ASTM C‐1019 covers sampling and testing of masonry grout. Lab tests are performed to establish material proportions for compliance with project specifications. Field tests are done to monitor uniformity of grout during construction for quality assurance. 

 

During construction, grout is placed within or between absorptive masonry units. Excess water must be removed from grout specimens in order to provide compressive strength test results more nearly indicative of the grout strength in the wall. Each test requires three grout specimens, which are formed in molds constructed of masonry units of the same type and moisture condition as those being used in the walls.
 

The latest version of C1019 mentions other techniques for obtaining grout specimens, including the use of slotted corrugated cardboard grout boxes made for this purpose. Be aware that samples formed in these boxes can be used for job‐site quality assurance testing, but are Not acceptable for compliance testing or acceptance testing. Make sure that the procedures in the standard are followed carefully, especially while curing the specimens, to ensure valid results.
 

Grout Testing Checklist; These steps outline the testing sequence.

• Select a level location, protected from traffic and vibration, where molds can remain undisturbed for 48 hours.
• Form the mold cross section with units.
• Line the units with absorbent material. (paper towel)
• Fill the molds in two approximately equal layers.
• Rod each layer 15 times.
• Overfill the mold and rod the second layer ½” into the lower layer.
• Strike off to produce a flat surface.
• Cover immediately with damp material. (wet rag, or paper towel)
• Then cover with plastic to keep moisture in.
• Keep the top surface damp and the specimens undisturbed.
• Within 30 minutes, add grout and strike off to a level surface. (due to absorption of H2O in the block the volume will decrease)
• Cover the specimens and keep them damp.
• Remove mold between 24 and 48 hours after production.
• Place specimens in a bucket of water or protective container and keep them damp.
• Transport to lab.