THE STUDY OF MECHANICAL PROPERTIES AND LOAD CARRYING ABILITY OF PLANT BASED FIBRE CEMENT COMPOSITES

Ganapathy Ramasamy N¹, Ashin M.P^2*, Manikandaprabhu Saravanan² and Sridhar M.B¹

¹Assistant Professor, Department of Civil Engineering, SRM University, Chennai, Tamil Nadu, India

²P.G. Scholar, Department of Civil Engineering, SRM University, Chennai, Tamil Nadu, India

*Corresponding Author:

Ashin M.P
E-mail: ganapathyramasamy19@gmail.com; ashin.mp@gmail.com

Received March 14, 2016; Accepted April 19, 2016

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Abstract

This paper describes the mechanical properties of plant based fiber cement composites. For this study we are using two different types of natural fibers like Hemp fiber and Kenaf fiber in different proportions. In this study the mechanical properties where obtained in compressive strength and tensile strength. The test where conducted using different combination of fibers with volumetric ratios which ranging from 0% to 2%. The compression test was conducted on 150 × 150 × 150 mm cubes and the split tensile test conducted on cylinders of 300 mm length and 150 mm diameter. Cracking is a characteristic feature of brittle material. Crack propagation in concrete, can lead to failure and FRC has a better resistance against cracking, which behaves like a crack bridge. The strength characteristics will be known by casting and testing the specimen for 7, 14 and 28 days for finding out at what percentage the strength will be achieved. Moreover, optimum compressive and tensile strength of the kenaf and hemp fiber reinforced concrete were getting at the level of fiber adding percentages of 0.5% and 1% respectively.

Keywords

Hemp fiber, Kenaf fiber, Fiber reinforced concrete, Mechanical properties

Introduction

Concrete has been the major important construction material all over the world and mostly used because of its low cost and outstanding mechanical properties. However concrete is strong in compression, week in tension, flexural strength and ductility (Alberti, et al., 2016). These strength parameters can be improved by using fibers in concrete. Fiber-reinforced concrete (FRC) are concrete incorporated with short and discontinuous fibers. Due to the dispersion and position of fibers in the concrete, the concrete transforms a ductile material to brittle. The FRC evolutionaims to control the two major deficiencies of cement-based composites: a rather low energy consumption capacity or toughness and a relatively low tensile strength (Li, 2011). Manufacturers and scientists have a keen interest towards natural fiber based composites because of its advantages over other fibers like biodegradability, non-toxic, light in weight and which are relatively strong, which are considered as honest products and it will be used for the production of furniture in various industries like construction and automation (Paukszta and Borysiak, 2013). Based on the origin, natural fibers are classified as animal based and plant basedfibers. The fiber like wool, silk, etc. areexamples of animal based fibers and natural fibers are based on plants like hemp, kenaf, sisal, coir, bamboo, etc. (Nunna, et al., 2012). Table 1 shows the quantity of specimens tested for plain concrete and both FRC.

Table 1: Quantity of specimens tested for both fibre concrete types of respective

In spite of these features shown by natural fibers, certain major deficiencies are also highlighted, like water absorption, lack in thermal stability and reduced impact properties (Adekunle, et al., 2011; Alawar, et al., 2009). Butthese can beimproved and overcomeby hybridization with either synthetic or natural fiber. Bast fibersare from natural fibers like kenaf, jute, hemp and flaxwhich have low density, high specific strength and are excessively used in several industrial utilizations (Zhu, et al., 2013). The main objective of this study is to compare the compressive strength and split tensile strengthof plain concrete with fiber reinforced concrete using the natural fibers of hemp fiber and kenaf fiber with various fiber adding combinations.

Methodology

The major processes involved were the study of literature reviews along with the testing of FRC samples and discussing the results. Preliminary tests were conducted for all the raw material. The specimens with conventional concrete andFRC are casted to find out the compressive and split tensile strength. After casting both the cube and cylinder specimens were allowed for curing to attain the required strength. The test was conducted on 7, 14 and 28 days to find out the compressive strength of the cubes of size 150 mm × 150 mm × 150 mm and tensile strength of the cylinder of size 300 mm length and 150 mm diameter. The cube and cylinder behavior of both hemp and kenaf FRCwere compared to that of plain concrete (Wang and Ramaswamy, 2003; Mahjoub, et al., 2014; Elsaid, et al., 2011).

