Durability Characteristics of Self-Compacting Concrete Incorporating Corn Cob Ash
Egbe-Ngu Ntui Ogork 1, Abdulkarim Muhammad Auwal 2
1,2 Department of Civil Engineering,
Bayero University, Kano
Email: egbenguogork@yahoo.com1, abuiyal1@gmail.com2
ABSTRACT
This paper assesses the effects of corn-cob ash (CCA) on the durability of self compacting concrete (SCC). The CCA used was obtained by controlled burning of corn cob to ash in a kiln to a temperature of 600 oC for two hours, and after allowing cooling, sieved through sieve 75 µm and characterized. The effects of CCA on durability of SCC grade 35 were investigated at replacement levels of 0, 5, 10, 15 and 20 %, respectively by weight of cement. A total of sixty number 150 mm x 150 mm x 150 mm cubes of SCC-CCA were tested for compressive strength at 3, 7, 28 and 56 days of curing in accordance with standard procedure. Crushed samples of the cubes of SCC from the compressive strength test at 28 days curing for the five mixes were weighed and exposed in 5 % concentration of sulphuric acid (H2SO4) solution and weight retained recorded at 7 days interval until the 28th day, to determine the resistance of SCC-CCA to sulphuric acid aggression. Also, fifteen number 100 mm x 100 mm x 100 mm cubes of SCC-CCA were tested for water absorption at 28 days curing. The results showed that the CCA has a combined SiO2, Al2O3 and Fe2O3 content of 71.32%, which can be classified as class F pozzolana. The compressive strength of SCC increased with increased in curing age and decreased with increase in CCA content. The 56 days compressive strength of the CCA-SCC ranged from 30.7 N/mm2 to 52.1 N/mm2, and up to 15 % CCA is recommended as partial substitute of cement for production of SCC. CCA decreased the resistance of SCC to sulphuric acid attack compared with control samples (6.27 to 11.29 % reduction) and also increased the water absorption of SCC.
Key words: Corn cob ash, Self compacting concrete, Sulphuric acid attack, Water absorption
