), which produced differing ratios of SiO2/Al2O3 and CaO/SiO. They were prepared as hot mixtures using sodium silicate and sodium hydroxide as activators before being heat cured in an oven at 80��C for 1, 2, or 4 hours. The study aimed to analyze the effect of these parameters all targets on the compressive strength and drying shrinkage using SEM, XRD, and FT-IR techniques. Measurements were taken after 2, 6, and 24 hours and 7 and 28 days.2. Experimental Section2.1. MaterialsThe metakaolin (MK) used in this study was collected from Narathiwat province. It was calcined at 750��C for 2 hours and used as Si-Al cementitious material. The chemical composition of the MK was analyzed using X-ray fluorescence (XRF). The physical properties of the MK are listed in Table 1. Grinding the raw materials in a ball mill produced small particles.

Figure 1 depicts the XRD pattern of the MK. The MK showed an apparent amorphous phase (between 20 and 35��2��) in its structure with peaks for microcline, quartz, and illite.Figure 1XRD pattern of MK.Table 1Chemical composition (wt.%) and physical property of MK and OPA.The OPA was obtained from a palm oil mill in Krabi province. It was sieved to remove any incompletely combusted fibers. The OPA was ground in a ball mill until the median particle size was approximately 19��m. The chemical composition and physical property of the OPA are shown in Table 1. Figure 2 shows the X-ray diffractogram of the OPA, which demonstrates outstanding crystalline phase materials with obvious detectable quantities of crystalline quartz, calcite, and sylvite.

Figure 2XRD pattern of OPA.The activator used was a mixture of sodium hydroxide (NaOH) in flakes of 98% purity and sodium silicate (Na2SiO3). The sodium silicate solution had a composition by weight of 14.14% Na2O, 27.67% SiO2, and 56.28% H2O.River sand was used as the fine aggregate component of the geopolymer mortars. The specific gravity of the river sand was 2.51, and the maximum size was 4.75mm.2.2. Mixture ProportionThe geopolymer mortars used in this study were prepared with MK, OPA, and the alkali activators sodium silicate and sodium hydroxide with a view to verify the viability of using geopolymer binders. All the samples contained a mass ratio of river sand:MK and OPA:alkaline activator:water of 3:1:0.83:0.45. The alkaline activator used was a mixture of sodium silicate and sodium hydroxide in a weight ratio of 2.

5:1. The sodium silicate and sodium hydroxide were mixed in water and produced an exothermic temperature of 74 �� 2��C. Later, the river sand, MK, and OPA were added to the mixture which reduced the temperature to 48 �� 2��C. Samples of four different concentrations of OPA were prepared: 0% (Control), 5%, 10%, and 15%. The samples Brefeldin_A were quite sticky and fast setting and required some effort to be cast in acrylic molds.