Microstructure And Strength Development Of Geopolymers At Lab And Outdoor Environmental Conditions

The cardinal aim of the study is fixed in the influence of negative temperature intervals on mechanical properties of the investigated material. The combination of two fly ash types(low calcium and high calcium) is used for generation of geopolymer. Five mixtures are chosen to monitor the properties changing under the quality variation of all mixture compounds. Mixtures are chosen according to paste early age properties especially setting time and workability. Moreover, preliminary strength tests are done to select a better raw material combination and the influence of aluminum addition on the frost resistance is also evaluated. The behavior of chosen patterns is investigated in different environmental conditions(the freezing machine and outdoors). The microstructural evolution is conducted by scanning electron microscopy, Fouriertransform infrared spectrometry, X-Ray diffractometry and mercury intrusion porosimetry.The results show that the setting time is influenced by the content of water glass in the solution. The more water glass in its composition leads to both short initial and final setting time. The strength exhibits the tendency to grow with time except the mixer with Al. Considering the strength at 90 days in different condition it is noticeable that the highest value is achieved by samples that were kept indoors. The groups from outdoors are at second place and then follow the normal condition and freezing machine patterns.Through SEM test the evidence of rapid reaction at early age properties are found. Along with EDS analysis SEM images of crystalline particles are investigated. XRD diffragtograms displays the changes in intensity of the peaks. FTIR plots don’t reflect any shifts. The humps intensity varies significantly. When the peak of Si-O bond shifts to higher wave number same with Al-O peak shifts in opposite direction the ordering of the gel is happening. This effect isn’t observed. Porosity development investigated with MIP shows the pore volume of geopolymer is concentrated in the interval 10-100 nm and porosity is around 43% at 3days, 28 days and 50 frost cycles. However, the pore structure shows distinctions between patterns from different environmental conditions for 90 days.