OBJECT: To Determine the splitting tensile strength of concrete.
STANDARDS:
ASTM C496/C496M-04 4.2
SCOPE:
This test method covers the determination of the splitting tensile strength of cylindrical concrete specimens, such as moulded cylinders and drilled core.
SIGNIFICANCE AND USE:
Splitting tensile strength is simpler to determine than direct tensile strength. Splitting tensile strength is used to evaluate the shear resistance provided by concrete in reinforced lightweight aggregate concrete members
APPARATUS:
Cylindrical Molds, Concrete Mixer, Trowel, Weighing Balance, Tamping Rod (Cylindrical), Water Tank, Compression Testing Machine etc.
MATERIALS:
Coarse Aggregates, Fine Aggregates, Cement, Water, Oil or Grease.
PROCEDURE:
1. Draw diametric lines on each end of the specimen using a suitable device that will ensure that they are in the same axial plane.
2. Determine the diameter of the test specimen to the nearest 0.01 in. [0.25 mm] by averaging three diameters measured near the ends and the middle of the specimen and lying in the plane containing the lines marked on the two ends.
3. Determine the length of the specimen to the nearest 0.1 in. [2 mm] by averaging at least two length measurements taken in the plane containing the lines marked on the two ends.
4. Center one of the plywood strips along the center of the lower bearing block.
5. Place the specimen on the plywood strip and align so that the lines marked on the ends of the specimen are vertical and centered over the plywood strip.
6. Place a second plywood strip lengthwise on the cylinder, centered on the lines marked on the ends of the cylinder.
7. Position the assembly to ensure the following conditions:
- The supplementary bearing bar or plate, when used, and the center of the specimen are directly beneath the center of thrust of the spherical bearing block.
- Position the bearing strips, test cylinder, and supplementary bearing bar by means of the aligning jig as illustrated in Fig. 3 and center the jig so that the supplementary bearing bar and the center of the specimen are directly beneath the center of thrust of the spherical bearing block.
8. Record the maximum applied load indicated by the testing machine at failure. Note the type of failure and the appearance of the concrete.
9. Apply the load continuously and without shock, at a constant rate within the range 100 to 200 psi/min [0.7 to 1.4 MPa/min] splitting tensile stress until failure of the specimen.
CALCULATION:
Calculate the splitting tensile strength of the specimen as follows.
T = 2P/πld.
T =……………
Where,
T= splitting tensile strength, psi [MPa],
P = maximum applied load indicated by the testing machine, lbf [N],
l= length, in. [mm], and
d= diameter, in. [mm].
PRECAUTIONS:
1. Apply the load continuously and without shock.
2. Apply load at a constant rate within the range 100 to 200 psi/min [0.7 to 1.4 MPa/min].
3. There must be no surface undulations of the test specimen.
4. The curing must be according to standards because it directly affects the strength.