DESIGN OF THE SPECIMEN

DESIGN OF THE SPECIMEN

CONCRETE TRAIL MIX

In this project, the bench mark concrete trial mix have been adopted form previous researchers to get concrete compressive strength after 28 days more than 40 MPa and the slump more than 100 mm. To study the effect of adding waste plastic materials on the behavior of RCC beams, two types of plastic have been used one thick and other one is thin.

While the replacement percentage varied from 5% to 20 % from the coarse aggregate by weight; ratio of fine aggregate to total aggregate 0.9 to 1.1; maximum coarse size to 10 mm. The concrete trial mix adopted in this study is recorded in Table 4.1

Table 0.1 Concrete Trail Mix

Cement (C)

400 kg/m3 Fine aggregate (S) 835.2 kg/m3

Coarse aggregate (G)

904.8 kg/m3 Water (W) 200 kg/m3

Total

2341 kg/m3

4.5

PREPARING, CASTING AND CURING

The procedures for concrete cube making are followed the British Standard BS 1881:1983 Testing Concrete. The acceptance criteria of quality of concrete criteria are mandatory and various provisions of the code have to be complied before the quality of concrete is accepted. In all the cases, the 28-days compressive strength shall alone be the criterion for acceptance or rejection of the concrete. In order to get a relatively quicker idea of the quality of concrete, optional test for 7 days compressive strength of concrete be carried out.

Three cubes or more of 150 × 150 × 150 mm size (the nominal size of aggregate does

not exceed 20 mm) is casted and tested at the day of beam test and a prism of 500 × 100 ×100 mm size was tested to get the concrete flexural strength. The sections applicable to site cubes are: CS1:1990: Section 1[16] (Sampling fresh concrete on site) & CS1:1990: Section 7[17] (Making test cubes from fresh concrete).

4.5.1

Preparing of Specimens

Coarse aggregate is replaced by waste plastic in terms of percentage with respect to the weight of plastic and coarse aggregate.

waste plastic = *x/100

, = plastic

The sample of specimens is mixed in the ratio shown in Table (

Casting of Specimens

During the mixing of fine aggregate, coarse aggregate, cement, plastic and water which is mixed by the machine mixture. The cubes were cleaned properly in order to prevent blockage of the sections from fitting together. After that oil has been paint inside the prisms, cubes and beams mold in order to prevent leakage and sticking of concrete.

Then the mixed concrete was casted and compacted by the vibrating poker to release the air voids from the concrete mixture. After that the excess concrete from the mold was scraped off from the top surface. Finally, cubes, beams and prisms were left 24 hour and then remove the formworks.

The test specimens were stored in place free from vibration and kept at a temperature of 27 ± 2℃ for 24 ± 1⁄2 from the time of addition of water to dry ingredients. After this period, the specimens were marked and removed from the molds and immediately submerged in portable water and kept there until prior to test. The specimens are allowed to become dry before testing.

There are standardized requirement for making and curing Portland cement concrete specimens. Specimens can be used to determine strength for mix design and quality control. The curing of the prisms, cubes and beams are shown in Figure 4.9.

Curing of Specimens

The test specimens were stored in place free from vibration and kept at a temperature of 27 ± 2℃ for 24 ± 1⁄2 from the time of addition of water to dry ingredients. After this period, the specimens were marked and removed from the molds and immediately submerged in portable water and kept there until prior to test.

The specimens are allowed to become dry before testing. There are standardized requirement for making and curing Portland cement concrete specimens. Specimens can be used to determine strength for mix design and quality control. The curing of the prisms, cubes and beams are shown in Figure 4.9.

Figure 0.9 Curing of Specimens

4.6

CUBE COMPRESSIVE STRENGTH TEST

This test measures the uniaxial compressive strength of concrete cubes which are made, cured and tested to very specific requirements. The test is measures the consistency of the concrete in terms of one particular property “compressive strength”. Different results could be found when the same concrete under different conditions have been tested, for example specimen size, specimen shape, curing temperature, loading rate, etc.

From a quality control point of view, the importance of the cube test results is not just the value of any individual result, but the variability is a series of valid test results. The compressive strength machine test is shown in Figure 4.10.

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Figure 0.10

Cube Compressive Test

Removed the specimen from water after specified curing time and wiped out excess Water from the surface. After that the bearing surface of the testing machine has been cleaned and then placed the specimen in the machine in such a manner that the load shall be applied to the opposite sides of the cube cast and aligned the specimen centrally on the base plate of the machine. Finally, wait the specimen until it fails

Mechanics of Materials Laboratory

Last Updated on February 10, 2019 by EssayPro