Abstract

For rehabilitation of existing concrete structures, strength and durability related properties of the reinforced element are of high importance. Assessment of these properties of existing structures can be performed by (i) destructive testing of drilled cores and testing the extracted samples in lab environment and (ii) indirect methods by using non- or semi-destructive techniques on site. The use of core-drilling is a time-consuming and labour-intensive method that weakens the existing concrete structure, leaving a lasting impression on it. As an alternative, many different non and semi-destructive techniques are available for the in-situ determination of compressive strength and durability related properties. An experimental program is conducted on concrete slabs of different strength classes intended for various exposure classes (according to EN206), based on a limestone aggregate matrix, which is typically used for Belgian applications. The plates have an age of approximately 5 years, which were also characterized at younger stage (in 2014). Besides destructive core drilling and testing (compressive strength tests, chloride migration testing, and determination of carbonation rate), several non-destructive techniques were selected for this study: the rebound hammer, the ultrasonic pulse velocity tester, the Wenner probe for concrete resistivity and the air permeability tester. Best fit correlations between the output of these different techniques were established. The effect of age (e.g. carbonation) on the established predictive models is being evaluated.

Abstract

In this work, the effect of graphene nanoplatelets (GNPs) addition in the mechanical, thermal and electrical properties of carbon fiber composites was studied. GNPs were incorporated into benzoxazine matrix and nanocomposites with a 0.5 and 2 wt.% of graphene nanoplatelets were manufactured. The effect of this nanoreinforcement in benzoxazine mechanical properties as well as in its thermal and electrical conductivity was evaluated. Carbon fiber composites has been manufactured by means of liquid resin infusion (LRI) technique using the nanocomposites prepared. The manufacturing process with the nanocomposite containing a 2 wt.% of GNPs presented some filtration problems which hindered its characterization. The laminate with a 0.5wt.% of nanoreinforcement showed an increase in both thermal and electrical conductiviy regading to the panel with unmodified benzoxazine.