Etymology[ edit ] The word concrete comes from the Latin word "concretus" meaning compact or condensed the perfect passive participle of "concrescere", from "con-" together and "crescere" to grow. Prehistory[ edit ] Small-scale production of concrete-like materials dates to BC, pioneered by the Nabataea traders or Bedouinswho occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan.
Materials Engineer, Roorkee Concrete Strength Cement like water, aggregates and some times admixtures is one of the ingredient of concrete. The mixing of these materials in specified proportions produces concrete.
Accordingly cement alone is not a building material, it is the concrete which is a building material. For a given cement and acceptable aggregates, the strength that may be developed by a workable, properly placed mixture of cement, aggregates, and water under same mixing, curing and testing conditions is influenced by the: Strength of concrete is directly related to the structure of the hydrated cement paste.
Air in concrete produces voids.
Excess of water in concrete evaporate leave the voids in the concrete. As the porosity increases, the compressive strength of the concrete decreases. The variation in strength of cement is due largely to the lack of uniformity in the raw materials used in its manufacture, not only between different source of supply, but also with in a quarry.
Further, differences in details of the process of manufacture and above all, the variation in the ash content of coal used to fire the kilin, contribute to the variation in the properties of commercial cements.
This is not to deny that the modern manufacturing of cement is a highly sophisticated process. It was found difficulty in obtaining high strength concrete with this cement.
The consumer has been normally finding it difficult to get consistent and ensured supply of high strength cement for prestressed concrete and certain items of precast concrete.
Now, the varieties of cement manufactured in India are: OPC Grade almost vanished from Indian market 2. Sulphate Resistance Cement SRC Test results of different brand of cement minimum to maximum compressive strength are given in the table Due to variation of cement strength, the concrete made from these cement will also have variable strength.
It is often observed that cement bags marked as OPC Grade may really be containing cement of much higher grade. Where as on bags it is marked as 43 MPa or 53 MPa. Site cement samples should be tested for its actual strength and other properties. There are instances where higher grade cement is being used even for low strength concrete, as mortar or even for plastering.
In low grade OPC, the gain in strength will continue beyond 28th day. Due to early strength gain of higher grade of OPC the concrete strength do not increase much beyond 28th day.
The heat of hydration of higher grade OPC being higher, the chances of micro-cracking of concrete is much greater.In the early s, experts predicted that the practical limit of ready-mixed concrete would be unlikely to exceed a compressive strength . Two buildings in Seattle, Washington, contain concrete with a compressive strength of 19, psi.
The primary difference between high-strength concrete and normal-strength concrete relates to the compressive strength that refers to the maximum resistance of a concrete sample to applied pressure. Compressive Strength of Cylindrical Concrete Specimens.
A test result is the average of at least two standard-cured strength specimens made from the same concrete sample and tested at the same age. In most cases strength requirements for concrete are at an age of 28 days.
Design engineers us the specified strength ƒ´ c to design structural elements. The ultimate strength of concrete is influenced by the water-cementitious ratio (w/cm), the design constituents, and the mixing, placement and curing methods employed. All things being equal, concrete with a lower water-cement (cementitious) ratio makes a stronger concrete than that with a higher ratio.
Concrete has relatively high compressive strength, but significantly lower tensile leslutinsduphoenix.com a result, [further explanation needed] without compensating, concrete would almost always fail from tensile stresses – even when loaded in compression.
The practical implication of this is that concrete elements subjected to tensile stresses must be .
Properly graded sand and gravel blended with portland cement for use as in general concrete applications. Use for: sidewalks, driveways, setting posts, footings, floors and curbs.
Reaches psi in 28 days. Designed for pouring concrete 2-in thick or more and building or repairing anything out of.