The abundant availability of LUSI (a short form of LUmpur SIdoarjo or Sidoarjo mud) mud of a mud volcano located in Sidoarjo, East Java, Indonesia, attracts interest of researchers to seek the possibility of utilizing it; among them is as construction material. This study focuses on the effect of calcinations temperatures of LUSI mud on the compressive strength of geopolymer mortar. Three different calcinations temperatures were investigated, i.e. 700, 800 and 900°C for five hours duration. Characterization of the mud, both the original and the calcined ones, was performed by using X-ray Diffraction (XRD) and X-ray Fluoresence (XRF) analyses. The calcined LUSI mud was then employed as precursor for making geopolymer mortar, and tested for its 7-day compressive strength. It is found that calcinations at 800°C is the optimum calcinations temperature producing the highest compressive strength.
