Masonry Grout Testing? ASTM C1019 4

[pelotoner]

Masonry grout is supposed to be tested based on ASTM C1019 using a masonry block form to absorb water and simulate field conditions. But how often is this done?

We specify the grout meet ASTM C476 proportions. The testing company usually takes cylinders of the grout and completes breaks.

Is testing required? Does anyone test grout based on ASTM C1019? Does it matter what the cylinder breaks are, since the test is invalid?

Tx,
Structural Eng in Florida

 

[Ron]

You can look at C476 in two different ways. You can accept that the prescribed proportions will achieve sufficient strength for the application or you can specify a compressive strength and use C1019 for the testing. Yes, the method is used routinely. Don't do both, though. Either specify the proportion method or the compressive strength method.

I have a bit of heartburn with C1019. It attempts to replicate the absorption conditions of the block, but none of the other conditions are intended to replicate any field condition, which of course you couldn't anyway.

Sampling and testing for compressive strength of any cementitious material should be done to check the mix design, not the in-place condition. For that reason alone, I don't like C1019. It actually does neither, so to me, the results are somewhat meaningless. But nevertheless, it is accepted and promoted by the industry.

 

[concretemasonry]

ASTM C1019 (the version I have handy and voted on) only refers to the concept of placing the grout sample in a absorbent mold as a an means to simulate the strength of the mortar actually placed. The concept of putting 11" slump gout into a non-absorbent mold will yield meaningless results regarding the performance of the structure and the results should be rejected.

All of the current code standards are based on the grout testing method that have be used as documentation of the grout for decades of testing and research because it provides the most realistic measure of properties.

Keep in mind that gout is one component in a structural element (the wall) and is not like a test of delivered concrete in cylinders made from placed concrete that is the main building component.

In masonry, the grout strength is not that important, since its purpose is to transfer the loads from the wall into the reinforcement usually and the grout strength should be approximately the strength of the net unit strength. Many engineers place a maximum limit of the grout strength as a small percentage (10%-20%) above the block unit strength to maintain a balanced structural unit.

Grout should not be used to increase the vertical strength of a wall, but is intended to transfers loads between the masonry units and the reinforcement if needed. Excessive grout strengths in prisms could result in the fibers with the highest stress to be lower than the average prism strength. Unless you have a very small application, it is much more practical and economical to use higher strength block, since doubling the strength is very possible.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[msucog]

concretemasonry is always spot on the mark