CONCRETE IN HOT ENVIRONMENTS - CHAPTER 4

Workability - 'Thi công bê tông có thể được định nghĩa là' tài sản xác định các nỗ lực cần thiết để thao tác một số lượng hỗn hợp bê tông tươi với một tính đồng nhất mất tối thiểu (ASTM C125). Trong định nghĩa này, thuật ngữ "thao tác" có nghĩa là bao gồm tất cả các hoạt động liên quan trong việc xử lý bê tông tươi, cụ thể là, vận chuyển, đặt, nén và cũng có thể, trong một số trường hợp, hoàn thiện. Nói cách khác, thi công là tài sản mà làm cho bê. | Chapter 4 Workability . INTRODUCTION The workability of concrete may be defined as the property determining the effort required to manipulate a freshly mixed quantity of concrete with a minimum loss homogeneity ASTM C125 . In this definition the term manipulate is meant to include all the operations involved in handling the fresh concrete namely transporting placing compacting and also in some cases finishing. In other words workability is that property which makes the fresh concrete easy to handle and compact without an appreciable risk of segregation. The workability may be defined somewhat differently and indeed other definitions have been suggested. Nevertheless and regardless of the exact definition adopted it may be realised that the workability is a composite property and as such cannot be determined quantitatively by a single parameter. In practice however such a determination is required and strictly speaking common test methods slump Vebe apparatus actually determine the consistency or the compactability of the fresh concrete rather than its workability . In practice however workability and consistency are usually not differentiated. Generally the workability is essentially determined by the consistency and cohesiveness of the fresh concrete. That is in order to give the fresh concrete the desired workability both its consistency and cohesiveness must be controlled. The sought-after cohesiveness is attained by proper selection of mix proportions using one of the available mix-design procedures . Copyright 1993 E FN Spon In other words once cohesiveness is attained the workability is further controlled by the consistency alone. This is usually the case and in practice indeed workability is controlled by controlling the consistency of the mix. Hence the sometimes indiscriminate reference to consistency and workability as well as the use of consistency tests such as the slump or the Vebe tests to control workability BS 1881 Parts 102 103 and 104 .

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