Answer by Rakshita Nagayach:
- Natural cement is obtained by burning and crushing the stones containing clay, carbonate and some amount of carbonate of magnesia.
- It is used in construction of buildings and various structures, as an ingredient of concrete.
- Its constituents comprise of Lime, Silica, Alumina, Calcium sulphate, Iron oxide, Magnesia, Sulphur and Alkalies.
- Its initial setting time is 30 minutes and final setting time is about 10 hours. (For Ordinary Portland Cement)
- The ingredients are burnt at very high temperatures under the 'Dry Process' and 'Wet process'.
- Most common grades of cement used in India are Grade 33, 43 and 53. The name Grade 33 implies that cement attains a compressive strength of 33 N/mm^2 after a curing period of 28 days.
- Packing of cement is mostly done in conventional jute or gunny bags.
- The field tests done are (i) Colour
(iii) Presence of lumps
- Laboratory tests are:(i) Chemical composition
(iii) compressive strength
(iv) Tensile strength
(vi) Setting times
- The cement concrete is a mixture of cement, sand, pebbles or crushed rock and water, which when placed in the skeleton of forms and allowed to cure, becomes hard like a stone.
- It has high compressive strength and is the major building material used in construction of structures.
- Its constituents comprise of Cement, aggregate and water. For RCC, steel is also introduced to concrete.
- Its initial setting time and final setting time is quite similar to that of cement.
- The process of selection of relative proportion of cement, sand coarse aggregate and water, so as to obtain a concrete of desired quality is known as proportioning concrete.
- Concrete is graded as M 20, M 25 etc. where M stands for the mix and the number stands for standard compressive strength of that mix (in N/mm^2) after 28 days.
- Concrete is mostly prepared on the site itself or is prepared at plants and brought to the site as Ready Mix Concrete.
- The lab tests of concrete include the tests of the constituents. One of them is aggregate and the tests are: (i) Abrasion test
(ii) Crushing test
(iii) Shape test
(iv) Impact test
(v) Soundness test
(vi) Specific gravity and water absorption test
(vii) Stripping value test
- Asphalt is commonly known as Bitumen in India. It is a petroleum product obtained by the fractional distillation of of petroleum crude. It is a complex organic material.
- It is used in laying of roads and sometimes in sealing road joints.
- It comprises of saturated Hydrocarbons, Naphthene aromatics, polar aromatics and asphaltenes.
- Setting of Asphalt is based on rate of curing/hardening after the application. Examples are RC-O, MC-O, SC-2, etc.
- It is prepared by fractional distillation of petroleum and melted at the site and then used.
- Its specific gravity lies in the range 0.97 to 1.02.
- The lab tests conducted are: (i) Penetration test
(ii) Ductility test
(iii) Viscosity test
(iv) Float test
(v) Specific gravity test
(vi) Softening point test
(vii) Flash and fire point test
(viii) Solubility test
(ix) Spot test
(x) Loss on heating test
(xi) Water content test.
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