Impact of Adding Waste Materials to Pervious Concrete Performance Under Freeze-thaw Conditions

As societies develop and populations grow, the need for resources increases, however, this could result in environmental stress, which should be addressed using unconventional solutions. Concrete is a widely used material due to the abundance of its ingredients in nature. Traditional concrete is a solid material with very low permeability, which results in some serious environmental side effects. A solution to some of these problems is presented by pervious concrete. The present experimental study was undertaken to develop a mixture that can satisfy a set of desired properties with the main aim to replace conventional concrete with a material that allows water to directly filter into the ground to naturally recharge aquifers and allow for evapotranspiration to maintain a low temperature above the subsurface. This was done by changing ingredient ratios or by including waste materials, such as crumb rubber and fly ash, to make the concrete more environmentally friendly. The goal was to evaluate the performance of different mixtures of pervious concrete and to examine their behavior under freeze and thaw conditions in fresh as well as salt water. A total of 432 2-inch cubes were made and tested. In addition to the aggregates and cement used in making the mixtures, crumb rubber particle sizes of 1 and 2 millimeters, synthetic tensile fibers, fly ash, and a chemical additive that acts as a superplasticizer were used. Tests were conducted to determine the compressive strength, permeability coefficient, and freeze-thaw durability in both fresh and saltwater. The results showed that, with respect to compressive strength, pervious concrete is generally weaker than conventional concrete; adding waste material such as crumb rubber or fly ash slightly increases the concrete’s resistance to freeze and thaw but it could negatively impact its compressive strength; resistance to freeze and thaw in salt water was significantly lower than that in fresh water; and tensile fibers and chemical additives increase the concrete resistance to compression and to freeze and thaw. The above observation should be considered only general trends. It is recommended that mixtures of pervious concrete be tailored to serve site-specific requirements. It is concluded that the performance of the concrete can be enhanced in many ways using additives that address various needs.