CBA RESULTS: coatings D and D+A
GREY CURVE (D): the increase of stress over displacement up to a rather constant value is explained by the debonding of the coating around the crack in the concrete (Fig. 1). It assured a greater area of coating available for bearing the imposed deformation and a higher CBA.
GREEN CURVE (D): some concrete particles detached themselves from the substrate coherently with the coating. The steep decreases of the stress in the curve are due to the formation of cracks through the whole thickness of the coating. The lowering of the stress value continued during the widening of the cracks. The lower, rather constant, stress values are reached when the aggregate particles arrest the running cracks.
PINK CURVE (D+A): the steep decrease of the stress after the maximum is due to the formation of cracks in the top-coat A. It is followed by a gentler decrease in the stress, due to the enlargement of the cracks in the top-coat. The final vertical line is due to the formation of a crack through the whole thickness of the coating. The presence of the less tough top-coat slightly reduced the CBA of the coating D+A with respect to the monolithic coating D.