Materials

Ordinary Portland Cement (OPC) of grade 53 was used. The specific gravity of cement used is 3.12. The initial setting time and fineness of the OPC were found to be 32 minutes and 9% respectively. River sand of zone II and specific gravity was found to be 2.61. The sizes of coarse aggregates used were 20 mm and specific gravity 2.72. Table 2 shows the mechanical properties of both hemp fiber and kenaf fiber. Hemp fiber is a type of natural fiber extracted from the blast of hemp stalk which is from the Hibiscus family. The length of hemp fiber used for this study is 30-50 mm and diameter is 70- 86 μm Kenaf fiber exist to the species of Hibiscus Cannabinus and family Malvaceae, obtained from stems of their plants. The length of kenaffibre used for this study is 30-50 mm and diameter 142-150 mm (Ramakrishna and Sundararajan, 2005; Keller, et al., 2001).

Table 2: Mechanical properties of kenaf fiber and hemp fiber

Results and Discussion

The mechanical properties such as compressive strength and split tensile strength of conventional concrete and FRC of hemp fiber and kenaf fiber results are discussed here.

Compressive strength test

This test is used to find out the compressive strength of the cube specimen. Table 3 and Table 4 shows the average compressive strength obtained for the conventional concrete and Hemp&Kenaf fiber added concrete for 7th day, 14th day and 28th day. The optimal percentage of Hemp FRC was 1.0% and Kenaf fiber was 0.5%. Based on the (Figure 1 and Figure 2) which is clearly seen that with the addition of 0.5% to 1% hemp and kenaf fiber the maximum compressive strength was achieved and if the fiber adding percentage is more than 1.5% then its starts to decreasing the compressive strength than conventional concrete (Wang, 2002; Kumar, et al., 1993).

Figure 1: Comparison between compressive strength of CC and Hemp FRC.

Figure 2: Comparison between compressive strength of CC and Kenaf FRC.

Table 3: The compression tests results of CC and Hemp FRC are given below

Table 4: The compression tests results of CC and Kenaf FRC are given below

Split tensile strength

This test is used to find out the tensile strength of the cylinder specimen. Table 5 and Table 6 shows the average split tensile strength obtained for the conventional concrete and fiber reinforced concrete for 7^th day and 28^th day. The split tensile strength of conventional concrete for 7 and 28 days was 2.27 N/mm² and 3.25 N/mm² respectively. The optimum split tensile strength is 3.28N/mm² for 7days and 4.64N/mm² for 28 days with 0.5% addition of Kenaf fiber. For Hemp FRC the optimum split tensile strength was 3.06 N/mm² for 7 days and 4.64 N/ mm² for 28 days.

Table 5: The compression tests results of CC and Kenaf FRC are given below

Table 6: The compression tests results of CC and Hemp FRC are given below

Based on the (Figure 3 and Figure 4) all FRC getting split tensile strength more than plain concrete. The maximum strength was obtained at the interval of 0.5%-1% addition of fiber to the plain concrete.

Figure 3: Comparison between split tensile strength of CC and Kenaf FRC.

Figure 4: Comparison between split tensile strength of CC and Hemp FRC.

Conclusions

1. The maximum compressive strength of Hemp FRC was achieved 33% more than that of plain concrete by adding 1.0% of Hemp fiber and for Kenaf FRC the maximum strength attained was 28% more than plain concrete with the addition of 0.5% Kenaf fiber.

2. Based on the results, it can be concluded that the maximum level of adding hemp fiber can be utilized upto 1.0%. Further addition of Hemp fiber results in decreased compressive strength and 0.5% of Kenaf fiber can be accepted to increase the strength properties of concrete.

3. For M35 grade, the maximum split tensile strength of Hemp FRC was achieved 26% more than that of plain concrete by the addition of 1.0% Hemp fiber and For Kenaf FRC the maximum split tensile strength attained was 42% more than that of plain concrete by adding 0.5% Kenaf fiber.

4. Finally it was concluded that, Hemp FRC and Kenaf FRC is a better material compared to conventional concrete with addition of less percentage of fibers like 0.5% to 1.0%.

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