Environmental resistance of cement concrete modified with low dosage nano particles

The negative impacts of aggressive environment on the durability of concrete materials have raised great concerns in recent years. Although the nano modification has been considered as a promising approach to enhance the durability of concrete materials with exposure to synergistic attacks from complicated aggressive environment, the investigation of the impacts of various chemicals on low dosage nano modified concrete, especially along with freeze/thaw and wet/dry cycles, is still very limited. In this study, the impacts of sodium chloride (NaCl) and potassium acetate (KAc) on laboratory fabricated concrete samples, which were modified with low dosage of nano SiO2 and nano TiO2 particles, were investigated. The mass loss, flexural strength, compressive strength, and relative dynamic modulus of elasticity were tested to evaluate the deterioration of low dosage nano modified concrete samples after exposure to F/T along with W/D cycles in KAc and NaCl solutions. The microstructure analyses demonstrate that both NaCl and KAc have negative impacts on the durability of concrete samples after F/T and W/D cycles. However, the addition of low dosage nano particles shows a distinctive enhancement of environment resistance of concrete samples. Through the microstructure analysis, three potential reasons were presented to help elucidate the deterioration mechanisms of concrete with exposure to aggressive environment. Moreover, based on the microstructure analysis, the different modification mechanisms corresponding to various nano materials were presented. This study not only shows the possibility of low dosage nano modification on the durability enhancement of concrete, but also provides potential modification mechanisms which help to design and fabricate durable concrete materials with exposure to complicated aggressive environment.