Pozzolans are partial substitute for cement in the construction industries. It can partially replace cement in the production of mortar, sandcrete blocks and concrete. Pozzolans are siliceous materials which by itself possess no cementitious properties but in processed and finely divided form, react in the presence of water with lime to form compound having cementitious properties [1] [2] . The use of pozzolans in cement industries is necessary to reduce the amount of CO₂ being emitted into the atmosphere during the production of cement and the high energy needed for cement production. In addition, agro-waste pozzolans help to manage our waste and improve our ecology system. Pozzolans from agricultural waste are very reactive in their finely divinely form and their performance could be optimized when calcinated at the right condition among which we have the right calcinating temperature. Calcinating temperature in pozzolans is the temperature at which the ashes were obtained. Morales et al. [3] studied the effects of calcinating conditions on the microstructure of sugar cane wastes ashes and discovered that calcinating conditions influence the microstructure and pozzolanic activation of pozzolans. Nuntachai et al. [4] also investigated the effects of loss on ignition (LOI) on the compressive strength and sulfate resistance of mortars as another calcinating condition and reported that LOI affects these two properties of the tested mortars at different ages of the concrete. Other researchers Salau and Osemeke [5] conducted their own research on the effect of calcinating temperature on pozzolanic characteristics of calcined kaolin (metakaolin). They discovered that the silica content of metakaolin increases with increase in calcinating temperature and time of calcination. They studied a temperature range of 600˚C and 1050˚C and recommended 750˚C for metakaolin production having considered the chemical and LOI properties of the pozzolans. In view of all these, there is active research in this area and hence the need to successful carry out proper analysis and test procedure contributes significantly to improving the overall use of any discovered pozzolan. This will in turn improve the quality of life by providing necessary infrastructure and other basic enhanced facilities. The reactivity of a pozzolan depends on its chemical and mineralogical composition, the type and proportion of its active phases which also depends on temperature. This research has been conducted on four different agro-waste ashes to establish their suitability under three different calcinating temperatures and the effect of the calcinating temperature on their chemical composition and microstructure. These four agro-waste ashes namely rice husk ash (RHA), groundnut shell ash (GSA), locust bean pod ash (LBPA) and bamboo leaf ash (BLA) has been previously discovered to improve the compressive strength of concrete as well as some other properties like chloride ion resistance [6] [7] [8] [9] .

Rice husk ash (RHA), groundnut shell ash (GSA), locust bean pod ash (LBPA) and bamboo leaf ash (BLA) were obtained and calcinated at different temperatures of 500˚C, 600˚C and 700˚C for 1 hour at a step of 100˚C in 1 hour in a close electric furnace. The ashes were then sieved using 50 μmm (2 μ inches) sieve as shown in Figure 1. Their chemical and microstructural analysis at different calcinating temperature (500˚C, 600˚C and 700˚C) were obtained alongside with their loss on ignition. The chemical compositions were obtained in term of their oxide compositions using X-ray fluorescence spectrometer [10] and their

micro-structures were obtained with the use of scanning electron microscope [11] [12] . The X-ray fluorescence spectrometer test was carried out on an energy dispersive X-ray fluorescence spectrometer Shimadzu EDX-702HS operated at 40 kV and 18 mA. The current was adjusted automatically with a maximum of 1 mA. The samples were loaded into chamber through the sample trays giving utmost consideration to the samples labels i.e. the slot numbers. The oxide compositions of the various samples were then obtained appropriately with the use of EDX Shimadzu software package. The scanning electron microscope used for this research work is shown in Figure 2, the accelerated voltage, displayed magnification and the scale are all shown in the result.

RHA was obtained by sun drying rice husk, BLA by sun-drying fallen bamboo leaf, GSA was obtained by sun-drying ground shell while LBPA was obtained by sun-drying locust beans pods. Their ashes were then obtained by calcinating in an electric oven at different temperatures.