EXPERIMENTAL STUDY OF CONCRETE PERFORMANCE

This study was experimental in nature and conducted with the view to make comparison between two samples. The first sample consisted of concrete with rice husk ash mixed in it and the other sample was without such addition. The first test conducted to test the performance was simple measurements. The results show that for the sample without addition of rice husk ash, the density was 2355.97 and for included sample, the density was 2354.44 with insignificant differences (t-stat= 0.766, P>.05). For V-B test, the sample without addition of rice husk as was 8.34 and for include sample, it was 8.01. The differences for V-B for both samples were statistically insignificant (t-stat=1.431, P>.05). The slump test without for the sample without addition of rice husk was 12.75 and for included sample, it was 18.56. The difference was statistically significant (t-stat=2.455, P<.05). The compressive strength for excluded sample was 24.32 and for included sample was 20.01. The results were statistically insignificant (t-value= 1.13, P>.05). For flexural strength test, for excluded sample, the average score was 9.02 and for included sample, the average score was 9.19. The difference was statistically insignificant (t-stat=1.45, P>.05). Overall, the results lead to the conclusion that there are insignificant differences of addition of rice husk ash in concrete.


INTRODUCTION
Concrete is important component of modern urban life. Because of different conditions, there is requirement of improving the strength of concrete by using various combination of materials. In this regard, a lot of researches are conducted to find out the optimum solutions. One component which was also researched and found to be providing greater strength to the concrete is the artificial fiber. These artificial fibers can consist of various combinations and improve concrete performance in terms of toughness, load bearing capacity after cracks, deformation capability, flexural impact, and general tensile strength. Thus, when artificial fiber is added to the concrete, its strength improves in terms of flexural toughness, ductility, tensile strength, and impact strength (Mohammadi, Singh, & Kaushik, 2006). Steel fiber reinforced concrete which is a type of artificial fiber-based concrete is the focus of the study. The use of the Steel fiber reinforced concrete is increased in settings such as mining, pavements, precast tunneling, housing, flooring and industrial usage (yazici, Inan, & Tabak, 2007). The characteristics of Steel fiber reinforced concrete can be changed by bringing variation in the concrete formulation and fiber material type including fiber concentration, fiber orientation, fiber distribution, fiber geometry, and so on (Zollo, 1997). Previous studies investigated the effects of concrete fiber combination on different qualities of concrete. For example, study by Eren and Celik (1997) investigated the steel fibers and silica fume effects on characteristics of high-strength concrete. The findings were that workability of concrete reduces as the proportion of fiber and fume is increased. In this study the objective is to investigate how addition of steel fiber influence the performance of the rice husk ash concrete performance in terms of modulus of elasticity, splitting tensile strength, flexural tensile strength and compressive strength.
EXPERIMENT DESIGN The design of the study is experimental means we made two separate samples. One sample was consisted of addition of rice husk ash concrete, while, the other sample was consisted of without rice husk ash concrete. The performance of the both samples were tested using various tests. The materials used in the experiment are as follows; The rice husk ash was used in the study which had specific gravity of 1.95 and bulk density of 0.835 g/cc. The Portland cement with a pecific gravity of 4.12 is used in the study. The initial and final setting times of the cement was 135 and 210 minutes respectively. Low carbon hooked end-based steel fiber was used in the experiment. It had length of 35 mm and diameter of 0.75 mm, with density of 8.43 g/cm3, and aspect ratio of 60. For maintenance of workability of fresh concrete, a commercial AC Green slump was used. It was kept constant in mass basis which was about 1% of binder content of concrete For fine aggregate, we used the good quality river sand. The river sand had dry density of 1735 kg/m3, specific gravity of 2.87, and fineness modulus of 2.45. The aggregate was passed from 20 mm and only 10 mm sieve were retained. The retained sieve had dry density of 1475 kg/m3 and dry density of 3.2.

Mixture Composition and Preparation
The mixed design is made by M10 and 20 grade concrete. Water cement ratio were kept constant at 0.5 for M20 and 0.45 for M10; and binder content was kept constant for 415 kg/m3 for M20 and 370 kg/m3 for M10. Aggregate weight was assessed using the volume of aggregate. By bringing change in the Portland cement concrete, fresh concrete containing 2.5% to 20% rice husk were prepared. Fresh fiber reinforced concretes which consisted of various ratios of steel fiber in volume basis ranging from 0.25 to 1% were prepared. By introducing fiber or rice husk ash, aggregate weight for cubic meter was adjusted. The procedure of mixing the fiber-reinforced concrete starts with sand and gravel placement in dry mixed and concrete mixer for approximately 60 seconds. The mixing water was continuously mixed for about 120 seconds. The remaining plasticizer and mixing water are added and mixed. The composition was cast into specific mold and vibrated for removing any trapped air. Next, 24 hours were waited for mold to settle down and for demolding.

