Concrete Mix Design Using Double Coating Method

Abstract

Considerable study, particularly in the last twenty to thirty years, has led to a much better understanding of the structure and behaviour of concrete.  This has accompanied by an improved and more sophisticated technology and the product now mad, in its variety of forms, is much more capable of satisfying the huge increasing demands required of it.  Because the behaviour of both fresh and hardened concrete is significantly related to their composition it should be possible, at least principle, to choose better ingredients with suitable proportion to gain the required satisfaction.   A good mix design for concrete mixtures is considered as a milestone for the construction of any concrete member or structure meets economical, service and durability requirements, as well as safety and efficiency throughout its life cycle.  Currently, there are many international methods locally approved for mix designs, such as: the ACI  method and the BS method, which are widely used in Libya at research centers, universities, and concrete batch plants as well as pre-cast concrete manufacturing plants (e.g.: pre-stressed concrete beams, concrete columns and slabs, etc.).  These methods depend on certain equations and graphs based on mathematical analysis of results obtained from previous field experience.  Generally speaking, mix design methods give some indication to the designer to validate and adjust them via experimental mixes in the local laboratories in order to check the variables related to the characteristics and properties of the local materials and the surrounding environment conditions.  This paper illustrates the steps used for mix design using the double coating method, which is currently used in some research centres in Poland and was recently applied in the laboratories of the Civil Engineering Department in the University of Tripoli in Libya.  Results obtained by this method using the local materials subject to local environmental conditions are presented and discussed.