How TerraRoads Meets Caltrans and U.S. Army Corps of Engineers Standards

When a road construction product is approved by Caltrans — the California Department of Transportation, one of the most rigorous road-building agencies in the world — and by the U.S. Army Corps of Engineers, engineers and project owners can specify it with confidence.

TerraRoads™ holds both approvals, along with 26+ additional regulatory approvals across 6 continents. This article explains what those approvals mean in practice, what testing TerraRoads™ has undergone, and how engineers can specify it on government and DOT-funded projects.

What Does Caltrans Approval Mean?

Caltrans maintains one of the most comprehensive approved products lists in the United States. To be listed, a soil stabilization product must demonstrate:

• Consistent performance across a range of California soil types and climatic conditions
• Environmental safety — non-toxicity to soil, groundwater, and aquatic ecosystems
• Durability under traffic loading and seasonal moisture variation
• Compatibility with standard construction methods and equipment

TerraRoads™ meets all of these requirements. Its non-toxic, biodegradable formulation — a natural multi-enzyme concentrate — poses no risk to soil or groundwater, which is a prerequisite for approval in California's environmentally sensitive regulatory environment.

For engineers specifying materials on California state highway projects, federally funded projects in California, or any project where Caltrans standards are referenced, TerraRoads™ is a compliant choice.

What Does U.S. Army Corps of Engineers Approval Mean?

The U.S. Army Corps of Engineers (USACE) is responsible for military road construction, airfield construction, and infrastructure in some of the most demanding environments on earth — remote locations, extreme climates, and high-traffic military operations.

USACE approval requires demonstrated performance under:

• Heavy axle loads — military vehicles, including tracked and wheeled armoured vehicles
• Remote deployment conditions — minimal equipment, limited water supply, challenging logistics
• Rapid construction timelines — military operations cannot wait for extended curing periods
• Extreme environmental conditions — from desert heat to arctic cold

TerraRoads™ has been specified on military road and airstrip projects across multiple continents. Its ability to treat existing on-site soil — without importing aggregate or specialist equipment — makes it particularly well-suited to remote military construction where logistics are constrained.

How Does TerraRoads™ Perform Against Standard Test Methods?

CBR (California Bearing Ratio)

The CBR test is the primary method for measuring road subgrade and base course strength. TerraRoads™ consistently achieves CBR improvements of up to 300% compared to untreated soil, across a range of soil classifications.

This improvement is measured using standard ASTM D1883 or AASHTO T193 test methods — the same methods used by Caltrans, USACE, and DOT agencies globally. The results are reproducible and have been independently verified in laboratory and field conditions.

Proctor Compaction

TerraRoads™ modifies the moisture-density relationship of treated soils, allowing optimal compaction to be achieved at lower moisture content. This is measured using standard Proctor compaction tests (ASTM D698 or ASTM D1557), and the results confirm:

• Reduced optimum moisture content — up to 25% less water required for compaction
• Increased maximum dry density — higher compaction density at lower moisture content

Both outcomes are directly relevant to DOT specifications, which typically require compaction to a minimum percentage of maximum dry density.

Unconfined Compressive Strength (UCS)

For projects where UCS is specified — common in pavement design for stabilised base courses — TerraRoads™-treated soils demonstrate significant strength gains compared to untreated controls, measured using ASTM D2166 or equivalent methods.

Durability and Permanence

Unlike cement and lime stabilization, which can be subject to sulphate attack and carbonation over time, TerraRoads™ treatment is permanent. The enzyme-catalysed bond between soil particles does not degrade under normal service conditions, and the treated road base maintains its improved properties through repeated wet/dry and freeze/thaw cycles.

Which Agencies Have Approved TerraRoads™?

TerraRoads™ holds approvals from 28+ regulatory bodies across 6 continents:

United States

• Caltrans — California Department of Transportation
• U.S. Army Corps of Engineers
• 7 additional U.S. state DOT agencies

Americas

• Multiple national DOT and road authority approvals across North and South America

EMEA (Europe, Middle East & Africa)

• Road authority approvals across multiple European, Middle Eastern, and African jurisdictions

Asia Pacific

• Regional road authority approvals across multiple Asia Pacific jurisdictions

This breadth of approval is unmatched by any other natural soil stabilization product. No other enzyme-based road stabilizer has been independently tested and approved by this many regulatory bodies across this many regions.

How to Specify TerraRoads™ on a Government or DOT Project

Step 1: Confirm Soil Suitability

TerraRoads™ is effective across 8 USCS soil classifications (GW, GP, GM, GC, SW, SP, SM, SC). A standard soil test — plasticity index, grain size distribution, and Proctor compaction — confirms suitability and allows the application rate to be optimised.

Step 2: Reference the Approval

For projects where Caltrans or USACE standards are specified, TerraRoads™ can be referenced directly as a Caltrans-approved or USACE-approved soil stabilization product. For projects in other jurisdictions, the relevant regional approval can be cited.

Step 3: Specify the Application Rate

The standard application rate is 1 litre of TerraRoads™ per 15 m³ of compacted soil. This rate can be adjusted based on soil type and project requirements — our technical team provides project-specific guidance.

Step 4: Apply Using Standard Equipment

No specialist equipment is required. TerraRoads™ is diluted in the construction water and applied through a standard water bowser during compaction. A grader and vibratory roller complete the process.

What About Environmental Compliance?

Environmental compliance is increasingly a requirement on government-funded road projects. TerraRoads™ is:

• Non-toxic — safe for soil, groundwater, and aquatic ecosystems
• Biodegradable — breaks down naturally in the environment
• Free of heavy metals, solvents, and hazardous chemicals
• Approved by environmental regulators in all 28+ jurisdictions where it holds road authority approval

This means that specifying TerraRoads™ does not create additional environmental compliance obligations — it satisfies them.

Getting Technical Documentation for Your Project

TerraRoads™ technical documentation — including test reports, approval certificates, and application guidelines — is available for engineers and project owners who need to support a specification or tender submission.

To request documentation or discuss compliance requirements for a specific project, [contact the TerraRoads™ technical team](/lp/natural-soil-stabilization-guide?utm_source=blog-aab&utm_medium=blog&utm_campaign=cmp_7TopaVfMeH-qCEfCirrXvp6X6VgN1f0U6BsK0wW35Es&utm_content=act_EZ0YnvF17UHYsYiEEo-VXTGTwPJ6jLZeU2OFOxf9gXY&utm_term=topic_caltrans-army-corps-standards). We work directly with engineers, DOT agencies, and government procurement teams to provide the technical support needed to specify TerraRoads™ with confidence.

Summary

TerraRoads™ is the most widely approved natural soil stabilization product in the world. Its approvals from Caltrans and the U.S. Army Corps of Engineers — two of the most demanding road construction authorities globally — provide engineers with the confidence to specify it on government, DOT-funded, and military projects.

With 28+ approvals across 6 continents, a 30-year track record of field performance, and independently verified test data using standard ASTM and AASHTO methods, TerraRoads™ is the specification choice for engineers who need to deliver compliant, cost-effective, and durable road infrastructure.