Abstract

The behaviour of concrete, whether fresh or har dened, depends basically on the beha viour of its components and the r elationship between them, ther efore, obtaining a concr ete with cer tain pr operties depends fundamentally on the concr ete mix design. Concr ete mix design gener ally includes two main steps: 1-Selection of the main components suitable for the concr ete (cement, aggr egate, water , and additiv es); 2-Determination of mor e economical mix r atios t o fulfil the workability , str ength and efficiency requirements. Curr ently, ther e ar e many international methods locally appr oved for mix designs. The y are all r elated t o each other , the y giv e r elatively the same quantities of the mix components and the y are all capable of pr oviding a good concr ete mix. It is impor tant t o consider that these methods giv e approximate quantities which should be check ed b y experimental mix es in or der t o obtain r esults suitable for the r equirements of the local envir onment and local materials. The A CI and BS methods ar e the most commonly used. Both of these methods depend on gr aphs and standar d tables deriv ed fr om pr evious research experience and actual concr ete pr oduction as well as studies of the pr operties of the materials used. This paper illustr ates a new appr oach for concr ete mix design named as: “Double Coating Method”, which is curr ently used in some r esearch centers in the r epublic of P oland and was r ecently applied in the laboratories of the Civil Engineering Depar tments in the Univ ersities of T ripoli and Benghazi in Lib ya. This paper describes experiment in which 24 mixtur es wer e used t o assess the usefulness of this technique for problem of pr oportioning concr ete mixtur es in gener

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