The rice husk samples were introduced to about 1/3 of the volume
of a 90 60 mm crucible. Thermal treatment of the rice husk
samples was carried out in a muffle furnace with its door half
opened to ensure sufficient air in it. The heating temperature
(600 and 700 C) and time (one and two hour) with heating ramp
of 5 C/min were controlled. In order to ensure its full combustion,
the rice husk needed to be stirred manually once using a dipper of
about 20 cm-long before the thermal treatment. The different samples
were represented with a unique designation throughout this
paper. For example, RHA600-1 h designated the RHA sample produced
at the temperature of 600 C for one hour. RHA600-2 h
and RHA700-1 h had the similar meanings. Chemical composition
of RHA and OPC used in the present investigation is shown in
Table 2.