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Defects in concrete

Problems and Defects in Hardened Concrete

Defects in concrete can often be related to the lack of durability of the concrete, resulting from the composition of the concrete, poor placement practices, poor Quality Control or the aggressive environment in which it is placed. Cracking, Spalling, Scaling, Honeycombing, Settlement, Alkali Aggregate Reactions, Piping, Loss of binding paste.
Cement Paste

Standard Test for Consistency of Cement Paste by Vicat Apparatus

This test method is used to determine the amount of water required to prepare hydraulic cement pastes with normal consistency, as required for certain standard tests. The percentage amount of water which is required to prepare standard cement paste when vicat plunger penetrate under 10±1mm reading is known as standard consistency or normal consistency
Cement Mortar

Standard Test Method for Air Content of Hydraulic Cement Mortar

Proportion the standard mortar using 350 g cement to 1400 g 20–30 standard sand and sufficient water to give a flow of 871⁄2 6 71⁄2 %. The flow is the resulting increase in average diameter of the mortar mass, as determined with the calipers, measured on at least four diameters at approximately equi-spaced intervals, expressed as a percentage of the original
Fresh Concrete Pouring

Behavior of Fresh Concrete after Placing and Compacting

From placing to final set, concrete is in a plastic, semi-fluid state. Heavier particles (aggregates) have tendency to move down (SEGREGATION) Mix water has a tendency to move up (BLEEDING). A layer of water (~ 2 % or more of total depth of concrete) accumulates on surface, later this water evaporates or re-absorbed into concrete.
Measuring Workability of Concrete

Methods for Measuring Workability of Concrete

Concrete is placed in an upper. Dropped into a lower hopper to bring it to a standard state and then allowed to fall into a standard cylinder. The cylinder and concrete weighed (partially compacted weight). The concrete is fully compacted, extra concrete added and then concrete and cylinder weighed again (fully compacted weight)
Prestressed Concrete

Prestressed Concrete - Definition and Methods of Pre-Stressing

In this method, the prestressing tendons are initially tensioned between fixed abutments and anchored. With the formwork in place, the concrete is cast around the highly stressed steel tendons and cured. When the concrete has reached its required strength, the wires are cut or otherwise released from the abutments. As the highly stressed steel attempts
Roller Compacted Concrete Mix Design

Roller Compacted Concrete Mix Design and Properties

The consolidation by a roller does not require special cements; however, when RCC is to be used in mass concrete, the recommendation of selecting cements with lower heat generation. Mineral admixtures are used extensively in RCC mixtures. The use of large amounts of mineral admixtures reduces both the adiabatic temperature rise of concrete and costs, and
Ready Mix Concrete

Ready Mixed Concrete - Definition and its Types

Ready mixed concrete production is a process, whereby, mixing and transportation of concrete is combining together and the product is delivered to the site, at the right time in the mould straight away. IS-4926, the definition of ready mixed concrete is: “Concrete delivered at site or in to the purchaser’s vehicle in a plastic condition and requiring no further treatment
Properties of Concrete

Properties of Concrete in Hardening Stage

When the concrete is first mixed it is like 'bread dough'. It is soft and can be worked or moulded into different shapes. In this state concrete is called PLASTIC. Concrete is plastic during placing and compaction. The most important properties of plastic concrete are workability and cohesiveness. A worker will sink into plastic concrete. Concrete then begins to stiffen. The
Concrete Doumentary Video

A Documentary Video on Concrete - Science of Concrete

Concrete is a composite material composed of coarse aggregate bonded together with a fluid cement that hardens over time. In its simplest form, concrete is a mixture of paste and aggregates, or rocks. The paste, composed of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates. Through a chemical reaction called hydration, the
Concrete Compression Test

Procedure for Concrete Compression Test

The compression test shows the best possible strength concrete can achieve in perfect conditions. The compression test measures concrete strength in the hardened state. Field concrete samples are prepared, cured and tested according to ASTM standard procedures. Specimens are prepared from concrete taken from different construction sites. Following
Non Destructive Tests of Concrete

Methods for Non Destructive Testing of Concrete

Non destructive testing of concrete can be defined as the test method used to examine the properties of concrete used in the actual structure. These test methods can also be said as in-situ tests or in-place tests. Traditionally these tests are said to be as the non-destructive test although some minor damage to the structure may be involved. An important feature of non
Mass Concrete For Dams

Mass Concrete For Dams - Applications and Problems

Mass concrete can be defined as any large volume of cast-in-place concrete with dimensions large enough to require measures to cope with the generation of heat and attendant volume change to minimize cracking. Like regular concrete, mass concrete too is primarily composed of cement, aggregate, and water. Additionally, it has pozzolans and other admixtures to
Concrete Mix Design

Design of High Strength Concrete Mix

The type of concrete generally with compressive strength of 6000psi (40MPa) or greater is called as HSC. Now what is mix design? Although the American Concrete Institute (ACI) doesn't use the term, preferring mix proportioning. But keeping in view the modern knowledge of concrete (especially in case of high strength concrete), we should improve the term
Lime Concrete

Preparation and Properties of Lime Concrete

A concrete made from a mixture of lime, sand, and gravel is said to be as lime concrete. It was widely used before the lime was replaced by Portland cement. Since long, Lime has been used to make things like plaster and mortar. Lime is usually made by burning of limestone.Chemically; lime itself is calcium oxide (CaO) and is made by roasting calcite

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