Table 2Mix proportions of geopolymer samples.2.3. Test ProcedureAfter curing for 1, 2, or 4 hours at 80��C, the geopolymer mortars were removed from the acrylic molds and stored at ambient temperature. Compressive strength tests were conducted on cast selleck kinase inhibitor specimens with dimensions of 50 �� 50 �� 50mm. The samples were tested in accordance with the relevant ASTM C109/C109M [13] at ages of 2, 6, and 24 hours and 7 and 28 days. Drying shrinkage tests were performed during a period of up to 30 weeks using a length comparator in accordance with the relevant ASTM C490 [14].A JMS-5800 LV model scanning electron microscope (JEOL, Japan) was used to identify the microstructure of the geopolymer mortars. Small scraps of the samples were tested using scanning electron microscopy.

Powder XRD was conducted using an X’Pert MPD X-ray diffractometer (PHILIPS, Netherlands) at angles from 5�� to 80�� (2��) using the clay and rock 0.4 program. The MK, OPA, and geopolymer paste were characterized directly. XRD was conducted to identify the dominant crystalline phases and to detect the positions of the peaks.FT-IR was performed on the geopolymer samples on an EQUINOX 55 spectrometer (Bruker, Germany) using the KBr pellet technique in 4000�C400cm?1 range.3. Results and Discussion3.1. Compressive Strength3.1.1. The Effect of the Ratio of SiO2/Al2O3 The compressive strengths of the mortar after being cured at 80��C for 1, 2, or 4 hours are shown in Figures Figures33 and and4.4. It can be seen that for all the mixtures the compressive strength generally decreased with an increase in the proportion of SiO2 (molar ratio) after 2 and 24 hours at ambient temperature (see Figures 3(a) and 3(b), resp.

).Figure 3Compressive strength of geopolymer mortar with different SiO2/Al2O3 and heat curing time measured after (a) 2 hours, (b) 24 hours, and (c) 28 days.Figure 4Compressive strength of geopolymer mortar heat cured for 2 hours.The development of the compressive Brefeldin_A strength of the Control, O5, O10, and O15 samples heat cured for 1, 2, or 4 hours is shown in Figures 3(a), 3(b), and 3(c), respectively. It was observed that the initial ratio of SiO2/Al2O3 had a significant effect on the development of compressive strength in the geopolymer binder systems.