POTENTIAL OF WEATHERED LA WIN TUFF FOR GENERATING FLY ASH CEMENT FOR WELL CEMENTING

This paper is mean to analyze the potential of weathered Lawin tuff in
generating fly ash cement especially for well cementing. Lawin tuff is a pyroclastic
rock by compacted volcanic ash obtained from Grik, Perak, Malaysia. Basically, fly
ash used as a replacement for some of the Portland cement content of concrete
because of its pozzolanic properties. Pozzolanic materials are typically high in Si02
and Al203, low in CaO with little or no reactivity when immersed in water.
However, with water and Ca(OH)2, fly ashes generally react to form a calcium
silicate hydrate. The pozzolanic and cementitious properties of fly ash making it a
useful cement replacement material for producing high performance cement. In this
study, sample of weathered volcanic tuff was taken from Lawin and analyses in term
of its physical and chemical properties and also performance when blend with Type
G cement. From the soil properties, the weathered volcanic ash can be classified as
silt fine grained with intermediate plasticity. The micrograph structure from SEM
analysis shown the ash particulates have different sizes and shapes. Proven with XRF
analysis which shown the weathered volcanic ash have high Si02 and Al203 content
and low in CaO content. Due to the low content of C02, the compressive strength of
the volcanic ash cement lower than Type G cement, but higher for long term
strength. Other quality tests conducted such as fluid loss, thickening time and free
water content in order to meet API standard for oil well cementing.