The Slump Apparatus

The slump apparatus is made of steel in the form of the frustum of a cone having a bottom diameter of 20 cm, top diameter of 10 cm and height of 30 cm. the internal surface of the mould is made smooth and clean. The mould is placed on smooth horizontal surface, filled with concrete in four layers of each approximately one quarter of the height of the mould and each layer is stamped with 16mm diameter, 0.6 m long steel rod rounded at one end for 25 times. At the end the concrete is leveled with a trowel. The mould is removed from the concrete immediately by raising the mould slowly in vertical direction.

The slump is measured in terms of millimeter of subsidence of the concrete during the test, the experimental setup is as shown in the Fig x. The compaction factor apparatus has an upper hopper with top internal diameter of 25.4 cm, bottom internal diameter of 12.7 cm and internal height of 27.9 cm. the lower hopper has a top internal diameter of 22.9 cm, bottom internal diameter of 12.7 cm and internal height of 22.9 cm. the cylinder at the base has an internal diameter of 15.2 cm and internal height of 30.5 cm.

The lower ends of the hoppers are closed with tightly fitted hinge trap doors having quick release catches. The sample of concrete is placed on the upper hopper and leveled. The trap door is opened for the concrete to fall into the lower hopper. After the concrete comes to rest the trap door of the lower hopper is opened and the concrete is allowed to fall into the cylinder. The excess of concrete remaining above the level of the top of the cylinder is cut by a trowel. The weight of the partially compacted concrete is noted. The same cylinder is refilled with concrete from the same sample in layer of about 5 cm deep and heavily rammed. The ratio of weight of partially compacted concrete to the weight of fully compacted concrete is noted as compaction factor. The flow table apparatus has a metal casting in the form of frustum of a cone with a base of 25 cm in diameter, upper diameter of 17 cm and a height of 12 cm. the flow table is capable of raising and dropping at a height of 12.5mm on a rate of 15 times per 15 seconds. The mould is filled with concrete in two layers, each layers ridded with 25 strokes. The mould is removed and the concrete is vibrated. The average spread of concrete is measured.