A need exists for a stabilizing material or method capable of strengthening weak, fine-grained soils sufficiently to support traffic for specific military operations. Research performed by the Massachusetts Institute of Technology for the Corps of Engineers showed phosphoric acid, used in conjunction with certain other chemicals, to be capable of improv-ing significantly the strength of certain clay soils at relatively low water contents. To investigate the use of this stabilizing system in wet soils, laboratory and field tests were made of a phosphoric acid anhydride (phosphorus pentoxide) that would utilize available water in the soil, convert to the acid, and proceed with the stabilizing reaction.nInitial laboratory tests revealed that 5% phosphorus pentoxide plus 0.5% sodium fluosilicate was capable of increasing the compressive strength of a lean clay soil (soil A) from 24 psi to 165 psi after 24-hr curing and to nearly UCO psi after 3-day curing. However, other laboratory tests con¬ducted on a similar soil (soil B) concurrently being used to construct the field test section showed the same stabilizer system used in the initial laboratory tests to be relatively ineffective for soil B. Analysis of soil B revealed the presence of concretions of calcium carbonate, which were-not present in soil A.
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