Sustainable Binary Blending for Low-Volume Roads-Reliability-Based Design Approach and Carbon Footprint Analysis

Area of Science:

• Geotechnical Engineering
• Sustainable Materials Science
• Civil Engineering

Background:

• Industrial by-products like granite sand (GS) and calcium lignosulfonate (CLS) are increasingly explored as sustainable alternatives to conventional soil stabilizers.
• Cohesive soils (clay) require stabilization for use as subgrade material in low-volume roads.
• Traditional stabilizers (lime, cement) have significant environmental impacts.

Purpose of the Study:

• To evaluate the efficacy of GS and CLS as stabilizers for clay soil.
• To determine optimal blend ratios and curing periods for enhanced California Bearing Ratio (CBR).
• To assess the environmental benefits, specifically carbon footprint reduction, of using GS and CLS.

Main Methods:

• Laboratory testing of clay soil stabilized with varying dosages of GS (30-50%) and CLS (0.5-2%) for 0, 7, and 28 days curing.
• Performance evaluation using unsoaked California Bearing Ratio (CBR) as the key indicator.
• Reliability-based design optimization (RBDO) to determine optimal mix designs.
• Carbon footprint analysis (CFA) comparing the proposed method with traditional stabilizers.

Main Results:

• Optimal GS dosages ranged from 32% to 35% for CLS dosages of 0.5% to 2.0%, respectively, to achieve a reliability index ≥ 3.0.
• The highest CBR value was achieved with an optimal mix of 70% clay, 30% GS, and 0.5% CLS.
• Significant reduction in carbon energy: 97.52% with GS and 98.53% with CLS compared to lime and cement stabilizers.

Conclusions:

• GS and CLS are viable and sustainable stabilizers for clay soils in pavement subgrade applications.
• The optimal mix (70% clay, 30% GS, 0.5% CLS) provides excellent performance for low-volume roads.
• Utilizing GS and CLS drastically cuts down the carbon footprint associated with road construction materials.