DETERMINATION OF WORKABILITY OF CONCRETE (SLUMP


DETERMINATION OF WORKABILITY OF CONCRETE (SLUMP TEST)
(IS: 1199 – 1959)
Object:

This method of test specifies the procedure to be adopted, either in the laboratory or during the progress of work in the field, for determining, by the slump test, the consistency of concrete.

Apparatus:

a) Mould: the mould for the test specimen shall be in the form of the frustum of a cone having the following internal dimensions:
                                   
                             Dimensions                            cm
                             Bottom diameter.                   20
                             Top diameter.                        10
                             Height.                                    30
b) Tamping Rod: The tamping rod shall be of steel or other suitable material, 16 mm in diameter, 0.6m long and rounded at one end.

Procedure:

The internal surface of the mould shall be thoroughly cleaned and freed from superfluous moisture and any set concrete before commencing the test. The mould shall be placed on a smooth, horizontal, rigid and non-absorbent surface, such as a carefully leveled metal plate, the mould being firmly held in place while it is being filled. The mould shall be filled in four layers, each approximately one-quarter of the height of the mould. Each layer shall be tamped with 25 strokes of the rounded end of the tamping rod. The strokes shall be distributed in a uniform manner over the cross-section of the mould and for the second and subsequent layers shall penetrate into the underlying layer. The bottom layer shall be tamped throughout its depth. After the top layer has been rodded, the concrete shall be struck off level with a trowel or the tamping the rod, so that the mould is exactly filled. Any mortar, which may have leaked out between the mould and the base plate, shall be cleaned away. The mould shall be removed from the concrete immediately by raising it slowly and carefully in a vertical direction. This allows the concrete to subside and the slump shall be measured immediately by determining the difference between the height of the mould and that of the highest point of the specimen being tested. The above operation shall be carried out at a place free from vibration or shock, and within a period of two minutes after sampling.

The slump measured shall be recorded in terms of millimeters of subsidence of the specimen during the test. Any slump specimen which collapses or shears off laterally gives incorrect result and if this occurs the test shall be repeated with another sample. 




























Comments

Post a Comment

Testing method

TEN PERCENT FINES VALUE.

Image
TEN PERCENT FINES VALUE. ( BS : 812 – PART – 111 ) INTRODUCTION: The ‘Ten percent fines’ value is a measure of resistance of the aggregates to the crushing. Object : To determine the ten percent value of aggregates by crushing machine apparatus. Apparatus : a) Steel cylinder with open ends, and internal diameter 152mm, square base plate, plunger having a piston of diameter 150mm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder. b) Cylindrical measure having internal diameter of 115mm and height 180mm. c) Steel tamping rod with one rounded end, having a diameter of 16mm and length 450 to 600mm. d) Balance of capacity 3 kg with accuracy up to 1gm. e) Compressive testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonnes per minute. Procedure : The aggregate passing 14mm IS sieve and retained on 10mm IS sieve is ...
Read more

DUCTILITY TEST. ( IS : 1208 – 1978 )

DUCTILITY TEST. ( IS : 1208 – 1978 ) INTRODUCTION : In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of the aggregates. Object : To determine the ductility of the bituminous material. Apparatus : a) Ductility machine. b) Briquette moulds. c) Knife. Procedure : The bitumen sample is melted to a temperature of 75 to 100 0 C above the approximate softening point until it is fluid. It is strained through 90 micron sieve, poured in the mould assembly and placed on a brass plate, after a solution of glycerin and dextrin is applied at all surfaces of the mould exposed to bitumen. After 30 to 40 minutes, the plate assembly along with the sample is placed in water bath maintained at 27 0 C for 30 minutes. The sample and mould assembly are removed from water bath ...
Read more

STRIPPING VALUE OF AGGREGATES.

STRIPPING VALUE OF AGGREGATES. (IS: 6241 – 1959) INTRODUCTION: Bitumen and tar adhere well to all normal types of aggregates provided they are dry and are not exceptionally dusty. Largely the viscosity of the binder controls the process of binding. When the viscosity of the binder is high, coating of aggregates by the binder is slower. In the absence of water there is practically no adhesion problem in bituminous road construction. Two problems are observed due to the presence of water. First, if aggregate is wet and cool it is normally not possible to coat with a bituminous binder. This problem can be dealt with by removing the water film on aggregate by drying, and by increasing the mixing temperature. Second problem is stripping of coated binder from the aggregate due to the presence of water. This problem of stripping is experienced only with bituminous mixtures, which are permeable to water. Object : To determine the stripping value of aggregates by static i...
Read more