Gypsum efflorescence on clay brick masonry is a growing problem, leading to a persistent grey-white staining of masonry facades. Gypsum efflorescence has been reported in the United Kingdom, the Netherlands and Belgium, with a specific occurrence on masonry facades erected over the last few decades. This article investigates the origin of this recent occurrence of gypsum efflorescence, with accelerated testing of the gypsum efflorescence sensitivity of separate and combined masonry components. It is demonstrated that both brick and mortar may provide a gypsum source, respectively, via the dissolution of anhydrite and the carbonation of ettringite. Neither does however directly result in gypsum efflorescence, as the released gypsum commonly subfloresces below the brick surface. The efflorescence is instead triggered by mortar admixtures, the application of which has indeed risen strongly in recent decades. Avoiding gypsum efflorescence on clay brick masonry hence requires an inert alternative for the mortar admixtures.

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粘土砖砌体上的石膏风化：潜在风化起源分析

粘土砖砌体上的石膏风化是一个日益严重的问题，导致砌体外墙持续出现灰白色。石膏风化在英国、荷兰和比利时都有报道，特别发生在过去几十年建造的砖石外墙。本文通过对单独和组合砌体组件的石膏风化敏感性的加速测试，研究了最近发生的石膏风化的起源。结果表明，通过硬石膏的溶解和钙矾石的碳化，砖和砂浆都可以分别提供石膏源。然而，两者都不会直接导致石膏风化，因为释放的石膏通常在砖表面下方形成亚花。风化是由砂浆外加剂引发的，近几十年来，它的应用确实强劲增长。为了避免粘土砖砌体上的石膏风化，因此需要一种惰性的砂浆外加剂替代品。