Title: The Use of Alternative Cements to Protect Concrete in an MICC Environment

Author(s): James Aldred

Publication: Web Session

Volume: ws_S21_Aldred.pdf

Issue:

Appears on pages(s):

Keywords:

DOI:

Date: 4/1/2021

Abstract:
Calcium aluminate cement (CAC) concrete is resistant to acidic environments down to a pH of approx. 3.5 and, in an increasingly acidic environment, CAC reacts to maintain the pH, thus slowing the rate of acidophilic bacterial growth. However, CAC will still be attacked by sewer environment albeit at a greatly reduced rate and allowance should be made by including a layer of sacrificial concrete cover if CAC is the primary protective system. CAC has references in wastewater applications for over 70 years. However, concerns with strength reductions due to conversion have generally limited the use of CAC to non-structural applications such as repair and linings. In Europe, CAC is covered by EN 14647 which summarises the guidelines for using CAC in construction, especially to manage strength reduction due to conversion. The performance of CAC in combination with Portland cement and Slag is promising. Geopolymer refers to alkali activated alumina-silicate binders and covers a wide range of potential products with greatly varying properties depending on the source of alumina-silicates and activators used. The information on its MICC resistance and other properties is encouraging. Geopolymer concrete appears to offer significant benefits in sewer applications but there are limited longer term field examples. If used as the only protective system, a sacrificial layer would be required to ensure the minimum structural thickness was achieved for the required design life.