Silica polymer bonding of stressed silica grains: An early growth of intergranular tensile strength

Abstract

h i g h l i g h t s• Micro-damaged amorphous silica grains under stress release silicic acid into near contact water.• Within 3-4 weeks above initial concentration of 300 ppm, silicic acid polymerizes and forms polymer bridges between the grains.• The force at rupture in a single polymer branch reaches up to 0.03 mN.• The cumulative force at rupture of the polymer network between the grains reaches 1-1.5 mN.• The latter value is 2-3 times higher than an analogous capillary bridge force. a r t i c l e i n f o b s t r a c tLaboratory tests on microscale are reported in which millimeter-sized amorphous silica cubes were kept highly compressed in a liquid environment of de-ionized water solutions with different silica ion concentrations for up to four weeks. Such an arrangement simulates an early evolution of bonds between two sand grains stressed in situ. In-house designed Grain Indenter-Puller apparatus allowed measuring strength of such contacts after 3-4 weeks. Observations reported for the first time confirm a long-existing hypothesis that a stressed contact with microcracks generates silica polymers, forming a bonding structure between the grains on a timescale in the order of a few weeks. Such structure exhibits intergranular tensile force at failure of 1-1.5 mN when aged in solutions containing silica ion concentrations of 200-to 500-ppm. The magnitude of such intergranular force is 2-3 times greater than that of water capillary force between the same grains.

Chemo-mechanical modeling of artificially and naturally bonded soils

“…In addition, some progress in experimentally studying the micro-scale multi-physics evolution of chemically bonded soils has been recently made [34], [35], [36], [37], [38]. However, quantification of that evolution requires a prior micro-scale model with its well-defined variables, and its quantitative upscaling procedure to allow a macro-scale verification.…”