High alumina cement
High Alumina Cement (HAC), sometimes known as calcium aluminate cement (CAC) or aluminous cement, is composed of calcium aluminates, unlike Portland cement which is composed of calcium silicates. It is manufactured from limestone or chalk and bauxite (Special clay having extremely high alumina content).
HAC was first developed by Lafarge, the cement producer, and became available in the UK in 1925. It was used in particular for marine applications where it was considered to be resistant to chemical attack. It became popular in the 1950s, 60s and 70s, as it developed strength rapidly and so was relatively fast to manufacture. It was widely used in structural concrete such as pre-cast beams.
However, HAC was prone to a crystalline re-arrangement (or ‘conversion’), which could result in reduced strength and also vulnerability to chemical attack when exposed to water for long periods (perhaps as a result of poor detailing or poor manufacturing). This resulted in five high-profile structural failures of roof beams (where the presence of water is more likely) during the 1970s.
In 1975, MP for Sutton and Cheam, Neil Macfarlane, said “Those words—or the abbreviation "HAC"—are rapidly and relentlessly becoming a combination of misery, apprehension, worry and fear for thousands of people in the United Kingdom.”
HAC is no longer used in structural concrete in the UK, although it is still prevalent in buildings constructed in the 50s and 60s, and continues to be used for non-structural uses under the name Calcium Aluminate Cement (CAC).
In 1975, The Department of the Environment (DOE) Building Regulations Advisory Committee (BRAC) published guidance for design-check procedures for High Alumina Cement. Commonly known as the BRAC rules, this guidance remains the best advice available and continues to be used to assess the structural performance of buildings containing pre-cast HAC concrete beams.
It should be noted that many buildings that contain HAC components are entirely problem free, and the problems that have occurred have been traced back to manufacturing faults. However, If the presence of HAC is suspected, testing should be carried out, and if it is confirmed, HAC components should be assessed for strength and long-term durability. This is likely to require expert advice.
[edit] Related articles on Designing Buildings Wiki
- Aggregate.
- Asbestos.
- Brick.
- Cement.
- Coal ash.
- Concrete v steel.
- Defects in brickwork.
- Deleterious materials.
- Demolition.
- Ferro-cement.
- Hempcrete.
- How scientists solved the riddle of cement’s structure.
- Lime mortar.
- Portland cement.
- Pre-construction information.
- Research on novel cements to reduce CO2 emissions
- Screed.
- Sustainable materials.
- Types of cement.
[edit] External references
Featured articles and news
C20 Society; Buildings at Risk List 2025
10 more buildings published with updates on the past decade of buildings featured.
Boiler Upgrade Scheme and certifications consultation
Summary of government consultation, closing 11 June 2025.
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
From project managers to rising stars, sustainability pioneers and more.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.
Comments