الفهرس 
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Abstract
Cement paste is a compound of water and cement only, water as a liquid is homogeneous and its flow is described as a laminar flow or a newtonian flow which means that to desribe its flow behavior, only one parameter needs to be measured.
To measure this parameter which expresses the flow behavior of such materials, it is required to test the material under one rate of shear or under on set of shearing conditions.
When cement grains are added to water, the resulting materials will have a different flow behavior than that of water, because cement paste which is considered as a concentrated suspension exhibits a resistance to flow and dose not flow at all till a certain value of an increasing stress affects on it. This value of shear stress called the yield point or the yield stress. So, to describe or identify the flow behavior of concentrated suspension like cement paste, two parameters need to be measured. Th measure thses two different parameters, the material should be tested at least two different rates of shear or under two diiferent sets of shearing conditions. Mnay researcher tried to develop instruments like viscometers and rheometers to measure the rheological parameters which describe the flow behaviour of cement paste, but each type of these instruments has special conditions, circumstances, and requirements of uses. Also the advantage of using rheometers or viscometers is that, it is very expensive to use 4000$ are not available at most of construction sites, and it is difficult to use outside the laboratory. Cement paste is considered the main constituent of fresh concrete that it governs flow behavior. Any change in rheology of fresh cement paste will affect the rheology of fresh cnocrete. This oushed many researchers to study the flow behaviour of cement paster and to express by certain models the flow behviour of fresh concrete. Therefore, we aim in this research to find out a simple testing method to measure or identify the consistency of fresh concrete, where addition of super plasticizer to fresh concrete improves the workability of concrete at low water ratios, but this workability is sometimes lost rapidly in the first hour after contact between cement and water. The effect od addition of a chemical admixture on the time of its addition during the batching and mixing sequence.
When a type of chemical admixture is selected to give certain properties to freshly mixed concrete, some tests should be performed to assure that these peopertise are really obtained. Therefore, it is necessary to find out a simple method of testing such materials to give an indication on their rheological propertise at site before performing the standard tests as mentioned at ASTM 494.
In this study we used a new sample technique based on the penetration of a falling needle made of plastic material with a cross section of 3mm diameter, 11 cm length and constant weight of 2.0gm. The needle falls from constant height in all tests and the penetration depth is measured at difficult circumstances of testing. Similar techniques such as viacat test and penetration depth have been adopted by previous researches, Assem used the penetration depth technique with a different way of testing rather than the method mentioned above to study the consistency of high alumina cement HAC.