Bio-Inspired Biopolymers for the Rheology and Hydration Control of Low-Carbon Cements

Reducing the carbon footprint of the cement industry requires a dual strategy combining the substitution of clinker with supplementary cementitious materials (SCMs) and the development of new admixtures compatible with these alternative binders [1]. However, current chemical admixtures are optimized for Portland cement and often fail to control the rheology, structuration, and hydration of blended systems containing slag (LF), metakaolin (MK) or fly ash (FA). 

This PhD project proposes a disruptive, bio-inspired approach using marine biopolymers such as carrageenan, alginate and ulvan, extracted from red, brown and green algae, as multifunctional modifiers for low-carbon cements [2]. These natural polysaccharides are able to form three- dimensional ionic networks and interact with Ca2+, Al3+ and Si species in cementitious pore solutions [3]. Their molecular structure suggests a unique capacity to modulate early hydration, promote reversible structural build-up, and stabilize suspensions without synthetic polymers [4]. 

The scientific objectives are (1) to elucidate the physicochemical mechanisms governing the interaction between algal biopolymers and multi-component binders (OPC–LF–MK–FA), (2) to assess their impact on rheology, hydration kinetics and microstructure formation through combined techniques (rheometry, isothermal calorimetry, ICP, XRD, SEM), and (3) to establish structure– property–performance relationships leading to predictive formulation rules. 

The methodology will involve systematic extraction and characterization of the algal biopolymers, followed by their incorporation at varying dosages into blended cements. Physicochemical and microstructural analyses will be complemented by modeling approaches to quantify adsorption and complexation phenomena. Comparative testing will evaluate compatibility with mineral additions and the reproducibility of performance across different batches of biomass. 

The expected outcomes include the design of new eco-admixtures derived from renewable marine biomass, improving both the performance and sustainability of blended cements. By replacing or reducing synthetic polymers, these biopolymers will lower the embodied carbon of admixture formulations and enable better control over the early-age behavior of cementitious materials. 

The thesis will lead to (i) the formulation of new low-carbon cement pastes incorporating optimized biopolymer admixtures, (ii) a mechanistic model linking molecular structure to rheological and hydration behavior, (iii) at least two peer-reviewed publications in high-impact journals (e.g., Cement and Concrete Research, Construction and Building Materials), (iv) one presentation at international conference, and (v) a potential patent or material transfer prototype for bio-based admixtures. 

In the long term, the project aims to contribute to the emergence of a new class of bio-based rheology modifiers tailored for low-carbon construction. Potential applications include self- compacting, 3D-printable, and marine concrete with enhanced durability and reduced environmental impact. This exploratory work will serve as a cornerstone for future ANR or ERC-type projects on algae-derived materials, circular economy strategies, and the bio-inspired engineering of cementitious systems.