Publication Date:
1989-08-01
Description:
According to Emerson's model of the soil aggregate, a large soure of physical weakness exists at the surface of sand particles within the aggregate, particularly when wet. The aim of this study was to simulate sand particles with glass beads and to test the hypothesis that a bed of glass beads can resist large compressive forces in water when a polymer is bonded to the bead surfaces using chemicals and conditions that produce hydrolytically stable, covalent bonding. Because carboxyl and amine functional groups can react to form the amide bond and silanes can bond to a silanol surface (e.g., sand or glass), polyacrylic acid (PAA: FW ≈ 50 000), amines, and silanes were used to test the hypothesis for glass beads (53-μm mean diameter). The pressure at which the bed surface of the glass beads (when water-saturated) was penetrated with a flat probe (radius = 1.37 mm) served as an index of strength imparted by various chemicals when these were introduced into the system individually and in various combinations. A dramatic increase in the strength of the bed surface occurred only when all the theoretical requirements were met for both covalent bonding between the polymer and the silane and silanol coupling between the silane and the glass surface. We conclude that the hypothesis is confirmed for a simple system of glass beads and that large increases in the efficiency of soil conditioners may be potentially realized in soil aggregates if the weak links between inorganic particulates (sand, silt, and clay particles) and organic polymeric materials (natural or synthetic) are augmented with, or replaced by, strong and water-resistant links. Key words: Soil structure, soil conditioners, polymers, coupling agents, soil aggregates
Print ISSN:
0008-4271
Electronic ISSN:
1918-1841
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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