Study On Performance Of Geopolymer Stabilized Recycled Macadam Materials

With the rapid growth of traffic in recent years,many roads are facing reconstruction and renovation,resulting in a large amount of construction waste such as waste cement concrete and other construction wastes,occupying land and polluting the environment,and natural stone resources are increasingly scarce.At present,most of the road base materials use cement stabilized macadam,which has poor shrinkage performance,and the production of cement not only consumes a lot of energy,but also pollutes the environment.In this paper,the geopolymer is prepared from waste cement concrete recycled micropowder and industrial solid waste slag powder,and it is used as cementitious material instead of cement.At the same time,30%concrete recycled aggregate is used to replace natural aggregate,and the mixture ratio is designed to prepare geopolymer stabilized recycled macadam materials.Its mechanical performance,water stability and shrinkage performance are studied.At the same time,its comprehensive benefits are analyzed,which provides a certain experimental and theoretical basis for the application of geopolymer stabilized recycled macadam materialsFirstly,the content of silicon-aluminum in recycled micropowder and slag powder was measured,and the ratio of recycled micropowder to slag powder,NaOH content,Na2SiO3 content and water-solid ratio were selected as factors.The best ratio of the geopolymer is obtained by designing the orthogonal test,taking 7d compressive strength as an indicator.The experimental study on the strength development of geopolymers revealed that the early strength of geopolymers developed rapidly.The influencing factors of the geopolymer preparation process were analyzed.It was found that the optimal stirring time of the geopolymer was 6 min,and the strength development speed increased with the curing temperature.Secondly,the performance of recycled aggregates was evaluated.The results show that compared with natural aggregates,the recycled aggregates have higher crushing values,lower needle-like content,lower apparent density and high water absorption.The blending ratio of the four base materials was designed with mixing no recycled aggregate and the 30%recycled aggregate,using the geopolymer and cement as the cementing materials.After the cement is replaced by geopolymer,the maximum dry density of the base material increases,and the optimum water content decreases.After adding 30%recycled aggregate,the maximum dry density of the base material decreases,and the optimum water content increasesThen,the mechanical performance,water stability and shrinkage performance of the geopolymer stabilized recycled macadam material were compared and analyzed.The results show that the mechanical performance of geopolymer stabilized macadam materials can meet the requirements of most road bases,and the application prospects are very broad.After the addition of 30%recycled aggregate,the mechanical performance and water stability of the base material can be slightly improved,but the shrinkage performance is obviously deteriorated.After the geopolymer replaces the cement,the mechanical performance of the base material decrease by 5%to 10%,the water stability can be improved,the shrinkage performance is obviously improved,and the dry shrinkage coefficient decreases by more than 20%.The geopolymer can significantly improve the shrinkage performance of the base material and effectively compensate for the lack of shrinkage performance of the base material caused by the addition of recycled aggregate.Finally,the economic benefits and social environmental benefits of geopolymer stabilized recycled macadam materials were analyzed.Compared with the cement stabilized macadam material,the eost of the geopolymer stabilized recycled macadaml material decreases by 7.5%.The geopolymer stabilized recycled gravel material saves resources,reduces pollution,and has good social and environmental benefits.