K-Silicate based Fiber-Reinforced Geopolymer Concrete

Abstract

The increasing focus on global climate change, the public and consumer preferences for "green" products, and the associated markets in carbon credits, have promoted the use of alternate cements in place of pure Portland cement binders. Using geopolymer- ization method, waste materials such as y ash and slag can be modified to replace ordinary Portland cement. In the present study, Potassium silicate (mole ratio of 1.57) which is harmless to use and has ow ability and viscous property like water has been used to geopolymerize the precursor y ash. Controlled Humidity and tem- perature conditions are chosen for curing. Fibers are added in the mix to reduce the shrinkage cracking and to increase the exural performance of geopolymer concrete. The research work was focused on characterizing concrete properties like compres- sive strength, static modulus of elasticity in compression, Average residual strength of fiber-reinforced concrete. For this total 75 number of samples are prepared. In order to analyse the microstructure of geopolymer cement paste, scanning electron microscopy and energy dispersive x-ray difraction techniques are used. Apart from laboratory analysis, 3' x 2' thin test panels of fiber reinforced geopolymer concrete are prepared with embedded sandwich type of strain gauges at UVic's materials lab to simulate the real environmental condition. Also, as a part of this research work, geopolymer pavers are constructed and placed at the experimental site developed at parking lot 6 of University of Victoria, Victoria BC, Canada. The Scanning Electron Microscopy and Energy Dispersive X-ray Di raction Spec- troscopy revealed that reaction of Fly ash Particles with K-Silicate is on the surface of the y ash particles and due to 14% CaO content present in the Fly ash, K-Silicate precipitates(Reaction of K-silicate with CaO) are found on the surface of the y ash which are re ected in the EDX image and x-ray spectrum. This leads to low com- pressive strength of concrete made with the same geopolymeric binder system. On the other hand, K-Silicate based Fiber-Reinforced Geopolymer concrete is more exible compared to normal fiber-reinforced concrete even though the density of the mixes are almost same. This exible concrete cannot be used as structural concrete but may be used in pedestrian pavements and pavers. Shrinkage analysis of the geopolymer fiber-reinforced concrete slab for 15 days re- vealed the negligible diference between GFRC and NFRC. More strain data is re- quired to establish the exact relationship.