The construction industry is one of the most polluting due to its high contribution to CO2 emissions. In addition to its significant environmental cost, its materials are made from non-renewable resources such as sand and gravel, making the search for sustainable alternatives an urgent challenge in a context where growing production demand must be balanced with environmentally responsible practices. The sector is, therefore, investigating the development of low-carbon-footprint materials within a circular economy and decarbonization strategy, replacing traditional materials with the waste and surplus of other industries that, in turn, struggle to dispose of their by-products.
A case in point is the paving block designed by a team with the Belmez Higher Polytechnic School (EPSB) at the University of Córdoba, which has succeeded in replacing natural materials with recycled ones. For the aggregates used in mortars and concrete, the team substituted them with a material derived from a type of waste with no industrial value whatsoever: mollusk shells ; specifically, those of Acanthocardia tuberculata , an edible saltwater clam species known as the corruco or langostillo , which is commercially produced and consumed in canned form.
"The canning industry generates tons of this waste, which ultimately piles up in landfills," explains Ágata González Caro, researcher in the Department of Inorganic Chemistry and the lead author of the study. The work proposes a way to find a commercial outlet for the waste from this sector, while at the same time addressing one of the challenges facing the construction industry: crushing the shells of this mollusk to produce a calcareous aggregate capable of replacing natural aggregates in mortars and concrete.
In addition to replacing the aggregate with one made from mollusk shells, the research team — which also includes UCO researchers José Ramón Jiménez, José María Fernández Rodríguez, and Antonio Manuel Merino Lechuga — set out to replace the remaining components in order to create a paving block made entirely from recycled materials . To replace the cement, thereby avoiding its high environmental production costs, waste from a spoil heap at the Guadiato Valley mine and fly ash were used, giving these residues, in turn, a new lease on life. When subjected to a process known as alkaline activation — through contact with a highly alkaline solution with a very high pH — a transformation occurred that produced new compounds very similar to those of cement.
The result, the researcher explains, is a durable paving block that meets the mechanical, durability, and safety criteria required for such materials — all without a single natural material in its composition, only the leftovers and waste of other industries. The result isa contribution to circular economy and decarbonization in one of the sectors most noted for its polluting potential, though still requiring further research to optimize aspects such as compaction and demolding, exploring greener activators and other ways of reducing dependence on conventional chemicals.
Materials and Structures
Experimental study
Not applicable
CO2-cured alkali-activated pervious paving blocks incorporating seashell sand
23-Dec-2025