At the present state of the art, brown discolourations should actually be things of the past. Unfortunately that is not the case at all. Observations in the field and the handling of complaints show that brown discolourations have been recurring lately, often years after they had been eliminated by successful measures in the production plants. Why is that the case? Knowledge is often lost through personnel changes, basic principles are no longer implemented when plants are modified or newly built due to pressures of cost and/or time, sometimes due to ignorance, but sometimes they are also quite simply ignored. This applies equally to the manufacture of cement and of concrete goods. Furthermore, the prescribed introduction of chromium reduction in the production of cement (if reducing with iron(II) sulphate) has not helped to minimise the brown discolourations. Lately, brown discolourations have been observed more frequently again in the case of in-situ concrete, where iron(II) reduced cement is often used. Experiences in the prevention of iron and lime efflorescence are summarised in this article with newer examples and investigations. Details can be found in the sources of literature [1-9].
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