Impact of Coconut Fibre and Polypropylene Fibre (RECRON 3S) On Concrete Mix Including Admixture

This paper describes the enhancement in the strength of the conventional concrete by the addition of fibres. Coconut fibres and polypropylene fibres (recron 3S) are used to increase the strength of the conventional concrete. The coconut fibres of various proportions from 1%, 1.5%, 2%, 2.5% and polypropylene fibres of proportions from 0.1%, 0.2%, 0.3% and 0.4% by volume of concrete were used in the M40 grade concrete mix. Slump test was carried on fresh concrete while compressive strength, split tensile strength and flexural strength were carried on hardened concrete. These tests are carried out to determine the mechanical properties of concrete upto 7, 28, and 56 days for compressive strength, 28 days for split tensile strength and flexural strength. A notable increase in the flexural and tensile strength was found..


INTRODUCTION
As we know that concrete which is usually made by mixing cement, water, fine and coarse aggregate and sometimes admixture in their right proportion is major construction material. As everyone known that we live in concrete age, then branch of Civil Engineering "Concrete Technology" becomes the backbone for development of infrastructure of every country. But due to increasing in rate of cement it becomes an obstacle for infrastructural development in the developing countries. And also during product stage of cement greenhouse effect which pollute the air and contribute to environmental as well as human hazardous. But to overcome this, many researches has been made on coconut fibre also which reduces the use of convectional cement and reduces the cost of concrete as well. The overall goal for this research is to make more and more awareness about the advantages and uses of coconut fibre and introducing it as a cheap and easily available natural fibre which did not affect the environment. Among this natural fibre which can be used for construction purpose is coconut fibre which can also be known with other names as Coir, Cocas nucifera, Arecaceae (Palm). Coconut fibre is extracted from the outer shell of a coconut. There are two types of coconut fibres, brown fibre extracted from matured coconuts and white fibres extracted from immature coconuts. Brown fibres are thick, strong and have high abrasion resistance. White fibres are smoother and finer, but also weaker. Coconut fibres are commercial available in three forms, namely bristle (long fibres), mattress (relatively short) and decorticated (mixed fibres). These different types of fibres have different uses depending upon the requirement. In engineering brown fibres are mostly used.
According to the official website of International Year For Natural Fibre 2009 the cultivation of coconut tree are around 12 million worldwide which produces 5,00,000 tones of coconut fibre annually. This coconut fibre can be used in the concrete which is very important part of any construction. Normally, in convectional reinforced concrete we use steel bars which increase the weight as well as the cost of the concrete which cannot be easily affordable to all rulers as well as urban civilians.
The polypropylene fibre has been one of the most successful commercial applications. The common forms of this fibre are smoothmonofilament and have triangular shape. Polypropylene fibres have some unique properties that make them suitable for reinforcement in concrete. The fibres have allow density, are chemically inert and non corrosive.

II. LITERATURE REVIEW
Roohollah et. al [2012] were investigating that Fibre addition was seen to enhance the physical and mechanical properties of lightweight concrete(LWC Another study with Coconut fibre and PPWF including admixture also proves that compressive strength of concrete cubes increases much more as compared to with and without admixture-concrete cubes (5).
Abhijeet et. al [2014] were investigated that coconut fibre which is natural fibre makes number of effect on environment and also increases the strength of concrete compare to use of convectional fibre. Concrete cylinders of dimension 150mm×300mm were cast to take the compressive as well as tensile strength test and it shows that the compressive strength of concrete increases with curing age but decrease with increase in quantity of coconut fibre whereas its tensile strength increases. The optimum tensile strength that we get was 3.0 Map. This research is carried out to bring awareness in field of Civil Engineering about the coconut fibre as good and hazardous less construction material. (6) III. MATERIALS AND METHODS A. Materials 1) Cement: Ordinary Portland cement of 43 grade (Ramco) conforming to IS 8112-1989 is used. Table 1 shows the test results of basic properties of cement.

C. Coarse Aggregate
Natural crushed stone with 20mm down size is used as coarse aggregate. Table 3 shows the test results of basic properties of coarse aggregates. Water absorption 0.39%

D. Water
Ordinary portable water is used in this investigation both for mixing and curing.

E. Super plasticizer (SP)
Conplast SP430 is used as a super plasticizer. It is a chloride free, super plasticizing admixture. It is supplied as a brown solution which instantly disperses in water.

F. Coconut Fibre
Coconut fibre was used in this study and it was collected from Coir Industries, near Bangalore Karnataka. The diameter of the coconut fibre used ranges between 0.29mm and 0.83mm with length of 6mm to 24mm and having approximate 150 as aspect ratio. Table 4 shows the test results of basic properties of coconut fibre. Polypropylene fibre was used in this study and it was collected from Reliance Industries Limited, Mangalore, Karnataka. The diameter of the polypropylene fibre used ranges between 34micron with length of 12mm and having approximate 320 as aspect ratio. Table 5 shows the test results of basic properties of polypropylene fibre.

H. Concrete Mix Design
Mix proportion used in this study is 1:1.61:2.65 (M40) with water-cement ratio of 0.4 and super plasticizer of 1.0%.

I. Batching and Mixing of Materials
Weight batching and machine mixing are adopted in this study for concrete production. The percentage of fibers and material weight are shown in Table 6.

J. Casting of Specimens
Mixing is done by using concrete mixer. For each proportion 12 cubes of size 100*100*100mm, 3 cylinder of 100mm diameter and 200mm in height and 3 beams of 100*100*500mm are casted. Mixing is done by adding aggregate to mixing drum first, followed by 25% of total water and super plasticizer to prevent cement sticking to blades or at the bottom of the drum. Super plasticizer will be added to water measured and stirred well. Then fibers and sand is added with 25% of water and super plasticizer again. After thoroughly mixing of aggregates, cement with admixtures if any is added and remaining 50% of water and super plasticizer is introduced. For each mix slump test is conducted to measure workability. Totally 288 cubes, 69 cylinder and 69 beams are casted. After casting concrete is filled into moulds and compacted on vibration table. Demoulding was done after 24 hours of casting. specimens are cured in curing tank. Water immersion method of curing is adopted. Cubes are cured for 7, 28, days and remaining specimens are cured for 28 days. Figure 1 shows the concrete placed in moulds.

IV. RESULTS AND DISCUSSIONS
The following figures represent the test results.      The figure 8 represents the 28 days split tensile strength of concrete. With the addition of CF, it shows greater strength than the corresponding control mix at 28 days curing period. It is clearly seen from the graph that the split tensile strength of concrete mix with 2% addition of CF has higher value as that of the control mix. The split tensile strength increases till 2% CF and then goes on decreasing with further CF addition.  From the graph 13 represents the flexural strength results of the concrete addition of both CF and PF. The graph shows that the addition of both CF and PF has greater flexural strength than that of the corresponding control mix at 28 days curing period. Flexural strength increases till 2% CF and 0.3% PF combination mix and decreases with the further addition.
V. CONCLUSION Based on the experimental investigation the following conclusion are drawn A. The workability of the fibre concrete (CF and PF) has been found to decrease with increase in coconut fiber and polypropylene fibre in the concrete mix. B. The compressive strength of the fibre mixed concrete has lower value than that of the control mix. C. The split tensile strength of the fibre mixed concrete has higher value than that of the control mix. D. The flexural strength of the fibre mixed concrete is comparatively very high than that of the control mix. E. With the increase in the addition of fibres to the concrete, the split tensile and the flexural strength increases to some extent and gradually decreases with further increase in the percentage of the fibers.