The Use of 1% Nano-Fe3O4 and 1% Nano-TiO2 as Partial Replacement of Cement to Enhance the Chemical Performance of Reinforced Concrete Structures

Abstract

The buildings can be exposed to ionic agents present in the environment (soil, water and air), such as chloride and sulfate, or even to the intern ones, added in the dosage process due the usage of some contaminated materials, such as alkalis and sulphur minerals presented in some aggregates. The contaminants tend to react with the cement hydrates and could modify the concrete or mortar properties, dropping the materials' lifetime. Especially in reinforced structures, these agents influence the double layer (concrete/bar) quality, promoting the bar corrosion due the ionic interaction or the modification of the environment alkalinity. Because of this, there is a necessity of stopping or avoiding these chemical reactions between the products of cement hydration and the aggressive agents. Currently, the most promising techniques involve the enhancement of concrete quality, especially from the permeability. Although, there are some advances in the nanoscale compound studies, which have raised the development of more chemically resistant concretes and also special treatments for the material presented on structures in early stages of degradation. The present article aimed for the development of a cause and effect study of distress mechanisms in concrete, with and without additions of nano-Fe3O4 and nano-TiO2 in 1% partial cement replacement, used to enhance the material's durability. For that, the nanoscale ceramic oxides were characterized and added in concrete dosages, as a partial replacement of cement. The obtained material was analyzed for physical and chemical measurements, to evaluate the structural performance and the durability characteristics under laboratory aggressive exposition. The obtained results showed there developed a new kind of concrete, with more homogeneous microstructure produced even in the early ages, by the reaction between the cement hydrates and the nano-materials. It improved the concretes mechanical and physicochemical properties, enabling the dosage of more durable materials.

Use of Clay and Titanium Dioxide Nanoparticles in Mortar and Concrete—A State-of-the-Art Analysis

“…These results were confirmed by [82]. A comparison between the influence of 1% Fe 3 O 4 and 1% TiO 2 on concrete water absorption was conducted in [79]. From the analysis, nano-titania particles succeeded in restricting the water absorption better than Fe 3 O 4 , also having a smaller void ratio.…”

“…As the water absorption and void ratio decreased, the probability of liquid infiltration was significantly reduced, as the chloride and sulphate exposure analyses proved. A higher level of steel reinforcement corrosion protection was gained by using nano-TiO 2 as supplementary material in concrete, according to [79]. The potentio-dynamic polarization test confirmed the benefits of using TiO 2 in the cement matrix as the reinforcement corrosion rates were lower for all adverse exposure environments studied (tap water, saline water, acidic solution), compared to the control specimen [69].…”

“…Unlike the tensile strength case, the compressive strength of the 1% TiO 2 concrete specimens was lower than for the 1% Fe 3 O 4 concrete specimens [79]. TiO 2 was used in combination with ZnO and 0.6% polypropylene fibers PPF to improve the concrete formula [71].…”

“…The value of the tensile strength of concrete when the cement was replaced with 1 wt% nano-TiO 2 was compared with the one obtained when the cement was replaced with 1 wt% nano-Fe 3 O 4 [79]. The results showed that the TiO 2 -modified specimen developed 18% higher values for the tensile strength.…”