Study On Shrinkage Law Of Cement Stabilized Macadam Material

Cement stabilized graded gravel material is a commonly used pavement base material in China,featuring large bearing capacity and good economic benefits.However,in the actual use of cement stabilized graded macadam base,such materials have some disadvantages,such as easy cracking,easy water damage,surface erosion and so on.At present,most high-grade highways adopt the traditional suspension compact-cement stabilized graded macadam base material.In recent years,based on the need of resisting the cracking of the base material,new skeleton compact-cement stabilized graded macadam base material has been developed.In order to explore the shrinkage performance of these two types of cement stabilized graded macadam under certain conditions and normal conditions,this paper uses the self-developed multi-dimensional expansion and contraction instrument to dry and shrink the law of cement stabilized graded macadam with different proportions.The experiment and exploration of the system were carried out to provide reference for the selection of the base material in the pavement engineering.Firstly,according to the research needs,this paper designs and develops an instrument and equipment for measuring the expansion and contraction performance of cement stabilized materials,which not only makes up for the deficiency of the old expansion and contraction instrument which can only measure the expansion and contraction in one direction,but also can automatically collect data to make the test results more accurate.Secondly,by changing the three main influencing factors of test environment,grading type and cement dosage,a series of experimental studies were carried out.The results show that by comparing the water loss rate,the water loss rate increases with the increase of the cement dosage,and gradually flattens after the fifth day of the test.Under the room temperature condition,the water loss rate of the suspension dense gradation is lower than that of the skeleton dense gradation.The average water rate is 3.23%.In the dry shrinkage tank,the water loss rate of the suspended dense grading is 2.76% higher than the water loss rate of the skeleton compact grading.The cement dosage is increased by 0.5%,and the suspension is densely graded at room temperature.The cumulative water loss rate increased the most on average,increasing by 5.50%.By comparing the dry shrinkage strain,cement dosage and dry shrinkage strain is,under the condition of room temperature,dry shrinkage strain of the suspended dense type grading type than the skeleton dense gradation of drying shrinkage strain is 5.82% higher on average,drying shrinkage,in the suspension type dense gradation of drying shrinkage strain than dry shrinkage strain of the skeleton dense type grading 14.13% higher than average,cement dosage per increased by 0.5%,dry shrinkage in the suspension type dense graded average dry shrinkage strain increased most,increased by 5.74%.By comparing the relationship between water loss rate and dry shrinkage strain,the water loss rate keeps increasing and the dry shrinkage strain also gradually increases.At room temperature,the water loss rate exceeds 3.5%,the dry shrinkage strain grows faster,and the water loss rate exceeds 3.0% in the dry shrinkage box,and the dry shrinkage strain grows faster.By comparing the temperature shrinkage coefficient,no matter in the high temperature environment or the low temperature environment,the temperature coefficient of the skeleton dense gradation is smaller than that of the suspension dense gradation.For every 0.5% increase in cement dose,the average temperature shrinkage coefficient of the suspension dense gradation increases by 5.56%,and the average temperature shrinkage coefficient of the skeleton dense gradation increases by 6.33%.Through the above test and calculation analysis,The multi-dimensional expansion and contraction instrument developed in this study has made a useful exploration of the multi-directional expansion and contraction law of the research specimens;the influence of temperature and humidity changes on the water loss rate is greater than the influence of cement dosage change on the water loss rate.The dry shrinkage strain of skeleton compacted cement-stabilized macadam is smaller than that of suspension compacted cement-stabilized macadam.At the same cement dosage,the temperature shrinkage coefficient of suspension compacted cement stabilized graded macadam mixture is higher than that of skeleton compacted cement stabilized graded macadam mixture.In order to reduce the reflection cracks caused by dry temperature shrinkage of cement stabilized graded macadam,the cement stabilized graded macadam with dense skeleton was selected as far as possible to strictly control the content of fine aggregate.