CETIM, in collaboration with the industrial fabric, developed a new binding material from construction and demolition waste and iron and steel slag, to minimise the environmental impact associated with the production of this type of material

One of the main challenges facing the construction sector is to find alternatives to Portland cement, a material with significant environmental burdens. It is the second-largest source of carbon dioxide emissions globally and a major consumer of resources, using a substantial amount of materials in its production. If we add to this the millions of tonnes of construction and demolition waste (CDW) generated each year, as well as electric arc furnace slag, the result is the need to seek solutions that relieve the sector of its environmental burden.

Addressing these challenges is the focus of CETIM through the KEOPS research project. The project aims to investigate comprehensive and high-value geopolymetric cementing solutions derived from construction and demolition waste and steel slag, promoting sustainability. Our Sustainable Construction Materials team at the Technological Centre has collaborated on this initiative with five leading companies in the construction sector in Spain: Extraco, Cementos Cruz, Adec Global, Cromogenia, and Prefhorvisa.

CETIM’s expertise

At CETIM we initiated the first stage of KEOPS research through the development and optimisation of different fast setting and low rebound geopolymeric formulations for shotcrete applications, for heavy metal capture for environmental remediation and high chemical resistance for chloride and sulphate resistant concretes.

Likewise, several tests were carried out in our Technology Centre to find the best formulation of the geopolymer paste for each of the applications proposed in the project. Finally, our Sustainable Construction Materials team managed to create a new binding material from construction and demolition waste and steel slag, eliminating one of the components with the highest carbon footprint used in cement production, clinker. The new cement, in addition to being more environmentally friendly compared to Portland cement, also has better properties of resistance to high temperatures, certain acids and salts, as well as greater capacity to capture heavy metals.

This is how we have managed to replace conventional cement with different RCDs and two types of steel slag through their alkaline activation in geopolymer concretes. And all this by carrying out a Life Cycle Analysis of both the mortar for 3D printing and the concretes. In this way, we found that the environmental impact of both materials is lower than with those conventionally used in practically all categories (global warming, environmental performance, water consumption, etc.).

KEOPS reaches its final goal

In the last KEOPS milestone, the project partners brought the most sustainable mixtures developed in the CETIM laboratory to industrial scale. Mainly, in the third and last milestone of KEOPS has been achieved:

• The realisation of a prototype of a full-scale mortar. The mortar has been created through 3D printing using a geopolymeric binder, replacing conventional cement paste.

 

• The manufacture of geopolymer concretes with better performance, such as greater resistance to chemical attack, better qualities against the uptake of heavy metals and for environmental remediation. Three demonstrators have been generated from this material in real environments, which are located on the AG-31 Ourense-Celanova motorway.

 

• The generation of new prefabricated blocks, with a specific formulation and totally viable industrially, with high resistance to fire and high temperatures.

 

All of this involved the conditioning and conversion of the waste into materials by Adec Global, and the generation of additives specifically formulated by Cromogenia Units.

KEOPS has already managed to provide a solution to the problems initially posed in the construction sector: reducing the environmental burden and revaluing waste with a high impact on the environment. All this thanks to the commitment to R&D and the circular economy of the partners involved in the project (Cementos Cruz, Extraco, Adec Global, Cromogenia and Prefhorvisa) and the collaboration of CETIM Technological Centre.