Leonardo Electronic Journal of Practices and Technologies ISSN 1583-1078 Issue 17, July-December 2010 p. 59-68 http://lejpt.academicdirect.org © 2010 by the authors; licensee AcademicDirect. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license: http://creativecommons.org/licenses/by/3.0/ . 59 [[[[ Effect of Hand Mixing on the Compressive Strength of Concrete James Isiwu AGUWA Department of Civil Engineering, Federal University of Technology, Minna, Nigeria E-mail: jiaguwa@yahoo.com Received: 13 November 2010 / Accepted: 10 December 2010 / Published: 24 December 2010 Abstract This paper presents the effect of hand mixing on the compressive strength of concrete. Before designing the concrete mix, sieve analysis of sharp sand and chippings was carried out and their fineness moduli were determined. Also the dry weight of chippings and the specific gravities of both sand and chippings were determined. A designed concrete mix of 1:2:4 was used and the number of turnings of the mixture over from one end to another by hand mixing was varying from one time up to and including seven times. The strengths were measured at the curing ages of 7, 14, 21 and 28 days respectively using 150mm concrete cubes cast, cured and crushed. The results revealed that the compressive strengths of concrete cubes appreciably increased with increase in number of turnings from one to four times but remained almost constant beyond four times of turning for all the ages tested. For example, at 1, 2, and 3 times turning; the compressive strengths at 28 days were 4.67, 13.37 and 20.28N/mm 2 respectively while at 4, 5 and 6 times turning; the compressive strengths at 28 days were 21.15, 21.34 and 21.69N/mm 2 . From the data, adequate strengths were not developed at turnings below three times of hand mixing, concluding that a minimum of three times turning is required to produce concrete with satisfactory strength. Keywords Compressive; Concrete; Curing; Hand-Mixing; Strength; Turning