Masonry Grout and the Code

Masonry grout is a cementitious mixture used to fill cores or cavities in masonry construction. Grout comprises cement, aggregates, lime (optional), and sufficient water to allow the ease of placement and ensure complete filling of grout spaces so that no voids exist within the grout system. The grout must be proportioned per the requirements in Table 1 of ASTM C476, “Standard Specification for Grout for Masonry.” The grout must attain a minimum compressive strength of 2,000 psi at 28 days and be placed in the masonry wall at a slump of 8 to 11 inches (unless otherwise specified).

There are two types of masonry grout: (1) fine grout, which is produced with cement and fine aggregate only, and (2) coarse grout, which is produced with cement and a combination of coarse and fine aggregates. All aggregates in the masonry grout mixture must comply with the requirements of ASTM C404, “Standard Specification for Aggregates for Masonry Grout,” which also governs the grading of the aggregates. ASTM C33 concrete sand is generally satisfactory for use in masonry grout unless it fails to comply with some of the quality tests required by ASTM C33.

Some important code-compliance criteria regarding grout observation at the project site:

• Remove masonry protrusions extending ? inch or more into cells or cavities to be grouted
• Place grout within 1 ? hours from the time that water was introduced into the mixture
• The time limitation of 1 ? hours can be waived as long as the ready-mixed grout meets specified slump requirements
• The addition of water is permitted at the time of initial discharge to adjust the slump; additional mix water cannot be added to ready-mixed grout after discharge of the grout has begun
• Discard ready-mixed grout that does not meet the specified slump without adding water
• Consolidate grout pours exceeding 12 inches in height by mechanical vibration and reconsolidate by mechanical vibration after initial water loss and settlement have occurred
• For cold weather grouting, maintain grout temperature above 70 F at the time of grout placement

Masonry Grout Lift Heights – TMS 602, Article 3.5D

When grout complies with ASTM C476, masonry has cured for at least 4 hours, and there are no intermediate bond reinforced bond beams between the bottom and top of the pour height, lift should not exceed 12 feet 8 inches. Grout slump should be maintained between 10 and 11 inches. High-lift grout rules apply. The maximum height for low-lift grouting is 5 feet, 4 inches.

For more information or further enthusiastic discourse on topics of CODE, please contact Alan Tuck at: [email protected] or 540.344.7939