Pozzolanic activity of elephant grass ash and its influence on the mechanical properties of concrete

This study was developed to investigate the pozzolanic activity of elephant grass ash (EGA) based on different experimental procedures. The production of EGA was performed from three procedures involving the controlled burning of in natura elephant grass and hot water washing and acid leaching pretreatments of grass before calcination. After burning and grinding, a detailed characterization of the ashes based on tests of electrical conductivity, modified Chapelle method and pozzolanic activity index was performed to identify the adequate conditions to produce ashes with high silica content and low loss on ignition. In addition, the calcium hydroxide consumption, based on thermal analysis, and the influence of 20% replacement of cement by a particular EGA on the compressive strength, Young's modulus and water absorption were evaluated. Results indicated that ashes with pozzolanic properties can be produced from elephant grass. Moreover, the EGA pozzolanic activity expressively increases when pretreatments of grass were used, especially acid leaching. Finally, the use of 20% cement replacement promoted no changes in compressive strength of a 35 MPa-concrete up to 28 days of curing.