CE 1205 CONSTRUCTION MATERIALS WEEK 10 Chapter 6

CE 1205 CONSTRUCTION MATERIALS WEEK 10 Chapter 6 PORTLAND CEMENT Power. Point® Slides by Salmaliza Salleh Last Updated: 2/9/2018 © LMS SEGi education group 1

Factors Affecting the Properties of Cement: 1. 2. 3. 4. 5. 6. Chemical composition Fineness Hydration of cement Setting time Soundness Loss on ignition Last Updated: 2/9/2018 © LMS SEGi education group 2

3. Hydration of Cement • • Heat is liberated as cements set and hardened by reacting with water It is the rate in which heat is released governed the strength of concrete • • • Last Updated: 2/9/2018 Depends on the composition of cement Rate of hydration and heat evolves increases with the fineness of cement but, Total amount of heat liberated in unaffected by fineness © LMS SEGi education group 3

3. Hydration of Cement Minimum compressive strength of concrete cubes specified by BS 4550 for Portland Cement Type of Portland Cement Compressive Strength (N/mm 2) 3 days OPC RHPC Portland-blastfurnace LHPC-blastfurnace Sulphate-resisting Last Updated: 2/9/2018 7 days 28 days 13 18 8 5 3 10 14 7 - 29 33 22 19 14 27 © LMS SEGi education group 4

4. Setting Time • • The time from the addition of water to the initial and final setting stage. Refers to changes of the cement paste from _____ to ______ Influenced by temperature, humidity of air, kneading of paste and quantity of gypsum in cement Can be determined with the VICAT apparatus (BS 4550). Last Updated: 2/9/2018 © LMS SEGi education group 5

• ______ Setting Time • • • Defined as beginning of the noticeable stiffening in the cement paste and it’s correspond to the rapid rise in temperature Normally takes about 45 -175 minutes Completion of setting The stiffening of cement paste increases as the hydration increases When complete, the final hardening process begins Takes about 3 – 10 hours ______ • Last Updated: 2/9/2018 Is referred to the gained of the strength of the cement paste © LMS SEGi education group 6

Setting time for different types of Portland Cement: Cement Type Setting Time Final setting time, minutes (max) OPC Initial setting time, minutes (min) 30 RHPC 30 600 LHPC 60 600 Last Updated: 2/9/2018 © LMS SEGi education group 600 7

5. Soundness • An excessive change in volume, particularly expansion of a cement paste after setting, indicates that the cement is unsound. • • The unsoundness is due to the presence of free lime and magnesia in the cement. The unsoundness may be reduced by: • • • Cracking Disintegration of concrete surface Limiting the Mg. O content to less than 0. 5%, Fine grinding, Allowing the cement to aerate for several days, and Thorough mixing. Test for soundness is the Le Chateliar as specified in BS 12: 1971 Last Updated: 2/9/2018 © LMS SEGi education group 8

6. Loss on Ignition • The loss on ignition test is carried out to determine the loss of weight when the sample is heated to 900 to 1000°C for minimum of 15 minutes. Normally the loss is around 2%. Maximum allowable is 4%. • The loss of weight is a measure of the freshness of cement. • The less the loss on ignition, the better the cement. Last Updated: 2/9/2018 © LMS SEGi education group 9

MANUFACTURE OF PORTLAND CEMENT 1. _____ and grinding the raw materials 2. ______ them intimately in certain proportions 3. _______ the prepared mix in a large-rotary kiln at a very high temperature 4. Cooling and grinding the burned product, known as ‘______’ to a fine powder with 5% of _______ added Last Updated: 2/9/2018 © LMS SEGi education group 10

MANUFACTURE OF PORTLAND CEMENT Definitions: • _____ Mill • The circular pit with revolving radial arms carrying rakes which breaks up the lumps of solid raw materials • _____ Mill • • Last Updated: 2/9/2018 • • _____ Kiln • • • A mill where coarse materials are grounded to fine particles • ______ A large steel cylinder lined with fire bricks or called ‘refractory lined’. © LMS SEGi education group A liquid of creamy consistence with water content of between 35% to 50% and only a fraction of the material (2%). Kept in storage tanks. E. g: Soda ash Na 2 CO 3 (Sodium Carbonate) to reduce viscosity Sodium Silicate Na 2 Si. O 3 is used to reduce moisture 11

WASH MILL Last Updated: 2/9/2018 © LMS SEGi education group 12

BALL MILL Last Updated: 2/9/2018 © LMS SEGi education group 13

Clinker • Last Updated: 2/9/2018 Is the product of slurry inside a rotary kiln where slurry undergoes chemical changes due to high temperature and lime, silica and alumina recombine mass then fuses into ball of 3 to 25 mm. © LMS SEGi education group 14

Manufacturing Process The mixing of raw materials can be done either in water or in a dry condition. They are called ‘wet’ and ‘dry’ processes. ‘Wet’ Process • Raw materials are mixed with water. ‘Dry’ Process • The correct proportions of raw materials are crushed and fed into a grinding mill • Dried and reduced in size to a fine powder called “raw meal” • Raw meal is pumped to a blending silo for final adjustment in requisite proportions of materials required. • Compressed air is used to obtain a uniform and intimate mixture Last Updated: 2/9/2018 © LMS SEGi education group 15

Last Updated: 2/9/2018 © LMS SEGi education group 16

SILO TRUCK BAGS Last Updated: 2/9/2018 © LMS SEGi education group 17

ANY QUESTIONS? Picture retrieved from http: //www. cartoonstock. com/directory/C/Cement. asp Last Updated: 2/9/2018 © LMS SEGi education group 18

References • Smith W. F. (1993). Foundations of Materials Science and Engineering, 2 nd edition, Mc. Graw-Hill International Edition • Neville, A. M. (1995). Properties of Concrete, 4 th edition. , Addison Wesley Longman Limited, England • John, V. B. (1992) Introduction to Engineering Materials, 3 rd edition, Mc. Millan Press Ltd. • Everett, A. (1996). Materials, 3 rd edition Addison Wesley Longman Limited, England Last Updated: 2/9/2018 © LMS SEGi education group 19