Mix Design And Mechanics Of Cement Stabilized Coal Gangue Brick Mixture

With the acceleration of urbanization in China,the number of urban construction waste is increasing day by day,which seriously affects the coordinated development of social economy and ecological environment.In this paper,coal gangue brick,one of the main construction waste in Shanxi Province,is taken as the object.According to its low strength and high water absorption,the mix design method and mechanical properties of cement stabilized pavement base material are studied.In the design of the test scheme,the natural gradation with the maximum nominal particle size of 25 mm is used as the reference gradation,and the volume method is used to design the mix ratio.The different particle sizes of fine aggregate and coarse aggregate are replaced respectively.The influence of the replacement ratio of coal gangue brick and the change of the replacement particle size range on the strength and compressive resilient modulus of cement stabilized recycled mixture is discussed.The following main results are obtained:（1）The main physical and mechanical properties of coal gangue brick aggregate were measured,and the mix design method of cement stabilized recycled mixture was explored.The optimal moisture content and maximum dry density of cement stabilized recycled mixture were determined by vibration compaction test.When coal gangue brick aggregate replaces fine aggregate or partially replaces coarse aggregate in different particle size ranges,the optimal moisture content gradually increases and the maximum dry density gradually decreases with the increase of coal gangue brick aggregate replacement rate.（2）When coal gangue brick aggregate replaces natural fine aggregate,the 7d compressive strength has a good negative correlation with the replacement rate of coal gangue brick aggregate,which satisfies the correlation of f_cu,7d=-0.04x+12.06.Compared with the 7d compressive strength,the strength of 90d compressive strength is significantly increased,and the substitution rate is 100%.The 7d compressive strength and 90d compressive strength are7.5MPa and 15.0MPa respectively,which are doubled.（3）The replacement rate of fine aggregate is 50%,and the replacement rate of coarse aggregate is 25%and 50%respectively.The particle size range of coarse aggregate is 4.75mm-9.5mm,4.75mm-16mm and 4.75mm-26.5mm respectively.At the same curing age,when the particle size range of coarse aggregate replacement is 4.75mm-9.5mm and 4.75mm-16mm,the7d compressive strength decreases linearly with the increase of replacement rate.When the particle size range of coarse aggregate replacement is 4.75mm-26.5mm,the compressive strength of coarse aggregate replacement rate of 25%and 50%at 7d and 90d of the same curing age does not change much,and the difference is only 0.5MPa.（4）The compressive resilient modulus of cement stabilized recycled mixture decreases with the increase of fine aggregate replacement rate,and increases with the increase of cement content.When the cement content is 7%and the replacement rate of fine aggregate of coal gangue brick is 50%and 100%,the compressive resilient modulus is 2138 MPa and 1931 MPa respectively.When the cement content is 7%,the replacement rate of coal gangue brick fine aggregate is 50%,and the replacement rate of coal gangue brick in the 4.75mm-26.5mm grain size range is 25%and 50%,the elastic modulus is 1418 MPa and 1363 MPa,respectively.The compressive resilient modulus decreases with the increase of the replacement rate of coal gangue brick coarse aggregate.（5）There is a significant linear correlation between 90d compressive resilient modulus and 90d compressive strength.The correlation is E_s=116.2f_cu+346.5,and the correlation coefficient is 0.946.（6）The replacement rate of fine aggregate has little effect on the flexural strength.Based on the above analysis,the influence of coal gangue brick aggregate on the compressive strength and compressive resilient modulus of cement stabilized recycled mixture is significant,but the influence on the flexural strength can be ignored.In spite of this,the cement content is 7%,the compressive strength of the cement stabilized mixture of the recycled coal gangue brick aggregate can meet the requirements of the secondary and secondary roads under the light traffic conditions,which provides a good technical support for the recycling of coal gangue bricks.It is conducive to promoting the application of coal gangue bricks in road engineering,promoting the carbon emission reduction of road engineering,and promoting the sustainable development of resources.