Composite Cement Reinforced Coconut Fiber: Physical and Mechanical Properties and Fracture Behavior

Published Date
Australian Journal of Basic and Applied Sciences, 5(7): 1228-1240, 2011 ISSN 1991-8178

Author 
Alida Abdullah, Shamsul Baharin Jamaludin, Mazlee Mohd Noor, Kamarudin Hussin
School of Materials Engineering, Universiti Malaysia Perlis. Kompleks Pusat Pengajian Jejawi 2, 02600 Arau, Perlis, Malaysia.

Abstract: This research paper reports the effect of natural fiber content on the physical and mechanical properties as well as fracture behavior of composite cement reinforced with coconut fiber. The mix design was based on 1:1 for cement:sand ratio and 0.55 was fixed for amount of water per cement ratio. Coconut fiber was added as reinforcement and replacing the composition of sand. Composites were developed based on 3 wt. %, 6 wt. %, 9 wt. %, 12 wt. % and 15 wt. % of coconut fiber by mixing and curing process. Composites were cured in water for 7, 14, and 28 days. It was observed that the composite reinforced with 9 wt. % of coconut fiber demonstrated the highest strength of modulus of rupture and compressive strength. Results of density, water absorption and moisture content are also presented.

INTRODUCTION

Malaysia has plenty of agricultural waste products such as coconut fiber, rice husk and oil palm frond fiber. Among the advantages of these fibers are: renewable, nonabrasive, cheaper, abundance and show less health and safety concern during handling and processing (Zulkifli, 2009). There is a research activity in the utilization of agricultural waste products as low cost construction materials especially in developing countries (Asasutjarit, 2009). Most recently, there have been considerable efforts to develop natural fiber-reinforced cementations composites for affordable infrastructure (Asasutjarit, 2009; Penamora, 1997; Asasutjarit, 2007). Among those agricultural wastes, coconut fiber or coir fiber has the potential to be used as reinforcement in the development of cement fiber composites. From previous investigations, there is limited application of the coconut fiber except some product based on polymer composite (Woolley, 1997; Savastano, 1999). Coconut fiber is the most interesting fiber as it has the lowest thermal conductivity and bulk density. Some researchers have reported that the addition of coconut fiber reduced the thermal conductivity of the composite samples (Asasutjarit, 2009; Asasutjarit, 2007; Khedari, 2005). Asasutjarit and co-workers (Asasutjarit, 2009) investigated the effect of chemical composition modification and surface modification of coconut fibers as reinforcement to the mechanical properties of cement composites. They reported that the mechanical properties of composites; modulus of rupture and internal bond, increased as a result of chemical composition modification and surface modification. Asasutjarit and co-workers (Asasutjarit, 2007) also researched the effect of fiber length, fiber pre-treatment and mixture ratio that affect the physical, mechanical and thermal properties of cement composites after 28 days of hydration. They observed that the boiled and washed fiber improved mechanical properties. In addition, the optimum fiber length was 1 to 6cm fraction and the optimum (cement:fibre:water) mixture ratio by weight was 2:1:2. Thermal property of composites revealed that coconut fiber-based lightweight cement board has lower thermal conductivity. Khedari and co-workers (Khedari, 2005) investigated on the development of a new type of soil–cement block using coconut fiber. Various compositions were tested. In their investigation, the use of coconut fiber as an admixture can reduce the block thermal conductivity and weight. The composition ratio of soil:cement:sand to produce good properties is 5.75: 1.25: 2. The compressive strength and thermal conductivity decreased when the quantity of fiber increased. From the previous studies, most of the works have been focused on the influence of fiber to the mechanical properties of cement composites. This paper reports on the development of coconut fiber based- green composites by conventional method of mixing and curing process. 

Table 1: Proportion of cement composites.

Sample 0
3
6
9 12 15

Cement : Sand 1:1
1:0.97 1:0.94 1:0.91 1:0.87 1:0.84

water/ cement 0.55
0.55
0.55
0.55 0.55 0.55

Coconut fiber (wt. %) 0
3
6
9 12 15

Aust. J. Basic & Appl. Sci., 5(7): 1228-1240, 2011

composite. The influence of coconut fiber addition to the physical and mechanical properties was investigated. Correlation between modulus of rupture and fracture behavior is also presented.

2. Experimental:
2.1 Materials and Samples Preparation:
The Ordinary Portland Cement (Blue Lion trademark), coconut fiber, sand as fine aggregate and water were used in this work. All raw materials were supplied locally. The size of sand used is less than 2.0 mm. All raw materials were weighed before the mixing process. The ratio of cement to sand was fixed at 1:1 and the amount for water per cement ratio also was fixed at 0.55. Coconut fiber was weighed according to the percentage ratio of cement weight. The details of the proportion are shown in Table 1.

The work has focused on six different ratios of cement to sand, and then coconut fiber was added to the mixture replacing the portion of sand. The weight percent starts from the reference sample which was 0 wt. % of coconut fiber and then increased to 3 wt. %, 6 wt. %, 9 wt. %, 12 wt. % and 15 wt. %.

The mixing process was carried out in a mechanical mixer where all of raw materials were mixed together until homogenous mixture was formed. At first, cement was added to mechanical mixer. Water was added in proportion to the cement to form uniform slurry. Once uniform slurry was formed, coconut fiber was added in proportion as well as sand and water. Water was constantly added in proportion so as to avoid balling effect by the coconut fiber.

The uniform wet mix was transferred to an empty mould according to the mould’s size to make composite. The size of mould is depending on the test that will be carried out for that composite. After setting (hardening), the composites were kept in the mould for 24 hours before curing. After 24 hours, the composites were de-molded and cured in water for 7, 14 and 28 days before mechanical testing.

2.2 Testing Procedures:
Morphological analysis of the raw materials was studied by a JEOL JSM-6460LA scanning electron microscope (SEM) with EDS analysis. The test samples were taken with care to avoid any damage and contamination that would affect the result. Density test of the samples was carried out by measuring its mass and volume for different days of curing. The sample size for density test was 100mm x 100mm x 40mm according to the BS 5669: Part 1. The sample size for water absorption tests was 100mm x 100mm x 40mm according to the BS 5669: Part 1. Samples were immersed in water for 24 hours and the difference in weight before and after immersion were measured.

For moisture content tests, sample size of 100mm x 100mm x 40mm (BS 5669: Part 1) was placed in oven at 100oC for 24 hours. The difference in weight before and after test was calculated. Modulus of rupture (MOR) test was carried out on the samples size of 400mm x 100mm x 16mm according to the British Standard (BS) standard BS 5669 part 1. The tests were conducted at a cross-head speed of 5 mm/min and the loading span was 384 mm. Compression test was done to determine the compressive strength of the samples under crushing loads. The sample size for compression test was 100mm x 40mm x 40mm (BS 5669: Part 1). The samples were compressed in vertical position by using the Universal Testing Machine (Gotech). Finally, fracture surface of the composites after modulus of rupture test was investigated under Stereo microscope model SZ2-STU1. This observation was performed in order to study the fracture behavior of the composites. Figure 1 shows the flowchart of the development and characterization of composite cement reinforced with coconut fiber. 

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