Code of Massachusetts Regulations
780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS
Chapter 21 - Masonry
Section 2105 - QUALITY ASSURANCE
Subsection 2105.2 - Acceptance relative to strength requirements

Universal Citation: 780 CMR MA Code of Regs 2105.2

Current through Register 1531, September 27, 2024

2105.2.1 Compliance with f 'm and f 'AAC. Compressive strength of masonry shall be considered satisfactory if the compressive strength of each masonry wythe and grouted collar joint equals or exceeds the value of f 'm for clay and concrete masonry and f 'AAC for AAC masonry. For partially grouted clay and concrete masonry, the compressive strength of both the grouted and ungrouted masonry shall equal or exceed the applicable f 'm. At the time of prestress, the compressive strength of the masonry shall equal or exceed f 'mi, which shall be less than or equal to f 'm.

2105.2.2 Determination of compressive strength. The compressive strength for each wythe shall be determined by the unit strength method or by the prism test method as specified herein.

2105.2.2.1 Unit strength method.
2105.2.2.1.1 Clay masonry. The compressive strength of masonry shall be determined based on the strength of the units and the type of mortar specified using Table 2105.2.2.1.1, provided:
1. Units are sampled and tested to verify compliance with ASTM C 62, ASTM C 216 or ASTM C 652.

2. Thickness of bed joints does not exceed 5/8 inch (15.9 mm).

3. For grouted masonry, the grout meets one of the following requirements:
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.

3.2. Minimum grout compressive strength equals or exceeds f m but not less than 2,000 psi (13.79 MPa). The compressive strength of grout shall be determined in accordance with ASTM C 1019.

TABLE 2105.2.2.1.1 COMPRESSIVE STRENGTH OF CLAY MASONRY

NET AREA COMPRESSIVE STRENGTH OF CLAY MASONRY UNITS (psi) NET AREA COMPRESSIVE STRENGTH OF MASONRY (psi)
Type M or S mortar Type N mortar
1,700 2,100 1,000
3,350 4,150 1,500
4,950 6,200 2,000
6,600 8,250 2,500
8,250 10,300 3,000
9,900 - 3,500
11,500 - 4,000

For SI: 1 pound per square inch = 0.00689 MPa.

2105.2.2.1.2 Concrete masonry. The compressive strength of masonry shall be determined based on the strength of the unit and type of mortar specified using Table 2105.2.2.1.2, provided:
1. Units are sampled and tested to verify compliance with ASTM C 55 or ASTM C 90.

2. Thickness of bed joints does not exceed 5/8 inch (15.9 mm).

3. For grouted masonry, the grout meets one of the following requirements:
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.

3.2. Minimum grout compressive strength equals or exceeds f m but not less than 2,000 psi (13.79 MPa). The compressive strength of grout shall be determined in accordance with ASTM C 1019.

TABLE 2105.2.2.1.2 COMPRESSIVE STRENGTH OF CONCRETE MASONRY

NET AREA COMPRESSIVE STRENGTH OF CONCRETE MASONRY UNITS (psi) NET AREA
COMPRESSIVE STRENGTH OF
MASONRY (psi)a
Type M or S mortar Type N mortar
1,250 1,300 1,000
1,900 2,150 1,500
2,800 3,050 2,000
3,750 4,050 2,500
4,800 5,250 3,000

For SI: 1 inch = 25.4 mm, 1 pound per square inch = 0.00689 MPa.
a. For units less than 4 inches in height, 85 percent of the values listed.

2105.2.2.1.3 AAC masonry. The compressive strength of AAC masonry shall be based on the strength of the AAC masonry unit only and the following shall be met:
1. Units conform to ASTM C 1386.

2. Thickness of bed joints does not exceed 1/8 inch (3.2 mm).

3. For grouted masonry, the grout meets one of the following requirements:
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.

3.2. Minimum grout compressive strength equals or exceeds f AAC but not less than 2,000 psi (13.79 MPa). The compressive strength of grout shall be determined in accordance with ASTM C 1019.

2105.2.2.2 Prism test method.
2105.2.2.2.1 General. The compressive strength of clay and concrete masonry shall be determined by the prism test method:
1. Where specified in the construction documents.

2. Where masonry does not meet the requirements for application of the unit strength method in Section 2105.2.2.1.

2105.2.2.2.2 Number of prisms per test. A prism test shall consist of three prisms constructed and tested in accordance with ASTM C 1314.

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