The Effect of Two Polymers and Water Qualities on Dry Cohesive Strength of Three Soils
- Saleh M. Aly and
- J. Letey
The effects of two polymers, cationic guar (CP-14) and anionic polyacrylamide (PAM), and two water qualities on dry cohesive strength of three soils were studied. The soils were Fallbrook sandy loam (fine-loamy, mixed, thermic, Typic Haploxeralf), Bosanko sandy clay loam (fine, montmorillonitic, thermic, Chromic Pelloxererts), and Hanford loamy sand (coarse-loamy, mixed, nonacid, thermic, Typic Xerorthents). The two polymers were applied with synthesized Friant-Kern Canal or well water typical of the San Joaquin Valley of California (EC 0.05 and 0.7 dS m−1, respectively). The soil was used either directly (nonpretreated) or pretreated by spraying the waters containing polymers to create concentrations of 0, 25, 50 and 100 mg polymer per kg soil and then air-drying the soil. Soil briquets and soil cores of pretreated soil were saturated with untreated water and nonpretreated soil was saturated with waters containing polymer concentrations of 0, 5, 25, 50 and 100 mg L−1. The saturated soil was drained, dried at 60 °C for 48 h and then the dry cohesive strength was measured by modulus of rupture (MR) of soil briquets and tensile strength (S) of soil cores. The rupture stress (RS) required for crushing three group sizes (2–4, 4–5.66 and 5.66–8 mm) of artificially prepared soil aggregates using the various solutions was also measured. Both polymers were effective in ameliorating soil hardness, but PAM was more effective than CP-14 in either water. The degree to which MR, S and R decreased with polymer applications was dependent upon the soil type, water quality, polymer concentration and method of polymer application. Pretreated Bosanko soil showed higher MR values in canal water than in well water for both polymers. Fallbrook soil showed the same trend as Bosanko soil with CP-14 and opposite results with PAM. Higher values of MR were obtained in nonpretreated soil than in pretreated soil for Bosanko soil in both canal and well water. In general, differences in MR between pretreated and nonpretreated Fallbrook soil were not great. Reasonable agreement was found between measured MR and RS of the three soils and predicted results based on flocculation and polymer adsorption on montmorillonite.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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