Mechanisms of CO2 Reduction
Using Strength-enhancing Cement Additives
The process effects and the economic benefits of chemical additives are well understood, but their potential to reduce the carbon footprint of cement is a new frontier for many producers. Chemical additives improve the reactivity of cement, allowing increased clinker replacement with limestone and other SCM's without loss of strength. This is an important lever for reducing cement plant CO2 emissions. This article discusses the mechanisms and sustainability benefits of strength-enhancing cement additives, including an industrial case study.
Alternative Fuels
The Additive Approach
Cement producers are striving to reduce their use of fossil fuels, in order to attain a lower carbon footprint, and to lower their production costs. The introduction of an alternative fuel often poses the cement plant several challenges, including potential detrimental effects on the final quality of the resulting cement and concrete products. Many of these downsides can be balanced by the use of an appropriate cement additive, allowing the cement quality to remain unchanged, whilst achieving significant economic savings, environmental improvements and carbon reductions.
Cement Pre-hydration
Pre-hydration of Cement
Cement pre-hydration degrades the performance of concrete, particularly strength and set times. Testing performed on 181 cements showed that more than one quarter had suffered enough pre-hydration to significantly affect performance. The study also showed that cements manufactured in vertical roller mills are much more likely to be affected by pre-hydration than cements made in ball mills. A controlled laboratory study of selected cements demonstrates that even mild pre-hydration causes measurable performance loss.
Limestone Cements
The Right Reaction
High-performance chemical additives can facilitate reductions in the clinker-to-cement ratio and help contribute towards carbon neutrality in the cement Industry. The adoption of GCP’s new quality improver contributes to cement producers’ abilities to match 2030 targets of clinker reduction and to reach 2050 targets of carbon neutrality, as well as the ability to enhance the economics of cement production.
Fly-ash Cements
Activation of Flyash Cement
Recent developments in the chemical activation of cements containing pozzolans. Mechanisms of action and case studies with modern quality improvers are reviewed, showing an enhancement of the hydration of fly-ash and natural pozzolanic cements.
Clinker Morphology
Under the Microscope
Whole clinker optical microscopy can often be used to identify subtle process changes in a clinker, which can subsequently be remedied by changes to the kiln or feed set-up, resulting in an improved quality clinker and, most importantly, significant cost savings. GCP maintains this capability in its customer ‘toolbox’ and this is one of the many technical support services offered to customers.
Customised Quality Improvers
Cost Versus Value
While simple grinding aids can create a modest net economic advantage, the use of fully-customised additives can maximise benefits and improve the efficiency of the grinding process as well as deliver a higher-quality end-product.
Next-gen Quality Improvers
New Generation of Strength
A new generation quality improvers by GCP allows for early strength improvement of up to 30 per cent. This increased cement strength can be used to allow higher rates of clinker substitution and lower production costs, further reducing the carbon footprint of cement.