The production of neem products from neem tree generates large quantity of waste annually. This paper is aimed to examine the effect of Neem Seed Husk Ash (NSHA) on workability of concrete. Neem seed husk was obtained from Bishop Smith Memorial College, Ilorin, sun – dried for 3 days and then calcinated at 650^o C. The calcinated neem seed husk was ground and sieved using 200 μm sieve to obtain NSHA. Pozzolanicity test was conducted on NSHA to determine its chemical composition. Concrete was produced with 5, 10, 15, 20 and 25% by weight of NSHA substitution for cement. Workability tests (slump and compacting factor) were performed for each percentage replacement. Compressive and tensile strength tests were conducted on 150 mm cubes and 150 x 150 x 760 mm beams, respectively at ages 3, 7, 14, 21, 28, 56, 90 and 180 days. All tests carried out were in accordance with British Standard codes. The chemical composition of NSHA showed that the combination of Al₂O₃, SiO₂ and Fe₂O₃ was 75.35%. The slump and compacting factors of NSHA concrete ranged from 5.50 mm to 10.00 mm and 0.91 to 0.95, respectively.

Key words: Neem, Pozzolanicity, Workability, Slump, Compacting factor.