Behaviour of metakaolin modified concrete paver blocks

Abstract

The current study involves the experimental investigation on the mechanical properties of high strength concrete paver blocks prepared with concrete containing commercially available metakaolin as mineral additive. A concrete mix of M40 grade , suitable for making concrete paver blocks for medium traffic was designed following IS 15658:2006 . Three different shapes Zig Zag , Dumbbell and I-shape paver blocks were considered for the study. The effect of replacing cement partially by 5% ,10% and 15% of metakaolin were studied in terms of 7-days and 28-days of compressive strength, flexural strength, water absorption and abrasion resistance. The results were compared with mix without metakaolin referred as control mix.. The results indicated that addition of metakaolin improve all characteristics of the paver blocks of all types. The mix with 10% replacement was found to give maximum compressive, flexural strength , abrasion resistance and minimum water absorption characteristics . The further increased percentage of metakaolin were found to adversely affecting these characteristics due to dilution of Cement. Comparing with control mix 20% increase in compressive strength, 12% increase in flexural strength, 16 % increase in abrasion resistance and 30 % decrease in water absorption were observed for the mix with 10% metakaolin. The microscopic study of hydrated structure of metakaolin modified concrete mix were conducted through XRD ,FESEM and EDX techniques. The XRD and EDX analysis indicated higher percentage of strength giving silicates hydrates phase and the FESEM images showed more refined , compact, smooth and layered micro structure for metakaolin modified concrete mix. The microscopic study of hydrate structures of different mix justify the results obtained from mechanical tests.