Recyclable Materials in Concrete by Using Palm Oil Fuel Ash and Brick (Research Paper Sample)

Recyclable Materials in Concrete by Using Palm Oil Fuel Ash and Brick
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Chapter 2: Literature Review
2.1 Introduction
This chapter explores previous studies that investigated the use of palm oil fly ash as a replacement of cement in terms of compressive strength, properties and application. Additionally, the review will focus on brick as a replacement of coarse aggregate based on properties and performance. Concrete as a human-made material, is extensively utilized building material within the construction industry. It features a rationally selected mixture of binding materials including water, coarse and well graded fine aggregates, and cement. Concrete possesses a high compressive strength, low maintenance, durability, and built-in-fire resistance. However, concrete can be considered an inherently shiny (brittle) material with low tensile strength compared to the compressive strength, thus require significant reinforcement.
According to Ahmad et al., (2008) one potential recycle material from the palm oil industry is palm oil fuel ash which has siliceous compositions and is reacted as pozzolans to generate a denser and stronger concrete. There are numerous experimental works undertaken by introducing recycled components such as palm oil fuel ash (POFA) as a cement substitute with various percentages to enhance concrete properties. Through research efforts and public concerns, the waste components have the potential of being used as construction materials to substitute traditional Ordinary Portland cement (OPC) (Ahmad et al., 2008).
2.2 Origin of POFA
Palm oil fuel ash is a by-product generated within palm oil mill. After the extraction of palm oil from the palm oil fruit, the palm oil shell and palm oil husk are burned in form of fuel within the palm oil mill boiler. Generally, after burning around 5% palm oil fuel ash (POFA) by weight containing solid wastes is generated (Sata et al., 2004). In some instances, the ash generated differs in color tone from darker shade to whitish grey based upon the content of carbon within it. Simply put, the physical properties of POFA are significantly determined by the operating system within the palm oil mill.
Practically, POFA generated within Malaysian palm oil mills is thrown away without profitable returns (Sumadi & Hussin, 1995). In the 20th or 21st century, POFA remains a nuisance towards the environment and is disposed off without being utilized for other purposes compared to other kinds of palm oil by products. Since Malaysia continues to increase palm oil production, thus huge quantities of ashes would be generated and failure of finding a solution in the use of the by-product would pose serious environmental concerns.
2.3 POFA a New Pozzolanic Material
Malaysia is the leading exporter and producer of palm oil and its related products (Rashid & Rozainee, 1993). The palm shell and fiber acquired as waste products in the industry are used generally as boiler fuel for generating steam for palm extraction and electricity production process. The ash generated by burning palm shell and fiber is regarded as a waste product, and disposing it causes numerous concerns. As a common practice, the ash is thrown into wastelands bordering the mills. However, experimental laboratory studies have indicated that the ash possesses ideal pozzolanic characteristics, which make it possible to replace cement within mortar and cement mixtures. Seemingly, POFA is known with different names such as oil-palm ash (Tay; 1990).
2.4 Chemical Composition of POFA
Both chemical analysis and physical properties showed that POFA can be considered a pozzolanic material (Sumadi & Hussin, 1993). This pozzolanic material may be categorized in Classes C and F as specified within ASTMC618-92a (1994). POFA has moderate silica content while the content of lime is low compared to OPC (Awal & Hussin, 1997). However, POFA’s chemical composition may differ because of the operating system within the palm oil mill.
2.5 Strength and Durability of POFA
Several studies have been undertaken in relation to POFA’s durability and strength, for instance Sata et al., (2004) diligently studied POFA to determine its benefits in concrete technology in terms of enhancing concrete properties such as durability and strength. Abu (1990) the researcher that pioneered POFA research has focused on examining agricultural ash and his findings showed that POFA was a pozzolanic material that could be utilized partially to replace upto 35% of cement within mortar mixes; additionally, the researcher found that POFA exhibited similar strength as that of control mortar. Another study undertaken by Awal & Hussin (1996) found that POFA concrete acquire significant strength when 30% of cement is substituted using palm oil fly ash. The findings revealed that the optimum strength increase took place under a 30% substitution rate; however, additional increments to the ash content led to a gradual decrease in concrete strength. Additionally, the two investigators stated that an increase in POFA fineness increased the strength of concrete compared to coarse ones (Awal & Hussin, 1996).
