aluminosis

Aluminosis is the progressive failure of concrete caused by a chemical reaction between the alumina in certain cements and the calcium hydroxide that forms as concrete cures. The result is expansion, cracking, and loss of strength over time. It occurs in concrete made with high-alumina cement (HAC), a binder that was widely used in the mid-twentieth century because it set quickly and resisted sulphate attack.

High-alumina cement was valued in construction for rapid early strength gain and for applications where sulphate resistance mattered, such as foundations in contaminated soil or near seawater. However, the material is vulnerable to a conversion reaction in the presence of moisture. The stable compounds formed during initial curing convert to less dense hydrates, particularly if the concrete experiences sustained heat or humidity. This conversion weakens the microstructure from the inside.

Recognition and outcomes

Aluminosis appears as fine crack networks, surface spalling, and sometimes a chalky white deposit on exposed concrete. The deterioration accelerates in damp environments and in structures where the concrete cannot dry out readily. Building surveys in the 1970s and 1980s identified aluminosis in thousands of structures, many of them residential blocks built in the 1950s and 1960s. The defect does not develop uniformly; some elements fail while nearby sections remain relatively sound, depending on local moisture conditions.

High-alumina cement is now heavily restricted or banned in most developed countries for structural use. In the United Kingdom, it was formally discouraged from the 1970s onward. Where aluminosis is confirmed, remediation typically requires partial or full replacement of affected concrete, or in some cases acceptance of reduced load capacity with ongoing monitoring. The cost of such repairs has made aluminosis a significant legacy problem in aging building stock.