High Alumina Cement (HAC) Testing

High Alumina Cement Testing

At the height of its manufacture during the 1960’s and early 1970’s High alumina cement was praised for its high rate of strength development, however HAC concrete achieved a certain notoriety following the collapse of several buildings in the 1970's & 80’s.

What is High Alumina Cement?

High Alumina Cement is manufactured from limestone or chalk and bauxite (the ore from which aluminium is obtained). The two materials are crushed and fired together using pulverised coal as a fuel. The materials fuse together and the melt is transferred into steel pans. It is finally cooled, crushed and ground into a dark grey powder.

An outstanding feature of high alumina cement is its very high rate of strength development; about eighty percent of its ultimate strength is achieved at the age of 24 hours.

What’s the Issue with HAC?

Unfortunately, in its converted form, high alumina cement becomes highly susceptible to chemical attack, both from sulphates and from alkalis. This can significantly compromise the integrity and longevity of concrete structures.

a ceiling made of high alumina cement beams

How do you Test HAC?

Assessing the condition of high alumina cement involves several key steps to ensure its integrity and performance in construction applications. The primary methods for evaluating its condition can include:

Visual Inspection: A thorough visual examination of the HAC, looking for signs of surface deterioration, such as cracking, spalling, or any unusual discoloration. Any physical defects may indicate underlying issues.
Thickness Measurement: Use of non-destructive testing methods, such as ultrasonic testing and electromagnetic scanning to measure the thickness of HAC structures. This approach helps assess the extent of any deterioration without compromising the material.
Physical Tests: Conducting standard physical tests, including compressive strength tests, to determine the material's load-bearing capacity. A reduction in strength can indicate that the HAC is no longer performing adequately.
Chemical Analysis: Performing a chemical analysis to evaluate the composition of the HAC. This may include assessing the alumina content and checking for the presence of impurities which could affect its properties.
Moisture Content Testing: High moisture content can lead to premature deterioration. Using moisture meters or gravimetric methods to measure the moisture levels within the HAC can alay any concerns relating to moisture.

Regular monitoring and assessment of high alumina cement is crucial to maintain its performance and longevity in construction applications.

Contact Us

Please contact our surveying team; using the form below, for further information or to discuss any potential HAC presence in a structure. Click here to find out more about our other concrete testing services.