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Answers

Why does the batch matter more than the colour?

Because cement and pigment are the colour. A terrazzo panel takes its colour from the binder and the pigment, and the code requires one colour layer to use one factory's pigment in one batch — which is why two panels ordered months apart from the same colour name are not the same colour, and why a repair in a different batch shows.
The four Chinese grades of terrazzoFor each of four grades, a bar shows the maximum water absorption in per cent and a figure gives the minimum average flexural strength in megapascals. From JC/T 507-2022 table 7.12468Standard terrazzo8%min. avg. 5 MPaHigh-performance6%min. avg. 8 MPaCement artificial stone4%min. avg. 10 MPaHigh-performance cement artificial stone1%min. avg. 15 MPaFour grades, not four points on a line: each is a separate product class.Water absorption, maximum permitted. From JC/T 507-2022 table 7. Axis starts at 1% because that is the lowest grade; it is not a zero-based axis.
The four grades of JC/T 507-2022 table 7, showing the maximum water absorption of each. The axis starts at 1%, not zero, and says so.

The figures, and where each one comes from

What has to match Why
Cement batch the matrix colour comes from the binder, not from the chips
Pigment batch one colour layer, one batch, by clause
Pigment content 3 to 6 per cent of the cement weight
The aggregate graded the same way, or the pattern is visibly different
⛔ What does not solve it a screen colour, a photograph, a colour name

Why the processes are not interchangeable

Terrazzo is normally specified for repeatability, which makes it unusually bad at matching an earlier batch: the colour is not a pigment added to a white base as a stain, it is the cement and a mineral pigment at 3 to 6 per cent, and both move slightly between batches. That is why the clause about one batch is written the way it is, and why it matters twice over: on a new floor it keeps the job internally consistent, and on a repair it is the reason a patch in a later batch is visible even when the colour name is the same. The practical answer is to order the repair material from the same production run as the floor, which means keeping a piece of the original panel.

What these figures are, and what they are not

The same-batch requirement, the same-factory requirement and the 3 to 6 per cent content are GB 50209-2010 clause 5.4.2. ⛔ We publish no batch number, no lead time and no guarantee that a later order matches an earlier one, and we do not offer a matching service: ⛔ what we do is say plainly that a second order is a second batch and will not match.

Measured data sheets and test reports

If you are specifying this

These are the forms we actually supply for this question, with production photographs where we have them:

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