How do you test blocks and bricks before they go into a Somaliland wall?

Testing blocks before they go into a wall means controlling the delivery, not the wall: put the size, strength and curing on a written order, check each pallet as it lands, and send units to a laboratory for a compression test before the mason starts. Sand, cement and water decide the block, and the buyer is the only person checking them.

What do you put on a block order in Somaliland?

The order should state the block size, the strength class or mix, the age at delivery and who pays for testing, because a block has no tag once it is on the stack. The supplier withholds the mix, so the order is where a buyer fixes what is being bought.

Ask for the units in writing: length, width and height, and whether they are solid, hollow or cellular. State the minimum strength in the units the laboratory will report (N/mm2), and the age of the blocks when they arrive. A concrete block gains strength with curing time, so a supplier delivering at three days and one delivering at twenty-eight days are selling different products. Name the testing laboratory in the order, and state who pays, the buyer or the supplier.

Keep a copy of the order on site. On delivery, ask for the delivery note number, the date and time of casting if the supplier knows it, and the number of pallets. Record all of it in the site file. This is not paperwork for its own sake.

How do you check blocks when the lorry arrives?

Check each pallet against the order before it comes off the lorry: measure a unit, look at the colour and ring it, break one open, and drop a sample into water for three days. Refuse a pallet that fails and write the refusal number on the delivery note.

Take a tape and measure one block from each pallet. A block short in length will not run to the string line, and the mason will fill the gap with mortar. Look at the colour and the face: even colour and sharp arrises point to a consistent mix, patchy colour and crumbling corners point to a lean mix or too little cement. Ring one block with a trowel handle. A dead thud instead of a clear note is a question to ask.

Break one block from each pallet across the break. Look at the inside face. A block should break through the aggregate, not around it, and the core should be dense, not honeycombed. Put a block in clean water for three days, weigh it and break it. A block that soaks up water like a sponge will pull water out of the mortar. Sand and cement are the bulk of the cost in a wall, so a cheap block that swallows mortar costs more by the square metre. Use the construction material calculator to work out how many units and bags the wall needs.

When should you test blocks in a laboratory?

Get a compression test on units at 28 days, or on units cut from the wall, before the mason lays the course that locks them in. A laboratory will give its own rate and its own sampling method; ask for the method in writing with the result.

A compression test reports the failure load divided by the loaded area. Ask the laboratory which area it used, full block or net section, because the two numbers are not comparable. The lab report should name the units tested, their age, their dimensions and the loading rate. A result sheet without those lines cannot be checked by anyone later.

A concrete block delivered at three days has not reached its design strength, so a test on it records green strength only. If a supplier casts to order, agree the delivery date against the curing period on the order. For blocks already on site, keep them dry under a sheet and out of standing water while they wait.

Two reference documents in the region are worth asking for: the project specification, and the laboratory's own test method sheet. If the project has no specification, ask the engineer to write the strength class into the order before the supplier casts. For load-bearing walls, do not accept a verbal assurance in place of a result. Where the buyer needs quantities pinned down first, the concrete calculator sets out the cement, sand and aggregate behind a mix, and the materials section holds the rest of the receiving checks.

What to do next

Take the block order off the shelf and write the size, strength class, age and named laboratory onto it before the next delivery. Then call two laboratories for their sampling method and rate, and put the cheaper one in the order as the agreed tester. From now on, no pallet comes off the lorry until one block from it has been measured, rung and broken open.