The Rammed Earth House by David Easton

Author:David Easton [Easton, David]
Language: eng
Format: epub
ISBN: 9781603581592
Publisher: Chelsea Green Publishing
Published: 2007-06-12T21:00:00+00:00

Field testing for durability. An easy method for evaluating the resistance of a proposed mix design to weathering is to subject a sample block to simulated wind-driven rain. The samples that are denser will erode less. Cement stabilization can make a sample impervious to weathering.

The Case for Importing Soil

In some cases, the soil on the building site is simply not suitable for construction, even with amendments and cement stabilization. It may be too rocky, too heavy in clay, too contaminated with tree roots and other debris, or have some other problems that make it too costly to use. Screening rocks and roots out of soil can require days of labor and equipment. Amending a site soil with sand can be expensive, since clean, washed sand, purchased from a gravel plant and trucked onto the site, is sometimes twice the price of other quarry products. Certain soil types, especially fine-grained silts and clays, take a long time to mix and are slow to compact. They require greater amounts of water for optimum compaction, and this in turn increases their likelihood of cracking as they dry.

For these reasons, the costs of cleaning or amending an on-site soil should be carefully compared with the cost of importing a ready-to-use soil material. Soils can sometimes be purchased from a quarry where they have been removed to gain access to other products. The major expense will be transportation costs. Long distances add up in trucking time. With luck, a suitable soil may be found very near the job site and hauling costs kept to a minimum. In some instances, local excavating or swimming pool contractors may be working on projects where they have material to dispose of and will deliver it to your job site for little or nothing.

In addition to the structural characteristics of the soil, the finished appearance is of great importance. The better the gradation of the soil, the smoother the wall, and the richer the color of the soil, the more attractive the wall. Finding a good import soil will take some looking. Although excavation occurring in the neighborhood may turn up as a free source of soil, quarries are always a reliable source. Many rock quarries make a product classified as a road base or structural backfill. Typically this will be primarily small rock and sand, with 10 to 20 percent fines. These soils will in most cases require cement stabilization, as they are too low in clay, but they will yield strong, durable walls. A high percentage of gravel can give the wall a coarse appearance. Road base and backfill cost less than clean rock or sand, because they are less processed. The quarry may even have a gradation report on file.

In some cases, a quarry may have a product identified as quarry fines, basically a leftover from the crushing and screening operation. The fines are what remain after the saleable rock has been shaken out of the bulk soil. As the name implies, fines are higher in small particles than road rock or structural backfill.

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