Concrete Admixtures: DOT Bridge Construction

Concrete Admixtures for Bridge Building

Concrete is a versatile building material commonly used in various construction projects, including bridges. Concrete admixtures modify the properties or behavior of fresh or hardened concrete to improve, among other things, durability, strength, workability, and sustainability. 

Bridge Decks and Concrete Admixtures

The horizontal surface of a bridge on which vehicles drive is called the (bridge) deck. A typical bridge deck is made using reinforced concrete to form a slab which hardens to become a composite section with the superstructure. This type of high-performance concrete requires some assistance from concrete admixtures. When designing concrete for use in bridge decks, key factors to consider when selecting concrete admixtures include:

Compressive & Flexural Strength

Compressive strength is the concrete’s ability to resist failure under a compressive load. Superplasticizers, or high-range water reducers, make concrete more workable so that less water is required to place the mix. Concrete admixtures which improve workability and allow for less water will result in concrete with higher compressive strength and lower permeability. These admixtures also accelerate the process of placing, consolidating, and finishing the concrete. Flexural strength is the concrete’s ability to resist bending or deformation under load. To improve this property, concrete often contains fibers made of fiberglass, polypropylene, or steel. These act as reinforcement to distribute the load more evenly, reducing cracking and the risk of failure.

Durability Factors

The durability of a bridge deck is crucial for ensuring its longevity and safety for the motoring public. Concrete admixtures should be considered as a viable means to increase the bridge deck’s durability when it will be exposed to:

• Chlorides or deicing chemicals 
• Harsh weather conditions 
•  Heavy Loads and Vehicle traffic 
• Salt water in a marine environment

Air-entraining admixtures are used to boost durability when concrete is exposed to repeated cycles of freezing and thawing in winter. In colder climates where freeze/thaw is common, bridge decks must contain the appropriate amount of air to absorb the expansion of freezing water inside the concrete’s capillary structure. This helps reduce the risk of the bridge spalling and cracking in cold climates. Corrosion inhibitors help protect the bridge’s steel reinforcement from corrosion. These inhibitors protect the steel, preventing oxygen and water from reacting to corrode its surface. Preventing corrosion of steel reinforcement helps maintain its bond with the concrete for a longer period of time, extending the service life of the bridge.

Bridge Support Structure and Concrete Admixtures

A bridge’s support structure is comprised of multiple elements including abutments, piers, columns, and girders which hold up the superstructure and deck. DOTs and the concrete industry use concrete admixtures to enhance concrete performance for bridge decks, including (but not limited to) compressive and flexural strength, and durability.

Compressive & Flexural Strength

Adding certain admixtures to concrete can help improve the bridge’s compressive strength and support structure. For example, water reducers and steel reinforcement help the bridge’s structural elements withstand the heavy compressive and flexural loading encountered when large, heavy vehicles traverse the bridge. 

Durability Factors

To improve long-term durability, concrete producers use concrete admixtures which enhance the concrete’s ability to resist water intrusion, weather, corrosion, erosion, chloride penetration, and  abrasion. Such admixtures can boost the durability and serviceability of the bridge for years.

Bridge Piers and Concrete Admixtures

Bridges built over or near water require a complex system of concrete bridge piers to guarantee durability in service. Admixtures are essential to achieve the low permeability necessary for concrete to be durable when placed in a marine environment. The concrete’s permeability must be low enough to prevent (salt) water from penetrating deep enough to form corrosion on the steel reinforcement.

Bridges, Weather, and Concrete Admixtures

Bridges are subjected to varying weather conditions including heavy rainfall, hot summers, and freezing temperatures. Using appropriate concrete admixtures can help improve the resilience and durability of the bridge under such extreme conditions. Air-entraining admixtures are ideal for reducing damage from freeze/thaw cycles. They work by allowing water to expand during freezing and contract during thawing without damaging the concrete. Admixtures designed to minimize permeability and increase abrasion resistance help protect the concrete from damage caused by weathering.

Get the Best Concrete Admixtures Today

Concrete admixtures are a vital tool in bridge design and construction because they improve durability, reduice cost, and make concrete easier to pump, place, and finish. If you’re looking for the best concrete admixtures,  EdenCrete® is thehe right option. Carbon nanotube-enriched admixtures offer multifaceted benefits in various applications. Our eco-friendly admixtures help improve the durability and toughness of concrete. EdenCrete enhances surface abrasion resistance and lowers permeability like no other product. Contact us today to learn more about this innovative product and place your order.