Layered Double Hydroxides in Cement-Based Materials

Layered double hydroxides (LDHs) are lamellar materials composed of positively charged metal hydroxide layers separated by galleries of exchangeable anions and water molecules. Their tunable composition, high anion-exchange capacity and memory effect make them versatile additives in cementitious systems. In Portland cement and low-carbon binders, LDHs can refine pore structure, control rheology, modulate hydration kinetics and immobilise deleterious species such as chlorides or sulphates. Thermal conversion of LDHs to mixed oxides restores the layered architecture upon rehydration, enabling precise adjustment of workability, strength development and durability. Furthermore, in alkali-activated materials LDHs form in situ to enhance chloride binding and mitigate alkali-silica reaction. By improving reinforcement protection and reducing permeability, LDHs contribute to longer service lives of concrete infrastructures and support sustainable construction practices worldwide.

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Recent work has demonstrated that mixed oxides derived from Mg–Al LDH can be tailored via thermal ageing to present different specific surface areas. Incorporation of low-surface-area oxides at small dosages improved paste workability by over 20 %, while high-surface-area variants accelerated consolidation by a factor of 2.4 and reduced porosity by nearly 37 %, attributed to enhanced nucleation of hydration products and competitive water absorption within the paste.

In alkali-activated slag systems, sodium aluminate activation has been shown to stabilise pore solution pH around 12.7 and promote the in-situ growth of Mg–Al LDH with abundant Al–O tetrahedra. This mechanism increases chloride binding while forming C–A–S–H simultaneously, offering a novel route to durable, low-carbon binders with improved resistance to aggressive ions.

Modelling studies of C30 concrete containing calcined hydrotalcite reveal that a 2 % replacement optimises resistance to chloride ingress, raising the 30-day diffusion coefficient by nearly 20 %. A diffusion model based on Fick’s second law, validated using finite-element analysis, accurately predicts chloride profiles and underscores the potential for hydrotalcite to bolster durability in marine or de-icing environments.

Layered Double Hydroxides in Cement-Based Materials publication trend

The graph below shows the total number of articles in layered double hydroxides in cement-based materials across all publications each year (not limited to Nature Index journals).

Technical terms

Layered Double Hydroxides (LDHs): Anionic clays comprising brucite-like layers of divalent and trivalent metal hydroxides with interlayer exchangeable anions.

Anion Exchange Capacity: The ability of LDHs to capture and replace interlayer anions (e.g., Cl–, SO₄²–) within their gallery spaces.

Mixed Oxides (MO): Porous materials obtained by calcining LDHs; they regenerate layered structures upon rehydration, influencing cement hydration and microstructure.

Alkali-Activated Materials (AAMs): Low-carbon binders formed by activating industrial by-products (such as slag) with alkaline solutions, where in-situ LDH formation can enhance durability.

References

1. Relevance of Specific Surface of Mixed Oxide Derived from Layered Double Hydroxides on the Rheological Properties and Porosity of Cement Pastes. ACS Applied Materials & Interfaces (2024).
2. In-situ formation of layered double hydroxides (LDHs) in sodium aluminate activated slag: The role of Al-O tetrahedra. Cement and Concrete Research (2022).
3. Experimental Study and Numerical Analysis of Chloride Ion Diffusion in Hydrotalcite Concrete in Chloride Salt Environment. Materials (2023).