Summary:

The experiment was carried out on fine uniform sand and fine uniform humus sand. Soil samples were collected from the surface of forest dirt roads located in the Noteć Primeval Forest. Portland cement and multi-component Portland cement were used for stabilization. Cement-soil mixtures were prepared with four doses (3, 6, 9, 12%) of both cements. Samples for strength tests were stored under conditions of optimum humidity, water saturation, freezing and thawing. Testing results were compared to strength criteria for road surfaces according to Polish Standard PN-S- 96012, 1997. Generally it was found that both soils, especially humus sand, are difficult to stabilize with cements. Portland cement exhibited 2-times better stabilization effects in comparison to multi-component cement. Mixes showed high water resistance and low freeze resistance. For the lower layer of reinforced subgrade compression strength criteria were met by fine humus sand with a 9% addition of Portland cement and fine sand with a 9% addition of multicomponent cement. For the upper layer of reinforced subgrade strength criteria were met only by the mixture of fine sand with a 12% addition of Portland cement. Further tests are required using larger doses of Portland cement and after testing of grain size upgrading of native soil prior to its stabilization with cement.