Question

The concreting is going to be made for precast concrete.

Choose the proper workability for the fresh concrete (find from the reference books and standards, and mention your reference in the homework report).

Design an experiment to measure the workability of the concrete. Mention the method you are going to use to measure the workability and give the aimed value planned to obtain with the chosen method. Explain the experiment.

Answer 1

workability is a property of raw or fresh concrete mixture.In simple words,workability means the easy of placement and workable concrete means concrete which can be placed and can be compacted easily without any segregation.

Slump cone Test

Apparatus;

1)Metalic Mould- 20cm Top diameter 10 cm bottom diameter Height -30 cm

2)Steel Tamping rod -16mm diameter 60 mm Height

Procedure;

Mould is Placed on a Horizntal smooth surface and non-absorbent surface and it is than filled in four layers of concrete with thickness of each layer of one-fourth of height of mould.Each layer is tamped with rod 25 times such that the concrete should be distributed uniformly.After filling the Mould with concrete remove the mould,then concrete will subside that is known as Slump.This operation should be carried out without jerks or vibrations and with in a period of 2 minutes after completion of final tamping.The difference between the height of the mould and highest point of the subsided concrete is measured.The subsided measured is the slump of the concrete.The slump may be

1)shear slump

2)collapse slump

3)True slump

The True slump is desired form of slump that is required.