Clay Grouts

Grouting Methods and Equipment
Page Navigation
15

5-818-6/AFM

88-32

asphalts,

emulsions, and diatomite. In addition to portland-cement grouts,

chemical

and pozzolan-cement grouts may be considered.

alter to a desired degree, the properties of an existing medium by the most

e c o n o m i c a l means. Therefore, where conditions indicate that local clays

Will produce a grout that will give the desired results, they should be con-

s i d e r e d . In the following paragraphs, the properties of clay soils that make

them suitable for a grout material are outlined, tests to be used in deter-

mining the suitability of clays are indicated, and guidance for the design of

clay grouts is provided.

-- . M a t e r i a l . Soils used as the primary grout ingredient can be divided

into two classifications. One includes the natural soils found at or near the

project with little or no modification required. The second includes com-

mercially processed clay such as bentonite. The selection of a natural or

processed material should be determined by an economic study considering

(1) grout properties necessary, to meet job requirements, (2) quantity of

grout required, (3) availability and properties of natural soils, (4) cost of

modifying natural soils, if necessary to meet job requirements, (5) cost of

importing a processed material that will meet job requirements, and (6) cost

of mixing grout using either material. Generally, where large quantities of

grout are needed, local materials will be more economical. For small

quantities, it is generally more economical to bring in prepared material

than to set up the required mining and processing equipment to use natural

soil. In addition, any specific job may present additional factors to be

considered.

b . Natural Soils. The use of natural soils is predicated on the existence

of a--suitable material within a reasonable distance of the project. Natural

soils for use as a grout ingredient are of two types: (1) fine-grained soils

with low plasticity that do not have gel properties and are more or less inert

(silt and glacial rock flour) and (2) fine-grained soils of medium to high plas-

ticity and with a high ion exchange capacity, which gives the material good

thixotropic and gel properties. The types of soil covered under (1) above

generally are used as fillers only. The types of soil covered under (2) above

may be used both as fillers and admixtures. The best source of soils for

grouts will be alluvial, eolian, or marine deposits. Residual clays may con-

tain excessive coarse-grained material, depending upon the nature of the

parent rock and the manner of decomposition. Glacial clays are generally

the least suitable because of the usually large gravel and sand content. The

properties of soils are for the most part determined by the quantity and type