The International Journal of Engineering and Science (IJES) || Volume || 10 || Issue || 2 || Series I || Pages || PP 24-29 || 2021 || ISSN (e): 2319-1813 ISSN (p): 20-24-1805 DOI:10.9790/1813-1002012429 www.theijes.com Page 24 Investigation of Pozzolanic Action of Biomass Ash from Clean Sawdust on Sandcrete Block 1 Nwachukwu, A. N., 2 Ibearugbulem, O. M., 3 Njoku, K. O., 4 Amasiatu, O.S., 5 Israel, V.F. 1,2,3,4,5 Department of Civil Engineering, Federal University of Technology, Owerri, Nigeria -------------------------------------------------------------- ABSTRACT------------------------------------------------------------------- This paper presents the investigation of pozzolanic action of ash from clean sawdust biomass. Sawdust biomass was obtained from timber market Owerri. It was cleaned by removing the earth and other impurities. After cleaning the biomass, it was incinerated to ashes inside a clean metallic drum. The ash deposit was collected and sieved using 425 microns sieve to remove coal and unburnt sawdust particles. When this was done, the ash was subjected to physical and chemical tests. Sandcrete blocks were made using sand, cement, water and the ash obtained herein. The ash was used to replace the cement at 5%, 10%, 15%, 20% and 25% levels. A constant water-cement ratio (by mass) of 0.6 was used. Three hollow blocks of 450 x 225 x 225 mm was molded for each mix ratio. The produced sandcrete blocks were cured for 3, 7, 14, 21, 28, 56 and 90 days. Curing was achieved by covering the blocks with a cloth (something like blanket), which was kept moist throughout the curing period.After curing the blocks were allowed to surface dry and tested for saturated surface dry (SSD) density and compressive strength in conformity with BS 1881: Part 115 (1986). From the obtained results, the specific gravity, loose bulk density (kg/m3) and fineness modulus are 2.15, 815 and 1.85 respectively. The pozzolanic oxides composition are 0.47, 0.23 and 0.23 for SiO2, Al2O3 and Fe2O3 respectively with CaO having the highest composition of 51.78 and loss on ignition of 16. Other major oxide compositions are 12.72 and 9.23 for K2O and MgO respectively. Compressive strength of sandcrete blocks increases linearly with increase in cement content and with increase in saturated surface dry density. It reduces linearly with increase in ash from clean sawdust biomass. The compressive strength also increases parabolic with curing age and this increase appears to flatten as curing age reaches 90 days and more. For all curing ages, the compressive strength is highest for sandcrete blocks with zero percent replacement with the ash from clean sawdust biomass. The percentage increases in compressive strength when compared with 7 days compressive strength are 16.67%, 24.24%, 43.95, 54.55% and 57.62% for the ages of 21 days, 28 days, 56 days and 90 days respectively. The highest recorded compressive strength is 2.95 MPa from 90 days of curing and zero percent replacement of cement. -------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 22-01-2021 Date of Acceptance: 06-02-2021 -------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION The major source of silicon to wood is the bark and natural holes in the trunk. Termites and other organisms carry soil mineral from the earth to the wood through the bark and these holes. Soil can also contaminate wood during harvest (Kofman, 2012).According to him, wood ash is composed of macronutrient, micronutrient and some heavy metals the tree took during its lifetime. These are phosphorus, potassium, calcium and magnesium, iron, sodium, manganese and copper, zinc, lead, cobalt and cadmium. Other nutrients taking up by tree but vented in the flue gasses during ashing include sulphur and nitrogen. The pH of wood ash is about 12. Ash content of the wood depends on the mineral it deposits after combustion. This generally will be high when the wood is contaminated with soil before combustion. Wood ashes with high silica content due to contamination with soil are predominant obtained from Hogfue (wood that has been crushed with a blunt instrument, unlike wood chip, that has been cut with sharp tools) from garden waste, stumps and roots. Bark of wood,Herbaceous wood,stumps and root(Kofman, 2012,Pitman, 2012 and Kang et al., 2014). The implication of this is that pure wood does not have silicon. Hence, any silica content of wood is due to secondary introduction (impurity or contamination). Calcium is the major mineral element in wood ash (Muse and Mitchell, 1995, Hakkila, 1989, Campbell, 1990 and Zajac, 2018). On Table 2 of Pitman (2012) the summation of the major elements (Calcium + Potassium + Magnesium) is more than 65% of the dry mass of the wood ash for different types of wood (both Conifers and Broadleaves).Misra et al. (1993) is in agreement with Pitman. According to them the major constituents of wood ash are calcium, potassium and magnesium and the very minor constituents (seen in traces) include iron, aluminum, copper, zinc, sodium, silicon and boron. However, manganese, sulfur and phosphorous are present in the neighborhood of 1% (See their Table 4).In another work, Fusadeet al. (2019)