Date of Final Oral Examination (Defense)

5-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Civil Engineering

Department

Civil Engineering

Major Advisor

George Murgel, Ph.D.

Abstract

Portland cement concrete pavements (PCCP) are susceptible to deterioration and decreased service life caused by the ingress of water. Water can dissolve and transport deleterious chemicals such as de-icing salts, carbon dioxide, dissolved oxygen, and sulfates into PCCPs through cracks and the concrete surface. These chemicals and water itself all have the potential to degrade PCCP by chemical and/or physical processes. Surface-applied concrete sealers have demonstrated the ability to increase service life of PCCPs by limiting the ingress of water and deleterious chemicals into concrete.

Concrete sealers are being increasingly used by the Idaho Transportation Department (ITD). However, little has been done in Idaho to establish either a long-term field observation program or to perform a comprehensive laboratory analysis and evaluation process of suitable compounds. Thus, before proper deployment and long term field evaluation of concrete sealers can be done, an extensive laboratory evaluation process of suitable compounds, laboratory sealer evaluation protocol development, and application/reapplication protocol development needs to be performed.

In this research, five surface-applied concrete sealer treatments were evaluated in the laboratory. The sealer treatments are as follows.

1. Silane (water repellent)

2. Epoxy (barrier coating)

3. High molecular weight methacrylate (HMWM) (barrier coating/pore blocker)

4. Silane basecoat with an epoxy topcoat (dual treatment)

5. Silane basecoat with a HMWM topcoat (dual treatment)

The treatments were evaluated in the following tests in the laboratory.

1. Water vapor transmission

2. Saltwater absorption

3. Chloride permeability

4. Sealer penetration depth or coating thickness

5. Resistance to alkali

6. Ultraviolet (UV) weathering and cyclic saltwater ponding

7. Freeze-thaw resistance

In addition, the same treatments were applied at four field locations near Boise in Southwest Idaho to initiate a long-term field study to be completed in phase II of this study. Only the initial water absorption performance (time zero) was evaluated using core samples in the laboratory. The duration of the initial phase of this study was insufficient for the analysis of the long-term (4 years +) performance of the field site applications.

The dual treatments comprised of a silane basecoat and an epoxy or HMWM topcoat consistently exhibited the best performance. Of single sealer treatments, the epoxy, silane, and HMWM had the best performance in descending order. Only the silane exhibited a consistently measurable depth of penetration and was the only treatment that had significant vapor transmission ability. The dual treatments also exhibited the least water absorption for the initial, time zero, field cores extracted from each of the four field sites. Dual treatments offer the advantage of a deep penetrating sealer (silane) combined with a barrier coating type sealer (epoxy or HMWM) able to seal cracks to limit the ingress of water and chemicals. Dual treatments offer the best protection for PCCPs. If vapor transmission is of concern, the silane sealer’s performance consistently surpassed threshold values recommended in the literature and would be recommended.

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