Technical - Type of Cements and On-site testing

Different types of cement:

TYPES OF CEMENT	COMPOSITION	SITUATUIONS	PURPOSES
Ordinary Portland Cement	OPC is manufactured by mixing limestone/chalk with shale/clay to form clinker which is then finely crushed to form grey colour cement	Commonly used for all type of construction works	Widely used in residential construction where special type of cement properties is not required
White Ordinary Portland Cement	WOPC is same as the Ordinary Portland Cement except the color	WOPC used in white washing purpose for aesthetic purpose	1. Used as a base coat before painting 2. Used to cover the hairline cracks on concrete surface to give smooth finish
Portland Pozzolana Cement	PPC is manufactured by adding pozzolana materials such as fly ash, shales, clays etc	It gains high compressive strength with age unlike rapid hardening cement. It is cheap and affordable	1. It is cheap and affordable 2. Mainly used in building construction where strength required with age 3. Water tightness
Rapid Hardening Portland Cement	RHPC manufactured by combining lime stone (finely grounded) and shale at high temperature	This type of cement is used where high strength is need to be achieved in initial stage quickly.	1. Road Pavement Works 2. Precast concrete casting (Beams, Colum’s etc)
Sulphate Resisting Cement	SRC is manufactured with less than 5% calcium aluminate to withstand Sulphate attacks	This type of cement is used where the concrete is direct contact with soil (which has high sulphate content)	1. Pile foundation 2. In Coastal area Works 3. Sewage and water treatment plants
Low Heat Cement	This type cement is produced by lowering the amount of tri-calcium aluminate (C3A) & di-calcium silicate (C2S)	This type of cement is used in mass constructions (like dams) and in high wear resistance required area	1. Mass Construction (Dams, Marine constructions) 2. Hydraulic Engineering Concrete 3. Retaining wall construction
Quick Setting Cement	This type of cement is manufactured by reducing the amount of gypsum and adding small amount of aluminium sulphate to accelerate setting time of cement	As the name suggests, it is used where the works needs to be done quickly	1. In Underwater Constructions 2. In Cold and Rainy weather Conditions
High Alumina Cement	HAC or CAC is produced from lime stone/Chalk and Bauxite	This cement is used in construction of refineries, factory or other workshop type structure because HAC is counter to high temperature	Used in Sewage structures and in acidic structures
Coloured Cement	Coloured cement is manufactured by mixing colour pigments (5-10 % ) with OPC	As the name suggests, It is used where coloured cements required for any aesthetic purpose	1. Artificial Marble 2. Floor finishing
Air Entraining Cement	AEC produced by mixing small amount of air entraining agent	It is used to fillup the gap in concrete which are produced by excessive amount of water during casting (later evaporated and leave the gap)	Used in frost resistance concrete (like said, frost also makes gap in concrete like water)
Hydrophobic Cement	This type of cement is manufactured by mixing admixtures like petrolatum, naphthalene soap which forms layer and act as water repellent	It is useful in wet climatic conditions	Useful when cement is stored for longer duration in wet climatic conditions
Expansive Cement	Expansive Cement is formed from the reaction of tri calcium aluminate (C3A) with Calcium Sulphate (C2SO4)	As the name suggests, it expands and increases in volume while settled. Used to avoid the shrinkage of concrete	1. Used in repair works (to create a bond with old concrete surface) 2. Used in Hydraulic Structures
43 Grade Cement:	Compression strength  43 MPa after 28 days	Where initial setting time is not a criteria.	Non-RCC structures, plastering works, pathways etc
53 Grade Cement:	Compression strength 53 MPa after 28 days of setting	Reinforced concrete structures, cement grouts, prestressed concrete structures of higher grades, instant plugging mortars etc.	It is used where earlier strength development is required

HOW TO CHECK QUALITY OF CEMENT AT SITE:

Cement is one of the most important materials used in construction. The strength of a structure depends upon several factors, cement quality is one of them. To achieve the desired strength of concrete and to increase the longevity of structure good quality cement should always be used.

So, it is important to check the quality of cement before using.

To check the quality of cement we need to pass some easy tests which are described below:

1. DATE OF PACKING: The strength of cement decreases with time. Check the manufacturing date in the bag before using. Generally, cement should be used before 90 days from the manufacturing date. The percentage of strength loss of cement is as follows:

a. 3 months old cement will provide 20-30% reduction in its specified strength.

b. 6 months old cement will provide 30-40% reduction in its specified strength.

c. 9 months old cement will provide 40-50% reduction in its specified strength.

2. CEMENT COLOR: The cement should be uniform in colour. Good quality cement should have grey colour with greenish shade.

3. CHECK FOR LUMPS: No lumps should be present in the cement. Lumps are formed due to contact of cement bags to moisture, dampness and rain at the time of transit or at the time of storage.

4. RUBBING TEST: Cement should feel smooth while rubbing in between fingers. If it gives a rough feeling that means cement is mixed with sand.

5 TEMPERATURE TEST: Simply insert your hand into the cement bag, it should give cool feeling if its quality is good. Otherwise, you may feel warm because of hydration reaction.

6. FLOAT TEST: Take some amount of cement and throw it in water. The cement should float for sometimes before it sinks in the water.

7. SETTING TEST: Make a thick cement paste with water and immerse it in water for 24 hours. It should be set and should not develop cracks.

8. STRENGTH TEST: Prepare a cement block of 25 mm x 25 mm and 200 mm in length. Now submerge it in water for 7 days. Now place it on supports 15 cm apart and load it with 34 kg weight. Block made from good cement will not show any signs of failure.