Concrete Test Hammer

Concrete Test Hammer

Concrete Test Hammer is an instrument which is easy to use, for quick and approximate measurement of the resistance to pressure of manufactured concrete products. The principles on which Concrete Test Hammer works are based on the rebound impact of a hammer on a piston which rests against the surface of the concrete products. The Greater the resistance of the concrete, greater is the rebounded impact. By reading this rebound impact on a scale and relating it to curves on graphs supplied with the instrument, the resistance to compression in MPa or PSI can be found, with 20% of actual

Consists of a barrel in which is housed a hammer mass attached to an impact spring which slides on a guide bar. A plunger is attached to the guide bar which is pressed against the surface to be tested. As the piston is pressed against the surface to be tested, on reaching the compressive strength, the hammer mass is released and rebounds to a certain extent (according to the strength of the surface) which is indicated by a rider on a calibrated scale. A lock button fixed on the body of the hammer locks the rider in place and the rider can be recared to zero position by using the same button. The equivalent compressive strength can be computed from the chart supplied. Each hammer is calibrated against at standard test hammer, and is suitable for specimen of compressive strengths 100 - 700 kg/cm. The instrument, complete with a grinding stone for polishing the test surface, is supplied in carrying case.

STUDY ON STRENGTH OF CONCRETE USING VARIOUS COARSE AGGREGATES, PART-21

CHAPTER – 7 

DISCUSSION

The following conclusion may be drawn from the experimental investigation. In this study, the strength of concrete varied with changing coarse aggregate in constant mix proportion. The design strength was 2800 psi but the experimental result shows that

           •   For compressive strength

Types of coarse aggregate	Average strength (psi)
Stone chips	2135.33
Brick chips	2229.67

So the ratio of the average strength of coarse aggregate is

                                       Stone chips: Brick chips = 2135.33: 2229.67

                                                                               = 1: 1.05

           •   For tensile strength

Types of coarse aggregate	Average strength (psi)
Stone chips	143.33
Brick chips	166.33

So the ratio of the average strength of coarse aggregate is

                                       Stone chips: Brick chips = 143.33: 166.33

                                                                               = 1: 1.16

          •   For flexural strength

Types of coarse aggregate	Average strength (psi)
Stone chips	525
Brick chips	450

So the ratio of the average strength of coarse aggregate is

                                       Stone chips: Brick chips = 525: 450

                                                                               = 1: 0.86

          •   For shear strength

Types of coarse aggregate	Average strength (psi)
Stone chips	98.33
Brick chips	84.5

So the ratio of the average strength of coarse aggregate is

                                       Stone chips: Brick chips = 98.33: 84.5

                                                                               = 1: 0.86

There are some limitations and difficulties which are as follows:

(1)  Compaction was done by tamping rod. At the time of compaction a little quantity of water was forced out of the mould that reduced the required quantity of water.

(2)  Twelve cylinders and six beams were tested. We think if we would increase the number of test specimens that would certainly give more accurate results.      

STUDY ON STRENGTH OF CONCRETE USING VARIOUS COARSE AGGREGATES, PART-20

6.2 Graphical form

6.2.1 For compressive strength

Fig No. 6.1: Variation of Compressive stress for different coarse aggregate

6.2.2 For Tensile Strength

Fig No. 6.2: Variation of Tensile stress for different coarse aggregate

6.2.3 For Flexural Strength

Fig No. 6.3: Variation of Flexural stress for different coarse aggregate

6.2.4 For Shear Strength

Fig No. 6.4: Variation of shear stress for different coarse aggregate

STUDY ON STRENGTH OF CONCRETE USING VARIOUS COARSE AGGREGATES, PART-19

CHAPTER − 6

EXPERIMENTAL RESULTS

6.1 Tabular form

Table No. 6.1. Materials test results

Constituents	Name of the experiment	Result
Sand	Fineness  modulus	1.18
	Specific gravity	2.48
Brick Chips	Fineness  modulus	6.45
	Specific gravity	1.72
	Unit weight	68.5 (lb/ft3)
Stone chips	Fineness  modulus	6.85
	Specific  gravity	1.75
	Unit weight	95 (lb/ft3)

Table No. 6.2: Stone Chips

Load Type	Sample Type	Sample no	Load (KN)	Stress (psi)	Average stress (psi)
Compression in 28 days	Cylinder	1	275	2216	2135.33
		2	260	2095
		3	260	2095
Tension in 28 days	Cylinder	1	70	564	143.33
		2	70	564
		3	75	605
Flexure in 28 days	Beam	1	25	625	525
		2	19	475
		3	19	475
Shear in 28 days	Beam	1	25	117	98.33
		2	19	89
		3	19	89

Table No. 6.3: Brick Chips

Load Type	Sample Type	Sample no	Load (KN)	Stress (psi)	Average stress (psi)
Compression In 28 days	Cylinder	1	285	2297	2229.67
		2	270	2176
		3	275	2216
Tension in 28 days	Cylinder	1	80	645	166.33
		2	100	806
		3	70	564
Flexure in 28 days	Beam	1	19	475	450
		2	17	425
		3	18	450
Shear in 28 days	Beam	1	19	89	84.5
		2	17	80
		3	18	84.5