In this laboratory experiment, we were required to produce a concrete mixture based on the BRE Manual Design of concrete mixtures which is attached to this report. It is then used to produce concrete cubes and prisms. The objective of this experiment is to learn the methods of producing concrete and concrete characteristics as well as comparing the theoretical values of the concrete’s Young’s Modulus with experimental values.

Procedure for concrete mix:

A concrete mix was designed based on the BRE Manual Design of concrete mixtures. Then, a total of 40kg of the required proportions of Ordinary Portland cement which includes water, fine aggregate, and 20mm size crushed gravel coarse aggregate was weighed out. The materials are then batched and mixed in a pan mixer. Next, a slump test for the concrete mixture was carried out. The concrete mixture was then used to produce 4 no. 100mm cubes and two 500 x 100 x 100 mm prisms based on table 1.1. Finally, the specimens were labeled and covered for curing. Sieving was also conducted on the fine and course aggregate to produce a sieving analysis chart.

Vibrating table| Hand Temper|

Air cure| Water cure|

Cube, CA1| Prism, PA1| Prism, PW1| Cube, CW1| Cube-7days, CW2| Cube, CW3| Table 1.1 Conditions of produced cubes and prisms

Procedure for tests:

Our group were given a target 28 day compressive strength of 30 (N/mm2) and a slump test of 20mm. A compressive test was conducted on 1 of water cured cubes after 7 days and the rest of the cubes after 28 days. A PUNDIT, ERUDITE, and flexural test was conducted on both the prisms after 28 days. The Portable Ultrasonic Non Destructive Instrument Tester (PUNDIT) was used to obtain results for transit time, velocity and elastic modulus for the prisms. The Electronic Resonant Ultrasonic Direct Instrument (ERUDITE) was used to obtain the concrete’s first natural resonant frequency. A set of measurements were taken for both the PUNDIT and ERUDITE tests and the average was used for calculations. The PUNDIT and ERUDITE tests are dynamic methods to find the static modulus of the concrete.

Results:

Criteria| Vibrating table| Hand Temper|

| Air cure| Water cure|

| Cube, CA1| Prism, PA1| Prism, PW1| Cube, CW1| Cube-7days, CW2| Cube, CW3| Weight, kg| 2.264| 11.411| 11.695| 2.344| 2.34| 2.311| Strength, N/mm2| 14.81| -| -| 13.2| 11.2| 12.72|

Table 2.1: Details of prisms and cubes

Prism (Air Cure), PA1|

Weight, kg| Volume, m3| Density, kg/m3| Transit time, µs| Velocity, m/s| Static Modulus, GN/m2| Frequency, khz| 11.411| 0.005| 2282| Pundit| Erudite|

| | | 129.8| 3849| 30.4| 2.08|

| | | 129.8| 3872| 30.4| 2.49|

| | | 130| 3849| 30.3| 2.31|

| | | 129.9| 3849| 30.3| 2.45|

| | | 129.5| 3846| 30.2| -|

| | | 129.8| 3846| 30.3| -|

Average =| 129.80| 3851.83| 30.32| 2.33|

Table 2.2: Test Results for air cured prism

Prism (Water Cure), PW1|

Weight, kg| Volume, m3| Density, kg/m3| Transit time, µs| Velocity, m/s| Static Modulus, GN/m2| Frequency, khz| 11.695| 0.005| 2339| Pundit| Erudite|

| | | 133.8| 3422| 23.5| 3.65|

| | | 133.8| 3385| 30.8| 4.05|

| | | 132.7| 3364| 30.5| 3.09|

| | | 129.6| 3888| 23.6| 4.51|

| | | 133.1| 3445| 24.3| 3.39|

| | | 132.6| 3878| 30.3| 4.55|

Average =| 132.60| 3563.67| 27.17| 3.87|

Table 2.3: Test Results for water cured prism

Average Static Modulus = 28.75 (GN/m2 or kN/mm2)

Prism| Failure load (kN)| Flexural Tensile Strength (N/mm2)| Air cured prism| 7.0| 2.1|

Water cured prism| 10.0| 3.0|

Table 2.4: Unitest Results for air and water cured prism

The dynamic modulus of the prisms from the PUNDIT test is calculated by using the formula: Ec(t)=ρV21+υ(1-2υ)1-υ×10-9 (kN/mm2)

Where dynamic Poisson’s ratio υ = 0.25

ρ = concrete...