Texas Department of Transportation 1 06/03–06/08

Tex-442-A, Determining Compressive Strength of Grouts

Contents: Section 1 — Overview..............................................................................................................2

Section 2 — Apparatus.............................................................................................................3

Section 3 — Test Sample .........................................................................................................4

Section 4 — Procedure .............................................................................................................5

Section 5 — Calculations .........................................................................................................6

Tex-442-A, Determining Compressive Strength of Grouts Section 1 — Overview

Texas Department of Transportation 2 06/03–06/08

Section 1 Overview

Effective dates: June 2003–June 2008.

This test method determines the compressive strength of grout cubes. Grout is formed in cubes, cured, and compressed.

This procedure is identical to ASTM C 942.

Units Disclaimer

The values given in parentheses (if provided) are not standard and may not be exact mathematical conversions. Use each system of units separately. Combining values from the two systems may result in nonconformance with the standard.

Tex-442-A, Determining Compressive Strength of Grouts Section 2 — Apparatus

Texas Department of Transportation 3 06/03–06/08

Section 2 Apparatus

The following apparatus is required:

♦ glass graduates

♦ three-gang molds, for 2 in. cube specimens

♦ baseplates

♦ trowel

♦ testing machine as specified in "Tex-418-A, Compressive Strength of Cylindrical Concrete Specimens"

♦ cover plates for specimen molds, capable of supporting a 15-lb. mass

♦ mass of 15 lb. for holding down cover plates

♦ release agent.

Tex-442-A, Determining Compressive Strength of Grouts Section 3 — Test Sample

Texas Department of Transportation 4 06/03–06/08

Section 3 Test Sample

The grout field-test sample will consist of approximately 1500 mL and will be representative of the sample in the mixer.

Tex-442-A, Determining Compressive Strength of Grouts Section 4 — Procedure

Texas Department of Transportation 5 06/03–06/08

Section 4 Procedure

The following table describes the compressive strength test.

Compressive Strength Test Step Action

1 Grease molds with release agent. 2 Mold sets of cube specimens.

♦ A 3-gang cube mold will constitute 1 test set. ♦ Provide at least 2 sets.

3 ♦ Fill each mold halfway. ♦ Puddle each with a gloved finger 5 times to release entrapped air. ♦ Fill the mold and puddle again. ♦ Bring the excess grout to the center and finish the surface by cutting off the excess with the

straight edge of a trowel held vertically and drawn across the top of the mold with a sawing motion.

4 ♦ Place the cover plate over the mold, taking care that the grout or loose grains of sand do not prevent seating of the plate.

♦ Place a mass of 15 lb. on each cover plate. 5 Store field specimens according to "Tex-447-A, Making and Curing Concrete Test Specimens." 6 ♦ Determine the average compressive strength of 3 cube specimens a minimum of 7 days.

♦ Test the final set of cubes, if needed, at 28 days. 7 ♦ Wipe each specimen to a surface dry condition, and remove any loose sand grains from the

faces that will be in contact with the bearing blocks of the testing machine. ♦ Check the faces with a straightedge. ♦ Plane curved surfaces by grinding or discard specimen. ♦ Make a check of the cross-sectional area of the specimens.

8 Apply the load to specimen faces that were in contact with the true plane surfaces of the mold. 9 ♦ Place the specimen in the testing machine below the center of the upper bearing block.

♦ Use no cushioning or bedding materials. 10 ♦ Bring the spherically seated block into uniform contact with the surface of the specimen.

♦ Apply the load rate at a relative rate of movement between the upper and lower platens corresponding to a loading on the specimen with the range of 200 to 400 lb./sec.

11 ♦ Record the maximum load indicated by the testing machine. ♦ Calculate the compressive strength of the cube. ♦ Take an average of the set of cubes.

Tex-442-A, Determining Compressive Strength of Grouts Section 5 — Calculations

Texas Department of Transportation 6 06/03–06/08

Section 5 Calculations

Determine the compressive strength as follows:

P/A Fm =

Where:

♦ Fm = compressive strength (psi)

♦ P = total maximum load (lb.)

♦ A = area of loaded surface (in.2).

Determine the average of the 3 cubes as follows:

3C C C Avg 321 ++=

Where:

♦ Avg = Average compressive strength of 3 cubes (psi)

♦ C1 = compressive strength of cube 1 (psi)

♦ C2 = compressive strength of cube 2 (psi)

♦ C3 = compressive strength of cube 3 (psi).