What is the meaning of the Itz interfacial transition zone in concrete?
This paper describes the so called interfacial transition zone—ITZ—in concrete. This is the region of the cement paste around the aggregate particles, which is perturbed by the presence of the aggregate.
Why is the transition zone called the weakest link in concrete?
Since the transition zone is more porous than the aggregate and bulk hydrated cement paste (HCP), water can more easily flow through transition zone, which results in a high permeability. The transition zone is generally considered the weakest link of the concrete chain.
What is transition zone in concrete technology?
A small region next to the particles of coarse aggregate.
What is concrete interface zone?
In fresh concrete a watercement (W:C) ratio gradient develops around the aggregate particles during casting, resulting in a different microstructure of the surrounding hydrated cement paste. This zone around the aggregate is called the interfacial transition zone (ITZ).
What is Wall effect in Itz?
A key feature of the ITZ is that it often contains a deficit of large cement grains that cannot physically pack close to the aggregate, i.e., the “wall effect” (Scrivener et al., 2004), leading to a higher effective water/binder ratio than in the bulk paste, which induces differences in chemistry and porosity.
Which is the weakest link in the concrete matrix?
Interfacial transition zones (ITZ) in concrete constitute the weakest link in the concrete matrix and significantly affect the properties of concrete.
What is creep in concrete structure?
Creep is indicated when strain in a solid increases with time while the stress producing the strain is kept constant. In more practical terms, creep is the increased strain or deformation of a structural element under a constant load.
How workability of concrete can be improved?
Explanation: Workability of concrete can be improved by more cement and water with proper water cement ratio. Explanation: Workability should be obtained by the use of a well-graded aggregate which has the largest maximum particle size possible.
What is admixture in concrete for?
Concrete admixtures are natural or manufactured chemicals or additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete, such as workability, durability, or early and final strength.
Why is tension brittle in concrete?
Concrete is weak in tension because of the presence of a weak link within the concrete matrix known as the Interfacial Transition Zone of ITZ. Concrete is mainly composed of rock aggregates that are glued together by a cement paste which is a mixture of cement and water.
What are honeycombs in concrete?
What Is It? Honeycomb is a rough and stony surface that appears on concrete when there are air voids between the course and the aggregate. This happens when insufficient fine material gets into the concrete mixture due to poor mixing or incorrect aggregate grading.
What is the permeability of concrete?
Permeability is a measure of the amount of water, air, and other substances that can enter the concrete matrix. Concrete contains pores that can allow these substances to enter or depart.