Why Latex Modified Concrete Is Used For Cold Climate Bridge Deck Overlays
In colder climates, bridge decks undergo a freeze-thaw cycle more severe than other types of concrete infrastructure. This is because they’re exposed to weather conditions on the top and bottom, unlike sidewalks and other concrete flatwork. These are structural components that contain an immense amount of reinforcing steel. Yet, latex modified concrete is a common way to protect the steel through a bridge deck overlay.
How Latex Modified Concrete Developed
In the 1960s, Dow Chemical developed an overlay material using a latex modified concrete. Laboratory studies showed potential for the usage of the resulting concrete for bridge decks. Then, field testing demonstrated the conventional concrete delivery systems provided underwhelming results. With these results, a Dow employee tried the newly patented and manufactured mobile concrete mixer, called the “Concrete Mobile.” This mixer gave engineers control over their concrete production on the job site. The latex modified concrete was now capable of reaching the potential shown in the laboratory studies. All specifications from that period on require the use of an on-site mixer to produce a latex overlay.
Another method of latex modified concrete overlay is the “Hi-Density” or “Iowa Low Slump” overlay. As the name suggests, it was developed in Iowa in the 1970s. The mix is a high cement content mix with a low water-cement ratio with a maximum water-cement ratio of 0.32 while plus or minus specifies the slump. This high cement content, low slump mix wasn’t tried in conventional delivery equipment as it would set up in the mixer without adding additional water. The mix competes with the previous latex modified concrete overlay on performance. Producing this mix requires the use of a mobile mixer at the job site so the mix is fresh. Again, this allows engineers to achieve actual field performance that matches observed lab performance.
How Ice & Snow Removal Practices Affect Bridge Decks
Citizens expect roads and bridges to be free of snow and ice shortly after a storm subsides. In response, highway departments use salt-based deicing materials on the surface to meet the demand. If the concrete has cracks, it allows the deicing salt materials to reach the reinforcement steel below, causing the steel to rust. Because rust occupies more volume than iron, the bridge deck deteriorates more quickly due to the rust expansion. Highway engineers now require a long-lasting material that repairs the damage and prevents deicing salts from reaching the reinforcement steel.
How A Volumetric Mixer Protects The Integrity Of Latex Modified Concrete
Mobile concrete mixers are commonly used to produce high-quality mix designs used to overlay bridge decks with latex modified concrete. Because both mixes are highly engineered, mixing concrete at the job site eliminates several downsides associated with conventional concrete delivery systems, including:
- Age of concrete;
- Tempering water; and
- Revolutions of the drum.
Cemen Tech volumetric mixers are the perfect partner for latex modified concrete, producing the exact mix design every time and meeting DOT specifications.
If you have comments or questions about the types of latex modified concrete, bridge decks, or mobile concrete mixers, we would love to hear them! Call us at (800) 247-2464 or send us a message on our Contact Us page.