Effectiveness of using Metakaolin and fly ash as supplementary cementitious materials in pervious concrete

The rapid increase in infrastructural development escalates the problem of storm water runoff and flash flooding in rainy seasons in urban areas due to insufficient drainage. To overcome this problem, the permeability of conventional pavements is improved by replacing normal concrete with Pervious Concrete or No-Fines Concrete (NFC). But the exclusion of sand leads to a reduction in workability as well as its strength which limits its practical applications. The present study investigates effect of using Metakaolin (MK) and Fly Ash (FA) as Supplementary Cementitious Materials (SCMs) to compensate for reduced strengths in the absence of fine aggregates on the mechanical strength in the form of compressive, split tensile and flexural strength along with permeation properties of water permeability, porosity, density, and water absorption in No-Fines Concrete. Results indicate significant improvement in compressive strength by 46% and 3.1% with 20% replacement of cement by MK and FA respectively at 90 days. Results obtained are well corroborated by dense and compact micrographs as obtained by microstructural analysis of NFC mixes obtained with different replacement levels of SCM’s. Permeation properties slightly decrease (by approx. 5%) with increase in percentage replacement with MK but improve with FA replacement along with better abrasion resistance. The use of these SCMs in pervious concrete not only leads to requisite strength enhancement without any appreciable compromise in permeation properties and is also environment friendly reducing the carbon print in addition to being cost effective.