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Research Article
ScienceAsia 32 (2006): 063-069 |doi: 10.2306/scienceasia1513-1874.2006.32.063
Effect of Finenesses of Fly Ash on Expansion
of Mortars in Magnesium Sulfate
Theerawat Sinsiri,a* Pichaya Teeramit,b Chai Jaturapitakkulb and Kraiwood Kiattikomolb
ABSTRACT: This paper presents the effect of fineness of fly ash on expansion of fly ash-cement mortar in
magnesium sulfate solution. Fly ash from the Mae Moh power plant in Thailand was classified in to three
different levels of fineness of Blaine of 3215, 4440 and 5890 cm2/g with a median particle size of 25.57, 7.69,
and 4.81 microns, respectively. Fly ash at each level of fineness was used to replace Portland cement type I
and type V at percentages of 0, 20, 30, and 40 by weight of the cementitious material, to cast mortar bars of
2.5x2.5x30 cm3. Expansion of the fly ash-cement mortar bars, which were immersed in 5% by weight of
magnesium sulfate solution, were measured at the age of 1 to 540 days. The results showed that the
replacement of Portland cement type I and type V by fly ash reduced expansion of the mortar bars. When the
same level of fineness and same percent of replacement of fly ash were used in the mortar bars, the replacement
of Portland cement type V by fly ash produced less expansion than that of Portland cement type I. For the
same level of fineness of fly ash, the mortar bars made with 40% fly ash replacement had less expansion than
those made with 20 and 30% replacement. The mortar bars with 20-25% replacement of fine fly ash (Blaine
fineness of 4440 or 5890 cm2/g) and the mortar bars with 40% replacement of original fly ash (Blain fineness
of 3125 cm2/g) had the same expansion. The smaller particle size of fly ash not only reduced expansion of the
fly ash-mortar bars but also produced higher strength activity index of mortar than the bigger particle size
of fly ash. Therefore, very fine fly ash could be used effectively for reducing the expansion and improving
sulfate resistance of mortar.
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a Department of Civil Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000,
Thailand.
b Department of Civil Engineering, King Mongkut’s University of Technology Thonburi, Bangkok 10140,
Thailand.
* Corresponding author, E-mail: sinsiri@sut.ac.th
Received 19 Apr 2005, Accepted 23 Sep 2005
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