One of the common types of failures in asphalt pavements is cracking. Considering the17 environmental importance of material recycling, in this research, calcium lignosulfonate (CLS) as18 a waste product of cellulose production, was used as a bitumen additive, and the cracking19 resistance of semi-circular bending (SCB) samples of asphalt mixtures containing bitumen20 modified with 5% to 20% CLS was investigated at low and medium temperatures. To measure21 the performance of asphalt mixtures, the parameters of fracture energy (Gf), fracture toughness22 (K1c), flexibility index (FI) and cracking resistance index (CRI) were used. Also, rotational23 viscosity (RV) test was performed to determine the pumpability of bitumens. The results showed24 that CLS particles can increase the stiffness and viscosity of bitumen in high-temperature25 conditions. However, it was lower than the maximum allowed amount. At low temperature, with26 the addition of CLS, K1c and Gf indices were increased, and their highest values were related to27 bitumen with a 15% additive. At intermediate temperature, Gf index was increased until before the28 critical load, and FI and CRI were increased up to 15% and then decreased slightly. But Gf index29 was increased with a decreasing trend after the critical load until the end

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