ABSTRACT:In order to study the basic behavior of natural banana stem fiber reinforced concrete, three type of tensile strength test namely split tensile strength, flexural strength and biaxial fatigue flexure strength were conducted. Comparison of these three type of tensile strength, their crack pattern and the way they fails were be analyzed and discussed. Results showed that the flexural strength value of the two type of biaxial tests are higher than the uniaxial test result( ASTM C-1550 have 47.046 % higher than ASTM C-78 and 37.871 % higher than ASTM C-496). The value of tensile strength as measured by ASTM C-1550-02 is slightly higher than the value of the flexural tensile strength as measured by the biaxial flexure test (21.062%). The lines of the crack pattern do not show clear macro fracture cracks before reaching the peak load. As observed, there are two peak load values found were the one occurred at the first cracked, after that the load stress curve decrease for a while and after a few seconds the load increase again to a value smaller than the first peak load value.This is because at the time of the first cracking in three axes symmetry, the load that can be maintained by the concrete specimen had reached its maximum but after that the load increase again because the stress has been transferred to the fiber, so the stress rises again until the fiber break off. This indicates that the fiber plays an important role in holding and redistributed the tensile load.

To obtain lightweight and environmentally friendly building materials that can be produced quickly at low cost, among others, can be obtained through the use of natural fiber based ferrocement concrete technology. The use of light weight building materials combined with natural fibers to form structural components is intended to reduce the weight of the building mass but also to protect the environment and benefit banana farmers' income. Ferrocement lightweight concrete (FLWC) can be obtained by partially substituting fine aggregate with pumice sand and by adding banana stem fiber to form a ferrocement lightweight fiber concrete (FLWFC) composition. Compressive and tensile tests on ferrocement lightweight concrete and ferrocement light fiber concrete were carried out at 7, 14, 21 and 28 days, respectively. The test results showed that the optimal composition of FLWC and FLWFC occurred in the substitution of pumice sand by 40% and banana stem fibers with a length of 3 cm by 0.05% of the weight of cement and obtained a concrete mass density of 1437 kg. The compressive strength and tensile strength of FLWC without fiber at 28 days were 8.4 MPa and 2.15 MPa respectively, while FLWC with fiber added increased by about 6%, namely 8.9 MPa for compressive strength and 83% for tensile strength is 3.94 MPa. Flexural tensile strength of Sandwich Wall Panels (SWP) at 28 days of prism-shaped specimens with dimensions of 60 x 30 x 5 cm, 45 x 15 x 4 cm and 30 x 10 x 3 cm respectively 1.60 MPa, 1.86 MPa and 2.4 MPa for FLWC without banana stem fiber. The increase in the flexural tensile strength of the SWP was 40.63% (2.25 MPa), 21.51% (2.26 MPa) and 18.75% (2.85 MPa) respectively in the SWP-FLWC using Banana Fibers (BF) or an average of 26% increase. The size effect of the SWP test object looks significant, that is, there is a tendency that the larger the dimensions of the test object, the smaller the flexural tensile strength value, but on the contrary, the role of banana stem fiber in contributing to the increase in flexural tensile strength is seen to be more significant.

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