Types of Portland cement
The properties of cement during hydration vary according to:
1) Chemical composition 2) Degree of fineness
It is possible to manufacture different types of cement by changing the percentages of their raw materials.
1- Ordinary Portland cement ( type I )
This type of cement use in constructions when there is no exposure to sulfates in the soil or groundwater.
L.S.F. is limited between 0.66-1.02
This factor is limited – to assure that the lime in the raw materials, used in the cement manufacturing is not so high, so as it cause the presence of free lime after the occurrence of chemical equilibrium which cause unsoundness of cement. While too low a L.S.F. would make the burning in the kiln difficult and the proportion of C3S in the clinker would be too low.
• Percentage of SO3 limited by 2.5% when ?7%, and not more than 3% when C3A>7%
• Loss of ignition L.O.I 4% (max.)
• Percentage of MaO 5% (max.)
• Fineness not less than 2250 cm2/g
• C3S limits ( 42 – 67 )%
• C2S limits ( 8 – 31 )%
• C3A limits ( 5 – 14 )%
• C4AF limits (6 – 12 )%
2- Rapid Hardening Portland Cement ( type III )
This type develops strength more rapidly than ordinary Portland cement. The initial strength is higher, but they equalize at 2-3 months .Setting time for this type is similar for that of ordinary Portland cement .The rate of strength gain occur due to increase of C3S compound, and due to finer grinding of the cement clinker ( the min. fineness is 3250 cm2/g (according to IQS 5). Rate of heat evolution is higher than in ordinary Portland cement due to the increase in C3S and C3A, and due to its higher fineness. Chemical composition and soundness requirements are similar to that of ordinary Portland cement.
Uses
a) The uses of this cement is indicated where a rapid strength development is desired (to develop high early strength, i.e.( its 3 days strength equal that of 7 days ordinary Portland cement), for example:
i) When formwork is to be removed for re-use
ii) Where sufficient strength for further construction is wanted as quickly as practicable, such as concrete blocks manufacturing, sidewalks and the places that cannot be closed for a long time, and repair works needed to construct quickly.
b) For construction at low temperatures, to prevent the frost damage of the capillary water.
c) This type of cement does not use at mass concrete constructions.
Note//For more details download the attached file.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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