Use of Polypropylene Fibers in Structural concrete.

Abstract
Abstract
All civil structures that are usually made up of steel reinforced concrete usually undergo corrosion of the inbuilt steel by numerous parameters such as salt, which causes in failure of such huge structures. In order for such circumstances not to happen continuous repairing and maintenance is required to enlarge the life cycle of such civil structures. Numerous such methodologies has been developed by years and incorporated to minimize such failures of the  concrete structures which is mainy made up of steel reinforced concrete. The best solution for such problem is to adhesively bond polymer fiber composites on the structures. Another alternative to this is by adding polypropylene fibers in the concrete; not only cost reduction takes place but also optimum utilization of material is achieved. The main goal behind this project is to study the strength of the properties of polypropylene fiber concrete for M2O which has grade with 0%, 1.5%, 5%, 7.5%, and 10% by weight of concrete. Experimental procedures for such program constituted of split tensile strength, compressive strength tests and flexural strength tests on polypropylene fiber concrete and mainly on conventional concrete. However, polypropylene fiber concrete is a special type of embryonic  construction material which is known for its properties such as stiffness, durability and the one which has high mechanical strength. 1.5% better results were seen when the sample was added with polypropylene fiber as compared to others. Hence, to improve the performance characteristics of the light weight cement composites, the influence of the polypropylene fibers has been studied in different fiber length and different proportions. The fibers used are of length 12mm by cement weight in the design mixture. Hence, due to such reasons this hybrid fiber reinforced concrete gives vulnerable performance without any increase in the cost of the concrete.
Example- Concrete, Polypropylene Fiber, Compressive strength, Split tensile strength





Introduction

Primary Reinforcement in the concrete pavement cannot be provided to polypropylene fiber because of certain disadvantage such as having low modules and strength values if compared with steel fibers. polypropylene fiber are mainly used to provide decreased plastic, improved toughness and shrinkage cracking. polypropylene fiber from previous decades has numerous applications. Few of which include its use in structural application in 1950's and most recently in paving application. Slab on grade and parking lot construction are the predominant paving type of application for polypropylene fibers. Several manufacturers has been using polypropylene fiber for various types of applications. To improve the concrete resistance as the secondary reinforcement, formation of plastic shrinkage cracking and as the replacement for welded wire fabric (WWF).
Concrete is brittle in nature; while the composite material is week in tension and strong in compression. Plain concrete has 10% tensile strength of its compressive strength. When concrete tensile strength produced from temperature changes, extremely applied loads or shrinkage in the member takes place cracking occurs. Formation of tensile cracks in reinforced concrete is a natural occurring phenomenon. As flexural members contain non-prestress reinforcement, it becomes unavoidable as it has low tensile straining capacity. Cracks having greater width  can be dangerous because there is a possibility of corrosive agents that attacks steel reinforcing bars. While cracks that are wide enough may be objectionable only due to its appearance. Excessive wide cracks may also lead to the failure of the structure. As the rehabilitation and repairing of the structures are much time consuming and costly, the deterioration of such structures is of great concern. Hence, in order to overcome such situations there is intense need to take measures that can cause control over the cracking of concrete and if this happens, it will obviously increase the life of the structure and cause the safety of the structure. Randomly distributed short discrete fibers contents are there in fiber reinforced concrete (FRC).
This plays the role of internal reinforcement so that the properties of cementous composit is enhanced.

Experimental Details-
1. Materials and Mix proportion cement- Earlier, locally available cement was being used (Birla Gold Cement) called as 53 grade portland. Pozzolana was used for all costing. As per IS: 8112-1989, the testing of cement is done. The cement used has 3.15 as its specific gravity with initial and final setting times of 30 and 600 min respectively. 54.0 was the compressive strength which was measured in standard mortar at 28 days. The physical properties are confirming to IS: 12269-1987 standard.
2. Coarse Aggregates- Crushed angular granite metal from a local source was used as coarse aggregates. Its bulk density was 1450Kg/ms with void percentage of 1.5 and the specific gravity was of 2.6.
3. Fine aggregate- The river sand was used as fine aggregate with specific gravity of 2.6 and conforming to zone:III having bulk density of 1680kg/ms. The physical properties are conforming to IS:2368-1968 standard.
4. Water- Tap water is being used to mix the ingredients of concrete.
5. Polypropylene Fibers- Fine polypropylene mono filaments were used as the fiber. Dolphin float private limited, Bhosri, Pune, Maharashtra supplied the fibers. 6mm, 12mm and 24mm are the three different sizes available. 12mm fiber length is used in the present investigation.
6. Mix Design- For various proportions the concrete mix design has been carried out and at final mixed proportion was used for combining the initial materials. The initial materials are mixed in the hand mixer. Concrete samples were prepared with fiber ratios of 0,1.5,5,7,5 and 10% by volume in this project. However, to have least penetration and a proper mixture design, the applied aggregates were graded according to the ratio of W/C = 0.50 i.e. water added to the cement.
7. Physical properties of Polypropylene Fiber-
Cut length                     = 12mm
Width Crossing             = Circular
Water Absorption          = 0
Melting Point                = 250 degree celcius
Specific Gravity            = 0.91 \(gr/cm^{3}\)

Objectives- The main objective id to improve the-
- Workability
- Split Tensile Strength
- Compression Strength
- Flexural Strength
The cylinders with 150*300 mm height and the cubes were cast in steel moulds of inner dimension of 150*150*150 mm, also the beam width with 150*150*700 mm. Various types of tests mainly comprising of Flexure test, Split tensile test and compression test was performed. Compression testing machine and universal testing machine was used for the testing of cylinders and beams.