Which material can be added to concrete slabs to enhance their tensile and flexural strength?

Adding synthetic fibers to concrete slabs enhances their tensile and flexural strength by improving the material's ability to resist cracking and increase its overall durability. These fibers distribute stress more evenly throughout the concrete, helping to minimize shrinkage and control micro-cracking that can lead to larger cracks over time.

Synthetic fibers, such as polypropylene or nylon, are particularly effective because they can bridge the gaps in concrete as it sets and cures. This bridging action allows the concrete to retain its integrity under tensile stresses, which are common in flat surfaces like slabs that may experience bending forces from loads.

In contrast, while steel reinforcement bars are traditionally used to strengthen concrete by improving its tensile capacity, the question specifically focuses on enhancing strength through the addition of materials rather than structural reinforcement methods. Cementitious materials can contribute to compressive strength but do not specifically address tensile or flexural enhancement in the same way that synthetic fibers do. Plastic aggregates are primarily used to reduce weight and improve workability, rather than to enhance strength characteristics.