Influence of recycled concrete aggregates and blended cements on the mechanical properties of pervious concrete

The paper presents the results of an investigation conducted to study the strength properties of pervious concrete containing coarse recycled concrete aggregates (RCA). In this study, 13 pervious concrete mixes were prepared with the use of RCA replacing coarse natural aggregates (NA) by 0, 25, 50, 75 and 100%. Keeping the water–cement (w/c) ratio constant, Viscosity Modified Agent (VMA) was added at 0.8% by weight of binder content. Being environmentally advantageous, 30% Fly Ash (FA) has been added with 70% Ordinary Portland Cement (PC) in the binder of control mix. Despite being environmentally safe product, metakaolin (MK) also tends to enhance the properties of concrete containing RCA. Therefore, keeping the PC content 70% for all mixes, FA was replaced with MK at two different levels of 5% and 10% to improve the properties of pervious concrete made with RCA. Specimens in the form of cubes, cylinders and beams were prepared for studying the mechanical properties at different ages of curing. The test results showed that there was significant loss in compressive, splitting tensile and flexural strength of pervious concrete while increasing the percentage of RCA replacing NA. Addition of 5% MK compensated the decrement noticed in the strength properties after replacement of NA with RCA. The mix with 25% RCA and 5% MK was having almost same compressive strength as that of reference mix. 10% MK further enhanced the strength properties and it was concluded that loss of compressive strength in pervious concrete due to addition of 50% RCA can be compensated by the addition of 10% MK.