SPECIFIC GRAVITY OF CEMENT

courtesy of Fisher Scientific

Specific gravity is defined as the ratio of density or unit weight of any object or liquid with that of water. But why do we need to check the specific gravity of cement for construction purposes? Knowing the specific gravity of cement is used in the calculation of mixture proportions. This is specifically working on the absolute volume of a concrete mix which can be determined exactly if the weight and the specific gravity of the components are known.

For example:

CA:        weight in kN / (sp gr of gravel x 9.807kN/cum)      = volume of CA

FA:         weight in kN / (sp gr of sand x 9.807kN/cum)        = volume of FA

Cement: weight in kN/ (sp gr of cement x 9.807kN/cum)    = volume of Cement

Water:    weight in kN / (1 x 9.807kN/cum)                        = volume of water

                                                       Total Volume             =  volume in cum

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FINENESS OF CEMENT

courtesy of  Gardener's Supply

There are different physical on-site tests done to check if the cement ordered is still in good workable quality. Few easy tests are as follows:

• Color quality would show the excess amounts of lime and clay.
• Smooth rub checks on sand adulteration.
• Cool feeling when hand is inserted in the bag would means absence of hydration reaction. 

Other tests would involved small procedures which can be done on site such as float test and shape test where cement would be combined with moisture or water.

courtesy of Indiamart

LUMPS are also one characteristic which would need to be given attention. The presence of lumps would connote that setting has already taken. With lumps, ASTM procedure of sieving would determine the particles of cement and presence of lumps. 

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LABORATORY TESTING OF CONSTRUCTION MATERIALS

Testing of materials is a crucial part of the construction process. Before any contractor will start using the materials, random sampling and laboratory testing are made in order to make certain that grades are as ordered and also to determine the suitable procedures necessary to work with them. Sampling is preferable immediately after the materials are delivered. However, with usual time constraints in the construction, sampling and testing are usually done only before materials are needed in construction. This can cause delays. 

Students are introduced not only on the characteristics and properties of construction materials but also to the various ways of testing. Laboratory experiments are according to ASTM.

Different basic materials will be under study in the course CE 415: Construction Materials and Testing.

• Cement
• Concrete
• Aggregates
• Steel 
• Timber
• Masonry

Laboratory experiments under the course are as follows:

• Introduction
• Fineness of Cement
• Specific Gravity for Cement
• Test for Cement Consistency
• Setting Time of Cement
• Mortar Test
• Specific Gravity and Moisture of Aggregates
• Bulk Density of Aggregates
• Sieve Analysis of Aggregates
• Slump Test
• Concrete Cylinder Test
• Test of Steel
• Test of CHB
• Test of Timber