Concrete Placement Checklist
The cement must be as per the approved mix design and fresh. The cement must be stored properly inside a closed container, room or must be stored on an elevated flat form and covered properly with tarpaulin.
Differences between Lab Concrete and Site Concrete
The concrete that is prepared at the site (for pouring) is not exactly the same that is made in the laboratory with the same ratio, this difference is due to low quality control measures and insufficient monitoring system. The term ‘labcrete’ is often used to define concrete or mortar that is made and tested under strict laboratory conditions,
Why to Study the Strength of Concrete
Strength is the ability of a material to resist an induced amount of stress that would make it fail, generally expressed in pounds per square inch (psi) or megapascals (MPa). The most analyzed and in a sense the most important mechanical property of concrete is its compressive strength.
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.
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
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
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.
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 - 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 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 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 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
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
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
