Granite is a natural igneous rock formed by the slow crystallization of minerals such as quartz, feldspar, and mica under high temperature and pressure. It is dense and hard, with a compressive strength typically exceeding 100 MPa, and some even approaching 200 MPa. Its elastic modulus is also much greater than that of concrete, making it rigid and resistant to deformation. Granite has a very low water absorption rate, typically less than 2%, and excellent wear resistance. It can maintain its structural integrity despite repeated freeze-thaw cycles and salt corrosion. Many ancient buildings that have stood for thousands of years are a testament to its durability. Furthermore, granite is heat-resistant, with temperatures up to 400°C showing little impact on its mechanical properties. It can be exposed outdoors for long periods without the need for additional protection.
Concrete is a man-made composite material, composed of cement, water, coarse and fine aggregates, and possible chemical admixtures, mixed in a designed ratio, and then allowed to set and harden. Conventional structural concrete generally has a compressive strength between 20 and 60 MPa, and a much lower elastic modulus than granite. It deforms significantly under stress and requires steel reinforcement to withstand tensile forces. The durability of concrete depends on its mix proportions and curing. In cold regions, air-entraining agents and antifreeze agents must be added, while chloride environments require increased density or the addition of an anti-corrosion coating. If curing is inadequate, carbonation, freeze-thaw, and steel corrosion will shorten its lifespan, typically requiring replacement every 15–30 years. Concrete also has poor heat resistance, rapidly degrading at 400°C. Fires often necessitate complete demolition and reconstruction.
From a construction perspective, concrete's advantage lies in its plasticity. It can be cast on-site into any shape or prefabricated and hoisted in factories, adapting to complex structural systems. Granite, on the other hand, can only be cut, polished, or carved, making it difficult to create delicate beams and slabs. It is more commonly used in exterior wall installations, plaza paving, curbstones, monuments, and other areas requiring high durability or decorative features. Concrete is difficult to reuse after demolition, while granite blocks can be completely dismantled and reinstalled, resulting in lower lifecycle costs. Using crushed granite as coarse aggregate in concrete significantly improves its strength after hardening. Both early and late compressive strength values are higher than those of conventional concrete using limestone aggregate. It also exhibits greater slump, improved workability, and can reduce material costs by more than ten yuan per cubic meter. However, concrete with granite aggregate is slightly less resistant to chloride ion penetration and carbonation, requiring stricter mix control and maintenance measures.
In summary, granite's advantages lie in its natural high strength, durability, and recyclability, making it suitable for "century-long" projects or those requiring extremely high aesthetic and wear resistance. Concrete, on the other hand, boasts plasticity, economy, and a mature design system, making it the preferred load-bearing system for modern buildings. For projects that prioritize both strength and cost, incorporating crushed granite into high-strength concrete can offer the best of both worlds.