Fire Resistance Levels are listed in Tables 1.3, 1.4 and 1.5 of CMAA’s Manual MA55 Design and Construction of Concrete Masonry Buildings Part B Chapter 1 Section 1.4 Design for Fire. If the proposed fire wall is for an office building, the Common Walls and Fire Walls FRL values will be 120/120/120 minutes for Structural Adequacy/Integrity/Insulation.
Please refer to CMAA’s Manual MA55 Design and Construction of Concrete Masonry Buildings Part B Chapter 8 Section 8.3 on Standard Designs. Depending on the exposure conditions, the required grout cover (c) value is 30mm for Very Severe Exposure, 20mm for Severe Exposure and 15mm for other applications. The values of the maximum effective steel depth (d) will be 117mm, 127mm and 132mm respectively.
Thermal Mass (also known as Thermal Inertia or Thermal Capacitance) is a measure of a material’s ability to retain its current level of heat energy when subjected to an external temperature differential. Thermal resistance (R-value) is the measure of the resistance to heat flow per unit temperature difference of the full thickness of the heat barrier. Masonry walls have high thermal mass.
Grout must be of pouring consistency because filling cores is more important than high grout strength. Also, units remove much of the water from the grout and a limit is placed on the grout strength that can be used in design calculations.
CMAA’s Manual CM03 provides a detailed guide on concrete masonry cleaning and maintenance. Efflorescence can be removed by dry brushing. If this is not effective, water washing, with or without pressure, can be used. Chemical cleaning such as acid treatment is not recommended as this often causes etching of the concrete masonry, and fading, streaking and colour changes on the wall.
Manufacturers usually have data tables for “Blocks Filled per Cubic Metre”. Please contact your supplier for this information.
The thermal resistance values of concrete blocks (R) with different densities and sizes can be found in CMAA’s Manual MA55 Design and Construction of Concrete Masonry Buildings Part B Chapter 9 – Thermal Performance. Please refer to the Table – THERMAL RESISTANCE, R on page 7.
Mortar is not grout – grout has to flow freely to surround steel and completely fill cores. Grout usually contains 10 mm aggregate and must be of at least 12 MPa minimum strength. Mortar uses fine aggregates (e.g. sand) and has a paste-like consistency and usually has around 8-10 MPa strength – so broadly you cannot replace mortar for grout. However, if you can achieve the above minimum grout requirements with mortar then that might suffice, providing all core spaces are completely filled.
Please refer to CMAA’s Manual MA55 Design and Construction of Concrete Masonry Buildings Part B - Chapter 4 Fire.
AS3700, Masonry structures, is the main standard for design, material and construction of masonry structures. AS4773, Masonry in small buildings, is a “minimal calculation” standard for use by small building designers and specifiers. For more information regarding Australian standards on masonry, please contact our technical team at (02) 8448 5500.
While CMAA’s publications are based on wide industry experience and deep knowledge, the information we provide is intended for general guidance only and in no way replaces the services of professional consultants who will be able to give you detailed advice on your specific project.
Concrete masonry density can vary between different manufacturers, due to a number of factors such as the density of the raw materials used as well as the manufacturing processes. CMAA Manual MA55 Design and Construction of Concrete Masonry Buildings includes a list of a number of block density options to cover these differences. Typically, fully core filled block densities range from 1850kg/m3 to 2200kg/m3.
Segmental Retaining Wall Blocks (such as Allan Block, Anchor, Cornerstone etc.) are mortar-less systems, they are built as gravity walls or as reinforced soil walls using geo-grids.