Abstract: In order to solve the problem of insufficient supply of traditional sand and gravel aggregate and large storage of industrial solid waste coal gasification slag, this paper uses coal gasification slag and gravel soil to prepare pavement base materials, and explores the best proportion of coal gasification slag, cement content and gravel soil blending. The feasibility of the application of coal gasification slag pavement base material in highway engineering was studied from the aspects of mechanical properties, road performance and durability of the mixture. The results show that the optimal ratio is that the mass ratio of coal gasification slag to gravel soil is 40% to 60% and the cement content is 7%. Under this ratio, the 7 d unconfined compressive strength, splitting strength and flexural tensile strength of cement stabilized coal gasification slag pavement base material can reach above 3.0, 0.5 and 1.5 MPa, which has good vertical deformation resistance ability. After five freeze-thaw cycles, the compressive strength loss rate B of specimens is above 90%, the mass change rate is less than 5%, and the water stability is good. After 180 d of dry shrinkage test, the cumulative dry shrinkage of a group (coal gasification slag content of 35 % and cement content of 7%) and C group (coal gasification slag content of 40% and cement content of 7%)specimens are less than 2.5 mm, showing good dry shrinkage strain. The formation mechanism of coal gasification slag strength is put forward by observing the types and spatial distribution characteristics of hydration products of cement stabilized coal gasification slag base material with SEM and XRD. It is concluded that calcium silicate hydrate (C-S-H) gel and Ca(OH)₂ are the main hydration products, which is conducive to the formation of strength of base mixture.

Key words: coal gasification slag, pavement base material, mechanical property, durability, C-S-H gel, microscopic mechanism