Shotcrete admixtures used by Department of Transportation DOT

Shotcrete Admixtures for Improved Performance in DOT Highway Construction

Understanding how shotcrete admixtures can be used by the Department of Transportation (DOT) for highway construction is critical for project success. Shotcrete is widely utilized in highway infrastructure owing to its durability, strength, and workability. Typically, shotcrete admixtures are incorporated  to improve performance and achieve  specific job site requirements. This article will discuss the various shotcrete admixtures utilized in DOT projects:

Department of Transportation Shotcrete Use for Highway Construction

Shotcrete, a form of sprayed concrete, is widely used by state DOTs for highway construction projects. It’s preferred over traditional concrete for various applications, including soil retention, bridge support, roadside features, and sound walls.

Shotcrete allows for quick erection of formwork and installation, is more easily applied to irregular surfaces, and it can carved to create concrete shapes otherwise impossible to achieve using traditional ready mix concrete in formwork. . Here are some of the different types of shotcrete admixtures used by the DOT  to improve performance in a variety of applications:

Admixtures for Strength

Admixtures are sometimes added to shotcrete to increase its strength, so that it may withstand exposure conditions when in service . The following are the types of admixtures commonly used for strength:

Chemical Admixtures

Chemical admixtures, such as retarders and accelerators, help speed up or slow down the setting time of shotcrete. These admixtures are used to change the natural rate at which shotcrete sets. Retarders provide more time for concrete to be transported, placed, and finished when conditions require. Accelerators can help speed up construction schedules and timelines, letting the shotcrete be put in service sooner.

Mineral Admixtures

DOTs use mineral admixtures such as fly ash, silica fume, and slag to improve shotcrete’s strength and durability. These are combined with chemical admixtures-to, make shotcrete more resilient in the field.

Fiber Admixtures

Fiber helps enhance shotcrete’s toughness and durability by improving tensile strength and boost its resistance to cracking. Fiber increases water demand and makes it more difficult to shoot out the nozzle and carve, however, which can cause shotcrete crews to seek out alternatives.

Admixtures for Durability

It is crucial that shotcrete used in highway construction have high durability. Admixtures help reduce permeability, prevent cracking, and protect against freeze/thaw cycles, all of which are factors to improve the durability of shotcrete. The following are some of the admixtures used to improve shotcrete’s durability:

Reduce Permeability

Permeability-reducing admixtures tighten up the capillary structure to help lower water ingress and minimize damage resulting from the harmful materials transported by water. They improve shotcrete’s durability by reducing its susceptibility to:

• Chemical attack
• Freeze/thaw cycles
• Extreme weather conditions

Crack Reduction

Crack-reducing admixtures like shrinkage reducers help enhance shotcrete’s durability by reducing the formation of cracks resulting from internal shrinkage strain. These admixtures offer increased resistance of shotcrete to shrinking and cracking.

Freeze/Thaw Cycles

Admixtures such as air-entraining agents and fibers help shotcrete to endure more freeze/thaw cycles. They make shotcrete more resilient to cold climates, reducing damage due to spalling and scaling which lead to maintenance and/or replacement, sooner.

Spalling, Delaminating, and Scaling

DOTs use specialized admixtures to boost the performance of shotcrete in harsh environments. Reducing the permeability of shotcrete helps protect against water infiltration and chemical attack, which can help reduce the likelihood that the shotcrete surface will spall, scale, or delaminate.

Admixtures for Workability

Workability is a key factor in shotcrete highway construction as it affects the ease of pumping, rebound/waste, and finishing/carving. These admixtures reduce the friction between the shotcrete as it moves through  the pump and hoses. Here are examples of admixtures to consider:

Pumping

Pumping aids help improve shotcrete’s workability without adding water. They reduce the friction between the shotcrete and the pump, making it easier to pump longer distances while minimizing the risk of blockages. These can include water reducers, viscosity modifiers, or specialty admixtures.

Rebound/Waste

Certain specialized admixtures help reduce the amount of shotcrete waste from rebound during application. They improve  adhesion to the substrate and  shotcrete’s ability to stack without sloughing, significantly cutting the waste from rebound.

Finishing/Carving

Admixtures such as water reducers and hydration stabilizers make it easier to finish and carve shotcrete on the job. They improve shotcrete’s texture and workability, allowing for easier carving and shaping.

Admixtures for Job Site Requirements

Shotcrete is often selected for its ability to cater to challenging job site environments such as irregularly shaped elements, narrow site access, etc. DOT uses the following admixtures to meet specific job requirements:

Longer Distance Pumping Requirements

Admixtures like viscosity modifiers and pumping aids help enhance shotcrete’s pumpability over longer distances. These admixtures reduce shotcrete-pump friction, allowing for seamless and more efficient pumping.

Cold Weather Pumping Requirements

In cold weather conditions, admixtures like accelerators help shotcrete spray, set, and cure properly. They can be risky to use if overdosed, however, so careful monitoring must be employed during cold weather application.

Get the Best DOT Shotcrete Admixtures Today

Admixtures play a crucial role in DOT shotcrete highway construction projects. They offer a great way to optimize the performance and longevity of your shotcrete structures. It is important to understand and choose the best admixtures for strength, durability, workability, and job site requirements.

If you’re looking for the best shotcrete admixtures, EdenCrete® is your one-stop shop. We offer EdenCrete®, a high-performing and effective carbon concrete admixture, for improving shotcrete durability, strength, sustainability, and workability. It increases surface abrasion resistance and reduces permeability while boosting the pumpability of shotcrete over longer distances like no other product. Contact us to learn more about the incredible features of our innovative shotcrete admixture, and place an order today.