DENSITY-MOISTURE RELATIONS OF SOME TRINIDADIAN SOILS INCORPORATED WITH SEWAGE-SLUDGE

Maximum dry bulk density (rho(max)) and optimum moisture content (W-op t), were measured in the laboratory for four Trinidadian soils (two sa ndy loams, clay loam and clay) mixed with cured sewage sludge at four levels (0, 4, 8, and 12% by mass) and compacted using 5, 15, and 25 st andard Proctor hammer blows. Compaction tests on the soils were carrie d out at different moisture contents ranging from 5 to 45%. Mean rho(m ax) decreased significantly (P<0.001)from 1.51 to 1.34 Mg m(-3), while mean W-opt increased from 24.2 to 29.5% as sewage sludge content incr eased from 0 to 12%. While with increasing content of the soils. The v alues of bulk density for the Proctor compaction curves were predicted using an equation that involved, rho(max), W-opt and an empirical coe fficient, S. The predicted values of bulk density when regressed on th e corresponding measured values, gave a near-perfect fit (R-2 = 0.977, regression constant = 1.00 and constant term = 0.012). Multiple regre ssion equations were developed to relate W sludge contents as well as to compaction effort Two equations, one physically based and the other empirically based, were developed to relate rho(max) to W-opt. The pr ocedure described provides a good method for quantifying the effect of sewage sludge incorporation on soil compaction.