Study On Component Design And Road Performances Of Phosphogypsum-based Road Base Material

Phosphogypsum-based road base material is a kind of environmentally friendly and practical new base material.In this paper,the relationship between material composition and the performance of cement phosphogypsum stabilized macadam and slag phosphogypsum based cementitious materials stabilized macadam were studied,respectively.Moreover,the mechanism of strength of this material was discussed.The results show that:?1?the strength properties and water stability of Phosphogypsum Cement Stabilized Macadam were controled by phosphogypsum content,small particles content of aggregate,cement dosage and other factors.With the increasement of phosphogypsum content,the strength properties and water stability of the material first increase and then decrease.the optimum mix amount of phosphogypsum changes with particle content of the aggregate whose diameter is 4.75mm or less.With the passing rate of 4.75mm particles increase from 30%up to 40%,cthe optimum mix amount of phosphogypsum changes from 5%to 10%.The performance of cement phosphogypsum cement stabilized macadam gradually improve as the increasement of cement dosage.in comparison to cement stabilized Macadam,the cement dosage of cement phosphogypsum stabilized macadam decrease by 1%to the same intensity level.When phosphogypsum content is 8%,considering the water stability of the material,cement dose should not be less than 4.5%.?2?Based on excellent mechanical properties and good water stability,material composition of Phosphogypsum Cement Stabilized Macadam is:cement dosage5%,phosphogypsum content 8%,aggregate gradation is the dense skeleton type that the passing rate of 4.75mm particles is about 35%.Road performance of the material show that compared to ordinary cement stabilized macadam of same cement dosage,its 7d unconfined compressive strength increase by 24%,28d splitting strength increase by 38%,modulus of resilience decrease a little,water stablity performance increase by 9.5%,shrinkage strain reduce significantly,dry shrink energy anti cracking coefficient increase by 62.5%,time of latency rolling molding delay by nearly 9h.?3?the influence of SO₃ content,slag content in strength properties of slag phosphogypsum based cementitious material were researched,the results show:reasonable value of SO₃ content is 3.5%in mortar System,while the value is4.11%in stabilized macadam system.Either in mortar System or in stabilized macadam,the reasonable value of slag content is about 50%.The material composition of slag phosphogypsum based cementitious materials stabilized macadam is designed by it.compared to ordinary cement stabilized macadam of same cement dosage,7d unconfined compressive strength of this material increase by 23.5%,28d splitting strength increase by 59%,modulus of resilience decrease a little,water stablity improve significantly,dry shrink energy anti cracking coefficient increase by nearly 80%,time of latency rolling molding delay by above 9h.?4?The filling effect and active effect of phosphogypsum in slag phosphogypsum based cementitious material stabilized macadam enhance with SO₃ content an then weak gradually.And the active effect also gradually enhances with the increasing of time.When the SO₃ content is 4.11%,the hydration generate a lot which interweave with each other and fill the gap with the unreacted phosphogypsum.Then,the strength of the material is formed.