Street scene with roadside buildings and a parked truck

That is how a great many blocks in this country are made, and it is not a caricature. Surveys of Nigerian block producers describe batching by volume using wheelbarrows, head pans and paint buckets, with mix ratios running anywhere from one bag of cement to three wheelbarrows of sand at one end, to one bag to seven at the other. Water is determined by trial and error.

Two yards on the same street can therefore be selling blocks with completely different strengths at the same price, and neither of them knows it.

The part that gets blamed and the part that is responsible

When a wall cracks or a building comes down, cement quality is usually first to be blamed. Sometimes fairly. But the research into sandcrete block quality keeps landing somewhere less convenient: the mix is guessed, and the compaction is never measured at all.

Compaction is what happens in the mould. Vibration settles the mix and drives out air. Get it right and the block reaches its designed strength. Get it wrong and you produce a block with voids in it that looks completely normal sitting in the yard, cures normally, stacks normally, and fails under load months later.

That delay is the dangerous part. Nobody connects a wall failing in February to a batch pressed in November.

What NIS 87 checks

Nigeria’s standard for sandcrete blocks sets compressive strength requirements. It does not come and inspect your vibration system. It tests the block.

Which means a producer running weak compaction has no early warning. Everything looks fine until a contractor sends a sample for testing and rejects the batch, and by then you have a yard full of blocks you cannot sell to anybody who tests.

Why this is a commercial problem, not a technical one

A yard that fails a test with a commercial buyer rarely gets a second test from that buyer. Contractors talk to each other. In a market where your customers are all within a few kilometres of each other, a reputation for weak blocks moves faster than your lorry does.

There is also a cost argument that runs the other way. Good compaction lets you reach the required strength at a leaner mix. Cement is the largest single line in your cost per block. A machine that compacts properly is therefore paying you back on every bag, quietly, forever. A cheap machine that forces you to add cement to pass a test has already cost you more than the good one, and it will keep costing you.

Vibration is the specification everybody claims to have and almost nobody quantifies. Ask for motor power in kilowatts and vibration frequency, in writing. Any supplier who will not put those numbers on paper is telling you something.

Comparing presses? Send us the quotes and we will tell you what the vibration specification actually says, before you commit. Get in touch.