Project Overview

Summary

In the wake of recent global events, where nations found themselves unprepared in the face of a microscopic adversary, resulting in loss of life and economic turmoil, a silver lining emerged. Amid these challenges, a remarkable reduction in greenhouse gas emissions occurred due to the temporary halt of numerous industrial operations, leading to visible environmental regeneration and an improved quality of life in cities once plagued by smog. While humanity continues to grapple with the pandemic, a notable global awareness has arisen, calling for an imperative shift in our societal values towards environmental betterment.

Concrete, the second most utilised material worldwide, trailing only water, forms the very backbone of our built environment. However, the production of Portland cement alone contributes to a staggering 7% of the planet's total CO2 emissions. Despite its integral role in national economic advancement, stakeholders are increasingly recognising the potential of non-Portland cement alternatives, particularly alkali-activated materials (AAM) which stand as leading contenders. Pioneering research has already demonstrated the feasibility of AAM, particularly in crafting high-strength structural elements, employing activated fly ash (FA) or blast furnace slag (BFS) as sole binding agents. Nevertheless, the production of FA is dwindling globally due to the pivot towards sustainable energy solutions, and in Portugal, BFS production has ceased entirely due to the transition from blast furnaces to electric arc ones.

In light of this scenario, the most promising strategy for viable AAM production revolves around utilising abundant reactive calcium aluminosilicate waste materials that lack clear outlets. Leading contenders include glass packaging waste rejects (WGR), municipal solid waste incinerator bottom ashes (MIBA), and electric arc furnace slag (EAFS). Notably, glass packaging in Portugal alone amounted to ~1.5 million tonnes in 2017, rivalling the cement production of ~2.6 million tonnes in 2018. However, despite the predominantly reactive nature of WGR, they carry a considerable load of contaminants due to flawed waste glass separation practices (30-70% of waste glass from kerbside collections are irrecoverable rejections).

In 2018, Portugal generated approximately 5 million tonnes of municipal solid waste (MSW), with a fifth being incinerated, predominantly leading to the accumulation of MIBA. Notably, ~100,000 tonnes/year of MIBA stem from Valorsul's incineration unit, which manages most of Lisbon's MSW, amassing in a landfill at the city's periphery. Meanwhile, EAFS, a calcium silicate waste product of steel recycling, registers a production exceeding 5 million tonnes/year in Europe. Unfortunately, much of it is underutilised in road pavement construction. Nonetheless, its promising reactivity and bulk production quantities suggest its potential incorporation into AAM.

In a bid to align with the Paris Agreement and the UN 2030 Agenda for Sustainable Development, the imperative to curb the construction industry's CO2 emissions has grown stronger. CO2-based curing has demonstrated prowess in enhancing the performance of calcium-rich cementitious materials. However, our knowledge of its effectiveness in AAM, especially involving WGR, MIBA, or EAFS, remains limited. Recent preliminary findings from our research team exhibit a remarkable five-fold increase in the strength of cement-free AAM reliant on MIBA or EAFS following seven days of forced CO2 curing, with ample room for optimisation. Given the limited avenues for WGR, MIBA, and EAFS utilisation—instead of relegating them to landfills or downcycling—a significant opportunity exists to elevate their worth by capitalising on their latent high activation potential. Moreover, their substantially lower carbon footprint in comparison to cement, combined with their remarkable CO2 storage capacity, brings the possibility of crafting carbon-negative construction materials tantalisingly close.

Harnessing the extensive expertise of our research team, spanning over ten research projects, and bolstered by a wealth of knowledge in eco-efficient cementitious composites (comprising five books and over 250 papers published in WoS/Scopus), this venture aspires to develop avant-garde CO2-enhanced cement-free and fully recycled AAM, culminating as sustainable binding systems for mortar and concrete, aligned with European standardisation benchmarks. An all-encompassing experimental campaign shall unfold, prioritising performance-driven optimisation of AAM's mixture design post-CO2 curing, culminating in the quantification of the material's permanent CO2 capture capacity. Numerical models, forged from the insights gained through prior experimentation, shall be devised, validated, and harnessed to conduct extensive parametric studies focused on the diffusivity of CO2 within specimens, aimed at optimising practical production output.

The technology's viability shall be gauged through an evaluation of its environmental performance, realised via a comprehensive life cycle assessment. Following a stringent safety assurance protocol, our collaboration with partners within the Municipality of Cascais shall pave the way for real-world application, serving as a pivotal gateway towards future commercialisation.

Goals and Objectives

Welcome to our visionary initiative! At the heart of our project lies a compelling mission - the creation of a revolutionary CO2-enhanced cement-free construction material. This innovation harnesses the potential of alkali-activated calcium aluminosilicate wastes, destined to power a new era in non-reinforced concrete elements. These elements, accounting for a substantial portion of the global annual concrete production, present an ideal canvas for our innovation to flourish, as carbonation concerns are mitigated.

Spanning across this endeavour, we're guided by not one, but three pivotal societal imperatives:

Guided by this resolute mission, we've crafted three strategic objectives, each a stepping stone towards our ultimate goal: