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From Industrial By-Products to Better Binders: Evidence Before Environmental Claims

An industrial by-product can become a useful raw material, but its origin alone does not make it a reliable construction product. The useful questions are more demanding: what does it contain, how does it react, which properties can be reproduced, and where is it appropriate to use?

Research co-authored by Alexander Nikolov, CONCREEF’s materials chemistry and geopolymer specialist, offers concrete examples of this approach. His studies examine how mineral residues can participate in binder systems, while also identifying the limits that matter when moving from laboratory work toward practical applications.

Start with the material, not the label

Cement kiln dust is a fine by-product of cement manufacture. In a 2025 study, Nikolov and colleagues characterized samples from three Bulgarian cement plants using particle-size analysis, X-ray and infrared methods, and electron microscopy. They found differences in physical, chemical and mineralogical properties associated with factors such as feed materials, kiln conditions and fuels. Nikolov et al., Journal of Chemical Technology and Metallurgy, 2025.

For material development, the implication is straightforward: “kiln dust” is not a universal specification. A recipe that works with one source needs evaluation when the supply changes. The same principle applies to other secondary raw materials. Traceability and characterization are part of making reuse technically credible.

Promising strength results come with application limits

A study published in Buildings investigated binders and concrete made from industrial by-products, including ladle furnace slag, coal ash and cement kiln dust. The reported 28-day compressive strengths were 34.5 MPa for mortar and 32.6 MPa for concrete under the study’s conditions. The authors also identified a crucial restriction: high chloride and sulfate concentrations made the material inappropriate for steel-reinforced applications. Nikolov et al., 2025.

Both parts of that result belong in the discussion. Mechanical performance suggests a development opportunity; chemical composition constrains its use. Those figures describe the researchers’ specimens, not CONCREEF products, and do not establish the printability of the formulations.

The paper’s title, Toward Zero-Carbon Concrete, should also be read as a research direction. Removing Portland clinker from a formulation does not, by itself, demonstrate zero lifecycle emissions. Processing, activators, transport, curing and the chosen comparison all belong in an environmental assessment.

More waste-derived material is not always better

Another 2025 study examined sunflower-shell fly ash as an alternative activator for a one-part binder based on ladle slag. In the tested pastes, adding 10 wt% ash increased compressive strength to nearly 30 MPa. Higher additions reduced strength. The authors called for further investigation of long-term stability, durability and potential heavy-metal leaching. Nikolov et al., Ceramics, 2025.

This is a valuable formulation lesson. Maximizing the proportion of a secondary ingredient is not the same as optimizing a material. The appropriate amount depends on its chemistry and on the performance required. A useful development programme must be willing to reject a higher recycled-content recipe when it compromises the intended function.

Carbonation is a mechanism to measure

Nikolov and colleagues also studied the carbonation of cement kiln dust in dry and hydrated forms. Their analysis identified the formation of carbonate phases, including calcite and vaterite, supporting further investigation of mineral carbon storage. Nikolov et al., 2024.

That finding does not give every kiln-dust product a carbon-negative status. A product-level claim would require measured uptake and a defined assessment boundary that includes the impacts of making and using the material. For CONCREEF, the useful lesson is to treat environmental performance as a quantity to establish, alongside technical performance.

What this means for CONCREEF’s development work

Alexander’s expertise provides a scientific basis for exploring alternative binders and asking suppliers more precise questions. Our practical interpretation is to evaluate candidate materials through a sequence of decisions:

  • Define the application. A planter, a furniture component and a reinforced structural element have different requirements. Specify the intended use before selecting a formulation.
  • Characterize the feedstock. Establish composition and variability, including constituents that may affect durability or environmental suitability.
  • Evaluate the process. A successful cast laboratory specimen is a starting point. Mixing, pumping, extrusion, shape retention and layer interfaces still need assessment for printing.
  • Validate the finished component. Use relevant specimens, exposure conditions and acceptance criteria. Retain a record of the formulation and processing conditions.
  • Substantiate the environmental comparison. Measure what changed and compare equivalent functions before claiming a reduction in impact.

This sequence is an editorial proposal for development, not a declaration that CONCREEF has commercialized the published recipes or completed these tests.

Circular materials need precise briefs

The opportunity is substantial: secondary raw materials can become ingredients in useful binder systems. The route to dependable products runs through chemistry, formulation, testing and a clearly defined use.

That is the value Alexander brings to the CONCREEF team: expertise that helps turn an interesting feedstock into a better research question, and a promising result into a carefully scoped next step.

Explore the materials expertise behind CONCREEF or start a project conversation.

Prepared by CONCREEF from the linked publications. Original studies are credited to their authors; Alexander Nikolov is not credited as the author or endorser of this editorial article. No published laboratory result is presented as a CONCREEF product certification or environmental declaration.