Project Description

Concrete Restoration – Sausalito Beach

The corrosive effect of salt water on the concrete foundation at Sausalito Beach

Heavily corroded rebar and delaminated concrete beams

Heavily corroded rebar and delaminated concrete beams

Back span of a cantilevered concrete beam being repaired

The back span repaired with Polymer Modified Concrete

Reconstructed concrete beams with Polymer Modified Concrete

Reconstructed concrete beams with Polymer Modified Concrete

Concrete Restoration

Concrete repair, strengthening, and renovation can be complex. A concrete contractor needs to adopt different restoration programs, depending on the problem to be addressed.

Common causes of concrete damage:

Corrosion related deterioration: Corrosion of the reinforcing steel is the most common cause of the deterioration of concrete structures. The exposure of the embedded reinforcing steel to water, oxygen and chlorides, such as salt, results in oxidation or rust. The oxidized iron can expand up to 10 times its original volume, bursting the surrounding concrete. This will, in turn, result in more moisture infiltration and eventual delamination of the concrete.

Poor quality concrete: High quality and properly consolidated concrete, placed with minimal voids and internal shrinkage, results in an environment that will protect the embedded reinforcing steel for years, and prevent deterioration.

Substandard workmanship: The most common problem in concrete construction is the misplacement of the reinforcing steel. This will eventually result in severe cracking. The second most common problem is the inadequate consolidation of concrete during placement, resulting in honeycombs. Cracks and honeycombs in areas with environmental exposure will lead to corrosion and eventual delamination.

Concrete repair methods and materials:

To repair delaminated concrete, the program should include chipping and removing the concrete cover, exposing and brushing the total circumference of the rusted bars to bright state, application of primer to the exposed bars, and application of appropriate repair material to replace the removed concrete.

Concrete repair material falls into two categories: cementitious and polymer modified concrete. The selection of the repair material must take into consideration the compatibility of the material with the parent concrete in elasticity and strength. This is especially important when repair patches are constrained.

Additional concrete restoration technologies include epoxy injection in cracks from 1/16” to full depth, as well as traditional application of shotcrete, encapsulation and Fiber Reinforced Polymers.

What is FRP?

Fiber Reinforced Polymer (FRP) is comprised of a polymer (such as epoxy, vinyl-ester, or polyester) that is reinforced with a fiber (such as carbon, glass, Kevlar, basalt, etc.); thus the name Fiber Reinforced Polymer or FRP. The fibers are the main source of strength and stiffness in FRP. The resin serves two primary purposes: a) to distribute the load among all fibers, and b) to protect the fibers from environmental effects, such as abrasion, etc. FRPs have physical properties that are different when measured along different axes or directions. By orienting the fibers in the desired direction, one can achieve the required strength in each direction.

Concrete Strengthening:

Structural concrete members are commonly strengthened by conventional methods of steel reinforced concrete. This method can be relied upon where access for the operation is readily available. When access is limited and the environment of the work area is confined and congested with other building material, the application of Glass or Carbon Fiber Reinforced Polymer (FRP) becomes highly advantageous and more economical. Among the other advantages of FRP are lighter weight, moisture resistance, and a more rapid course of installation than conventional methods of concrete strengthening.

To discuss your concrete restoration project, please contact concrete contractors SteelCore Builders at: 415-331-0525.