The Benefits of Lime

This fall has brought with it a ton of rain to the Dallas/Fort Worth area. Are you finding your construction site to be bogged down with mud? You can’t wait for the sun to dry up the wet soil. You may just get more rain. You may be working inside a building where the sun can’t dry up the mud. You don’t want to dig up the mud and cart it away-too expensive and disruptive. Lime is the answer!

Lime, in the form of either quicklime or hydrated lime, dries up wet soil quickly, so that it can be compacted readily, forming a working table that will resist further wetting as well so you can get back to work! Quicklime and hydrated lime are both highly effective in drying wet clay and silt soils. Highway contractors have found that lime expedites construction in rainy weather, due to its drying action and the formation of a firm working table. Building contractors have been discovering the same thing.

Low Cost Solution

For most soil drying applications, approximately 3 to 5%lime (based on dry weight of soil) is required, depending on degree of wetness. This is about 5 to 10 lbs./sq. yd. for 6 in. of compacted depth. The result is a low cost solution when compared with other methods, especially when time is not on your side.

Convenient

Both quicklime and hydrated lime may be used for soil drying. Quicklime has somewhat greater drying capacity and dries more rapidly than hydrated lime. Quicklime is generally used in pebble form, but also in ground and granular forms. Hydrated lime is available in several types (e.g., Type N, or chemical lime, and Type S, or mason's lime), any of which may be used for drying. Lime is available in bulk or in bags. (Pulverized limestone, or "aglime," is not a substitute for lime for this use).

Easy to Apply

Use of lime for drying has three simple steps: 1) Lime spreading 2) Mixing lime and soil 3) Compaction The most rapid lime spreading is achieved with a pneumatic bulk truck equipped with a spreader at the rear, or by other mechanical delivery of bulk lime. However, bagged lime may also be used. Bags may be moved to the desired location and then emptied. In very wet conditions, the spread lime should be left in place for 1 to 2 hours before mixing to permit the drying of excess water.

Mixing

After spreading, the lime and mud are mixed by a pulvimixer or similar equipment to a depth of 6 inches (or deeper in exceptionally spongy spots). Other equipment that can be used for mixing includes: a front-end loader equipped with bucket teeth, scarifiers, and disc harrows. Several passes are made until the soil is dry enough for compaction. By mixing a small area first, it is possible to determine if the desired degree of drying is achieved. If not, the rate of application can be increased.

Compaction

Initial compaction is generally performed with a sheepsfoot roller, followed by a pneumatic or flat wheel roller. However, the lime-soil mixture may be dry enough for the latter rollers to do all compaction. For temporary haul roads, compaction with the sheepsfoot alone may suffice, since haulage trucks will provide additional compaction. If compaction is thorough, subsequent rains should not soften the treated subgrade, and it should not revert to mud.

Lime Can Prevent Mud

The best solution to a mud problem is to prevent it from occurring in the first place. After initial grading of a building site, lime can be mixed into the soil and compacted. Then, if it rains, equipment will not bog down in mud. There is no slipping and wheel spinning, and worker productivity and comfort are improved.