Antonios Kanellopoulos

Behavior of RC Beams Retrofitted with CARDIFRC after Thermal Cycling

This study investigates the effect of thermal cycling on the performance of concrete beams retrofitted with CARDIFRC, a new class of high performance fiber-reinforced cement-based material that is compatible with concrete. Twenty four beams were subjected to 24 h thermal cycles between 25 and 90°C. One third of the beams were reinforced either in flexure only or in flexure and shear with conventional steel reinforcement and used as control specimens. The remaining sixteen beams were retrofitted with CARDIFRC strips to provide external flexural and/or shear strengthening. All beams were exposed to a varied number of 24 h thermal cycles ranging from 0 to 90 and were tested in four-point bending at room temperature. The tests indicated that the retrofitted members were stronger and stiffer than control beams, and more importantly, that their failure initiated in flexure without any signs of interfacial delamination cracking. The results of these tests are presented and compared to analytical predictions. The predictions show good correlation with the experimental results.

Large scale application of self-healing concrete: design, construction and testing

The work reported in this paper was carried out as part of the EPSRC funded project Materials for Life (M4L), reference EP/K026631/1 and supported with PhD studentship funding from Costain Group PLC.

Research data supporting "Autogenous self-healing of cement with expansive minerals-II: Impact of age and the role of optimised expansive minerals"

This research data presents the results of expansive minerals (magnesium oxide, bentonite clay, and quicklime) optimum mix proportions with PC and the establishment of a quantitative approach for correlating autogenous healing to the age of contentious materials. Healing performances were assessed in terms of load recovery, crack sealing efficiency and gas permeability. The microstructure of materials was investigated using XRD, TGA and SEM-EDX.

Research data supporting "Autogenous self-healing of cement with expansive minerals-I: Impact in early age crack healing"

This data presents the results of early age autogenous self-healing of cement paste with expansive minerals (magnesium oxide, bentonite clay, and quicklime). The healing performance was compared using flexural strength recovery, crack sealing, and permeability tests, and performance was investigated at microstructural level.

Research Data Supporting "The effect of varying volume fraction of microcapsules on fresh, mechanical and self-healing properties of mortars"

Data supporting the findings on the use of varying concentrations of microcapsules for self-healing in mortar matrices.

Effect of different types of polymeric microcapsules on the self-healing efficiency of cement based composites

Several different healing agents and mechanisms have been put forward for use in autonomous healing of small cracks in cementitious composites. While the existing research on this topic focuses mainly on the use of polymeric materials as encapsulated healing agents, this study aims at assessing the efficiency of inorganic silica precursors as potential healing materials. This work investigated the effect on self-healing of different types of polymeric microcapsules containing silica precursors. The microcapsules were embedded in three different types of cement-based matrix, namely mortar, paste and grout. The results in all cases showed that the inclusion of microcapsules resulted in a marginal reduction of compressive strength in more cases for low volume fraction additions. Increasing the microcapsules concentration increased the reduction in the compressive strength. However, the observed crack healing % and durability recovery were substantially larger than any reduction on the mechanical properties. In addition, the incorporation of polymeric microcapsules in the cementitious matrix resulted in slight improvement of the composites’ fracture toughness.

Towards more sustainable and environmentally-friendly concretes: The use of silica fume

Concrete is the most widely used construction material. At the same time, however, the concrete industry is a major CO2 emitter thus contributing towards global warming. While enhanced efficiency in the production of concrete is not likely to dramatically reduce the CO2 emissions, cement replacement by a supplementary material or mineral additive, such as silica fume, which is not associated with CO2 emission, can substantially reduce the aforementioned problem. The present work discusses the benefits of incorporating mineral additives in concrete and shows that these additives can improve both the mechanical and physical properties of the end-product, and hence its durability, albeit with a reduction in cement content.