3.1.4 Flakiness and Elongation Index of Coarse Aggregate (ASTM D 4791)
Add up to partials are said to be flaky when they have thickness under 0.6 times of the more significant estimation and the flakiness list (FI) is the rate by weight of flaky particles in an illustration, while on the multifaceted nature the drawn out particles are those whose more noticeable estimation is more than 1.8 times its mean size while the augmentation document (EI) insinuates the rate by weight of broadened particles in a sample.BS-1241 decides a flakiness record not outperforming 30% paying little respect to add up to measure. The barrel for the test should be picked by the aggregate size decided for the test, and the material utilized as a part of the test must be stove dried. Strainer examination is performed for a known measure of aggregate, after that a measure of aggregate hung on solitary sifter is weighed and for flakiness the held material is experienced a space of the predefined thickness along the thickness on legitimate opening of the check, and for the extending rundown of the aggregate the held material is checked autonomously for the length long measure. The weight should be recorded for the material which passes the thickness of the measure for the flakiness test while the material which does not experience the length check is recorded for the extending test.
The flakiness and expansion record was figured using underneath conditions: Most extreme allowed lengthening list is 35,40 or 45% for total size 2 1/2″
– 2”, 1 ½” – ¾” and ½” – 3/8”
Both Flakiness and Elongation tests are not relevant to sizes littler then 6.3mm i.e. ¼” strainer.
Allude annexure-viii for the aftereffects of flakiness and lengthening list of coarse total utilized as a part of this test program.
3.1.5 Water
Faucet water was utilized all through the trial work. The capacity of water in concrete is to respond synthetically with bond frame the coupling glue for mortar and coarse total. It empowers the solid blend to stream into formwork.
3.2 Concrete Mix Design (ASTM_211)
The strategy for decision of mix degrees given in this section is apropos to conventional weight concrete.
Despite whether the strong traits are suggested by the subtle elements or are left to the individual picking the degrees, establishment of bunch weights per m3 of bond can be best refined in the going with gathering through a formal mix diagram.
Mix diagram in this endeavor was finished by ACI 211 for 15MPa Compressive Stress with following genuine advances:
Stage 1. Choice of hang
Stage 2. Choice of most outrageous size of aggregates
Stage 3. Estimation of mixing water and air content
Stage 4. Assurance of water bond extent
Stage 5. Check of bond content
Stage 6. Estimation of coarse aggregate substance
Stage 7. Estimation of fine aggregate substance
Stage 8. Changes of aggregate clamminess
Stage 9. Fundamental bunch modifications
Allude annexure-ix for the detail blend plan count and results utilized as a part of this trial program.
CEMENT : FINE AGGREGATES : COARSE AGGREGATES
271.5 : 794.326 : 1073.05
1 : 2.92 : 3.95
Table 3. 2: Batch quantities per cubic meter of concrete
Materials Batch Weights (Kg/m3)
Cement 271.5
Fine Aggregate 794.326
Coarse Aggregate 1073.05
Water 215.64
Figure 3. 1: Concrete samples in molds
3.3 Tensile Strength of Confining Materials
The fundamental idea of a flexible test is to put a case of material between two devices called “holds” which prop the material. The material has known estimations, like length and cross-sectional zone. After that apply weight to the material toward one side while the contrary end is settled. We keep growing the weight (habitually called the load or power) while meanwhile assessing the modification long of the case.
3.3.1 Tensile Test (ASTM_D 3759)
Measure the adjustment long while including weight until the point when the part starts to extend lastly breaks.
The consequence of this test is a diagram of load (measure of weight) versus dislodging (sum it extended). Since the measure of weight expected to extend the material relies upon the span of the material (and obviously the properties of the material), examination between materials can be extremely testing. The capacity to influence a legitimate correlation with can be essential to somebody outlining for basic applications where the material must withstand certain powers.
We require a method for straightforwardly having the capacity to look at changed materials, making the “quality” we report free of the span of the material. We can do that by basically isolating the heap connected to the material (the weight or power) by the underlying cross-sectional zone. We additionally separate the sum it moves (dislodging) by the underlying length of the material. This makes what material researchers allude to as designing pressure (stack isolated by the underlying cross-sectional zone) and building strain (relocation partitioned by beginning length). By taking a gander at the building pressure strain reaction of a material we can think about the quality of various materials, autonomously of their sizes.
3.3.2 Tensile Test of Duct Tape
Figure 3. 2: Tensile strength of Duct Tape
Figure 3. 3: Load-Displacement curve of Duct Tape
Figure 3.3 shows the behavior of the duct tape when load applied on it. It shows that the duct tape; loose its strength, upon applying loads.
