resistance Cement Blast Furnace Cement Expanding Cement Coloured Cement High Alumina Cement Hydrophobic Cement Low Heat Cement Oil Well Cement IRS-T 40 Special Cement

29. Acid Resistance Cement This Cement composed as following, 1.Acid-Resistance Aggregate – Ex: Quartz 2.Additive- Ex: Sodium Fluosilicate (Na 2 SiF 6 ) 3.Aqueous Solution of sodium silicate or soluble glass. Na 2 SiF 6 - Accelerates the hardening and increase the resistance of cement to acid. Binding Materia l of acid resistance cement is soluble glass .

30. Blast Furnace Cement For this cement Slag obtained from blast furnace is used. The slag is waste product in the manufacturing process of pig iro n and it contains. It contains alumina, lime and silica. This cement more or less same as Ordinary Portland Cement . Its strength in early days is less and hence is requires longer curing period .

31. Expanding Cement This cement produced by adding an expanding medium like Sulpo-aluminate . About 8-20 parts of the Sulpo-aluminate clinker are mixed with 100 parts of Portland cement and 15 parts of stabilizer . Use of expanding cement requires skill and experience. This cement used in Water retaining Structures and repairing damaged concrete surface .

32. Coloured Cement Coloured cemen t will be obtained by mixing of pigments with ordinary Portland cement. The amount of coloring material may vary from 5 to 10 %. If this percentage exceeds 10 % the strengt h of cement is affected. SI .No Pigment Colour 1 Chromium Oxide Green 2 Cobalt Imparts Blue 3 Iron Oxide in different proportion Brown , Red, Yellow 4 Manganese Dioxide Black or Brown Coloured cement are widely used Finishing Interior exterior, Flooring and artificial marble.

33. High Alumina Cement This cement produced by grinding clinkers formed by bauxite and lime . The bauxite is an aluminum Oxide(Al 2 O 3 ) . In this cement alumina content should not less then 32%. Ratio of weight of alumina to the lime should not be between 0.85 to 1.30 . It can stand high temperature. It sets quickly and attains higher ultimate strength short period. It is not suitable for mass construction as it evolves great heat .

34. Hydrophobic Cement This type of cement contains admixture s which decrease the wetting ability of cement grains. The usual hydrophobic admixtures are acidol , naphthenesoap , oxidized petrolatum, Oletic acid and Stearic acid. Above substance formed water repellent film around each cement grains. This film protects them form the bad effect of moisture during storage and transportation . The film is broken out when the cement and aggregate are mixed together at the mixer exposing the cement particles to normal hydration.

35. Low Heat Cement Formation of cracks in large body of concrete due to heat of hydration . So, concrete technologists produce a kind of cement which produces less heat during hydration process. This cement will be used in mass construction . Low heat evolution is achieved by reducing the contents of C 3 S C 3 A . SI. No Days Heat produced by low heat cement (cal/gm) Heat produced by OPC (cal/gm) Cal-Calories 1 Calories = 4.2 joules 1 7 Not more than 65 89-90 2 28 Not more than 75 90-100

36. Oil Well Cement Oil well are drilled through sedimentary rock s through a great depth of in search of oil. That oil or gas may escape through the space b/w steel casing and rock formation. This cement may resist corrosive condition from sulphur gase s or water contains dissolved salts . It will be used in 175 o C temperature and 1300 kg/m 2 pressure . This cement obtained in two ways: Adjust cement compounds or adding Retarders. Adding workability agents .

37. IRS-T 40 Special Cement This cement is manufactured as per specification laid down by ministry of Railways under IRS-T40: 1985. It is Very fine cement with high C 3 S content for high early strength. It will be used to manufacture of concrete sleepers for Indian Railways . This cement also used in prestressed concrete elements, high rise buildings, high strength concrete.

38. References M S Shetty , Concrete Technology Theory and Practice, S Chand & Company Pvt Ltd,2011. Dr M L Gambir , Concrete Technology Theory and Practice, Tata McGraw Hill Education Pvt Ltd, 2015. P Kumar Mehta, Paulo J M Monteiro , Concrete Micro Structures, Properties and Materials, Tata McGraw Hill Education Pvt Ltd, 2008. S C Rangwala , Engineering Materials(Material Science), Charotar Publishing House Pvt Ltd, 2009. PPT from , Hydration of Cement, Institut de Mineralogie et Petrographiem University de Fribourg. Dr.Abbas Oda Dawood , Concrete Technology, Lecture Notes, Department of Civil Engineering- Misan University .

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