Brick Waste as Cement and Coarse Aggregate Replacement
Husain et al. (1995) investigated the use of treated or untreated crushed bricks with cement syrup as partial replacement of coarse aggregates. The investigator discovered that the compressive strength of crushed brick concrete ranged from 75% - 80% compared to that for conventional concrete at 4 weeks whereas the splitting tensile strength was higher compared to that of normal concrete, and the elasticity modulus is lower compared to that for normal concrete.
Khalaf and DeVenny (2004) investigated the thermal characteristics of brick aggregate concrete and discovered that brick aggregate concrete had a similar and even better performance compared to coarse aggregate concrete within high temperatures. Debieb and Kenai (2008) indicated that it was possible to generate concrete having crushed bricks (fine and coarse) with properties that resemble those of normal aggregate concrete given that the brick aggregate percentage is restricted to 50% and 25% for the fine and coarse aggregates.
A study by Rashid et al. (2009) to examine characteristics for higher-strength concrete produced using clay brick in place of coarse aggregates discovered that strengthened concrete with an of fcu of 31.0 - 45.5 N/mm2 containing brick aggregates with strength surpassing the uncrushed clay brick is achievable, thus showing that clay brick concrete in terms of compressive strength may be improved through reduction of the ratio of water to cement. Clay bricks are durable and strong construction materials, with ideal characteristics of bearing loads. Many investigations have been undertaken to determine brick absorption, permeable levels, as well as porosity. Additionally, experimental studies have been undertaken to obtain higher-strength concrete with clay brick aggregates. Moreover, study findings reveal that old bricks might be recycled and utilized to replace coarse aggregates within concrete mixes. Kesegic et al.’s (2008) study revealed that recycled clay brick in construction and demolition sites might be used to produce concrete.
Cachim (2009) examined the characteristics of concrete prepared using crushed bricks substituting natural aggregates. Observed results showed that ceramic residuals might be utilized partially for replacing natural aggregates within concrete without reducing concrete characteristics for 15% substitution alongside reductions of up to 20% for 30% substitution.
Mohammad Abdur Rashid et al. (2009) undertook a study to obtain higher strength concrete using crushed brick as aggregates and analyzed the mechanical characteristics. Test results from the study showed that the compressive strength of brick aggregate concrete may be enhanced by reducing the ratio of water to cement and utilizing admixture when required for workability. The cylindrical strength was found to be around 90% of that for cube strength.
Another study by Murdock et al. (1991) revealed that clean broken bricks of high quality may offer satisfactory aggregates, the density and strength of concrete based on the kind of brick; additionally, the study found that allied and engineering bricks when crushed make good concrete with medium strength. Notably, in the use of crushed bricks, it is imperative to remove plaster because if not removed calcium sulphate that is within can delay or prevent setting and trigger short –time disintegration. Bricks with soluble sulphates in the excess of 0.5% ought to be avoided. Brick aggregates ought to undergo saturation prior to use due to its high absorbency (Neville & Brook, 2001). Porous bricks must not be utilized as aggregates to reinforce concrete work due to the possibility of moisture penetration that might cause corrosion to steel reinforcement (Murdock et al., 1991).
Conclusion
The review of the literature focused on the use palm oil fuel ash as a partial replacement of cement in concrete and the use of clay brick as a partial replacement of coarse aggregate in concrete. Based on the findings of previous studies, it can be concluded that POFA was a pozzolanic material that could be utilized partially to replace upto 35% of cement within mortar mixes; additionally, the findings revealed that POFA exhibited similar st...