Testing Method
The fiber reinforced rice husk ash concrete qualities were investigated in this experimental study. For experiment, slump cone was used and the tests included compressive strength, flexural strength and splitting tensile strength. For experiment purpose, two separate samples were designed. One set of sample labelled as Sample 1 had rice husk ash added in to concrete; while, for sample 2 was the label for second sample which was without the rice husk ash added in to it. For both samples, a total of 36 sub-samples were collected at different time intervals in order to get the reliable results.

RESULTS
Results of the study are as follows;  In total, there were two main samples as one without rice husk ash and the other with rice husk ash. There were total of 36 sub-samples for both main samples. Results shows that for sample 1, the density kg/m3 without rice husk ash was 2488 and with rice husk ash it was 2590. For 0 500 1000 1500 2000 2500 3000 S1 S3 S5 S7 S9 S11 S13 S15 S17 S19 S21 S23 S25 S27 S29 S31 S33 S35 Sample 1-Density Kg/M3 Sample 2-Density Kg/M3 sample 2, the density for excluded sample was 2434 and included sample was 2576. For sample 3, the density for excluded sample was 2490 and included sample was 2574. For sample 3, the density for excluded sample was 2490 and included sample was 2574. For sample 4, the density for excluded sample was 2467 and included sample was 2543. For sample 5, the density for excluded sample was 2456 and included sample was 2578. For sample 6, the density for excluded sample was 2400 and included sample was 2400.For sample 7, the density for excluded sample was 2461 and included sample was 2412. For sample 8, the density for excluded sample was 2491 and included sample was 2389. For sample 9, the density for excluded sample was 2455 and included sample was 2376. For sample 10, the density for excluded sample was 2412 and included sample was 2365. For sample 11, the density for excluded sample was 2387 and included sample was 2345. The Average density for excluded sample was 2355 and for included sample was 2354 which shows that they are almost same. The statistical difference was also insignificant (t-stat= 0.766, P>.05).

Figure 2: V-B Comparison
The results for the V-B shows that for sample 1, the VB for excluded sample was 6.5 and included sample was 7.5. For sample 2, the VB for excluded sample was 6.8 and included sample was 7.3. For sample 3, the VB for excluded sample was 6.1 and included sample was 8.2. For sample 4, the VB for excluded sample was 6.4 and included sample was 8.4. For sample 5, the VB for excluded sample was 7.3 and included sample was 8.5. or sample 6, the VB for excluded sample was 7.4 and included sample was 8.7. For sample 7, the VB for excluded sample was 7.9 and included sample was 7.9. For sample 8, the VB for excluded sample was 7.4 and included sample was 9.1. For sample 9, the VB for excluded sample was 8.2 and included sample was 8.3. For sample 10, the VB for excluded sample was 7.4 and included sample was 8.5. For sample 11, the VB for excluded sample was 7.5 and included sample was 8.5. For sample 12, the VB for excluded sample was 7.5 and included sample was 8.4. For sample 13, the VB for excluded sample was 8.2 and included sample was 8.3. For sample 14, the VB for excluded sample was 8.7 and included sample was 7.6. For sample 15, the VB for excluded sample was 8.4 and included sample was 8.4. For sample 16, the VB for excluded sample was 8.9 and included sample was 8.9. For sample 17, the VB for excluded sample was 9.1 and included sample was 8.4. For sample 18, the VB for excluded sample was 9.2 and included sample was 7.5. For sample 19, the VB for excluded sample was 9.4 and included sample was 7.3. For sample 20, the VB for excluded sample was 9.4 and included sample was 7.2. For sample 21, the VB for excluded sample was 9.3 and included sample was 7.3. For sample 22, the VB for excluded sample was 9.9 and included sample was 7.1. For sample 23, the VB for excluded sample was 9.8 and included sample was 8.3. For sample 24, the VB for excluded sample was 9.1 and included sample was 8.8. For sample 25, the VB for excluded sample was 9.4 and included sample was 8.9. For sample 26, the VB for excluded sample was 9.2 and included sample was 8.4. For sample 27, the VB for excluded sample was 9.4 and included sample was 8.2. For sample 28, the VB for excluded sample was 9.1 and included sample was 0 2 4 6 8 10 12 S1 S3 S5 S7 S9 S11 S13 S15 S17 S19 S21 S23 S25 S27 S29 S31 S33 S35 Sample 1-V-B Sample 2-V-B 7.4. For sample 29, the VB for excluded sample was 8.9 and included sample was 7.8. For sample 30, the VB for excluded sample was 8.7 and included sample was 7.5. For sample 31, the VB for excluded sample was 8.4 and included sample was 7.9. For sample 32, the VB for excluded sample was 8.2 and included sample was 7.5. For sample 33, the VB for excluded sample was 8.1 and included sample was 7.2. For sample 34, the VB for excluded sample was 8.5 and included sample was 7.3. For sample 35, the VB for excluded sample was 7.9 and included sample was 7.7. For sample 36, the VB for excluded sample was 7.4 and included sample was 8.3. The average VB for excluded sample was 8.34 and for included sample was 8.01. Statistically, the difference was insignificant (t-stat=1.431, P>.05).

