Pozzolanic activity and characteristic of “Saw Dust Ash (SDA)” as partial replacement of cement for concrete production.
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Date
2019-10
Authors
AFOLABI, O A
Journal Title
Journal ISSN
Volume Title
Publisher
FEIC 2019
Abstract
Concrete is an important construction material, and presently the production cost is becoming unreasonably higher and increasing exorbitantly, which was believed to be the result of high price of cement. These suggested the search for possible alternatives, which could serve as cementitious binder effectively and comparatively with Portland cement. Research studies on the use of pozzolans, provides the opportunity to investigate saw dust ash (SDA) as a pozzolan for possible use in concrete production as alternate material with cement. The objective of this study includes, the determination of binding strength and capacity of SDA, and properties of concrete produced with SDA as partial replacement of cement in concrete, using the standard test procedures as indicated in “BS 1881 – Testing Concrete”, for laboratory investigations, report and analysis of result. Preliminary study on constituent materials to ascertain their quality and characteristic properties were implemented, which includes, dry and bulk density, sieve analysis, aggregate crushing value test, and chemical properties of SDA and OPC were also determined to ensure the concrete produced are of adequate engineering characteristic properties. The investigation on binding capacity and cementitious activity index was done using the setting times method for cement paste, and the observed results, gave a mean time different between the initial and final setting time as 42mins, 58mins, and 78mins, for the 0%, 7.5%, and 15% replacement level. Concrete specimens were, prepared using a mix-proportion of 1:2:4, and with varying percentage replacement of SDA as, 0, 7.5%, and 15%, by weight of cement, for the workability and strength evaluation. The workability test was implemented to determine, the consistency, homogeneity, and compatibility of fresh concrete, since this phase/stage of concrete, has direct influence on property of hardened concrete, when not adequately prepared. The result of the workability indicated a low slump value, (between 20-40mm), which was specified according to the BS code as 0.85 compacting factor, an indication that describes inadequate fluidity. Specimen concrete cubes (150x150x150mm), were cast for the compression test. They were cured within the laboratory environmental condition with portable water before testing at 3, 7, 14, 21, and 28 days, and the observed results were used for the comparison and analysis of pozzolanic activity and performance of SDA with ordinary Portland cement concrete. Similarly, 9 Nos Concrete beams were prepared and tested for flexural behavior at 28 days. The observed flexural strength value are 6.83N/mm2, 6.44N/mm2, and 5.88N/mm2, for 0, 7.5 & and 15% replacement of SDA, this indicated a reduction with increase in SDA content. Similarly, the failure moment gave a very low magnitude compared to the moment of resistance for concrete beam-section, thereby showing that concrete is weak in tension. In conclusion, the strength activity index were found to be 100%, 83.6%, and 73.4% for the 0, 7.5% and 15% SDA replacement level, which expresses comparable performance and binding capacity of SDA in concrete, and also that the replacement up to 15% SDA is recommended for concrete construction work, where low strength is required.
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Keywords
Pozzolans cementitous-paste concrete mix-design setting times Concrete properties
Citation
AFOLABI O A