In spite of the best precautions taken to store cement, it is found that its strength is reduced due to long storage. Efforts should, therefore, be made to store the cement for lesser time. The strength of the cement, which has been stored for a long time, should be checked before it is used on … Read more
Objective To determine the workability of freshly mixed concrete by using of Vee – Bee consistometer apparatus. Scope and Significance The workability of fresh concrete is a composite property, which includes the diverse requirements of stability, mobility, compactability, placeability and finishability. There are different methods for measuring the workability. Each of them measures only a … Read more
The following points should be remembered before proportioning a concrete mix a per IS-10262-2009. This method of concrete mix proportioning is applicable only for ordinary and standard concrete grades. The air content in concrete is considered as nil. The proportioning is carried out to achieve specified characteristic compressive strength at specified age, workability of fresh … Read more
Bleeding cannot be completely prevented as it is an inherent property of concrete. But it can be minimized if following precautions are taken. By proper proportioning of concrete mix. By mixing the concrete uniformly and completely. By using finely divided pozzolanic materials ( as it creates a longer path for the water to traverse and … Read more
What is Laitance? Laitance is caused by bleeding of concrete. In case of bleeding, only water accumulates at the top of the surface, but in case of laitance, along with water certain quantity of cement also comes to the surface, forming a thin layer of cement paste at the surface. This formation of cement paste … Read more
Bleeding of Concrete Bleeding is one form of segregation, where water comes out to the surface of the concrete, being lowest specific gravity among all the ingredients of concrete. Bleeding can be easily identified in the field by the appearance of a thin layer of water in the top surface of freshly mixed concrete. Effects … Read more
The danger caused by segregation is difficult to repair and very costly. Therefore necessary precautions should be taken to avoid segregation. Precautions to Take The concrete mix should be properly designed with optimum quantity of water to make a cohesive mix. Such concrete will not exhibit any tendency for segregation. Field quality control must be … Read more
Following are the effects on concrete due to segregation. Effects on Concrete A segregated concrete is very weak in strength Due to segregation after placing, the concrete in the lower part of a pour of any significant depth can be stronger than that in the upper part. Segregated concrete does not give a homogeneous mass … Read more
Segregation usually implies separation of: (a) coarse aggregate from fine aggregate, (b) paste from coarse aggregate, or water from the mix and the ingredients of the fresh concrete no longer remain uniformly distributed. The points given below are the primary causes of segregation of concrete in field. Causes of Segregation on Site Poorly graded aggregate … Read more
What is Segregation? Wordweb dictionary defines the term “segregation” as – Separation or isolation of one thing from another and place in a group apart from others. In concrete technology, segregation can be of two types. Firstly the coarse aggregate may separate from the main mass of concrete in its plastic state. Secondly, the grout … Read more