Sand bulking allowed for before the mix is batched
Damp sand swells. Measure it by volume without allowing for that and you put far less sand in than you think — or, correcting the wrong way, far less cement. It is the most common reason a site that believes it is mixing 1:6 is not.
What to look at
- A bulking test done when the sand stack has been rained on
- The gauge box count adjusted after rain rather than kept constant
- Sand stored covered so its condition is at least consistent
How to check it yourself
Damp sand occupies noticeably more volume than the same sand dry — the effect is largest at low moisture, exactly the state sand is in on a covered stack after rain. The field test is simple: fill a container with damp sand, then saturate and settle it, and compare levels. Kerala sites in monsoon are the ones that most need it and least often do it.
Where this comes from: IS 2386 (Part 3) — Methods of test for aggregates, bulking of fine aggregate; IS 2250 for mortar proportioning (indian standard or building code)
More masonry and wall checks
- Photograph before this is covered
- Bricks or blocks soaked before laying, and joints filled
- Masonry cured, and lintels bear the specified length
- Laterite blocks: soaked properly, and laid with the right mortar
- Burnt clay bricks: water absorption within the standard
- Concrete blocks: cured and aged before they go into a wall
- AAC blocks: thin-bed mortar, and never soaked
- Fly ash bricks: to the standard, and the right mortar for them
- Mortar measured by gauge box, not by shovel
- Mortar used within its working time, and never re-tempered