Research On Design And Road Performance Of Magnesium Cement Stabilized Crushed Stone Mixture

In the structural design of asphalt pavement in China,semi-rigid base is often used as pavement base,cement stabilized crushed stone material is the main material used in semi-rigid base course,it has the advantages of good integrity and high rigidity,but because it uses ordinary portland cement as inorganic binder,the curing cycle is long and the early strength growth is slow,it usually takes 7 days for maintenance to carry out the next construction.In order to improve the above shortcomings,the inorganic binder in the traditional Portland cement stabilized macadam material is replaced by magnesium cement,magnesium cement is a new type of early strength and quick setting gas hard cement.Adding magnesium cement into crushed stone material can greatly improve its strength and reduce the curing time of stable crushed stone material,so as to improve work efficiency.In this paper,magnesium cement stabilized macadam materials are studied.Firstly,the performance and cost of magnesium oxychloride cement,magnesium oxysulfate cement and magnesium sulfate cement are compared and analyzed.Finally,magnesium oxychloride cement is the best cementing material.The raw materials were tested and studied,and the mix proportion of magnesium oxychloride cement stabilized macadam was determined by the method of progressive filling theory and orthogonal test.In order to study the road performance of magnesium oxychloride cement stabilized macadam,this paper studies the unconfined compressive strength,water resistance,indirect tensile strength,dry shrinkage property and freeze-thaw property,and studies the growth rule of unconfined compressive strength with time.In view of the poor water resistance of magnesium oxychloride cement stabilized macadam material,this paper designs the sealing material.Through the above research,the following conclusions are obtained:(1)The application of magnesium cement in road base is realized,and its mechanical indexes meet the requirements of specifications;(2)5% magnesium oxychloride cement can meet the use requirements of highway pavement base of grade II and below.Both compressive strength and flexural strength are higher than the upper limit of the specification.In the design of cement stabilized macadam,the thickness of pavement base can be appropriately reduced or the dosage of cement can be reduced;(3)Through the dry shrinkage test,it is found that the dry shrinkage performance of magnesium cement stabilized macadam is similar to that of ordinary silicate stabilized macadam;(4)Through the freeze-thaw cycle test,it is found that the strength loss of dry magnesium cement stabilized macadam is very small at low temperature;(5)The results show that the strength of magnesium oxychloride cement stabilized macadam increases rapidly within 1-2 days of curing period,and the strength increases slowly in the later stage,so the next construction can be carried out after two days of curing;(6)The water resistance of magnesium oxychloride cement stabilized macadam is poor,and its strength decreases with the increase of immersion time.It can be maintained excellent performance through the measures of pavement seal coat,its cost performance ratio is higher than that of cement stabilized macadam.