Adhesion of Self-Compacting Overlays Applied to Different Concrete Substrates and Its Prediction by Fuzzy Logic

An experimental and analytical study was performed to evaluate the adhesion between concrete and overlays using five different substrate surfaces and six different mixtures of self-compacting concrete and mortar. Saw cut surfaces of high strength concrete slabs were used as substrate. After the application of self-compacting concrete or mortar layers to dry, saturated surface dry, saturated surface wet, dry with bonding grout, and saturated with bonding grout surfaces of concrete slabs, they were covered with wet hessian and polythene sheets for curing. At the age of 28 days, friction-transfer tests were performed to evaluate the adhesion. The results indicate that while dry and saturated wet surfaces produced the lowest bond strength, the application of cement bonding grout improved the bond strength significantly. The results also showed that despite the noticeable correlations between the adhesion and the results of different flow tests, aggregate/cement ratio, fly ash/cement ratio, compressive strength, and water/powder ratio, the effect of the other constituents of the employed self-compacting overlays on their adhesion were not so significant. In order to predict the adhesion of self-compacting mixtures applied to concrete substrates, a fuzzy logic model was also devised. The results obtained from the fuzzy logic prediction model were compared with the average results of the friction-transfer method and found to be in very close agreement. The results show that fuzzy logic can be used to predict adhesion of self-compacting overlays.