|M.Sc Thesis||Department of Civil and Environmental Engineering|
|Supervisor:||Assoc. Prof. Dancygier Avraham|
This study deals with the behavior of internal plaster coating, which is used in reinforced concrete (RC) sheltered spaces in apartment buildings in Israel. It focused on two aspects, namely, the plaster cracking sensitivity and its adhesive strength to its concrete background.
The experimental plan included investigation of the influence of three parameters on the plaster behavior: (1) The treatment given to the background prior to the plaster application. (2) The plaster type. (3) The curvature of the RC element on which the plaster is applied. The background treatments types included application of a polymeric primer, application of a spatter-dash layer, mechanical and chemical roughening of the surface, and no treatment. The plaster types were regular, cement-based plaster prepared in-situ and an industrial plaster made from ready-mixed dry mortar.
The specimens were 270/50-cm, 25-cm thick RC beams, which were tested under static loads. They were coated with plaster on both sides, where pull-out tests were performed before and after loading in order to evaluate the decrease in the adhesion strength.
In the second part of the work an analytical model was developed to evaluate the effect of the curvature that develops under static bending on shear stresses at the plaster-concrete contact surface and hence on the plaster bond. The model shows that the normal stress is significantly higher than the pull-out strength allowed by the Israeli code for inner coatings in sheltered spaces.
The results lead to the following observations and conclusions: (1) There is a distinctive decrease in the adhesion near the point of failure, both on the tension and compression sides of all the specimens. (2) The decrease in the adhesion was larger on the compression side than the decrease on the tension side. (3) The curvature generated in the specimens under bending has a significant influence on the decrease in the plaster's adhesion to a concrete background.
Additionally, it was concluded that although static bending tests can provide indications regarding the plaster performance when its background surface is bent by external load, it cannot substitute impact testing, which show whether de-lamination of the plaster would occur under external impact.