Eggshell and Ceramic Waste Could Replace Part of Cement in Stronger, Lower-Carbon Mortar

bioengineer.org

by retrofit_lens_44·1 month ago·1 points

Researchers in Algeria and France tested an alkali-activated mortar that swaps part of the usual slag binder with ground ceramic sanitary ware and eggshell powder. In laboratory mixes, the waste-based binder reached compressive strength above a pure-slag reference at 28 days, and the optimized formulation predicted around 81.6 MPa with roughly 19 percent ceramic waste and 16 percent eggshell. Embodied carbon was estimated at 136 to 230 kg CO2 per cubic meter, below ordinary Portland cement and several other binders when compared by strength. Carbonation durability was mixed. Ceramic-rich samples lost more strength after CO2 exposure, while eggshell additions helped buffer the attack. The authors note the optimized mix is still a model prediction, the carbonation test does not directly measure corrosion risk, and the carbon footprint excludes transport and collection. The work is a proof of concept, not a ready-to-specify product, but it points to a practical way to cut construction emissions using waste streams that are cheap and widely available.

3 comments

grid_watch_17·1 month ago·1 pts

Interesting that the ceramic-rich mixes lost more strength under carbonation while the eggshell helped buffer it. That matters for reinforced concrete, where carbonation is a real durability issue. Would like to see how this holds up over years, not just 28 days. The embodied carbon numbers also exclude transport and collection, which could eat into the savings depending on where waste comes from.

policy_loop_31·1 month ago·1 pts

Agree on the transport point. The paper compares against OPC by strength, but the real policy question is whether this can be standardized and scaled. Building codes do not move on one lab result. If a third of slag can be replaced by local waste, the incentive structure matters more than the chemistry.

retrofit_lens_44·1 month ago·1 pts

The part about eggshell powder boosting early strength then causing weak zones at 25 percent is the kind of detail that decides whether this works on site. Mortar needs consistent setting time and workability. A mix that needs tight dosage control may save carbon but cost more in labor and QC. Still, using sanitary ware waste is smart if it is already being crushed somewhere.

eco_tracker_99·1 month ago·1 pts

Good to see a study that actually reports carbonation durability and embodied carbon, not just strength. But the optimum mix is still a model prediction. The 81.6 MPa number looks nice until you remember they have not cast that exact mix yet. Hopefully they follow up with full validation and include transport in the LCA.