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
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
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
Effects of Aggregate Properties on Concrete
Variation in the size of Aggregates changes the water demand, cement content, micro-cracking (strength) in concrete. It also effects pumpability, and durability of concrete. Grading of aggregates depends on the proportions of coarse and fine aggregate. If grading of aggregate is varied, it also changes cement paste content (cost economy), workability of the mix,
Video on Methods of Finishing Concrete
The most basic type of concrete finish is a smooth surface created through the use of screeds and trowels. Immediately after concrete has been placed in forms, concrete finishers utilize a screed to level out the concrete surface. Screeds often consist of long pieces of metal or wood that are pulled and pushed across the concrete surface to remove excess
Flexural Strength of Concrete - Applications and Problems
Flexural strength is one measure of the tensile strength of concrete. It is a measure of an un-reinforced concrete beam or slab to resist failure in bending. It is measured by loading 6 x 6 inch (150 x 150-mm) concrete beams with a span length at least three times the depth. The flexural strength is expressed as Modulus of Rupture (MR) in psi (MPa) and is determined
Procedure for Concrete Sample Preparation
Concrete is placed in the molds using a trowel in three layers of approximately equal depth and is remixed in the mixing pan with a shovel to prevent segregation during the molding of specimens. The trowel is moved around the top edge of the mold as the concrete is discharged in order to ensure a symmetrical distribution of the concrete and to minimize
Deterioration of Concrete and Remedial Measures
Calcium silicates can be used to fill the pores and decrease the permeability. This can be done by treating calcium hydroxide with diluted sodium silicate (also known as Water-Glass). Pores can also be filled by treating Calcium Hydroxide with Magnesium Fluosilicate followed by the formation of Colloidal Silicofluoric Gel to withstand acid attack. Allowing the
How to Remove Stains from Concrete
It is always better to remove the contaminant and clean the concrete surface as soon as possible because if it penetrates into the concrete, the removal of stains may be more difficult. To reduce the risk of contaminants penetrating into the concrete and make stain removal easier, a suitable sealer can be applied to the concrete surface when new or after cleaning.
Types and Causes of Cracks in Concrete
One of the major causes of cracks in concrete is contraction and cooling due to heat evolution during the process of hydration which leads the concrete towards the setting. Cracks can appear in the section which is smaller and attached to the larger section due to differential expansion and contraction. The rapid drying usually occurs during hot weather when concrete
Concrete Accelerators - Definition, Examples and Effects
Accelerating Admixture - an admixture that causes an increase in the rate of hydration of the hydraulic cement and thus shortens the time of setting, increases the rate of strength development, or both. Accelerating admixtures are added to concrete either to increase the rate of early strength development or to shorten the time of setting, or both. Chemical
Concrete Basics - Properties, Concepts and Composition
Concrete is made by mixing: Cement, water, course fine aggregates and admixtures (if required). The aim is to mix these materials in measured amounts to make concrete that is easy to: Transport, place, compact, finish and which will set, and harden, to give a strong and durable product. A concrete mix is designed to produce concrete that can be easily placed at the
Properties of Fresh Concrete and Factors Affecting Properties
Fresh concrete is that stage of concrete in which concrete can be moulded and it is in plastic state. This is also called "Green Concrete". Another term used to describe the state of fresh concrete is consistence, which is the ease with which concrete will flow. The transition process of changing of concrete from plastic state to hardened state. Setting of concrete is
Properties of Hardened Concrete
It is mainly due to the binding properties of cement that the ingredients are compacted together. If the paste has higher binding strength, higher will be strength of concrete. It is mainly the aggregate that provide strength to concrete especially coarse aggregates which act just like bones in the body. Rough and angular aggregate provides better bonding and
