Study On The Performance Of Cement Stabilized Sandstone Macadam Pavement Base

Stones commonly used in cement-stabilized macadam bases include limestone,granite and gravel.These rocks usually have high strength and crushing values,which can meet the technical requirements of semi-rigid base layer laying.In view of the lack of high-quality rocks along highways in some areas of China,a large number of sandstones are distributed along the line.If such sandstones can be applied in semi-rigid bases,it will greatly reduce the project cost,achieve local resources,make full use of resources and protect the environment.In this paper,the application of Chongqing sandstone gravel to the semi-rigid basement of cement-stabilized macadam is carried out.The physical properties such as density,water absorption,porosity and weathering of sandstone are tested and compared with the properties of limestone.According to the aggregate test procedure,The crushing values of sandstone and limestone aggregates and the effect of saturated water on the properties of sandstone aggregates were studied.The cement dosage was 5%.The mechanical properties and durability of cement-stabilized limestone macadam,cement-stabilized sandstone gravel and sandstone cement mixture with a certain proportion of limestone were studied.The following research results were obtained:?Compared with limestone,the true density and bulk density of sandstone are big,water absorption is good,porosity is large,and uniaxial compressive strength is small.?The crushing value of sandstone is smaller than that of limestone.The effect of saturated water on the crushing value of limestone and sandstone coarse aggregate is different.The comparison of crushed value of limestone and sandstone aggregate in0d~9d immersion shows that the sandstone after water immersion has a large variation range.The influence of sandstone strength is obvious.This is due to the porous nature of sandstone,which has a high water absorption rate and is more susceptible to erosion than limestone.?The 7d unconfined compressive strength of the sandstone mixture used was0.72 MPa.It was found through experiments that the sandstone had a high mud content.After cleaning and drying,the cement-stabilized sandstone mixture was measured for 7d unconfined compressive strength of 2.27.MPa,according to the strength requirementsof the cement-stabilized materials for the base and subbase in the Technical Specifications for Highway Pavement Construction(JTGT F20-2015),such sandstone can only meet the basement of medium and light traffic roads below the secondary and secondary roads..?Adopting the same particle size percentage replacement method,using sandstone instead of limestone to prepare cement-stabilized gravel mixture(CSSL),the nominal maximum particle size of 9.5mm is used as the limit,and the 7d unconfined compressive strength test is carried out on the mixture of sandstone partially replaced limestone.The results show that all of the above 9.5mm is limestone,and the average strength of the 100% replacement sandstone of 9.5mm or less sandstone reaches3.15 MPa,which can meet the requirements of high-grade and first-class heavy traffic road base,advanced and first-class medium and light traffic and secondary and The strength of the base layer of heavy,medium and light traffic roads below the secondary level requires that the average strength of the 50% replacement sandstone of 9.5 mm or less sandstone reaches 4.3 MPa,which can meet the requirements of high-grade and first-class medium and light traffic road bases,secondary and secondary.The strength requirements of the heavy and heavy traffic road base;all of the below 9.5mm are limestone,and the average strength of the 100% replacement sandstone of 9.5mm or more is 3.1MPa,which can meet the basic and secondary levels of the advanced and primary heavy traffic roads.The strength requirement of the base layer of the medium and light traffic roads below the second level,the average strength of the mixture of50% replacement sandstone of 9.5mm or more reaches 3.8MPa,which can meet the high Strength requirements for primary and secondary medium and light traffic road bases,secondary and secondary heavy traffic road bases.?The durability test of the cement-stabilized mixture of sandstone partially replaced limestone(CSSL)shows that the frost-resistant coefficient of the cement-stabilized macadam mixture partially replaced by limestone is smaller than that of the cement-stabilized limestone mixture,but larger than the cement cement stabilized sandstone mixture,the cement is stable.The freeze-thaw strength ratio of the limestone mixture at the age of 28 days is 95%,and the freeze-thaw strength of the cement-stabilized mixture after the 100% replacement of the sandstone with a particle size of 9.5 mm or more is 4.95 MPa,the freeze-thaw strength ratio is 92.1%,and the particle size is 9.5 mm or less.The cement-stabilized mixture after 100% replacement of sandstone has a freeze-thaw strength of 5.7 MPa and a freeze-thaw strength ratio of80%.After reviewing relevant literatures at home and abroad,the residual strength of the test piece after the freeze-thaw cycle test is not less than 50% of the strength of the standard test piece as the evaluation standard.It can be seen that the replacement of limestone by the sandstone partially has a certain influence on the durability of the mixture and cement.The stabilized sandstone partial replacement limestone macadam mixture meets the technical requirements.?The strength and durability of the cement-stabilized sandstone limestone macadam mixture with different replacement quantities meet the performance requirements of the road base.The sandstone can partially replace the limestone as the aggregate.The greater the replacement ratio,the greater the impact on the performance of the mixture.The sandstone partially replaces the limestone rock cement-stabilized macadam mixture for high-grade and first-class medium and light traffic,secondary and secondary heavy,medium and light traffic pavement base or advanced and primary heavy traffic pavement subbase.