Significance of Evaluation Methods for Surface Applied Corrosion Inhibitors

Goodwin, Fred (BASF Construction Chemicals) | Huang, I-Wen (Evan) (BASF Construction Chemicals)

OnePetro 

ABSTRACT

Surface Applied Corrosion Inhibitors (SACI) remain controversial as to effectiveness and the ability to compare materials from different manufacturers and technologies. These materials are liquids applied to the surface of concrete to control the corrosion of embedded reinforcing steel. This presentation will discuss the performance and relative importance of a recent testing program for corrosion inhibition and other performance parameters using documented test methods. The applicability of the tests to evaluate the performance of the material will be described as well as showing comparative data for different generic materials.

INTRODUCTION

Concrete is the second most common man-made material (after potable water) with ~3/4 cubic meter (about 1 cu. yd. or 2 tons) used for every person on the planet per year amounting to more concrete than all other construction materials combined. Construction amounted to $814B of the United States GDP in the first quarter of 2017.1, 2. Based on cement usage figures, of the 82.9 million tons of portland cement and 2.5 million tons of masonry cement produced in the US in 2016 amounting to $10.7 billion, most cement was used to make concrete, worth at least $60 billion. About 70% of cement sales went to ready-mixed concrete producers, 10% to concrete product manufacturers, 9% to contractors (mainly road paving), 4% each to oil and gas-well drillers and to building materials dealers, and 3% to others.3 The American Society of Civil Engineers Report Card estimates $2 trillion is required to just return the infrastructure of the United States to the quality it was in 1988.4 Both the construction industry as well as our infrastructure have significant parts of these estimates relating to concrete usage. It was estimated in 1990 that between $1 and $3 trillion is required to rehabilitate all the reinforced concrete structures suffering from distress.4 Why is concrete so popular? It is inexpensive, versatile, durable, and easily produced from common materials that are not resource constrained (i.e. limestone, silica, iron, aluminum, and gypsum), resistant to fire, flooding, and vermin attack; but concrete is not perfect. The production of cement has been estimated to account for much as 4.5% of global carbon dioxide emissions.5 Concrete has the weaknesses of relatively low tensile strength, brittleness, it is heavy, it absorbs moisture and dissolved chemicals, and deteriorates rapidly in acidic environments. Failure of concrete is usually shown by cracking. Once concrete cracks many of its properties are compromised. Steel reinforcement is added to concrete to improve the tensile properties and although protected (passivated) by the high pH of concrete; it will eventually rust. The protection of steel by concrete is reduced by chloride ion ingress, lowering of the pH through carbonation, and occasionally DC current leakage or dissimilar metal galvanic corrosion. Two universal rules of concrete construction are that concrete cracks and steel rusts.