Sulfate heave has wrecked roads and pads from Sherman to Laredo, usually a year or more after a lime job passed inspection. The fix starts with knowing your number. This page covers how to test, what the thresholds mean, where the sulfate belt runs, and which treatment fits each level. Hasten supplies the materials for all of them.
We will tell you what fits. Same-day response.
Four ingredients together grow ettringite, a mineral that takes up about twice the volume of what it replaced: a calcium stabilizer, clay, sulfate minerals such as gypsum, and water. The reaction runs until an ingredient is gone and can take years to surface. Lime is the calcium. Add more and you feed it.
Ettringite forms slowly. The subgrade passes density, the pavement goes down, and the heave arrives with the first wet season or the third.
On US 82 near Sherman the surface read 4,160 ppm and 41 inches down read 27,840. Gypsum washes down. A cut-and-fill job can bury a clean test and expose a bad one.
On FM 3338 in Webb County an 8-mile job tested under 2,000 ppm everywhere until a re-test found a 40,000 ppm section. One test across a project is not a test.
The Geologic Atlas of Texas flagged six of eight failure sites in the TxDOT research before anyone set foot on them. Look for selenitic or gypsiferous in the legend.
From TxDOT guidance and research project 0-4240.
| Soluble sulfate | TxDOT guidance | Treatment Hasten supplies |
|---|---|---|
| Under 3,000 ppm | Normal construction with calcium stabilizers | Lime, kiln dust, or fly ash-lime blend; buy the cheapest calcium that does the job |
| 3,000 to 7,000 ppm | Modified construction: single lime application, mellowing 2 to 10 days, moisture 2 percent above optimum | Same materials, different method; slag-lime removes the mellowing wait and the risk |
| Above 7,000 ppm | Lime alone not recommended | 5% slag cement + 1% lime, or Class F fly ash + lime |
Two counterintuitive findings from the research worth saying out loud: a single lime application reduces swell better than a double application, and higher molding moisture beats optimum moisture. The 7,000 ppm ceiling came from contractor and TxDOT field experience, not theory.
Hasten crews can carry the conductivity meter to a site and tell a contractor his soil has a sulfate problem before anyone places material. Most people apply lime and hope.
SH 161, SH 183, US 67 west of Midlothian. Eagle Ford formation. The original failures.
US 82 near Sherman. Sulfate seven times higher at depth than at the surface.
Blackland Prairie and Eagle Ford through Waco, Temple, Austin and San Antonio. Subdivisions and roadways on gypsiferous clay.
FM 3338 in Webb County, where TxDOT wrote the slag-lime special provision, and a section near Eagle Pass above 32,000 ppm built with 4 percent slag and 1 percent lime.
Blaine formation gypsum on US 287, the Aguja on SH 118, bolson deposits on SH 54. Not only a Blackland problem.
The slag-lime numbers, the four field sites, the 5:1 and 5:2 ratios and the TxDOT construction sequence, on one page for the engineer.
Testing guidance and stabilization materials anywhere in Texas. Materials load in Houston.
TxDOT guidance treats soils above about 7,000 to 8,000 ppm soluble sulfate as unsuitable for lime alone. Between 3,000 and 7,000, lime can work with modified construction: single application, mellowing, extra moisture.
Tex-146-E conductivity in the field, three minutes, flags problem areas. Tex-145-E colorimeter gives ppm in about 30 minutes. Sample every 100 feet and at depth, and read conductivity twice, ten hours apart.
Five percent slag cement with 1 percent lime is the only treatment TxDOT research recommends above 7,000 ppm. Class F fly ash with lime is a live second option where the sulfate is gypsum. Hasten supplies both.
Class C fly ash is a calcium donor and can, though it delivers less free lime per ton than lime and sets faster, which shortens the window. Above 7,000 ppm it is not the researched answer.
Sometimes. TxDOT lists removal, blending with granular material, and no treatment as alternatives above 8,000 ppm. On a low-plasticity soil, doing nothing can be the right call, and we will say so.
Send the sulfate and PI numbers, the county and the depth. We will tell you what fits and what it costs per treated ton.
Call 832-655-7763