Abstract
The behaviour of concrete, whether fresh or hardened, depends basically on the behaviour of its components and the relationship between them, therefore, obtaining a concrete with certain properties depends fundamentally on the concrete mix design. Concrete mix design generally includes two main steps: 1-Selection of the main components suitable for the concrete (cement, aggregate, water, and additives); 2-Determination of more economical mix ratios to fulfil the workability, strength and efficiency requirements. Currently, there are many international methods locally approved for mix designs. They are all related to each other, they give relatively the same quantities of the mix components and they are all capable of providing a good concrete mix. It is important to consider that these methods give approximate quantities which should be checked by experimental mixes in order to obtain results suitable for the requirements of the local environment and local materials. The ACI and BS methods are the most commonly used. Both of these methods depend on graphs and standard tables derived from previous research experience and actual concrete production as well as studies of the properties of the materials used. This paper illustrates a new approach for concrete mix design named as: “Double Coating Method”, which is currently used in some research centers in the republic of Poland and was recently applied in the laboratories of the Civil Engineering Departments in the Universities of Tripoli and Benghazi in Libya. This paper describes experiment in which 24 mixtures were used to assess the usefulness of this technique for problem of proportioning concrete mixtures in general. arabic 5 English 37