# Mechanical Properties of Cement Composites Using Modified Plastics by Gamma Irradiation
## 4 Conclusions  
In this study, plastic pellets (PP, PE and ABS) induced by crosslinking through gamma-irradiation technology were substituted to produce cement composites, and their physical performance was evaluated. As a result of the experiment, it was confirmed that there was no significant impact on flexural strength; conversely, it had a significant effect in achieving weight reduction by showing a significant decrease in the unit volume mass. It was determined that there was an effect of gamma irradiation on compressive strength, which increased and decreased according to the irradiation dose. 1. Comparing the compressive strength test results of the cement composites with substitution of PP (poly propylene) pellets induced by crosslinking through gamma-irradiation technology and PP (poly propylene) pellets without gamma irradiation, it was confirmed that the compressive strength of the PP pellets substituted cement composites increased when PP pellets were irradiated with gamma irradiation dose of 25, 50, 75 and 100 kGy. The compression strength of the cement composite increased due to the change in the properties of the surface of the plastic pellet where the crosslinking reaction occurred through gamma irradiation resulting in increased adhesion to cement paste. The compressive strength increases further as the strength of the plastic aggregate irradiated with gamma increases, compared to the strength of the plastic aggregate that is not irradiated with gamma rays. 2. Comparing the compressive strength test results of the cement composites with substitution of PE (poly ethylene) pellets induced by crosslinking through gamma-irradiation technology and PE (poly ethylene) pellets without gamma irradiation, the compressive stress of the cement composite produced by substitution of the plastic pellets irradiated with gamma rays increased as the irradiation dose increased and the compressive stress decreased at 100 kGy as in PP. It is determined that the surface properties of PE aggregates irradiated with gamma rays are modified through crosslinking, which improves the performance between aggregates and pastes, thereby increasing compressive stress and improving the strength of the cement composite. 3. ABS (acrylonitrile butadiene styrene) pellets were found to vary in compressive stress of cement composites when the pellets through gamma irradiation were substituted as aggregates of cement composites. In this case, it is found that the plastic properties of ABS are resistant to gamma irradiation rather than to crosslinking through gamma irradiation. Conversely, compared to ABS that non-investigated gamma rays, an increase in strength occurred when ABS that irradiated with gamma rays was used, which is considered to require further study. 4. When the cause of the increase in strength of the modified plastic aggregate-substituted cement composite was confirmed through SEM analyzing, in the case of PP or PE, there is the surface change according to gamma irradiation. However, in the case of ABS, no significant change in the surface due to gamma ray irradiation was found. Accordingly, it affects the strength properties, as the surface of the cement composites are modified. Based on the case of ABS, it seems that when gamma-ray irradiation is irradiated, not only the effect of surface modification but also the internal reaction occurs, and through these results, it is considered that further research is necessary. 5. When the flexural strength was analyzed for cement composites using the plastic aggregate modified by gamma ray irradiation, the variables of PP and PE showed a decrease or no tendency. For ABS plastic aggregates, it was possible to confirm the highest bending stress when non-irradiated plastic aggregate was used. In the case of flexural strength compared to the compressive strength, it was confirmed that the results were different from those of the previous experiments. Thus, it is judged that additional experiments are needed. 6.