Use of palm oil fuel ash as a supplementary cementitious material for producing high-strength concrete

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Abstract

The objective of this study is to investigate the use of ground palm oil fuel ash with high fineness (GPA) as a pozzolanic material to produce high-strength concrete. Samples were made by replacing Type I Portland cement with various proportions of GPA. Properties such as the compressive strength, drying shrinkage, water permeability, and sulfate resistance, were then investigated. After aging for 28 days, the compressive strengths of these concrete samples were found to be in the range of 59.5–64.3 MPa. At 90-day the compressive strength of concrete containing GPA 20% was as high as 70 MPa. The drying shrinkage and water permeability were lower than those of high-strength concrete made from Type I Portland cement. When the concrete samples were immersed in a 10% MgSO4 solution for 180 days, the sulfate resistance in terms of the expansion and loss of compressive strength was improved. The results indicated that GPA is a reactive pozzolanic material and can be used as a supplementary cementitious material for producing high-strength concrete.

Introduction

High-strength concrete is widely used in civil engineering projects throughout the world because most of its mechanical and durability properties are better than those of normal-strength concrete. In addition to the advantageous properties, using high-strength concrete enables reduction of the size of structural members that are essential in high-rise buildings, such as beams and columns. The use of lighter and slender structures reduces the volume of concrete needed in building structures, resulting in cost savings for construction projects.

According to ACI 363 [1], concrete with a 28-day compressive strength higher than 41 MPa is considered high-strength concrete. Typically, high-strength concrete has a low water to binder ratio of 0.20–0.45 with high binder content [2] and superplasticizer is used to increase its workability. In addition, supplementary cementing materials, such as fly ash and silica fume, are widely used as pozzolanic materials in high-strength concrete. They are normally used to create extra strength by pozzolanic reactions, to reduce the permeability, and to improve the durability of the concrete.

Palm oil fuel ash (POFA) is one of agro-waste ash from which palm oil residue, such as palm fiber and shells, are burnt at temperatures of about 800–1000 °C to produce steam for electricity generation in biomass thermal power plants. In Thailand, more than 100,000 tons of POFA are produced annually, and this amount increases every year because palm oil is one of the major raw materials used in the production of bio-diesel. POFA contains large amounts of silica and has recently been accepted as a pozzolanic material in concrete [3], [4]. However, the utilization of POFA as a pozzolanic material to partially replace Portland cement has not been investigated extensively, especially in high-strength concrete.

In this study, an effort was made to evaluate the usefulness of POFA as a cement replacement for producing high-strength concrete. The effects of POFA on the compressive strength and durability of high-strength concrete in terms of drying shrinkage, water permeability, and sulfate resistance were investigated. If POFA can be used as a pozzolanic material in producing high-strength concrete and can improve its durability, it will lead to reductions in cement usage and the cost of high-strength concrete and will also be beneficial for the environment by reducing the volume of waste disposed of in landfills. Furthermore, using POFA as a replacement for cement will also encourage researchers to investigate the use of other by-products from biomass power plants, which will ultimately lead to their development as a more environmentally friendly way of generating energy.

Section snippets

Cement

The physical properties and chemical compositions of the Type I and Type V Portland cement used in this study are shown in Table 1, Table 2, respectively.

Aggregate

Local river sand with a fineness modulus of 2.68, specific gravity of 2.60, and water absorption of 0.63% was used as a fine aggregate. Crushed limestone with a maximum size of 12.5 mm, specific gravity of 2.72, and water absorption of 0.80% was used as coarse aggregate.

Palm oil fuel ash

Palm oil fuel ash (POFA) used in this study was collected from a biomass

Compressive strength

The results of compressive strength and normalized compressive strength of concretes containing GPA with high fineness are shown in Table 4. Normalized compressive strength is defined as the ratio (in percentage) between the compressive strength of concrete containing GPA and the compressive strength of CTI concrete. For concrete mixtures containing various proportions of GPA, the compressive strength at 28 days was more than 55.0 MPa, with GPA30 and GPA20 concrete samples showing values of 58.8

Conclusions

Based on the results of this study, the following conclusions can be made.

  • 1.

    Ground POFA with high fineness (GPA) can be used as a cement replacement to produce high-strength concrete with a compressive strength as high as 70 MPa at 90 days when used to replace Type I Portland cement at 20% by weight of binder. At the age of 28 days, concretes containing 10–30% GPA exhibited higher compressive strength than concrete made from Type I Portland cement.

  • 2.

    Use of GPA in high-strength concrete resulted in a

Acknowledgments

The authors are grateful for financial supports from the Thailand Research Fund (TRF) under the TRF Senior Research Scholar, Contract No. RTA5080020, the Royal Golden Jubilee Ph.D. Program, and the Commission on Higher Education, Ministry of Education, Thailand.

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