Effects of nanosilica and aggregate type on the mechanical, fracture and shielding features of heavyweight concrete

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With recent developments in nuclear technology, the safety versus nuclear radiations with negative environmental influences is of great importance. Heavyweight concrete (HWC) is an effective absorbent material, capable of providing adequate shielding versus nuclear radiations because of its acceptable structural characteristics. However, the role of aggregate type in the shielding and fracture characteristics of HWC has not been explored comprehensively. On the other hand, nanosilica is one of the reactive pozzolans which is employed for improvement of concrete properties. Thus, in this investigation, the influences of aggregate type (magnetite and hematite) and nanosilica on the mechanical, fracture and shielding features of HWC were studied. Four different cement replacements by nanosilica (0, 2, 4 and 6 %) were used to evaluate its influence on the properties of HWC. The results depicted that the fracture energies increase 18.8 and 16.8 % for heavyweight magnetite and hematite concretes with increasing nanosilica up to 6 wt% (wt.%) of cement, respectively. Furthermore, characteristic length declines from 385.6 to 364.8 mm and from 562.6 to 522.9 mm for heavyweight magnetite and hematite concretes with increasing nanosilica up to 6 wt% of cement, respectively. The results also showed that application of magnetite aggregates in HWC can more effectively shield against nuclear radiations than hematite ones which this issue becomes more obvious with increasing nanosilica content to 4 wt% of cement.