Introduction to Blockwork
Production of Alphalite masonry units began in 2005 and gained immediate acceptance from masonry contractors, being faster and easier to lay. Industry-standard blocks of the same strength were 30% heavier.
Environmental responsibility
Alphalite is made from a patented combination of by-product materials. This saves quarrying of natural sands and coarse aggregates. Alphalite is 30% lighter than standard concrete masonry. This reduces the transport emissions. Alphalite is kiln-cured, but unlike clay masonry units, the heat is low and largely exothermic, with some steam added for even curing. This low embodied energy combines with higher durability to make a favourable life-cycle analysis; at the close of which, Alphalite masonry can be crushed and re-used.
Strength
Alphalite hollow blocks have a characteristic unconfined compressive strength (ƒ ‘uc) of 15MPa generally. 4-hour fire-rated blocks and 90mm solid blocks are 10MPa. Alphalite masonry unit strengths are measured through the face shells. The strength of Alphalite masonry in terms of compression, bending, shear and robustness are explained in the following sections of this manual with worked examples and reference graphs.
Fire Resistance Levels (FRLs)
In 2006, Alphalite material was fire-tested and achieved much higher FRLs than industry-standard masonry units:
- Structural Adequacy FRL:
- The maximum slenderness ratio, which governs the Structural Adequacy FRL, is 25.15 for Alphalite material at a 120-minute FRL (The industry-standard is 16).
Integrity FRL:
The 90mm thick Alphalite fire test achieved a 240-minute Integrity FRL which is the highest requirement in the Building Code of Australia (BCA).
Insulation FRL:
The Insulation FRL from the fire tests was also proven to be much higher than the industry standard. Alphalite masonry requires 78mm of material to achieve a 120-minute FRL (standard concrete masonry requires 120mm).
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Sound Ratings (Rw + Ctr)
In 2007, Alphalite masonry was acoustic-tested with various lining systems at the National Acoustic Laboratory.
The test with an independent (impact rated) 64mm independent stud wall system achieved Rw + Ctr 50; the BCA requirement for walls separating home units. Further tests and assessments identified innovative options for thinner lining systems. Full details are in Section 6.
Workability
A small percentage of Twinbricks and Chaser Blocks are made with slots for splitting part sizes. When split in half, both pieces are used rather than one piece becoming shrapnel on the worksite.
Alphalite bricks and blocks can be cut with a tungsten-tipped hand saw. Self-tapping screws can be hand-screwed into Alphalite.
Alphalite bricks and blocks are easier to lay because they are 30% lighter than standard masonry units and they have an effective initial rate of absorption. This allows short walls to be laid faster as the mortar in each course firms quickly, giving better support to the next course.
Render
Render also benefits from this initial rate of absorption: The moisture absorbed by the Alphalite masonry migrates slowly to the surface, through the render, slowing its curing rate which makes the render stronger and less likely to “craze” (those fine cracks than can occur on a hot, dry day when the render cures too quickly).
Render bonds with Alphalite by physically keying with the surface texture. Bonding is further enhanced by a chemical reaction between the mineral aluminosilicate in Alphalite and the hydrating cement in the render to form calcium aluminosilicate.
Durability
The masonry structures code: AS3700:2001, Section 5, defines what areas require higher durability and prescribes AS/NZS4456.10 as the method of test.
When tested to AS/NZS4456.10, Alphalite masonry units achieved the “Exposure Grade” rating which AS3700 requires for masonry in “severe marine environments” (areas within 1km of a surf coast or within 100m of tidal waters).
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