civi321_lab3

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McGill University *

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392

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Mechanical Engineering

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Dec 6, 2023

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CIVI 321 – LAB REPORT #3 Mechanical Testing of materials Submittes to: Dr. Ahmed Solim March 16 th 2023 – Concordia University Objective 1

The objective of this lab is to test the specimens prepared during the previous experiment and determine their properties. The compressive strength of different batches of concrete cylinders will be tested in this experiment. The flexure strength of beams with reinforced steel and with no reinforcement will be determine. Introduction Tests are used to evaluate the properties of hardened concrete to ensure its quality. These tests can be destructive or non-destructive. The Compressive Strength Test is commonly used as it's simple and there's a correlation between compressive strength and concrete properties. This test is important in determining if the concrete can support a load and resist weathering. A higher compressive strength generally means better quality concrete. The Rebound Hammer Test is a non-destructive test that measures surface hardness and can indicate the strength of the concrete. A higher rebound number suggests a harder surface and greater strength. Procedure To assess the strength of each batch of concrete, we first use a Schmidt hammer to determine the rebound number of one cylinder 10 times. Next, we place the cylinder in a load test machine and apply a uniform load until it fails, recording the load value. We repeat this process for all cylinders. For concrete beams, we place them in the load test machine, ensuring proper positioning to avoid errors. We apply and release the load until the beam fails, with the computer automatically recording the deflections and loads. Cylinder Stress Max Load Applied (N) Average Standard Deviation Failure Mode fc' W/C 2

Mix 1 1 32.5 143580.60 151768.38 8023.787 2 34.35 0.55 2 34.43 152107.08 3 3 36.13 159617.45 3 Mix 2 1 17.88 78991.42 79654.10 1109.75 2 18.03 0.55 2 18.32 80935.28 3 3 17.89 79035.60 3 Mix 3 1 37.41 165272.32 160677.74 14473.95 3 36.37 0.42 2 32.7 144464.17 2 3 39 172296.72 2 The diameter of the cylinders was 75mm. which gave it a cross sectional area of 4417.86 mm 2 Table 1: Strengths and failure modes for tested concrete cylinders As expected, the mix with the highest strength is the one with the lowest w/c ratio. The consistency concrete is the weakest due to the addition of air entrainer in the mixture. Table 2: Rebound Hammer readings for cylinder 1 of each mix Rebound Data 1 24 2 23 3 19 4 22 5 22 6 22 7 26 8 25 9 24 10 26 Average 23.3 Table 2shows the results of the rebound hammer test. The results were obtained with no error, although if the readings seem to be far off then that may be because air-pockets sue to improper packing of the unhardened concrete. With all the rebound hammer test values, we were able to conclude that the average was 23.3. 3

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Figure 1: Deflection of reinforced and unreinforced concrete beams under loading 0 1 2 3 4 5 6 -10 0 10 20 30 40 50 60 70 Reinforced vs Non-Reinforced Reiunforced Beam Unreinforced Beam Deflection (mm) Load (KN) From figure 1, it can be seen that ass the applied load increased, the deflection of both unreinforced and reinforced concrete beams increases. The trajectory of the deflection is the same up until a certain moment where the reinforced beam has a greater deflection than unreinforced. The reinforced concrete beam is clearly stronger. Table 4: Dimensions of Cylinder reinforced beam Unreinforced beam P = Maximum applied load 64277 15513.2 L = Span Length 457.2 457.2 4

b = Average width of specimen 152.4 152.4 d = Average depth of specimen 152.4 152.4 A = L/3 152.4 152.4 E = 5000sqrtfc' 29305.85834 29305.85834 Inertia = bd^3/12 44952993.96 44952993.96 Table 5: Modulus of rupture & Maximum deflection of reinforced and unreinforced beam Modulus of Rupture Maximum Deflection Reinforced Beam 8.30246243826 0.165506108 Unreinforced Beam 2.00379234092 0.03994476 Discussion 2. Appendix Mix 1 Strength 5