Shape Memory Alloy Applications in Cementitious Composites

Shape memory alloys (SMAs) are metallic materials capable of recovering large strains through thermo‐mechanical transformations. When incorporated into cementitious composites, SMAs impart active crack‐closing, self‐centring and energy‐dissipation functions that are unattainable with conventional steel or polymeric fibres. In such composites, SMA elements may be introduced as straight wires, crimped fibres or knotted ends to enhance bond performance. Upon heating or mechanical loading, the martensitic‐austenitic phase transition generates recovery stresses that actively close cracks and rebalance internal stresses. This active reinforcement promotes durability by mitigating crack propagation, reducing residual deformations and extending service life. Applications span from self‐healing mortars and engineered cementitious composites (ECC) to ultra‐high performance concretes (UHPC) utilising prestrained SMA rebars for internal prestressing. Global interest has surged in developing novel SMA geometries, optimising fibre‐matrix interfaces and integrating pseudoelastic behaviour for seismic resilience and deflection control.

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Research from all publishers

Advanced shape memory alloy fibres have been devised with segmented pseudoelastic architectures to enhance crack‐closure and re‐centring performance in cementitious beams. In static and cyclic flexural tests, composites containing 0.5–1.0% of these fibres exhibited crack‐closure ratios above 50% and re‐centring ratios up to 80%, significantly outperforming steel‐fibre counterparts. Digital image correlation revealed uniform strain distribution and reduced crack widths at high deflections, demonstrating superior energy dissipation and toughness.

A study of Fe–Mn–Al–Ni SMA rebars for ultra‐high performance concrete demonstrated the feasibility of internal prestressing without external jacking devices. Prestrained rebars embedded in UHPC were thermally activated to develop approximately 130 MPa of prestress, resulting in marked increases in flexural strength and stiffness. This approach addresses prestress losses from shrinkage and creep, offering a sustainable alternative for long‐span and lightweight structural elements.

Investigations into engineered cementitious composites reinforced with knotted‐end SMA fibres have elucidated critical bond characteristics under direct pullout loads. By varying fibre diameter, end geometry and embedment length, researchers achieved pullout stresses exceeding 900 MPa and fibre utilisation rates above 80%. Knotted ends provided robust anchorage, enabling full exploitation of superelastic properties and yielding self‐centring beams with minimal residual deformations.

Shape Memory Alloy Applications in Cementitious Composites publication trend

The graph below shows the total number of articles in shape memory alloy applications in cementitious composites across all publications each year (not limited to Nature Index journals).

Technical terms

Shape memory alloy (SMA): An alloy that recovers predefined shapes or generates stress through reversible martensitic–austenitic phase changes.

Cementitious composite: A construction material combining cement‐based matrix with reinforcing fibres or particles to improve mechanical performance.

Superelasticity: The ability of an SMA to undergo large, recoverable strains under mechanical loading without permanent deformation.

Self‐centring: The capacity of a structural element to return to its original configuration after unloading, minimizing residual displacements.

Prestressing: The introduction of internal stresses into a composite prior to service loading to counteract external forces and control cracking.

Engineered cementitious composite (ECC): A ductile fibre‐reinforced cementitious material designed for tight crack width control and high energy absorption.

References

1. Advanced shape memory alloy fibers designed to enhance crack closure and re-centring performance in cement-based composites. Construction and Building Materials (2024).
2. Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete. Materials (2023).
3. Bonding Mechanical Properties between SMA Fiber and ECC Matrix under Direct Pullout Loads. Materials (2023).