THE INFLUENCE OF SESQUIOXIDES ON LATERITIC SOIL PROPERTIES

Abstract

THE BREAKDOWN OF THE CHARACTERISTIC GRANULAR STRUCTURE OF LATERITIC SOILS BY REMOLDING IS KNOWN TO ALTER THE PLASTIC, TEXTURAL, AND ENGINEERING CHARACTERISTICS OF THESE SOILS. THIS LABORATORY STUDY WAS AN INVESTIGATION OF SOME MINERALOGICAL, CHEMICAL, PHYSICAL, AND ENGINEERING PROPERTIES OF A LATERITIC SOIL IN ORDER TO EVALUATE MORE FULLY THE BASIC REASONS FOR THE EFFECTS OF REMOLDING. RESULTS OF X-RAY DIFFRACTION AND SCANNING ELECTRON MICROSCOPY STUDIES SHOWED THAT THE HYDRATED IRON AND ALUMINUM OXIDES (SESQUIOXIDES) COAT THE CLAYEY CONSTITUENTS OF THE SOIL AND BIND THEM INTO COARSER MICRO-AGGREGATIONS. ANALYSES OF DRAIN SIZE INDICATED THAT THE REMOLDING PHENOMENON DISAGGREGATES THE MICRO-AGGREGATIONS INTO FINER CLAYEY CLUSTERS BECAUSE OF THE FRIABLE NATURE OF THE SESQUIOXIDIC CEMENTING AGENTS. DTA AND CHEMICAL ANALYSES REVEALED THE PRESENCE OF SUBSTANTIAL QUANTITIES OF AMORPHOUS MATERIAL IN THE SOIL. ATTERBERG LIMIT TESTS ON SESQUIOXIDE-FREE SOIL INDICATED THAT THE ABNORMALLY HIGH MOISTURE CONTENTS OF THIS LATERITIC SOIL ARE A RESULT OF THE HIGH MOISTURE-RETENTION CAPABILITIES OF THE AMORPHOUS COLLOIDS AND THE POROUS MICRO-AGGREGATEIONS IN THE SOIL. ALTHOUGH REMOLDING GREATLY ALTERED THE INDEX PROPERTIES, LITTLE CHANGE WAS OBSERVED THE INDEX PROPERTIES, LITTLE CHANGE WAS OBSERVED IN THE STRENGTH CHARACTERISTICS OF THE VARIOUS SOIL STATES. THE MAGNITUDE OF THE ANGLES OF INTERNAL FRICTION DETERMINED BY TRIAXIAL COMPRESSION TESTS REFLECT A GREATER AMOUNT OF INTERLOCKING BY THE MICRO-AGGREGATIONS THAN WOULD BE PRODUCED BY A PLATEY STRUCTURE. UNCONFINED COMPRESSION TESTS SHOWED THAT LIME WAS AN EFFECTIVE STABILIZER FOR THIS LATERITIC SOIL. /AUTHOR/