Mechanical and Permeability Behavior of Porous Concrete When Using Different Aggregate Sizes and Adding Polypropylene Fiber

Increased stormwater runoff due to urbanization has highlighted the need for faster water removal. Porous concrete has high void content and porosity; however, it has poor mechanical properties. Its performance can be improved by changing parameters such as cement content, aggregate size, water-to-cement ratio, gravel-to-cement ratio, and additives. Contact surface area and aggregate interlock are the main factors to consider in the design of porous concrete. This study investigated the influence of varying aggregate size and adding polypropylene fiber on the density, mechanical properties, porosity, void ratio, and permeability of porous concrete. Twenty-six mixtures that combined different aggregate sizes and polypropylene fiber content were considered. The results revealed that increased contact surface area and void ratio using multiaggregate sizes provided adequate compressive strength and permeability performance. The best performance was achieved when aggregate sizes of $9.5–6.7\mathrm{mm}$ and $6.7–4.75\mathrm{mm}$ were combined at a $3:1$ ratio and 0.1% polypropylene fiber was added.

Many applications in civil engineering might be both financially and environmentally beneficial. Compared with pond retention systems, porous concrete systems showed a major benefit in controlling stormwater runoff and avoiding soil degradation influenced by water when used as a trenching system for the upcoming water surrounding the building’s foundations. Further benefits as the natural hydrological cycle restoration are achieved by infiltrating water back into the soil rather than pouring it into the sewage system. However, porous concrete relies on voids in its design, reducing its mechanical capacity, and thus cannot withstand heavy traffic. In addition, freezing and thawing cycles in cold weather countries might degrade its capacity. This article collected the aggregate sizes that could be susceptible to porous concrete production and combined at least two sizes to attain the best mechanical and permeability performance. Optimized mixes were discussed in both cases; single and combined aggregate sizes along with fiber additives to enhance the optimized mixes mechanical response and increase their bending capacity for improved traffic resistance. The optimized mixes also showed higher compressive strength than control porous concrete mixes.