Geopolymer Mortar as Retrofitting Material for R.C. Element

Abstract

Geopolymer has been subject of research in recent years. There are many studies which are carried out to examine viability of geopolymer mortar as an alternative material to Ordinary Portland Cement. Deterioration in OPC is unavoidable so we need to repair or replace it. There are many repair techniques as well as materials such as cementitious mortar, polymer modified cementitious mortar etc. Use of ordinary Portland cement as binder material will lead to higher emission of carbon dioxide gas CO2 whereas geopolymer contributes nearly 80% less CO2. Geopolymer material mainly consist of replacement of cementitious material by industrial waste like fly ash, blast furnace slag, bottom ash, metakaolin, Silica fumes etc. so in such way the industrial waste will be used judiciously. The objective of this research is to develop geopolymer mixture for repair of R.C. elements by using industrial waste material. Here in this research work industrial waste material such as metakaolin, GGBS and Fly ash were used for Geopolymer mortar (GPM) preparation. Sodium hydroxide and Sodium Silicate were used as alkali activators for activation of binder material in Geopolymer mixture preparation. Six different trials of geopolymer mortar were done here for strength evaluation of different proportions of binder ratio. 10M and 12M cubes were prepared for adequate strength check. Ratio of alkali activator NaOH: Na2SiO3 was used as 1:2 and 1: 2.5. It was observed that, while using metakaolin as binder material the strength obtained at 7 days were comparatively low. Using fly ash in mortar cubes will lead to quick settlement of mix but it doesn’t contribute much in higher strength gain. Increasing proportion of GGBS lead to higher compressive strength in geopolymer mortar at 7 days. Geopolymer paste (GPP) was prepared with 80:20 (GGBS: Fly ash) ratio as repairing material from observing the results obtained by geopolymer mortar compositions. Plain cement concrete cubes of size 150 × 150 × 150 mm was cast for checking the required strength of M25 grade of concrete. Once the required strength was achieved then total of 36 beams of size 100 × 100 × 500 mm were cast with M25 grade and other 4 beams with size 150 × 200 × 1350 mm were cast. Mixture consists of Ordinary Portland Cement (grade 53), Coarse aggregate (20 mm downsize), Fine aggregate, Portable water and super plasticizer. Concrete mix design was finalized based on provisions given in IS: 10262(2019). Compressive strength of concrete cubes was evaluated on 7 and 28 days. Prepared beams were damaged by applying two-point flexure load until cracks were developed and then from all the beams some were repaired by filling cracks with Dr. Fixit Crack X Paste and other with geopolymer material and then final total flexure load carrying capacity was evaluated for beams and some of the cast beams were kept under fire for 4000 and 6000 C temperature and after cooling of all the beams 8 beams of 4000 C were developed cracks under flexure testing machine as after fire exposure only colour change was observed and other 8 beams of 6000 C were directly checked for ultimate flexure load carrying capacity as after fire exposure hair line cracks and some chunk removal was observed so beams damaged under fire were repaired with coating the whole beam by repairing material and then were checked for ultimate load carrying of beams at 7 days and 28 days. Results of this research shows that after repairing control beams and checking them for ultimate flexural capacity, an increase in capacity by 14.12% with geopolymer repairing material and decrease in its capacity by 11.32%with Dr. Fixit Crack X Paste was observed. While in beams repaired after exposing them to elevated temperatures of 4000 and 6000 C, an increase of 13.5% by geopolymer material and simultaneously decrement of 20% after applying other material in the flexural load carrying capacity the beams was observed. Full scale beams gave more load carrying capacity upto 5 kN increased while using Geopolymer paste than Dr. Fixit Crack X Paste. Hence using geopolymer as repairing material turns out to be advantageous than other material used in research.