The usage of carbon fiber reinforcement polymer and glass fiber reinforcement polymer for retrofit technology building

Fiber Reinforcement Polymer has been used as a material technology since the 1970s in Europe. Fiber Reinforcement Polymer can reinforce the structure externally, and used in many types of buildings like beams, columns, and slabs. It has high tensile strength. Fiber Reinforcement Polymer also has high rigidity and strength. The profile of Fiber Reinforcement Polymer is thin and light, installation is simple to conduct. One of Fiber Reinforcement Polymer material is Carbon Fiber Reinforcement Polymer and Glass Fiber Reinforcement Polymer. These materials is tested when it is installed on concrete cylinders, to obtain the comparison of compressive strength CFRP and GFRP. The dimension of concrete is diameter of 15 cm and height of 30 cm. It is amounted to 15 and divided into three groups. The test is performed until it collapsed to obtain maximum load. The results of research using CFRP and GFRP have shown the significant enhancement in compressive strength. CFRP can increase the compressive strength of 26.89%, and GFRP of 14.89%. For the comparison of two materials, CFRP is more strengthening than GFRP regarding increasing compressive strength. The usage of CFRP and GFRP can increase the loading capacity.


Introduction
The development of concrete's technology at present has made concrete become a priority as a construction material. Construction of concrete has many advantages, besides the material is very easy to obtain, it has several advantages such as the relatively affordable price, high compressive strength, and easy maintenance, so many buildings are prefer to choose concrete as a construction material.
The selection of materials as construction has made experts create external reinforcements for concrete. The reinforcement are considered as important materials, especially for construction at the recent time that requires everything that is practical, efficient, without reducing the quality of the concrete. The evolution of an external reinforcement has been introduced to a new design for the binding of reinforced concrete columns. One method for enhancing reinforced concrete columns is using FRP (Fiber Reinforcement Polymer) Composites as reinforcement. [11] The use of FRP as one of the new alternatives in the improvement and strengthening concrete structures, is able to offer repair solutions that are easier in terms of implementation and can be applied by every contractor. Application of strengthening methods with polymer fibers requires proper planning, both in terms of design (behavioral analysis of concrete structures), field conditions (environmental influences) and maintenance of fiber types. This is essential to avoid the repair process so that no failure occurs in the reinforcement system. The use of polymer fibers under an extreme environmental conditions will require a system of protection of the fiber surface from the effects of temperature, chemicals and ultraviolet radiation. [4] 2. Literature Review One of the structural reinforcement materials is Fiber Reinforcement Polymer which can strengthen the structure externally, and is now used in many types of buildings. It is due to the great tensile strength possessed by FRP (Fiber Reinforcement Polymer). Fiber Reinforcement Polymer also has high stiffness and strength. And the installation is very easy to conduct. FRP composites are a promising material in the construction improvement industry. This material may be obtained in the form of sheets in which its application is applied with resin or epoxy. This material has been widely used and applied. The common traditional method is using steel plate material tied with epoxy on a reinforced concrete column structure. But gradually, this technique or method began to shift with the presence of a new material called FRP. With this material reinforcing the structure can result the substantial increases in strength (axial, shear, bending, and torque). [15] FRP can be made from different materials such as glass, carbon, aramid, boron, and other products. FRP is strong against tensile and has the highest strength along the longitudinal direction. The advantages of using glass materials are affordable, possessing high tensile strength and high chemical reaction, whereas the disadvantages are having low tensile modulus, relatively more dense and sensitive to abrasion. The advantage of using carbon material is the ratio of tensile strength to the heavy weight and tensile modulus to the heavy weight. The advantage of using aramid material is the absence of melting point, good plant integrity level to high temperature. [6] FRP can increase the strength 25 % of carbon material [11] and can increase 11.86% -15.25% of glass material. [13] The characteristics of FRP are highly resistant to chloride ions and chemical reactions, also having greater tensile strength than steel but weight only a quarter, moreover, GFRP has low electricity and thermal conductivity. [8] The advantages of FRP are for strengthening purpose. The addition of FRP on both sides of the block affects the pattern of the crack that occurs. Cracks in the concrete switch/ occur to a position where the GFRP reinforcement does not exist. It makes concrete even more practical. [2] To obtain the compressive strength of concrete, it needs a concrete cylinder test object with 150 mm diameter and 300 mm high. For the calculation of the thrust strength of cylindrical concrete test object, the following formula can be used; The elasticity modulus of concrete is the slope of the concrete strain stress curve in linear or even approaching linear conditions. For normal concrete, values may be used is (SNI 03-2847-2002 Section 8.5.1): To obtain the concrete strain, Hooke law is used: These are some of the compressive strengths equations expressed by previous researchers on the compressive strength of concrete with FRP (f'cc) by Richart's Model (1928) in (ACI Committee 440.2R, 2008). In principle, the analytical confinement model expresses the relationship between compressive strength and lateral stress arising from confinement. The basic equations describing the relationship can be described as follows: Note, ߝ ′ = the strain of concrete (MPa) K b = the efficiency factor of the cross section shape (for round shape =1) f l = confined strength caused by FRP (MPa) f'c = compresive strength of unconfined concrete (MPa) ߝ = the effective fracture strain (= 0.004 ≤ 0.75 ߝ ௨ , ߝ ௨ = ultimate strain of FRP) ߝ′ = the strain of unconfined concrete

Research Methodology
The method in this study is an experimental study conducted at the Material Laboratory on Faculty of Engineering, University of Sumatera Utara and The Centre of Educators and Teachers Development and Empowerment Laboratory. The test object used in this study is cylinders with diameter size of 15 cm and height of 30 cm with three types of specimens with 5 pieces each.   The test was conducted to the concrete in day 28 for each concrete variation with 5 pieces each. The variation of concrete can be seen in figure 3 and 4 below.

Figure 4. Test Object in Compression Machine
For the analysis, the analytically was done by the method of ACI Committee 440R-02, 2008 and Richarts Model in section 2, and the experimentally tests were conducted based on SNI 1974: 2011.

Finding Compressive Strength and Strain of Cylindrical Concrete
Before the testing, it requires an analysis so that the experiment do not fumble, therefore we need the calculation of the compressive and stretching strength of the concrete, the analysis was done by the method of ACI Committee 440R-02, 2008 and Richarts Model.