Figure 3 Effect of temperature on the depth of Carbonation From table 4 and figure 3 it can be seen that as temperature goes up, the depth of
carbonation becomes increased. It is more prominent for concrete without steel fiber compere to concrete with steel fiber. The effect of temperature on can be explained on carbonation depth is
also explained from the compressive strength point of view. With the decreasing of compressive strength, the length of carbonation has been increased in case of both normal and SFRC or vice-
versa. As earlier of this research it was found that as temperature increases, the compressive strength was reduced at normal as well as SFRC condition.
The carbonation test result of this research has the similarity with previous carbonation test result. Chi and co-workers in 2002 carried out an experimental investigation to study the effect of
carbonation on mechanical properties and durability of concrete, where they found the depth of carbonation decreases with an increase in compressive strength. According to their opinion, this
approach appears to be very logical, since both carbonation and compressive strength are significantly controlled by the pore structure of concrete.
Wang in 2014 used the mixing amount of steel fiber 0, 0.5, 1.0, 1.5, and 2.0 to influence the carbonation depth of concrete. The results demonstrated that appropriate amount of steel fiber
can impede the speed of concrete carbonation; the concrete carbonation speed is the slowest when the fiber content is 1.5, and the carbonation speed is accelerated when the fiber content is
increased to 2. Likewise, Fattuhi in 1986 and Wierig in 1984 pointed out that the depth of carbonation
decreases with increasing compressive strength for all types of concrete, but these relations depend on the type of cement and curing.
Indeed, carbonation is one of the major factors to cause structure deterioration. The basic factor influencing carbonation is the diffusivity of the hardened cement paste. Carbonation rate is
controlled by the ingress of CO
2
into concrete pore system by diffusion with a concentration gradient of CO
2
acting as the driving force. Factors affecting diffusion rate include the type and
amount of cement, porosity of the material, time of curing, type and quantity of pozzolanic additions. Moreover, several mechanical properties of concrete such as compressive strength,
surface hardness and resistance to aggressive agents may change due to carbonation Chi et al., 2002.
V. CONCLUSION AND SUGGESTION
1. Conclusion
The research findings of this study is concluded that 1.
The addition of 1 and 1.5 steel fiber in concrete mix is advantageous for concrete. 2.
Overall the compressive strength of concrete was increased as the percentage of steel fiber in concrete increases. Up to 1.5 , Steel fiber reinforced concrete showed a better overall
residual strength and better crack resistance than non-fiber concrete. 3.
The carbonation process for concrete with steel fiber is a little influenced by temperature compare to concrete without steel fiber.
4. The concrete with 1.5 steel fiber demonstrated the highest compressive and modulus of
elasticity value, 23.5 and 17172 MPa at 600 C respectively. It is expected that in future
concrete having steel fiber will act as a fire protective considerably.
2. Suggestion
To continue this study with better output, this research need to some more consideration that can included following ways
1. Special care is required in translating observations on laboratory – made concrete specimens
into useful information on full structures. For instance, the behavior of elements of concrete in a real fire is highly complicated and the inner section of a heavy member differently
affected from outer areas. 2.
To further understand the microstructure of concrete after exposure to high temperature it is suggested to study also the decomposition changes due to heating before and after the
sintering process. To investigate the cracking situation, Scanning Electron Microscopy SEM or X-ray Diffraction XRD tests are required.
3. The usage of steel fiber with shorter dimension so that the load may be spread all over the
structure and the bond between mortars become stronger.
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