write mechanics of material lab (Torsion Tests of Metal specimens lab & Concrete lab)

Objective:

To prepare a batch of concrete from a premixed bag; perform a slump test; prepare 6” x 12” cylinders; perform compression tests on the cylinders at 7 and 28 days; determine and draw stress/strain curves from test results; determine E and f’c at 7 and 28 days.

Equipment:

UHTM

Slump test equipment

Cylinder molds

Concrete mix

Compressometer

Ruler

Theory:

1)Stress = σ = =

2) Strain= ε = =

3) at

4)E(ACI)=

Procedure:

Concrete mix is combined with water to form concrete. The slump test is performed first, which calls for the following: fill the metal cone 1/3 of the way with the mixed concrete, use a rod to dab the concrete 25 times, fill the metal cone 2/3 of the way with the mixed concrete, use a rod to dab the concrete 25 times again, fill the remainder of the cone, dab concrete 25 more times, and finally remove the cone and measure the slump or workability of the concrete. Next, two cylinders are filled with the concrete. On the 7th day, the compression test if performed on one of the concrete cylinders using the UHTM and the results must be recorded. On the 28th day, the compression test is performed on the second concrete cylinder and results must be recorded.

Data and Results:

Charts and Graphs:

Calculations:

1) 7 day compression:

= Pmax/A = 52537/28.3 = 1856.431 psi

σ = ()/2= (1856.431)/2 = 928.216 psi

Econcrete = = [(928.216)/(.000125)] = 7425728 psi

Ec= = 570002455920.259 psi

2) 28 day compression:

Same process as in the 7 day compression.

Discussion and Conclusion:

The experiment was successful because it showed that the concrete handles compression better if you let it settle for a longer time. For the 7 day test, the concrete could not handle the compression well because it was not allowed to settle all the way. The 28 day test showed that concrete can withstand a higher compression loading because it had a longer time to settle. Also, the experiment shows that the concrete is not good from shear compression. The objectives of the experiment were met. The stress and strain charts were drawn from data record from the tests. The f’c for the 7 day test was 1856.431 psi, for the 28 day compression it was 2770.424 psi. If you look at the maximum load for each compression and the strain that was yielded by those loads, it proves that the concrete gets stronger if the concrete has a longer time to settle.

Curves for the two compressions

7-Day

0.0 0.000125 0.00025 0.000375 0.0005 0.000625 0.00075 0.000875 0.001 0.001125 0.00125 0.0 245.9010600706714 456.2897526501766 636.0424028268551 816.8904593639576 969.293286219081 1113.180212014134 1227.985865724381 1344.204946996466 1440.848056537102 1528.409893992933 1st 28-Day

28-Day

2nd 28-Day

Strain, ∈ (in/in)

Stress, σ (psi)

Stress vs Strain: 7 Days

Strain, ∈ (in/in)

Stress, σ (psi)

Stress vs Strain: 28 Days

Strain, ∈ (in/in)

Stress, σ (psi)