Many studies are carried out in this area from early1980’s (Van der Wegen and Bijen, 1985). Most of the preparation methods ofartificial aggregates involve sintering process that in turn creates theproblem of large energy usage. Some of the waste materials used as a sourcematerial for artificial aggregates are mining residues, heavy metal sludge(Su-Chen Huang et al.
, 2007), marine clay (Laursen et al., 2006), palm shell(Okpala et al., 1990; Mannan and Ganapathy, 2002; Payam Shafigh et al., 2011),paper sludge (Chin-Tson Liaw et al., 1998; Ahmadi and Al-Khaja, 2001; Garcia etal., 2008), pet bottles (Yun-Wang Choi et al., 2005), sewage sludge (Cheesemanand Virdi, 2005; Mun, 2007), steel slag (Maslehuddin et al., 2003; George Wang,2010), fly ash (Bijen, 1986; Peter Neumann et al.
, 1991; Gokhan Baykal and AtaGurhan Doven, 2000; Ramamurthy and Harikrishnan, 2006; Manikandan andRamamurthy, 2007, 2008; Niyazi Ugur Kockal and Turan Ozturan, 2010, 2011a,2011b; Ioanna Kourti et al., 2010; Verma et al., 1998), bottom ash (Geetha andRamamurthy, 2010, 2011; Kim and Lee, 2010) Several works are done in fly ashaggregates compared to other artificial aggregates, may be due to itsavailability in large volumes and high quantity of disposal. Coal is used forpower generation and the residues of which is disposed as landfills in nearbyareas (Bijen, 1986; Manikandan and Ramamurthy, 2007).Concretes which manufactured from artificial aggregatewill develop compressive strength of at least 17MPa and normally been used forbuilding and bridge construction (Mindess, 1981). Generally, these aggregatewill be used for low dead weught load support since it is light in weight. Palm oil industries can play a major role in theeconomic development of different tropical countries.
These industries produce alarge amount of solid waste by-products – fibers, nut shells, and empty fruitbunches- during the processing oil-palm fruit for oil extraction. There will beapproximately 20 tonnes of nut shells,7 tonnes of fibers, and 25 tonnes ofempty bunches discharged from the mill for every 100 tonnes of freshfruitbunches processed (Tay, 1995). Palm oil fuel ash is commonly known as POFA,which is about 5% ofsolid waste product, have the potentiality to be used aspozzolanic materials in concrete industry (Sata, 2010).It is the ashes producedfrom fiber and shell of palm oil burning for the generation of energy in palmoil mill.
It is a promising pozzolanic and available material in many parts ofthe world. The by product from palm oil industry such as palm oil residue, palmfiber and shells, when burnt at temperatures of about 800-10000C toproducesteam for electricity generation in biomass thermal power plants are known asPOFA (Tangchirapat,2009). In Thailand, more than 100,000 tons of POFA areproduced annually (Chindaprasirt, 2007), and thisamount increases every yearbecause palm oil is one of the major raw materials used in the production ofbio-diesel. It has recently been accepted as a pozzolanic material in concretedue to its large amounts of silica.The material is similar to other pozzolanicmaterials, such as silica fume and fly ash. However, due to thepozzolanicproperties of POFA, it is not only used as replacement of cement but also usedin making strongand durable concrete (Awal, 1997).
Palm oil fuel ash (POFA) is an agro-waste resultingfrom the combustion of oil palm plant residue in palm oil industry. Malaysia,Indonesia and Thailand are the main producers of palm oil, which is a leadingagricultural cash crop in these tropical countries. After the extraction of oilfrom oil palm fruit, both husks and shells are burnt in boiler to produce steamfor the turbine engine, which generates electricity for use in palm oil mills(Mahlia et al., 2001). After burning, the resulting ash, known as POFA, is generallydisposed of in open fields, thus creating environmental and health problems(Tonnayopas et al.
, 2006). In order to find the solution to these problems,several studies were conducted to examine the feasibility of using POFA inconstruction materials. Starting from 1990, many researchers reported thatproperly processed POFA is adequately reactive and possesses good pozzolanicactivity (Abdullah et al.
, 2006; Sata et al., 2004; Hussin and Awal, 1997), andtherefore can be used successfully as a supplementary cementing material forthe production of concrete. Tay (1990) used unground POFA to partially replaceordinary portland cement (OPC) and showed that unground POFA shall not be usedwith a content higher than 10% of cement by weight due to its low pozzolanicproperty. Hussin and Ishida (1999) used 20 – 40% ground POFA by weight of OPCin concrete. They found that the compressive strength, modulus of elasticity,Poisson’s ratio, shrinkage and creep of concrete were comparable to that of OPCconcrete up to 30% replacement of cement. In addition, Hussin and Awal (1996,1997) had shown that it is possible to use 40% ground POFA without affectingthe concrete strength. It was also shown that the POFA concrete is sufficientlydurable in addition to having a good strength.
According to Sumadi and Hussin(1995), ground POFA can be used up to 20% cement replacement level with adurability factor at least comparable to that of OPC concrete. Ground POFA hadshown good resistance to expansion due to sulfate attack (Awal and Hussin,1997a; Jaturapitakkul et al., 2007) and alkali-silica reaction (Awal andHussin, 1997b). POFA has been used not only in normal concrete but also inspecial concretes such as high-strength, highperformance, and aeratedconcretes.
Sata et al. (2004) made high-strength concrete with POFA and showedthat the concrete containing up to 30% ground POFA provided a highercompressive strength than OPC concrete at later ages. Awal and Hussin (1999)used POFA to produce high-performance concrete with reasonably a gooddurability.
In addition, Abdullah et al. (2006), and Hussin and Abdullah (2009)used ground POFA in aerated concrete. Thus, the published literature shows thatPOFA has a good potential for the production of different types of concrete. Therecent research studies show that POFA can also be used in other constructionmaterials such as bricks and stone mastic asphalt (Ismail et al., 2010;Kamaluddin, 2008; Nasly and Yassin, 2009). Ismail et al.
(2010) produced brickswith satisfactory compressive strength using POFA and paper sludge. Nasly andYassin (2009) mentioned that POFA can be incorporated in interlocking blocksfor use in sustainable housing. Besides, Kamaluddin (2008) used POFA as afiller material to produce stone mastic asphalt with enhanced stability,stiffness, and tensile strength.