Preferred test methods to select suitable surface repair materials in severe climates

Abstract

In severe climates, the surfaces of concrete sidewalks, parking decks, bridges, canals, dams and other structures deteriorate progressively due to variety of causes. For their repair and maintenance, countless surface repair mortars are abundantly available on the market and are constantly used without prior testing in the laboratory. For this reason, 40 different mortars, comprising of cement-based mortars, polymer-modified cement-based mortars containing styrene-butadiene rubber and acrylics, epoxy mortars and emulsified epoxy mortars from different manufacturers were subjected to a battery of mechanical and durability tests. These tests included: bond strength, abrasion-erosion resistance, shrinkage-expansion, compressive strength, thermal compatibility with base concrete, etc. (-50 C to +40 C), etc. All these tests are considered important and essential but different views and opinions exist in the literature regarding their order of preference or importance. This paper presents the test data obtained from these tests. The test data revealed that over 65% (dry cure) and 89% (wet cure) of the mortars had a bondstrength better than the reference cement mortar, while over 90% performed better in the abrasion-erosion resistance test. Similarly, over 80% of the mortars exhibited higher compressive strength (84% in dry curing and 81% in wet curing) than the reference mortar. In the shrinkage-expansion test, 53% and 66% of the surface repair mortars showed lower than 0.15% net change and 0.2% total change, respectively, as specified in ASTM C928. However, in the thermal compatibility with base concrete test, only 36% of the mortars performed better indicating its importance and preference in severe climates. The latter test was therefore conclusive to select suitable surface repair mortars prior to a major maintenance and rehabilitation concrete work and should be performed as representing the most important selection criteria for mortars and concretes, especially those exposed to severe climatic conditions.