Carbon Footprint Analysis on the Expansive Soil Stabilization Techniques
Mohammed Ashfaq, Arif Ali Baig Moghal, B. Munwar Basha, Afzal Ali Baig Moghal
Abstract
Expansive soils exhibit substantial swelling and shrinkage with the fluctuation in seasonal moisture content. Due to their widespread presence across the world, addressing the problems associated with their volume change has garnered global attention. Traditionally, chemical stabilization using additives like lime and cement was extensively adopted in addressing the swelling phenomenon of expansive soils. In recent times, the use of non-traditional additives like ground-granulated blast-furnace slag (GGBS) in addressing the swelling and shrinkage of expansive has extensively been promoted as an economical alternative to existing calcium-based additives. Currently, the choice of stabilization technique is primarily driven by design and economic efficiency. However, efforts to quantify environmental impacts prior to the selection of stabilization are scarce. In the present study, carbon footprint analysis (CFA) was performed for lime stabilization, and it was compared with GGBS as an alternative stabilizer in borehole and ponding methods of in situ stabilization. Further, the CFA was also performed for an up-scaled scenario of stabilizing 1-million m2 area. From the results, it was observed that the increase in the area of stabilization in the up-scaled scenario has resulted in exponentially rising in the overall emissions 7 × 105 times. Further, it was observed that in in situ stabilization of expansive soils, emissions related to embodied carbon are relatively much higher than the haulage/procurement related emissions. From the results, it was inferred that irrespective of the type of additive and scale (volume/area) of stabilization, the application of borehole drilling method with GGBS as an additive could be a prudent practice with substantially lower CO2 emissions compared to the ponding method.