Figure 3: Slump Comparison
The slump test for both samples are as follows. For sample 1, the slump score for excluded sample was 17 and included sample was 22. For sample 2, the slump score for excluded sample was 16 and included sample was 21. For sample 3, the slump score for excluded sample was 15 and included sample was 20. For sample 4, the slump score for excluded sample was 18 and included sample was 20. or sample 5, the slump score for excluded sample was 19 and included sample was 18. For sample 6, the slump score for excluded sample was 20 and included sample was 19. For sample 7, the slump score for excluded sample was 21 and included sample was 19. For sample 8, the slump score for excluded sample was 20 and included sample was 18. For sample 9, the slump score for excluded sample was 17 and included sample was 17. For sample 10, the slump score for excluded sample was 16 and included sample was 17. For sample 11, the slump score for excluded sample was 17 and included sample was 17. For sample 12, the slump score for excluded sample was 14 and included sample was 18. For sample 13, the slump score for excluded sample was 13 and included sample was 18. Sample 14, the slump score for excluded sample was 12 and included sample was 18. For sample 15, the slump score for excluded sample was 11 and included sample was 19. Sample 16, the slump score for excluded 0 5 10 15 20 25 S1 S3 S5 S7 S9 S11 S13 S15 S17 S19 S21 S23 S25 S27 S29 S31 S33 S35 Sample 1-Slump (cm) Sample 2-Slump (cm) sample was 12 and included sample was 19. Sample 17, the slump score for excluded sample was 12cand included sample was 19. For sample 18, the slump score for excluded sample was 11 and included sample was 18. For sample 19, the slump score for excluded sample was 10 and included sample was 17. For sample 20, the slump score for excluded sample was 8 and included sample was 16. For sample 21, the slump score for excluded sample was 9 and included sample was 19. For sample 22, the slump score for excluded sample was 9 and included sample was 18. For sample 23, the slump score for excluded sample was 8 and included sample was 17. For sample 24, the slump score for excluded sample was 8 and included sample was 19. For sample 25, the slump score for excluded sample was 8 and included sample was 19. For sample 26, the slump score for excluded sample was 7 and included sample was 17. For sample 27, the slump score for excluded sample was 9 and included sample was 15. For sample 28, the slump score for excluded sample was 12 and included sample was 16. For sample 29, the slump score for excluded sample was 11 and included sample was 17. For sample 30, the slump score for excluded sample was 11 and included sample was 17. Sample 31, the slump score for excluded sample was 12 and included sample was 19. For sample 32, the slump score for excluded sample was 13 and included sample was 20. For sample 33, the slump score for excluded sample was 11 and included sample was 22. Sample 34, the slump score for excluded sample was 10 and included sample was 22. For sample 35, the slump score for excluded sample was 10 and included sample was 21. Lastly, for sample 36, the slump score for excluded sample was 12 and included sample was 20. The average for slump test for excluded sample was 12.75 and for included sample was 18.56. The difference was statistically significant (t-stat=2.455, P<.05).

Flexural Tensile Strength
Flexural tensile strength test is conducted on steel fiber reinforced concrete with and without rice husks ash.  The results for flexural strength test are given in the table above. For sample 1, the flexural strength for excluded sample was 8.56 and for included sample was 8.56. For sample 2, the flexural strength for excluded sample was 8.65 and for included sample was 8.52. For sample 3, the flexural strength for excluded sample was 8.65 and for included sample was 8.65. For sample 4, the flexural strength for excluded sample was 7.9 and for included sample was 8.56. For sample 5, the flexural strength for excluded sample was 8.6 and for included sample was 8.65. For sample 6, the flexural strength for excluded sample was 9.65 and for included sample was 8.52. For sample 7, the flexural strength for excluded sample was 9.56 and for included sample was 8.06. For sample 8, the flexural strength for excluded sample was 9.65 and for included sample was 8.61. For sample 9, the flexural strength for excluded sample was 9.65 and for included sample was 8.66. For sample 10, the flexural strength for excluded sample was 9.65 and for included sample was 8.66. For sample 11, the flexural strength for excluded sample was 9.76 and for included sample was 8.75. For sample 12, the flexural strength for excluded sample was 0 2 4 6 8 10 12 S1 S3 S5 S7 S9 S11 S13 S15 S17 S19 S21 S23 S25 S27 S29 S31 S33 S35 Sample 1-Flexural Strength Sample 2-Flexural Strength