Effect of fines on the mechanical properties of composite soil stabilizer-stabilized gravel soil

[Display omitted] •The effect of fines on the mechanical properties of CSSSGS was estimated.•Composite soil stabilizer was compared with cement for stabilizing gravel soil.•Gradation design was also considered to evaluate the use of natural gravel soil.•New models have been proposed to predict the UCS of CSSSGS and CSGS. It is necessary to reduce the use of crushed stone and cement in base courses because of environmental concerns and cost issues. The objective of this study was to evaluate the effect of fines on the mechanical properties of composite soil stabilizer-stabilized gravel soil (CSSSGS) compared with cement-stabilized gravel soil (CSGS) in laboratory performance tests. These laboratory tests included unconfined compressive strength (UCS), splitting tensile strength (STS) and compressive modulus of resilience (CMR). Five different contents of fines were adopted—5%, 20%, 35%, 50% and 65%. The dosages of binders used in this study were determined on the basis of the target UCS (4.5MPa). The study revealed that increased fines content (exceeding a certain threshold for STS) had a considerable adverse influence on the mechanical properties of CSSSGS and CSGS. Increasing fines content of CSSSGS and CSGS diminished the advantages of the gradation design with respect to the UCS and STS. Additionally, new models based on mixture proportions have been established to predict the UCS for mixture design and base course construction. Overall, CSSSGS can be used as base course material from the perspective of mechanical properties if the fines content is well-controlled.