Figure 3. 4: Load-Time curve of Duct Tape
The graph in figure 3.4 indicates that, beside that the duct tape has low tensile strength; it has very high elasticity.
Figure 3. 5: Stress-Time curve of Duct Tape
The graph in figure 3.5 indicates that the maximum stress applied on Duct tape is 21.5 MPa in 0.15 seconds.
3.3.3 Tensile Test of Strapping Band:
Figure 3. 6: Tensile Test of Strapping Band
Figure 3. 7: Polypropylene Load-Displacement graph
Figure 3. 8: Polypropylene Load-Time graph
The graph in the figure 3.8 shows the behavior of PP strap band under load, and the time took it until fiber failed. It shows the high elasticity of the fiber too. The time took the fiber to fail, is around 6.35 minutes.
Figure 3. 9: Polypropylene Stress-Time graph
The graph in figure 3.9 indicates that the maximum stress applied on PP Strap Band is 13.5 MPa in 369.83 seconds.
3.4 Tests on Fresh Concrete
3.4.1 3.4.1 Slump Test (ASTM C 143)
Hang test is used to choose the value of new concrete. The hang test was finished according to ASTM C 143. It is suitable to use in the examination office and moreover at site. In spite of the way that the test is clear, yet the testing must be done purposely due to a gigantic hang may get if there is any disrupting impact all the while. The hang test will give a sensible indication of how easily a mix can be places in spite of the way that it doesn’t direct measure the work anticipated that would negligible the strong. It also determined that a hang under 25mm will demonstrate a solidified concrete and a hang that more than 125mm will exhibits a to a great degree runny bond. This hang regard varies for different structure segments. Hang test is driven on a truncated cone of steel; 12″ stature, 8″ estimation at the build, 4″ separate crosswise over in light of the best and gave handles. Estimation of hang shifts for different structures and segments as showed up in Table 3.2 after are the hang shapes that for the most part happen while doing hang of bond.
Table 3. 3: Recommended slumps for various types of concrete
Technique:
1. Slump test form was hose and was set on a soggy, level, non-retentive, hard surface.
2. Then by filling the form to 1/3 by volume and bar that layer with 25 uniformly separated blows.
3. After that by filling the form to 2/3 full, hits 25 quantities of hits to that layer.
4. Thus by filling the shape at the best, same 25 quantities of blows was hit.
5. In the wake of filling the shape with received methodology form was evacuated vertical way deliberately.
6. Instantly by expelling it was put topsy turvy simply close to droop cement and pole was set on a level plane on that form for estimation of droop an incentive in inches.
Allude annexure-x for the aftereffect of Slump.
3.4.2 Compressive Strength of Concrete
Quality of solidified cement estimated by the pressure test. The compressive quality of cement is a measure of the solid’s capacity to oppose loads which tend to pack it. The compressive quality is estimated by pounding round and hollow solid examples in pressure testing machine. The compressive quality is computed from the disappointment stack partitioned by the cross-sectional region opposing the heap and revealed in units of pound-compel per square inch (psi) or US standard units (MPa). Concrete compressive quality prerequisites canary from 2500 psi (17MPa) for private cement to 4000 psi (28MPa) and higher in business structures. Higher qualities up to and surpassing 10000 psi (70MPa) are indicated for specific applications.
Figure 3. 10: Standard concrete compressive strength graph
3.4.3 Concrete Cylinder Compressive Test without Confinement:
Figure 3. 11: Compressive strength of control specimen
Figure 3. 12: Load-Time Curve of Control Specimen
Figure 3. 13: Time-Displacement Curve of Control Specimen
Figure 3. 14: Time-Displacement Curve of Control Specimen
3.4.4 Concrete Cylinder Confined by Duct Tape 1-Layer
Figure 3. 15: Concrete Cylinder Confined by Duct Tape 1-Layer
Figure 3. 16: Load-Time Curve of Concrete Cylinder Confined by Duct Tape in 1 Layer
The graph in the figure 3.16 indicates, how the confined fiber influenced the concrete behavior, under load.
Figure 3. 17: Load-Displacement Curve of Concrete Cylinder Confined by Duct Tape Layer-1
The graph in Figure 3.17 shows that the confinement was done and both concrete and fiber took action at the same time which ultimately increased the compressive strength of concrete. After the peak load, the sudden decrease and again increase shows that the concrete sample start spalling but confining material then took the load and it shows a gradual increase
Figure 3. 18: Stress-Strain Curve of Concrete Cylinder Confined by Duct Tape 1-Layer
The figure 3.18 indicates that concrete sample confined by duct tape in 1 layer can withstand the load upto 6%.
