Performance of Treated Soft Clay with Nano-Modified Cementitious Binders at Reference and Cold Temperatures

Lime is considered the preferred choice for the treatment of the high plasticity clayey soils; however, for environmental concerns (quality of water and vegetation), it is prohibited in many regions, including Manitoba, Canada. Hence, it is imperative to find a suitable treatment alternative that provides an optimal solution for such a problematic soil type during different periods of the construction season. Hence, improvement of problematic/weak soils such as soft clay by nano-modified cementitious additives was tested under normal and cold conditions. This approach may significantly impact the construction of roads/pavements in cold regions. This current study focused on investigating the effects of single, binary, and ternary cementitious systems, comprising General Use cement (0–15%) with/without slag (0–15%), and nano-silica (0–3%), on the properties of soft clay (Type A7/CH) under reference (22 ± 2 °C) and cold temperatures (+ 5 °C). The mechanical performance of the control and treated mixtures were tested in terms of California Bearing Ratio (CBR) as well as unconfined compressive strength at 7, 28, 56, and 91 days of curing, while the durability properties were assessed based on the resistance to freezing–thawing cycles [durability factor (DFF/T)]. Moreover, thermogravimetry and scanning electron microscope analyses were conducted to corroborate the trends of the aforementioned tests. In comparison to the untreated clay, increasing the binders’ content significantly enhanced the mechanical/durability properties of the soil treated herein. The ternary mixtures comprising cement, slag and nano-silica showed the highest mechanical and durability properties at both reference and cold temperatures. Its CBR, 7-day compressive strength, 28-day compressive strength, and DFF/T were 46.3 and 31.6%, 700 and 562 kPa, 1349 and 891 kPa, and 94 and 71%, respectively. Such mixtures may present a viable option for soft clay stabilization at low temperatures, thus contributing to extending construction activities during fall and spring periods in cold regions.