and Sousa-Coutinho, 2013).
Rice husk ash (RHA) is a natural
agricultural waste from rice mill factories and
contains pozzolanic material. Rice mill factories
create a waste product called raw husk which is
used as heating fuel in rice mill processing and
produces the RHA as a byproduct from the burnt
raw husk. Office of Agricultural Economics of
Thailand (2013) reported an annual rice production
of approximately 30 million t of which more than
20% becomes raw husk. As this husk is fired,
approximately 25% RHA is generated, though the
amount of RHA varies considerably according to
the heating process, burning temperature and rice
type (Koteswara et al., 2011).