Effect of Humic Acid and Fulvic Acid on Mechanical and Durability Properties of Geopolymer Stabilized Soft Soil

•The effects of organic matter on the mechanical and durability properties geopolymer stabilized soft soil were studied.•Limit value existed for the effect of organic matter on the UCS of geopolymer stabilized soft soil.•The geopolymer stabilized soft soil changed from brittle damage to plastic damage with the increase of organic matter.•Organic matter accelerated the rate of deterioration of geopolymer stabilized soft soil under sulfate attack.•The XRD and SEM characterization were used to analyze the microstructure mechanism.