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.

ObservationsConcrete 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


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 AggregateWe 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 AggregateOften called sand. We need 6kg of the fine aggregate.

WaterDrinking 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

2) Add on 3.75kg 10mm aggregate


Fig. 1. Aggregate: 20mm size

Fig. 2. Aggregate: 10mm size

3) Add on 6kg of sand

4) Add on 5.5kg the cement

5) Dry mix procedure: mix all dry materials together

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. 3. Fine aggregate

Fig. 4. Cement pouring

Fig. 5. Crushed all the dry materials

Fig. 6. Watering the mixture procedures

7) Check the concrete Slump test

a) Fill the slump cone 1/3 full with the mixture b) Stand on foot and hold the cone firmly in place tamp down the mixture 25

times per layer.c) 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.d) Produce a cone of concrete ( 3 levels of layers)e) Produce a TRUE type of cone. f) Take a measurement from the top of the cone concrete to the underside of

the Barr. (Test Slump = 3.5cm)

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


Slump Cylinder

Vibrating tableTampler

Fig. 7. Student taking measurement of the slump.

3.5 cm

Fig. 8. Slump test

8) Produce sample moles (4 cubes and 2 cylinders)

Dimensions of cubes 100x100 mmmDimensions 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


Table seconds corrispondings

Fig. 9. Cylinder mould Fig. 10. Cube mould

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.

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 sample2) hit a the 4th corners of the sample 3) record the reading


Fig. 11. Compression test

Calculations

CUBE 1 LOAD APPLIED = 505KNCROSS READING RESULTS = 25, 17, 18, 15, 15




CUBE 5 LOAD APPLIED = 930KNCROSS READING RESULTS = 22,16,16,16,18


CYLINDER 1 LOAD APPLIED = 88KN

CYLINDER 2LOAD APPLIED = 121KN

VEE-BEE TEST WORKABILITY = 7.85secSLUMP CONE WORKABILITY = 35mm


CONCLUSIONAs a result form the compression all the 6 cubes had a perfect X shape in the middle as shown at Fig. 12.

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. 12. Compression test on a cube

Cylinder 1: Split in the middle

Cylinder 2: Split in

Fig. 13. Compression results

Properties of Fresh and Hardened Concrete - LAB REPORT

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