Factors affecting bond strength at early age between cladding plaster and concrete substrate

Abstract

The bond strengths of two types of cylindrical composite specimens made of cladding plaster, concrete substrate with/without sticking slurry were evaluated by the splitting tensile strength. Two kinds of control factors, divided into two categories, were used for the investigation. The first is the constituents of concrete substrate including the fraction of fly ash to binder by weight (FL), the ratio of water to binder (W/B), the fraction of fine aggregate to total aggregate (FA) and the total volume of aggregate (Tot A). The second is the cladding plasters with or without sticking slurry in two curing conditions. The Taguchi method with L9(3⁴) orthogonal array and the analysis of variance were used to analyse the experimental data. Experimental results show that raising either FL or Tot A, being the two most influential factors, tend to lower the bond strength at early ages. Whereas, an increase of W/B from 0.45 to 0.55 significantly lowers the bond strength for cladding plaster without sticking slurry, but only has a minor effect on those with sticking slurry. The composite concrete specimen with six-day-water-curing condition without sticking slurry shows an apparent decrease of bond strength after exposing to air condition for 7 days.

Keywords:

• bond strength
• plaster
• concrete substrate
• fly ash
• Taguchi method

Acknowledgement

The authors gratefully acknowledge the financial support of this work by National Taiwan University of Science and Technology through the scholarship.