3.4.5 Concrete Cylinder Confined by Duct Tape 2-Layer
Figure 3. 19: Concrete Cylinder Confined by Duct Tape in 2 Layers
Figure 3. 20: Load-Time Curve of Concrete Cylinder Confined by Duct Tape in 2 Layers
The figure 3.20 indicates that, not only fiber increased the concrete compressive strength but also delayed the spalling and collapsing.
Figure 3. 21: Load-Time Curve of Concrete Cylinder Confined by Duct Tape in 2 Layers
Figure 3. 22: Load-Time Curve of Concrete Cylinder Confined by Duct Tape in 2 Layers
3.4.6 Concrete Cylinder Confined by Duct Tape 3-Layer
Figure 3. 23: Concrete Cylinder Confined by Duct Tape Layer-3
Figure 3. 24: Load-Time Curve of Concrete Cylinder Confined by Duct Tape in 3-Layers
The figure 3.24 indicates the time, after failure of concrete sample. The graph shows that the confining material protect concrete sample from sudden failing and it gives some time which means it increases the concrete ductility upto some extent.
Figure 3. 25: Load-Displacement Curve of Concrete Cylinder Confined by Duct Tape in 3-Layers
Figure 3. 26: Stress-Strain Curve of Concrete Cylinder Confined by Duct Tape in 3-Layers
3.4.7 Concrete Cylinder Confined by PP Strap Band
Figure 3. 27: Concrete Cylinder Confined by 1-Layer PP Strap Band
Figure 3. 28: Load-Time Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band
Figure 3.28 shows the duration between concrete complete failures and spalling. It took 9.75 minutes after start spalling till the sample completely failed. PP strap band make the concrete more ductile as compared to the duct tape.
Figure 3. 29: Load-Time Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band
Figure 3. 30: Stress-Strain Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band
3.4.8 Concrete Cylindrical Confined by PP Strap Band at Mid only
Figure 3. 31: Concrete Cylinder Confined by 1-Layer PP Strap Band at Center
Figure 3. 32: Load-Time Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at center
Figure 3.32 shows that the concrete sample confined by PP strap band on mid portion only gives the same compressive strength just like given by the sample confined by PP strap band on whole cylinder. The difference in these two samples is time between concrete spalling till failure. Concrete cylinder confined by 1-Layer PP strap band is become more ductile as compared to the concrete cylinder confined by the PP strap band at mid portion only.
Figure 3. 33: Load-Displacement Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at center
Figure 3. 34: Load-Displacement Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at center
3.4.9 Concrete Cylinder Confined by PP Strap Band on ends
Figure 3. 35: Concrete Cylinder Confined by 1-Layer PP Strap Band at both ends
Figure 3. 36: Load-Time Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at both ends
Figure 3. 37: Stress-Strain Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at both ends
Figure 3. 38: Displacement-Time Curve of Concrete Cylinder Confined by 1-Layer PP Strap Band at both ends
Figure 3.38 indicates the strain corresponding to the stress on vertical axis. Comparing this graph, with the one in figure 3.33 and 30.32 the time elapsed between concrete failures, and spalling is almost identical to the condition in which concrete cylinder is confined at mid. The difference between these two conditions is that, in the former case compressive strength increased more than in this case.
3.5 Concrete Ductility in Terms of Time
The following table 3.6 shows the compressive strength comparison based on age of concrete, number of layers of confinement materials, location of wrapping material and types of confinement material with which the samples are confined. Tensile strength of the fiber play the important role in strengthening the concrete.
Table 3. 4: Comparison of Compressive Strength of Control Specimens with confined samples
Specimen Peak Stress
(MPa) Peak Stress Time
(Sec) Failure Stress
(MPa) Failure Stress Time
(Sec) Ductility in terms of Time from peak Stress to Failure Stress (Sec)
Control Specimen 16.80 91.40 13.58 112.50 21.10
1-Layer Duct Tape 17.1 38.60 8.48 88 49.40
2-Layer Duct Tape 18.15 19.80 10.75 109 89.20
3-Layer Duct Tape 19.15 60.95 3.96 225 164.05
1-Layer PP Strap Band 18.49 74.55 4.97 660 585.45
1-Layer PP Strap Band at Mid 19.09 37.25 11.88 58 20.75
1-Layer PP Strap Band at ends 20.09 27.50 13.00 37 9.50
In table 3.4, the average values of 3 concrete cylinders compressive stress is given in which one is peak stress and its time and the other is Failure stress and its time. In this table the difference of time between Failure stress and Peak stress time is calculated and shows which shows the ductility of concrete.
Figure 3. 39: Time-wise elasticity of different confining materials
In figure 3.39, numbers on the vertical axis represent time took after starting spalling of concrete till failed and the horizontal axis represents concrete samples confined by different confining material in different layers.
Figure 3. 40: Compressive strength of concrete
