Investigation of mechanical properties of repair mortars containing high-volume fly ash and nano materials

Innovations for mineral and chemical additives used in concrete cause a rapid development in concrete technology. Thus, high-performance fiber-reinforced cement composites (HPFRCC) that exhibit ductile behavior under axial loads are produced. With the development and widespread use of nano technology, the production of nano materials that can be used in concrete has led to the development of concrete properties. The first studies about nano and fiber materials used in concrete show that the performance of the concrete develops when they are used together in concrete. In this study, two basic mixtures were designed as fly ash (55% by weight of total cementitious material) and without fly ash mixture. In both of two basic mixtures, HPFRCC mixtures were prepared using the ratio of nano materials (nano silica, nano alumina, and nano calcite) determined by the preliminary test and the additive materials. According to results for all mixtures, the highest compressive and flexural strengths belong to the mixture containing 0% fly ash and nano silicate which is 109.7 and 17 MPa at 90 days, respectively, and the lowest compressive and flexural strengths belong to the mixture containing 55% fly ash and without nano materials which is 23.36 and 12.02 MPa at 1 day, respectively. The results show that mixtures containing nano materials improve the compressive and flexural strengths.