Microstructure and Pore Structure of Impact-Compacted Clays

Abstract

Abstract-The microstructures of impact-compacted kaolinite and illite clays, after drying, were investigated by pore size-distribution measurements, X-ray orientation determinations, and scanning electron microscopy. Clays compacted on the dry side of the optimum moisture content exhibited a domain structure with adjacent domains largely separated by micrometer-size interdomain voids; clays compacted at or above the optimum moisture content showed a more nearly massive structure, large interdomain voids being absent. Parallel orientation was observed within domains, but neighboring domains were generally tilted with respect to each other. In kaolinite compacted on the wet side of optimum, regions of local parallel orientation could be identified at high magnification as domain units. A significant volume of 200 A-800 ,~ dia. pores in this clay was identified with spaces observed between the kaolinite plates within domains, for samples compacted both on the wet and dry sides of optimum. The subdomain structure was tentatively classified as "intergrown" in character. (001)/ (020), (002)/(020), (001)/(060), and (002)/(060) orientation indices were calculated for the compacted kaolinite and compared with analogous measurements for fully-random and fully-oriented specimens of the same clay. The results indicated only a small degree of preferential orientation normal to the axis of compaction, with little difference between samples compacted either wet or dry of optimum. These results were consistent with scanning electron microscope interpretations, which suggested that the domains did not appear to orient themselves significantly under the influence of the compaction employed.

DISCUSSION: Compaction behaviour of clay. A. TARANTINO and E. DE COL (2008). Géotechnique 58, No, 3, 199–213

“…Although the microstructure of soils compacted dry of optimum (including a kaolinite) had been described by Diamond (1970) as 'a domain structure with adjacent domains largely separated by micrometer-sized interdomain voids' (domain being another term for aggregate), Sridharan et al did not refer to any aggregate microstructure in their interpretation of the nature of the pores. The results of Sridharan et al can be redrawn as shown in Fig.…”

Prediction of Soil Equilibrium Water Content and Mineralogy Effect on Permeability Using Pore Size Distribution : Interim Report

“…The pore size distribution was determined from the pressure and intrusion data using Equation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) …”

“…Predictive equations already created for frost heave rate in such soils require no modifications . 17. Key Words soil fabric; pore size distribution; air permeability, water permeability; frost heave rate; soil-moisture characteristic curve; equilibrium water content; mineralogic effects 18.…”

Pore Size Distribution of Sandy Soils and the Prediction of Permeability : Interim Report

“…Hence Equation (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) can be rewritten as: The term G(x.) defined in Equation (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) (4)(5)(6)(7)(8)(9)(10)(11)(12) . A subroutine called "CADRE" in the Purdue University CDC 6500-6600 computer library was utilized to carry out this numerical integration.…”