Evaluation of Roadbond EN-1 for Soil

Stabilization on LAK-2-7.76

By: Peter Narsavage

Office of Construction Administration Ohio Department of Transportation

In-House Research Sponsored by: Ohio Department of Transportation, Office of Research

And The Federal Highway Administration

State Job Number 526980A Technical Summary No. FHWA/OH-2012/9

August 2012

Notice

This document is disseminated under the sponsorship of the Ohio Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

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Unclassified20. Security Classif. (of this page)

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$9,500

17. Key Words

Sulfate, Heaving, Stabilizer, Roadbond, Soil

8. Performing Organization Report No.

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

State Job No. 526980A

1. Report No.

FHWA/OH-2012/9

2. Government Accession No. 3. Recipient's Catalog No.

5. Report Date

August 2012

16. Abstract

Heaving problems caused by a reaction between sulfates in the subgrade soil and the calcium found in lime and cement have caused heaving of the

pavement due to a reaction between calcium (cement) from the subgrade stabilization, other minerals in the soil, and water to form a new mineral

called ettringite.

The objective of the laboratory testing was to determine if the Roadbond EN1 chemical will work with the subgrade soils on a specific construction

project to reduce or eliminate heaving. It was concluded that adding the Roadbond EN1 product to the subgrade stabilization would not allow ODOT to

significantly reduce the amount of cement, nor would it reduce the amount of expansion due to sulfates. Therefore, it is not recommended to use the

Roadbond EN1 for subgrade stabilization on this project, as it appears there is no benefit to using it rather than using cement for subgrade

stabilization.

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized

12. Sponsoring Agency Name and Address

Ohio Department of Transportation1980 West Broad StreetColumbus, Ohio 43223

9. Performing Organization Name and Address

Ohio Department of Transportation1980 West Broad StreetColumbus, Ohio 43223

4. Title and subtitle

Lab Testing of New Stabilization Chemical to Prevent Sulfate Heaving7. Author(s)

Peter Narsavage

13. Type of Report and Period Covered

Final Technical Summary

15. Supplementary Notes

14. Sponsoring Agency Code

6. Performing Organization Code

OHIO DEPARTMENT OF TRANSPORTATION CENTRAL OFFICE, 1980 WEST BROAD STREET, COLUMBUS, OHIO 43223

Evaluation of Roadbond EN-1 for Soil Stabilization on LAK-2-7.76

Office of Construction Administration August 14, 2012

Summary In order to reduce the amount of sulfate heaving in the stabilized subgrade on project

LAK-2-7.76, we have tested a proprietary stabilization product called Roadbond EN1. According

to the supplier, this product can be used to replace or reduce the amount of lime or cement

required for subgrade stabilization.

We conducted the tests on soil samples from the project that were mixed with Roadbond

EN1 and cement. The results indicate that the product did not increase the strength of the

samples any more than would be expected based on the cement alone, and that the product did

not reduce the amount of expansion. Consequently, I do not recommend using the Roadbond

EN1 for subgrade stabilization on this project, as I don’t believe there is any benefit to using it

instead of just using cement for subgrade stabilization.

Background Within the past two years, the Department has discovered that the subgrade soils along State

Route 2 in Lake County contain unusually high levels of sulfates. The sulfates have caused

heaving of the pavement due to a reaction between calcium (cement) from the subgrade

stabilization, other minerals in the soil, and water, to form a new mineral called ettringite. We

discovered the problem on the LAK-2-7.76 project when we had to spend 1.4 million dollars in

2011 to repair heaved pavement. After we became aware of the sulfates, we adjusted our

procedures to attempt to minimize the amount of sulfate heaving. We first looked at replacing all

cement stabilization with undercuts, but the estimated additional cost was over 10 million

dollars. Instead we decided to test the subgrade soil for sulfates, perform undercuts in the areas

with high sulfates, and cement stabilize the rest. Although we were successful in reducing the

amount of heaving, we still ended up spending about $750,000 to repair heaved pavement this

year.

There is a product called Roadbond EN1 that is a non-calcium based alternative to lime or

cement for subgrade stabilization. To determine if this product would be beneficial on the

LAK-2-7.76 project, I arranged for the contractor to perform laboratory testing to determine the

strength and expansion of samples of the subgrade soil mixed with the Roadbond EN1 chemical.

Based on the subgrade soils on the project, the supplier of Roadbond EN1 recommended that

we use a combination of cement and Roadbond EN1 to provide the necessary subgrade

improvement. The chemical will not provide enough improvement used by itself.

