A laboratory optimisation of a urea-formaldehyde soil stabiliser

Abstract

The Indirect Tensile Strength (ITS) was used to characterise the soil stabilising properties of a urea-formaldehyde (UF) resin. The test soil was brown shale gravel. Synergistic strength improvements were obtained when combining the resin with anionic bitumen emulsion and dosing both at 2%. Performance levelled off above these concentrations. For full strength development, the soil moisture content must be reduced to below 3%. Optimum indirect tensile strength is obtained at formaldehyde to urea molar ratio of 2:1. Soil strength increases as the reaction pH is lowered but the need for adequate application times restricts it to pH > 4,5. The experimental results also suggest that the presence of appropriate organic matter is critical for effective soil stabilisation with UF resin.Die Indirekte Treksterkte (ITS) is gebruik om die grondstabilisasie-eienskappe van ‘n urea-formaldehied hars (UF) te kwantifiseer. Die toetsgrond was ‘n bruin skaliegruis. Kombinasie van die hars met ‘n anioniese bitumen emulsie toon sinergistiese sterkteverbetering wanneer beide doseer word op die 2% vlak. Werkverrigting plat af bokant hierdie konsentrasies. Vir volle sterkteontwikkeling moet die grondvogtigheid verlaag word tot onder 3%. Optimale indirekte treksterktes word behaal met ‘n formaldehied-tot-urea molverhouding van 2:1. Grondsterkte neem ook toe soos die reaksie pH verlaag word maar vir pH < 4,5 word die beskikbare aanwendingstyd ontoereikend. Die eksperimentele resultate dui ook daarop dat die teenwoordigheid van ‘n geskikte organiese fraksie in die grond krities is vir effektiewe stabilisasie met UF hars.