In 2006, a series of fire tests were done on Alphalite masonry. When calculated to the requirements of AS3700:2001, Section 6, they were proved to achieved much higher FRLs than standard concrete masonry units.

Achieving the required FRLs
The Insulation FRL is the easiest to prove. It is governed by the material thickness of the masonry unit. The 12-01 2-core block has a material thickness of 74mm which gives it a 90-minute Insulation FRL.

All other Alphalite masonry units have a material thickness greater than 80mm, which gives them a minimum 120-minute Insulation FRL, calculated as per AS3700:2001, Clause 6.5.4(b) (ii).

The highest FRL requirement is 240-minutes. BBC achieve this by reducing the core size of 15-01 and 20-01 blocks to give them a material thickness of 117mm as per AS3700:2001, Clause 6.5.2. To distinguish these from the 120-minute rated blocks, their code numbers are 15-401 and 20-401.

The Integrity FRL os 240 minutes in all non-loadbearing masonry. In loadbearing masonry, it is 240 minutes when the Structural Adequacy is 240 minutes; otherwise, it is 120 minutes.

The Structural Adequacy FRL is the most complicated. It is governed by three formulae in AS3700:2001, Clause 6.3.2.2 which use the masonry panel's height, length, thickness and restraint conditions around the perimeter to calculate the panel's Slenderness ratio for fire (Srf).

The maximum Slenderness ratios for Alphalite Masonry are:

• 27.80 at 60 minute FRL
• 27.10 at a 90 minute FRL
• 25.15 at a 120 minute FRL
• 22.40 at a 180 minute FRL
• 20.45 at a 240 minute FRL

Graphs and more details can be located in the downloads section.