CIGMAT Report: Center Studies Concrete Coatings And Repair Methods For Corroded Steel Piles

By C. Vipulanadan, PhD, P.E., professor and director of Center for Innovative Grouting Materials and Technology (CIGMAT) and Texas Hurricane Center for Innovative Technology (THC-IT), Department of Civil and Environmental Engineering, University of Houston | October 2012, Vol. 67 No. 10

The specimens were totally immersed in selected test reagents in closed immersion jars. The two test solutions selected for the study were (1) tap water (pH = 7 to 9) and (2) 15% NaCl solution (representing the accelerated test condition in marine systems) as recommended by NCHRP 244 (Pfeifer et. al. 1981). In this test, changes in weight of specimen and appearance of specimen were monitored for 21 days (CIGMAT CT-1, ASTM G 20) (ASTM 1998, CIGMAT).

In order to study the drying pattern of coated concrete, the NCHRP 244 (Pfeifer et. al. 1981) method was used. The weight changes in the coated and uncoated concrete were monitored at regular intervals for up to 21 days. Drying of the coated specimens is shown in Fig. 1.

cigmat1.png
Figure 1: Specimens being dried for measuring the weight change during the drying cycle

Test results

Wetting Phase (in water)
The relationships between the percent weight change and time for coated specimens in water and 15% NaCl solution are shown in Figures 2, 3, 4 and 5 respectively. The average weight increase in water after 21 days, for specimens coated with Silane-1 was 1.09% as compared to 0.69% for specimens coated with Silane-2. Similarly, weight increase for coated specimens with Silane-1 and Coating-1 combination was 2.3% as compared to 1.21% for Silane-2 and Coating-1 combination. Maximum weight gain was observed for specimens coated with Coating-1 as compared with any other combination. This implies that Coating-1 absorbed more water and governed the water intake for cases where Coating-1 was the outer layer.

Wetting Phase (in 15% NaCl solution)
Weight increase in 15% NaCl solution after 21days, for specimens coated with Silane-1 was 0.69% as compared to 0.26% for specimens coated with Silane-2. Similarly weight increase with specimens coated with Silane-1 and Coating-1 combination was 2% as compared to 1.51% for Silane-2 and Coating-1 combination. Weight gain of specimens coated with Coating-1 was similar with specimens coated with Silane-1 and Coating-1, which reinforces the fact that Coating-1 governed the solution uptake in the cases where Coating-1 was the outer layer. However it can be observed that the combination of Silane-2 and Coating-1 was more effective in resisting the solution intake in all cases as compared to the Silane-1 and Coating-1 combination.

Buyer's Guide