Selling Blocks to Contractors in Syria: Tolerances, Curing and Delivery Batches

Selling blocks to contractors in Syria is settled at the gate of the buyer's site, not in the sales office. The foreman tapes ten blocks, looks at the corners and asks which pallet came off which mould. Three things answer him: the block sits inside the tolerance on the order, the concrete has cured long enough to hold its corners, and the load is one batch from one mix on one mould.

Two of those three are fixed before the truck moves. A press at 31.5 MPa with vibration at 3,800 to 4,500 times per minute holds a block size only while the mould holds its own dimensions. A cuber that builds a stack the clamp cannot grip breaks a good batch in the yard.

What a contractor checks at the gate

The test at the gate is physical. Length, width and height are measured on blocks pulled from three pallets, never from the top of the stack, because that layer dried in the open. The foreman stands a block on its corner and checks the arris, then reads the ticket and asks whether the rest of the load came from the same mould.

A signed reference sample from the first delivery, marked with its batch number, ends most arguments. So does a photographed pallet ticket. A rejection argued with a sample and a number is a technical conversation. One argued from memory is a discount.

• Ten blocks from three pallets, measured on the same faces each time.
• Arris checked by hand, since a soft corner reads as a mix fault on site.
• Batch number, mould number and demoulding hour on every pallet ticket.

Where a worn mould becomes a rejected truck

The mould is the only tool that touches the block, so it wears where the load lands. Frame, mould core, base plate, guiding assembly and positioning mechanism each push the finished dimension a different way. Core wear at the corners lets a 390 x 190 x 190 mm hollow block grow, wall thickness follows, and the wall it goes into needs more mortar and loses the mason's line.

Wear is never even, so the fault does not arrive as one bad block. It arrives as a drift across a pallet, then across a truck. When a contractor rejects twice on the same dimension, stop measuring blocks and measure the mould: cavity length, width and depth on four cavities, plus the gap at the guiding assembly. Write the band in millimetres with a plus and a minus in the order.

How many days must a block cure before dispatch?

Curing counts hours from demoulding, not days of weather. Fix the number with the contractor, stamp the demoulding hour on the pallet ticket, and hold each pallet until its count is complete. A clerk who counts from the order date ships a soft stack in the first busy week.

Stacking and curing are one decision. Blocks cubed wet and stacked high crush their own bottom layers, and the mason finds it when he opens the stack. Lay the curing yard out around pallet count, not block count: pallet footprint plus aisle, times the stack height the cuber allows, 1,400 mm on the QS-1200A. A 240 x 115 x 51 mm brick and a 390 x 190 x 190 mm hollow block release water at different rates, so a yard holding both needs two zones and two dispatch counts.

Batch consistency is three settings, not a promise

One batch means one mix, one mould and one vibration setting, and the plant has to prove all three on paper. Vibration at 3,800 to 4,500 times per minute on a 15 to 25 s cycle gives a density. Move either setting and the same mould delivers a block that weighs differently and breaks differently, which the contractor finds on the second truck.

A mould change inside an order does the same damage. On a QST6-15 the 390 x 190 x 190 mm hollow mould yields 6 per mould; the 240 x 115 x 51 mm standard mould yields 32 to 36 per mould. A swap moves the count, the load per cycle and the identity of the batch at once. Close the batch at the mould change, number the next one, and never load two moulds on one truck.

How is a delivery batch built and loaded?

The cuber builds the batch and the clamp moves it, so both must agree on one number. The QS-1200A builds a stack 1,000 to 1,200 mm square at 15 to 18 s per layer, 125 standard solid bricks or 18 standard hollow blocks to a layer. The clamp opens 680 to 1,150 mm, grips at a 1,000 mm width and carries 1,000 x 1,000 x 1,000 mm at 2,000 kg, with 100 mm of lateral movement to line up.

A stack built at 1,200 mm square does not sit cleanly in a 1,000 mm grip: one corner closes on air and the stack shifts on the forks. Build at 1,000 mm square and each bite is 500 to 800 standard bricks or 40 hollow blocks, 10 standard layers or 5 hollow layers. Count the delivery in bites and full cube stacks, and the load that leaves the gate is the load the contractor signed for. The 2,000 kg bite also sets the forklift class and the aisle width.

What goes into the supply agreement?

Four fields make a rejection measurable, and they fit on one page. Block size drawn and dimensioned, not named. Tolerance band in millimetres with the plus and minus stated, and the instrument that settles a dispute. Curing days counted from demoulding, with the hour on the ticket. Batch size per delivery, in clamp stacks and bites.

Add a sampling rule, because a rejection without one is an opinion: ten blocks per delivery from three pallets, a steel tape on the same faces, against a reference sample both sides signed at the first delivery. Add the outcome, so a pallet outside the band is replaced or re-measured at the plant's cost and its batch number goes on the report. Add the change rule: no mix, mould or vibration setting moves inside a numbered batch.

The decision rule is short. Agree the measurable acceptance criteria before the first truck leaves, and print the same four numbers on the delivery ticket as on the contract. After that a rejection is a measurement and a batch number. Before that, it is a negotiation lost at the gate with a full truck.