There are two possible ways the Roadbond EN1 product could reduce the amount of sulfate

heaving. The first way is to reduce the amount of cement needed to stabilize the subgrade soil. If

the combination of Roadbond EN1 and cement results in greater compressive strengths than

obtained with just cement alone, then we can reduce the amount of cement used in the subgrade

Evaluation of Roadbond EN-1 for Soil Stabilization on LAK-2-7.76

August 14, 2012

Page 2

stabilization. This would then reduce the amount of calcium available to form ettringite and

thereby reduce the amount of sulfate heaving. The second way is for the product to somehow

interfere with the formation of the ettringite. This would result in a reduced amount of expansion

in the samples containing the Roadbond EN1 product as compared to samples that were mixed

with only cement.

Testing The testing was performed by EDP Geosciences of Kirtland, Ohio, under contract with Cem-

Base, Inc. Cem-Base is the subcontractor on the project who is performing the subgrade

stabilization. EDP’s report of testing, dated August 3, 2012, is attached.

EDP collected two different soil samples from the project for testing. One soil was an A-4a

(sandy silt) soil according to the ODOT modified AASHTO classification system, and the other

soil was an A-6a (silt and clay) soil. The samples contained visible signs of gypsum, which is a

source of sulfates. EDP prepared three different mixtures from the soil, shown below.

3% Roadbond EN1 + 2% cement

3% Roadbond EN1 + 4% cement

6% cement

Specimens from each of the mixtures were allowed to cure for 7 days, 14 days, and 28 days.

After the 7 and 14 day cure periods, the specimen was soaked for 24 hours. After the 28 day cure

period, the specimen was soaked for 4 days. EDP measured the circumference and height of each

of the specimens before and after soaking to calculate expansion during soaking. For the 4 day

soak, EDP also took measurements every 24 hours. After soaking, EDP tested the compressive

strength of each of the specimens.

Test Results The test results are shown in Figures 1 through 4. Typically with cement stabilization, the

compressive strength of the subgrade soil increases linearly with the amount of cement added to

the soil (at least within the normal range of cement content – 2 to 10 percent). Therefore, Figures

1 and 2 include dotted lines that show the expected linear increase of strength with increasing

cement content. You can see in Figure 1 for the A-4a soil that the strength at 6% cement and no

Roadbond EN1 lies on the dotted line for the 7 and 14 day cures (there was not enough data for

the 28 day cure, see the footnote to Figure 1). From this I conclude that the Roadbond EN1 had

no significant effect on the strength of the A-4a samples.

In Figure 2 for the A-6a soil, you can see that the strength at 6% cement and no Roadbond

EN1 lies above the dotted line for the 7 day cure and below the dotted line for the 14 and 28 day

cures. From this I conclude that the Roadbond EN1 may have increased the strength of the

mixtures after a 14 day cure. However, ODOT determines the percentage of cement used in

subgrade stabilization based on the strength after a 7 day cure. After only a 7 day cure, the

samples with Roadbond EN1 did not show an increased strength beyond what we would expect

for the cement alone. Even if we did use the 14 day strength to determine the amount of cement,

the addition of Roadbond EN1 would result in less than 0.5 percent difference in the cement

content.

Figures 3 and 4 show the expansion test results. In almost every case, the expansion of the

samples with Roadbond EN1 was greater than the samples with just cement.

Evaluation of Roadbond EN-1 for Soil Stabilization on LAK-2-7.76

August 14, 2012

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Figure 1. Compressive strength results for A-4a soil

Note: The strength of the 3% Roadbond EN1 + 2% cement at 28 days was not tested, as the

cylinder was destroyed because it became too soft to handle after the first day soak.

Figure 2. Compressive strength results for A-6a soil

Evaluation of Roadbond EN-1 for Soil Stabilization on LAK-2-7.76

August 14, 2012

Page 4

Figure 3. Expansion test results for A-4a soil

Figure 4. Expansion test results for A-6a soil

Conclusion and Recommendations Based on these test results, I conclude that adding the Roadbond EN1 product to the subgrade

stabilization would not allow us to significantly reduce the amount of cement, nor would it

reduce the amount of expansion due to sulfates. Therefore, I do not recommend using the

Roadbond EN1 for subgrade stabilization on this project, as I don’t believe there is any benefit to

using it instead of just using cement for subgrade stabilization.

By Peter Narsavage, P.E.

Ohio Department of Transportation, Office of Construction Administration