Effect of Slag Sand on Mechanical Strengths and Fatigue Performance of Paving Grade Geopolymer Concrete

Geopolymer concrete with time is gaining recognition as a sustainable alternative to Portland cement concrete, offering lower carbon emissions and utilising industrial by-products. While prior research focussed on its mechanical properties for structural purposes, this study explores its potential for paving applications. A unique geopolymer concrete mixture suitable for paving, referred to as paving quality geopolymer concrete (PQGC), was developed by incorporating slag sand (SS) as a substitute for river sand (RS). The investigation primarily assessed fatigue life PQGC mixes. The findings demonstrate that the inclusion of SS in PQGC has no significant impact on its setting times or workability. However, PQGC formulated with 100% SS, w.r.t PQGC containing RS, exhibited enhanced mechanical strength of 7% in compression, 16.7% in flexure and 8.3% in split tensile tests at 28 days of open-air curing. Following a 14-day period of curing, PQGC achieved a compressive strength of 46 MPa, surpassing the minimum requirement of 40 MPa as per IRC:58 2015 for pavement quality concrete (PQC) by 15%. To evaluate fatigue performance, PQGC beam specimens were subjected to repeated loading at stress levels ranging from 0.9 to 0.6. The resulting fatigue data were employed to develop stress-fatigue life (SN) and Weibull two-parameter fatigue failure models. Comparative analysis with fatigue failure models such as Indian Road Congress (IRC) and Darter revealed that PQGC exhibits superior fatigue resistance and longer life expectancy compared to PQGC. In conclusion, this study confirms that PQGC incorporating SS is an efficient and eco-friendly choice for constructing rigid pavements with advantages such as curing without water, enabling early opening of roadways to traffic, and excellent resilience under cyclic loads.