Properties of Fresh and Hardened Concrete - LAB REPORT

“Properties of Fresh and Hardened Concrete” Laboratory Class 3 University of Strathclyde Ermand Mani - 25 marzo 2015 LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI Introduction The purpose of this experiment is to measure the workability of the concrete mixture. In total, 4 cubes and 2 cylinders would be cast for calculating compressive stress of concrete specimen. Observations Concrete is a mixture of cement, sand (fine aggregate), aggregate, water, and and OPC cement (ordinary portland cement). Proportions of each ingredient are adjusted to obtain a well balanced-mix in oder to be sent to be built. Concrete will roughly set between the 9 and the 10 hours and continues to harden. However, the workability of fresh concrete can be determined by using the VEE-BEE and the SLUMP tests and the cement material is cured in a humid environment in order to avoid loss of moisture through evaporation Procedure LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI The concrete mixture Concrete is a mixture of five components: coarse aggregate, fine aggregate, water, and Portland cement. The control of the quality of all ingredients, the mixing time, mixing procedure, and curing strictly influence influence the quality of the final cement material. Coarse Aggregate We are using two different of aggregate : 7.5 kg for 20mm of coarse aggregate particle and 3.75kg for 10mm coarse aggregate particle size. Fine Aggregate Often called sand. We need 6kg of the fine aggregate. Water Drinking water is usually good enough for concrete. We will need 2000cc of water. OPC - Ordinary Portland Cement OPC consists essentially of calcium silicates and reacts chemically with water and hardens. We will need 5.5kg of OPC cement. The mixing procedure of the dry materials Step 1 - Batching 1) Starting scaling 7.5kg of 20mm aggregate Fig. 1. Aggregate: 20mm size 2) Add on 3.75kg 10mm aggregate Fig. 2. Aggregate: 10mm size LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI 3) Add on 6kg of sand Fig. 3. Fine aggregate 4) Add on 5.5kg the cement Fig. 4. Cement pouring 5) Dry mix procedure: mix all dry materials together Fig. 5. Crushed all the dry materials 6) Add water (total 2 liters) on and mix the materials adding some water per time and making sure the material left on the borders are re-centered. Fig. 6. Watering the mixture procedures LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI 7) Check the concrete Slump test Slump Tampler a) b) c) d) e) f) Cylinder Vibrating table Fill the slump cone 1/3 full with the mixture Stand on foot and hold the cone firmly in place tamp down the mixture 25 times per layer. Move the glass disc attached to the swivel arm and touch the top of the concrete cone, and note the initial reading on the graduated rod. Produce a cone of concrete ( 3 levels of layers) Produce a TRUE type of cone. Take a measurement from the top of the cone concrete to the underside of the Barr. (Test Slump = 3.5cm) 3.5 cm Fig. 7. Student taking measurement of the slump. Fig. 8. Slump test g) Switch on the electrical vibrations and let the concrete to remold by spreading out in the cylindrical container. The vibrations are continued until the concrete is completely remolded and record the time required for complete remolding. Test VEE-BEE = 7.85 seconds LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI Table seconds corrispondings 8) Produce sample moles (4 cubes and 2 cylinders) Dimensions of cubes 100x100 mmm Dimensions of the dam = 100mm and h = 200mm 9) Fill the steel cubes stamps with fresh concrete ut to the middle point 10) Hammer 25 times and refill the example till full. 11) Switch the vibrating table that helps to get the air out and brings the water up. 12) After 24 hrs, take the samples out The surface should not presents holes. Use reinforce bars or clear to wrap the surfaces of the examples. 13) Curing time Keep 14 days in water because the air cure develops cracks Fig. 9. Cylinder mould LABORATORY CLASS 3 Fig. 10. Cube mould PROPERTIES OF CONCRETE ERMAND MANI 14) Compression Test 1 - Switch on the machine. Place one concrete specimen in the centre of loading area. 2 - Lower the piston: Lower the piston against the top of concrete specimen by pushing the lever. 3 - Carefully apply the load: 4 - Increasing pressure: Apply the load gradually without shock. 5 - Test is complete: When it begins to break stop applying load. 6 -Record the ultimate load on paper displaying on machine's display screen. The compression test of concrete controls the loads that can be applied to a concrete structure. For this reason it is crucial to apply the compression test in order to know which are the forces acting to the structure. When preparing the mix design the quality control ensures the concrete mixed satisfies those specified strengths required from the project design. Compression test determine the forces the concrete sample resists in order to ensure a stable structure. The equipment we use to perform the compression test is a compression-testing machine, having a capacity of 2500 N. Fig. 11. Compression test 15) Schmidt Hammer The Schmidt hammer defines the rebound of a force impacting against the surface of the sample. We need to measure 5 times: 1) first hit must be at the center of the surface of the sample 2) hit a the 4th corners of the sample 3) record the reading LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI Calculations CUBE 1 LOAD APPLIED = 505KN CROSS READING RESULTS = 25, 17, 18, 15, 15 CUBE 2 LOAD APPLIED = 495KN CROSS READING RESULTS = 22, 14, 21, 12, 13 CUBE 3 LOAD APPLIED = 450KN CROSS READING RESULTS = 18, 15, 18, 12, 16 CUBE 4 LOAD APPLIED = 410KN CROSS READING RESULTS = 22, 19, 17, 18, 19 CUBE 5 LOAD APPLIED = 930KN CROSS READING RESULTS = 22,16,16,16,18 CUBE 6 LOAD APPLIED = 440KN CROSS READING RESULTS = 19, 22, 20, 15, 14 CYLINDER 1 LOAD APPLIED = 88KN CYLINDER 2 LOAD APPLIED = 121KN VEE-BEE TEST WORKABILITY = 7.85sec SLUMP CONE WORKABILITY = 35mm LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI CONCLUSION As a result form the compression all the 6 cubes had a perfect X shape in the middle as shown at Fig. 12. Fig. 12. Compression test on a cube But as we were compressing the cylinders, one of the has split in the middle and the second one, actually split in 4 pieces. Fig. 13. Compression results Cylinder 2: Split in Cylinder 1: Split in the middle LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI LABORATORY CLASS 3 PROPERTIES OF CONCRETE ERMAND MANI