An investigation of pozzolanic reactivity of ultrafine treated rice husk ash (UFTRHA) was evaluated using electrical conductivity measurement. This paper is aimed to identify the effect of grinding duration via high speed milling process to the pozzolanic reactivity level. This pozzolanic reactivity assessment was completed by incorporating UFTRHA powder samples prepared at several milling duration in saturated portlandite solution at 40°C. Structure of these mesoporous substances after grinding processwere captured using Field Emission Scanning Electron Microscopy (FESEM) accordingly. Based on the findings, experimental results analysis reveal that UFTRHA ground at 15 min has highest pozzolanic reactivity level among all specimens. Hence, short period of grinding is sufficient to attain huge amount of specific surface area (SSA) by using high speed milling process. Excessive grinding aid i.e. 60 min produced lower specific surface area hence lower pozzolanic reactivity level. Larger amount of specific surface area leads towards vigorous and higher pozzolanic reactivity. © 2016 Taylor & Francis Group, London.