Grout Strength with 2xw2 cubes 1

[tlzannino]

We recently were required to cast 2x2 cubes to test grout for two different types of piles. On both projects with different contractors and grout suppliers, we had very inconsistent strengths. We were required to evaluate strength by 3 cubes at 7 and 28 days. Many times the strength did not increase much between the 7 and 28 day tests. We looked at all the usual suspected sources of error and could not come up with anything on our end. The grout on one job was a pre-mix product that should be very consistent. On the other job this was the first time the plant made the design mix. On that job we made companion 3x6 cylinders that always did much better than the cubes. Has anyone had similar issues?

 

[miningman]

Who prepared the cubes?? Had they previuos experience in preparing test cubes or were just labourers assigned a task with no training? How much water did they use?? What were the conditions where the cubes were stored prior to testing?? Unless you have answers to all these points you are completely in the dark.

 

[Ron]

Yes. Have had similar results multiple times. I'm not a fan of cubes being used in the field. In most cases, the mass of the cube mold is much greater than the mass of the sample, so easier to disturb the sample. If the grout has ANY coarse aggregate in it, the stress distribution in a cube (which was originally intended for lab use to check cement and mortar strengths, using fine aggregate in a specific gradation)...will be thrown off.

Cylinders are more indicative of the strength and easier to control with consistency. There are many who will disagree with me, but those are my observations for a lot of testing over the last 30+ years.