Influence of the Oxidation Process of Carbon Material on the Mechanical Properties of Cement Mortars

The present research investigates how the addition of processed carbon materials affects the mechanical properties of cement mortars. Five types of oxidation treatments (air at 250°C, air at 410°C, ozone, H2O2, and HNO3) were applied to graphite powder, powdered carbon fiber, and short carbon fiber to assess the influence of the modification of the carbon material surface in the interaction between cement paste and carbon material. The best oxidation treatment in terms of mechanical strength improvement was oxidation by air at 410°C because this procedure yielded the highest amount of oxygen surface functional groups, thus producing a better interaction with cement paste. Ozone treatment has also been shown to produce a high level of improvement in mechanical properties, but in this case the properties are improved because of the rough surface of the carbon materials.