Concrete’s cobra effect: unintended results of embodied carbon reduction

Once the active curing period is completed, concrete requires further protection from re-wetting (e.g. from rain, snow, and ice), freezing conditions, open flame heaters (i.e. carbonation), and other weather conditions that can affect durability of lower carbon concrete.

The contractor should have a quality management program describing their standardized approach to managing concrete curing and protection procedures which include provisions for preconstruction activities; quality assurance (QA) and quality control (QC) activities undertaken by the contractor and trades; and reporting of the implementation of the various protection and curing procedures used during construction.

The specifier must explicitly state in the specifications the basis of design curing procedures that are acceptable for the project, describe curing of unformed and formed surfaces, and state acceptance requirements for contractors proposed modifications based on their project schedule. Specifiers can confirm whether there are any special curing and protection requirements by coordinating with the lower carbon concrete supplier, and using their recommendations as specific requirements in the project specification.

Education and documentation

New curing methods, such as lower carbon ingredients, are still only a single part of making sustainable concrete practices work. New methods are not going to help anyone, no matter how good they are, unless people are educated on how to succeed in the design and building of proper curing with low-carbon concrete, they will still fall into the same trap as the colonial British in dealing with too simple solutions in ridding the cobras.

In documentation, if one is no longer using cure and seals, curing membranes, and silicates then those specifications will need to be intelligently updated. Design decision makers, structural engineers, and specifiers will have to not only update, but get used to the idea of fewer moving parts in their specifications.

Specifiers will have to research, interrogate, and incorporate their materials and methods to be successful. Similarly, professionals in the field will have to adapt to small, but meaningful behavioural changes that come with internal curing. There will be less bleed water. A common reaction in the past might have been to add additional water to the surface (water of convenience) or an epoxy skim coat, believing incorrectly that the concrete is drying out too quickly, but this is no longer the case. Internal curing also means the concrete is malleable much longer than 100-year-old surface curing. This will affect how and when builders cut joints, and possibly how many joints they need to cut. Jumping into anything new needs to be thoughtful and eased into so questions can be asked, answered, and understood prior to the real deal.

However, it is not just a projects documents that need to change. It is likely that actors outside of the project team, but still directly connected with construction, need updated approaches as well. One example might include updating credits to not only include low volatile organic compounds (VOCs), but also credits for eliminating the need for products with any amount of VOCs in the first place with more modern approaches to curing. Environmental product declarations (EPDs) likely need to be modified as well to include performance characteristics, such as permeability to avoid regrettable substitutions for seemingly low carbon outcomes, while not fully appreciating lifecycle and performance.

Control the content you see on! Learn More.
Leave a Comment

Leave a Comment


Your email address will not be published. Required fields are marked *