R.C.C. BEAM

1. MATERIALS

a. Cement:

Cement used shall be of 53 grade for Birla super make. The cement should be fresh (within 2 months from the date of manufacture). 

b. Coarse Aggregate:

Coarse aggregate shall be of basalt stone. It should be well graded. The particles should be angular and sharp. The aggregate shall be free from soft materials,  organic materials, silt or other deleterious material

c. Fine aggregate:

Fine aggregate shall be river sand. It should be well graded. It should be free of excessive amount of silt (not more than 8%). It should not contain organic impurities. If the sand is wet it should be tested for bulking. If the sand has bulked, extra sand shall be added of the required percentage volume. Crushed stone can also be used as fine aggregate if allowed by the structural Engineer. The amount of crushed stone used as fine aggregate shall be as per the instructions of the Engineer.

d. Water:

Water used shall be potable water. It should be free from organic and chemical impurities and excessive amount of salt. If in doubt the water shall be got tested from the laboratory.

e. Reinforcement:

The reinforcement bars shall be TMT bars (Thermo mechanically treated). The grade of the steel used shall be Fe415. Test report of the steel shall be obtained from the manufacturer. The bars shall be free from excessive amount of rust and scaling.

2. FORMWORK:

The formwork used shall be made from timber planks or plywood.  The props used shall be wooden bullies or steel props. The formwork shall be so designed as to be water tight, strong enough to take the loads from the materials, labour and vibration. The formwork shall be so designed that the sides of the formwork can be removed after 24 hours without disturbing the bottom plank which shall be kept till the full period of setting as specified. The props used shall be strong enough and should be connected to each other by bracing.

3. PROPORTIONING:

The different ingredients of concrete shall be mixed together by volume using a measure box of 35 litres volume.  Cement shall be added as one bag of 50 kg, sand shall be added as 2 boxes of sand and course aggregate as four boxes to get a proportion of 1:2:4.  Water shall be added as per the water cement ratio specified as per the following formula (water in litres = 50xwater cement ratio) where 50 is the weight of one bag of cement in kg

4. MIXING:

All the ingredients shall be mixed in a mechanical mixer. The mixer shall be turned for a period of 1.5 minutes.

5. COVER BLOCKS:

Cover blocks of the required cover distance as specified shall be either made on the site from rich mortar or may be of readymade plastic type. The cover blocks shall be tied properly to the reinforcement so as to maintain the adequate cover required.

6. PLACING:

The cement concrete mix shall be placed within the formwork in such a way as to avoid segregation. The concrete shall not be dropped from a height exceeding 900mm. Care shall be taken to see that the concrete covers all the reinforcement.

7. VIBRATING:

The beam shall be vibrated by means of needle vibrators and by roding. Excessive vibration shall be avoided.

8. CURING:

After 12 hours of casting the sides of the beam formwork shall be removed and the beams shall be kept continuously wet by spraying water for a period of 14 days.  If required the beams shall be kept covered with gunny bags which shall be constantly wetted

9. TESTING:

During the casting minimum two test cubes shall be taken as per the procedure laid out in Indian Standards. The cubes shall be cured and sent to the lab for testing. Crushing strength of concrete shall be tested after 7 days and 28 days of casting.

10. Measurement:

The concrete shall be measured in cubic meters. The steel shall be measured separately in kg.