Micropile Grout Compressive Strength

[RileyW]

Recently received grout compressive strengths back with 28 day data all over the place. Design was for 4500 psi and breaks are from 3500-6500psi. I have both flow test and mud balance data as well that do not align with test results. Additionally, multiple days where grout compressive strengths are higher for 14 days than 28 days. Average strength was 4950psi and median 4900psi.

Should the client be concerned with the outliers?

P.S. This is Type I/L grout with a water reducer to thicken grout.

 

[TigerGuy]

Tell us more about these micropiles. Does their load carrying ability come exclusively from the soil to grout interaction? Are they end bearing into a stronger layer of soil/bedrock? Are the loads all compressive, or are there some tensile loads? What about steel within the element (size, strength, etc)? How long are the individual piles?

3,500 psi for a design strength of 4,500 psi would be concerning, but there are numerous factors that may eliminate that concern.