concrete
The grey stuff of pavements, bridges, and buildings. It is a particle-reinforced composite: a paste of Portland cement and water (the matrix binder) glues together sand and gravel (the aggregate particles). The cement paste hardens by a chemical reaction called hydration, not by drying, cementing the stones into an artificial rock.
Aggregate is cheap, strong, and dimensionally stable, so using roughly 60 to 80 percent aggregate by volume cuts cost and shrinkage and adds stiffness, while the cement paste binds it. Concrete is strong in compression (about 20 to 40 MPa typical, over 100 MPa for high-performance grades) but weak in tension (only about one tenth of its compressive strength) because it is brittle and full of tiny flaws. So real structures add steel rebar (making reinforced concrete) or squeeze it with tendons (prestressed concrete) to carry the tension.
Concrete is the most-used engineered material on Earth by mass, and its story is honest engineering: pair a cheap, brittle, compression-loving matrix with steel exactly where tension appears. Its weaknesses, tensile cracking and rebar rusting when chlorides or carbonation reach the steel, dominate durability design.
A highway bridge deck: concrete carries the compression on top, while steel reinforcing bars near the bottom carry the tension where the deck sags between piers, each material placed where it is strong.
A brittle, compression-loving matrix teamed with steel exactly where tension appears.
Concrete cures by hydration chemistry, not by drying out; it even hardens under water. On its own it is brittle in tension, so the steel in reinforced concrete is doing the tension job.