Types Of Cement PDF

12/03/1446 TYPES OF CEMENT Cements of unique characteristics for desired performance in a given environment are being manufactured by changing the chemical composition of OPC or by using additives, or by usin...

12/03/1446 TYPES OF CEMENT Cements of unique characteristics for desired performance in a given environment are being manufactured by changing the chemical composition of OPC or by using additives, or by using different raw materials. Some of the cements available in the market are as follows 1 12/03/1446 RAPID HARDENING PORTLAND CEMENT has high lime content and can be obtained by increasing the C3S content but is normally obtained from OPC clinker by finer grinding (450 m2/kg). The basis of application of rapid hardening cement (RHC) is hardening properties and heat emission rather than setting rate. This permits addition of a little more gypsum during manufacture to control the rate of setting. RHC attains same strength in one day which an ordinary cement may attain in 3 days. However, it is subjected to large shrinkage and water requirement for workability is more. The cost of rapid hardening cement is about 10 per cent more than the ordinary cement. Concrete made with RHC can be safely exposed to frost, since it matures more quickly. Uses: It is suitable for repair of roads and bridges and when load is applied in a short period of time. RAPID HARDENING CEMENT 2 12/03/1446 HIGH ALUMINA CEMENT Uses: It is resistant to the action of fire, sea water, acidic water and sulphates and is used as refractory concrete, in industries and is used widely for precasting. It should not be used in places where temperature exceeds 18°C. SUPERSULPHATED PORTLAND CEMENT Uses: Supersulphated Portland cement is used for similar purpose as common Portland cement. But owing to its higher water- resisting property, it should be preferred in hydraulic engineering installations and also in constructions intended for service in moist media. RCC pipes in ground water, concrete structures in sulphate bearing soils, sewers carrying industrial effluents, concrete exposed to concentrated sulphates of weak mineral acids are some of the examples of this cement. This cement should not be used in constructions exposed to frequent freezing-and-thawing or moistening-and-drying conditions 3 12/03/1446 SULPHATE RESISTING PORTLAND CEMENT use of sulphate resisting cement is particularly beneficial in conditions where the concrete is exposed to the risk of deterioration due to sulphate attack; concrete in contact with soils or ground waters containing excessive sulphate as well as concrete in sea water or exposed directly to sea coast. LOW HEAT PORTLAND CEMENT properties: Less heat is evolved during setting low heat Portland cement. When tested by Le Chatelier method and autoclave test the expansion should not be more than 10 mm and 0.8%, respectively. The minimum initial setting time should not be less than 60 minutes, and the final setting should not be more than 600 minutes. Uses: It is most suitable for large mass concrete works such as dams, large raft foundations, etc. 4 12/03/1446 PORTLAND PUZZOLANA CEMENT Uses: It has low heat evolution and is used in the places of mass concrete such as dams and in places of high temperature QUICK SETTING PORTLAND CEMENT Uses: It is used when concrete is to be laid under water or in running water. 5 12/03/1446 WHITE AND COLORED PORTLAND CEMENT Properties: The compressive and transverse strength of this cement is 90 per cent of that of 33 grade ordinary Portland cement Uses: These cements are used for making terrazzo flooring, face plaster of walls (stucco), ornamental works, and casting stones. AIR ENTRAINING AGENT 6 12/03/1446 STORAGE OF CEMENT Portland cement is kept in sacks of 0.035 m3 (50 kg) capacity for local use. These are stored for short period of time in air tight room avoiding moisture and dampness, at some distance from walls and at some height from floors. The stack should be covered with suitable coverings to avoid circulation of air through the stack and not more than ten bags should be stacked one over another. OBJECTIVE QUESTION 1. Pick out the incorrect statement (a) Cement is adhesive as well as cohesive material (b) Portland cement is of hydraulic type (c) For civil engineering works generally calcareous cements are used (d) Portland cement is an example of natural cement 7 12/03/1446 3. The temperature range in a cement kiln is (a) 500 to 1000° C (b) 1000 to 1200° C (c) 1300 to l500°C (d) 1600 to 2000°C 4. Consider the following statements: When cement is tested for setting time; on gauging its shows quick setting. This phenomenon known as “Flash set” of cement is due to the presence of high 1. tricalcium Aluminate (C3A) in cement 2. alkalis in cement 3. tricalcium silicate (C3S) in cement Which of these statements are correct? (a) 1, 2 and 3 (b) 2 and 3 (c) l and 2 (d) l and 3 5. Pick out the incorrect statement. (a) For hydraulic structures, a cement with small percentage of C3S and more C2S is recommended. (b) Setting and hardening of cement stop as soon as the concrete becomes dry. (c) The product C-S-H gel is known as tobermorite gel. (d) The stiffening of cement without strength development is caused because of C4AF 6. The rate of heat evolution of the following four compounds in decending order is 1. C3S 2. C2S 3. C3A 4. C4AF (a) 1, 2, 3, 4 (b) 3, 1 ,4, 2 (c) 3, 4, 1, 2 (d) 3, 4, 2, 1 7. The rate of heat of hydration of the four Bogue compounds in decending order is (a) C3S, C2S, C3A, C4AF (b) C3S, C3A, C2S, C4AF (c) C4AF, C3A, C2S, C3S (d) C4AF, C3S, C3A, C2S 8. The bound water (by weight) % required for complete hydration of cement is about (a) 15 (b) 23 (c) 38 (d) 40 9. Which of the following pairs is not matched correctly? (Cement test) (Apparatus) (a) Fineness Nurse and Blains (b) Consistency Vicat (c) Soundness Le-Chatelier (d) Sp. gravity Lea and Nurse 8 12/03/1446 10. Ordinary Portland cement should have surface area not less than (in mm2/g x 102) (a) 2250 (b) 3000 (c) 3250 (d) 4000 11. To produce low heat cements, it is necessary to reduct the compound (a) C3S (b) C2S (c) C3A (d) C4AF 12. For complete hydration of cement the w/c ratio needed is (a) less than 0.25 (b) more than 0.25 but less than 0.35 (c) more than 0.35 but less than 0.45 (d) more than 0.45 but less than 0.60 13. High alumina cement is produced by fusing together a mixture of (a) limestone and bauxite (b) limestone, bauxite and gypsum (c) limestone, gypsum and clay (d) limestone, gypsum, bauxite, clay and chalk 14. Consider the following statements: High early strength of cement is obtained as a result of 1. fine grinding 2. decreasing the lime content 3. burning at higher temperatures 4. increasing the quantity of gypsum Of these statements (a) 1 and 2 are correct (b) 1 and 3 are correct (c) 2, 3 and 4 are correct (d) 1, 3 and 4 are correct 15. Four main oxides present in ordinary Portland cement are: CaO, A12O3, SiO2 and Fe2O3. Identify the correct ascending order of their proportions in a typical composition of OPC (a) Al2O3, Fe2O3, CaO, SiO2 (b) A12O3, CaO, Fe2O3, SiO2 (c) Fe2O3, Al2O3, SiO2, CaO (d) Fe2O3, SiO2, Al2O3, CaO 9 12/03/1446 16. Match List-I with List-II and select the correct answer using the codes given below the lists: List-I List-II (Type of cement) ( Characteristics) A. Air entraining Portland cement 1. Suitable for very large structures B. Low heat Portland cement 2. Unsuitable for very large masses of concrete C. Hydrophobic Portland cement 3. Greater resistance to frost attack D. Rapid hardening Portland cement 4. Safe storage under unfavourable conditions of humidity Codes: (a) A B C D (b) A B C D 4 2 1 3 3 4 1 2 (c) A B C D (d) A B C D 3 1 4 2 4 1 2 3 17. Match List-I (Type of cement) with List-II (Chracteristics) and select the correct answer using the codes given below the lists: List-I List-II (Type of cement) ( Characteristics) A. Ordinary Portland cement 1. The percentage of C3S is a maximum and is of the order of 50% B. B. Rapid hardening cement 2. The percentage of C2S and C3S are the same and of the order of 40% C. Low heat cement 3. Reacts with silica during burning and causes particles to unite together and development of strength D. Sulphate resistant cement 4. Preserves the form of brick at high temperature and prevents shrinkage Codes: (a) A B C D (b) A B C D 2 4 1 3 3 1 4 2 (c) A B C D (d) A B C D 2 1 4 3 3 4 1 2 10 12/03/1446 18. Consider the following oxides: 1. Al2O3 2. CaO 3. SiO2 The correct sequence in increasing order of their percentage in an ordinary Portland cement is (a) 2, 1, 3 (b) 1, 3, 2 (c) 3, 1, 2 (d) 1, 2, 3 19. 19. Consider the following statements: High Alumina Cement 1. has highly early compressive strength and high heat of hydration than OPC 43 grade 2. is not suitable to be used in cold regions Which of these statements is/are correct? (a) 1 alone (b) 2 alone (c) both 1 and 2 (d) neither 1 nor 2 11 12/03/1446 12 12/03/1446 13 12/03/1446 14