ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effect of Polymer on Structural Characteristics and Steel Corrosion of Cement-Poor Mortar

I. Janotka and Ľ. Krajči

Institute of Construction and Architecture, Slovak Academy of Sciences, SK-845 03 Bratislava

E-mail: Ivan.Janotka@savba.sk

Received: 29 January 2003

Abstract: Results of the study of styrene—acrylate dispersion influence on mechanical properties, hydrate phase, and pore structure formation as well as steel corrosion development in Portland cement mortar are discussed. Mortars with low cement content are used for the tests instead of usually studied mortars of cement-rich content. The object of interest was to ascertain the effect of polymer addition on cement-poor mortar behaviour using unfavourable mortar mixture composition and bad conditions for cement hydration. The specimens were exposed to 240-day dry (60 % R.H.) and wet (95 % R.H.) air cure at 20°C. Polymer increases absorption capacity, capillarity, total pore volume, and porosity of the mortar relative to that without styrene—acrylate dispersion. Dynamic modulus of elasticity and compressive strength are declined. The main reason of this lies in lower bulky mass of hydrate phase and higher cumulative volume of pores in polymer-modified cement mortar (PMCM) compared to those found in control cement mortar (CCM). Air voids occur in PMCM instead of bulky cementitious material due to foaming effect of polymer. Its addition decreases alkalinity of cement mortar and increases the permeability, making the pore structure coarser than that formed in CCM. The capability of moist air transport through the bulk of mortars determines the corrosion rate of steel. Steel corrosion characteristics are evaluated by three independent methods indicating a close connection between the developed pore structure and the corrosion rate of steel in the mortars.

Full paper in Portable Document Format: 582a79.pdf

Chemical Papers 58 (2) 79–86 (2004)