Effect of excessive cement in stabilised subbase

[defg]

Ihave carried out laboratory test for subbase stabilisation trial test.According to the test results revealed that the use of 2.5%cement is adequate to aquire a strength of more than 1MPa including the initial consumption of lime/cement.But in practice when the Contractor has started to lay the stabilised layer on the road under construction,the quality control of the materials taken from the road during spreading of the stabilised subbase.When moulded and cured for seven days and soaked for four hours and crushed it yield a high strength than anticipated.The stregth obtained varied from (2.87 to 2.06)MPa.This seems to be biger than 1MPa minimum given in the specifications.In the specification no maximum has been given only minimum which is 1MPa.This increment will not affect the works such as craking of the stabilised layer?Can Iaccept the section if no craking of the pavement layer has been observed?

 

[Ron]

Two common problems exist. The first is that you'll get more shrinkage in the cement stabilized material. This will cause cracks and they will reflect through a flexible pavement layer (asphalt).

The second problem is bonding. You will definitely need to apply a strong tack coat to make sure you don't lose bond between the asphalt and base. Since you mentioned that this is a subbase, you might want to consider some roughening of hard surface prior to adding base layer if it is a granular layer as opposed to an asphalt layer.