Background

dormant period concrete

Effect of superabsorbent polymer on the foam-stability of ...

It can be seen that the dormant period and the main peak appear at approximately 1–2 h, and 9–12 h, separately. The main peak of the foamed concrete decreases slightly with the inclusion of dry SAPs due to the water absorption and storage of SAP in the very early ages.

Hydration of Cement | Heat of Hydration |Stages of ...

This is called as the Dormant Period. The existence of the dormant period allows the concrete to be transported to the construction site and placed and finished in the forms. Stage 3 - Hydration Acceleration: The end of the dormant period shows the beginning of the setting at which time the cement starts to react more rapidly with water.

What is induction or dormant period in hydration of cement ...

Answer (1 of 2): During the hydration of cement heat evolves due to aluminates & sulphates(present as components of cement) this heat can be ceases by added the ...

Retarders for Concrete - Mechanism, Types and Effects on ...

Adding a retarder, dissolved in the mixing water or sprayed on the surface of the concrete, temporarily interrupts the hydration reactions, which creates a longer dormant period. The mechanisms that appear depend on the combination of …

Why Concrete Temperature is Important, Especially During ...

This is the period at which the fresh concrete is being transported and placed since it has not yet hardened and is still workable (plastic and fluid). The length of the dormant period has been shown to vary depending on multiple factors (cement type, admixtures, w/cm). The end of the dormant period is typically characterised by the initial set.

Setting and hardening | SpringerLink

Mixing cement with water produces a plastic workable paste. For some time these characteristics of the paste remain virtually unchanged, and this period of time is known as the 'dormant period'. At a certain stage, however, the paste begins to stiffen to such a degree that, although still soft, it becomes unworkable.

Solved The first few hours after cement and water are ...

The first few hours after cement and water are mixed are called the dormant/induction period (stage II). At the end of the dormant period, the concrete sets. The popular theory to explain the dormant period is called nucleation- control/nucleation-dissolution theory. (a) Briefly describe the nucleation control theory.

How Concrete is Made ( New Research) - Cement Concrete

The existence of the dormant period allows concrete to be transported to the construction site and placed and finished in the forms, the end of the dormant period represents the beginning of setting, at which time the cement again starts to react more rapidly with water as new hydration products are formed.

Cement Hydration - an overview | ScienceDirect Topics

Other explanations of the dormant period are sometimes advanced. In any event, a few hours after rapid hydration recommences, sufficient hydration product is generated to induce setting, marking a conversion from fresh concrete (a dense suspension) to newly-hardened concrete (a porous viscoelastic solid).

CIVL 1101 - Part 4 - Hydration of Portland Cement

Stage 2 - Dormant period - causes cement to remain plastic (2-4 hours). The reaction slows. CH crystallizes from the solution, C-S-H develops on the surface of the C3S and forms a coating. As the thickness increases, the time it takes water to penetrate the coating increases, thus the rate of reaction becomes diffusion controlled.

Plastic Shrinkage Cracking of Self-compacting Concrete ...

The dormant period was prolonged by increasing the w/c ratio, using coarser cement and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure build-up rate and the length of the dormant period. Keywords [en]

How to Design and Select the Right Concrete Crack Repair ...

Typically, cracking caused by concrete drying shrinkage will be active at the beginning but eventually stabilize and become dormant as …

Cement Chemistry - The Concrete Portal

is termed as the 'dormant' or the 'induction' period. This period is followed by the main peak of cement hydration, which is associated with the rapid dissolution of C3S to form CSH and CH, and formation of ettringite (AFt) from C3A. A slowdown of the hydration process beyond the main

Cement hydration

In the aim of interest is the early stage of reaction, after the initial mixing and the first reaction climax and before the concrete starts to harden. This period is so called the dormant period. For the building practice this period plays an important roll, because it controls the time in which the concrete is workable and placeable.

CONSTRUCTION TECHNIQUES, EQUIPMENT AND PRACTICES

dormant period when the concrete is plastic and can be placed. At the end of the dormant period, the hydration rate increases and a lot of calcium silicate hydrate and calcium hydroxide is formed relatively quickly. This corresponds to the setting time of the concrete. Retarding admixtures delay the end of the dormant period and the start of ...

NPCA - National Precast Concrete Association

During the dormant period when the fresh concrete is plastic and able to be handled, prior to initial set, the action of set accelerators can last anywhere from 10 minutes in a hot mix to 2 hours for a cold mix. During the setting period, after initial set but prior to final set, accelerators can provide rapid strengthening for up to 10-12 ...

How to Evaluate and Troubleshoot Concrete Cracks ...

Active cracks should be repaired or sealed with flexible repair materials to accommodate future crack movements. Whereas, dormant cracks can be repaired with either flexible or rigid repair ...

Stages of Hydration

Stages of Hydration For about two to four hours after mixing, there is a dormant period, during which these events occur: • The C-A-S – -H is controlling aluminate* reactions. Little heat is generated, and little physical change occurs in the concrete. from dissolving The concrete is plastic. • During dormancy, as silicates (C 3 S and C 2

Concrete Placements Exposed to Rain

dormancy period and impact the slab's finish. However, the dormancy period typically extends several hours, allowing time for the rain to stop and finishers to remove excess water prior to finishing. Covering the slab may not be the best option. In cases of intense rain or on sloped surfaces, covering the slab with

Study of aggregate dormancy and its effects on the ...

Keywords: aggregate; aggregate dormancy; building; concrete; compressive strength 1. Introduction According to the American English Dictionary (AED), dormancy is defined as a state of quiet-ness or inactivity, hence, aggregate dormancy is defined in this study as a period of inactivity of aggregates before utilization in construction works.

What is Cement Hydration? - Maturix Concrete Monitoring

Phase 2: Dormancy. A result of the reaction described in phase 1 is a surface coating of the cement particles. This coating keeps increases, but also slows down the reaction (hydration) as the access to H2O isn't as good as when the concrete was mixed. ... The length of this period depends on each individual concrete mix and can, therefore ...

Stages of Hydration

For about two to four hours after mixing, there is a dormant period, during which these events occur: • The C-A-S –-H is controlling aluminate* reactions. Little heat is generated, and little physical change occurs in the concrete. from dissolving The concrete is plastic. • During dormancy, as silicates (C 3 S and C 2 S) slowly dissolve,

What Is Concrete Setting? - Maturix Smart Monitoring of ...

The initial setting time of concrete, indicated in the graph above, occurs when the reaction starts to gain speed and the heat emission increases at the end of the dormancy period. During the third phase, the concrete starts gaining stiffness quickly and heat is released due to the chemical reactions. A few hours after the beginning of phase 3 ...

cement - The major cements: composition and properties ...

Following the dormant period (which can last several hours), the cement begins to harden, as CH and C–S–H are produced. This is the cementitious material that binds cement and concrete together. As hydration proceeds, water and cement are continuously consumed.

(PDF) On the Origin of the Dormant Period of Cement Hydration

3. S, a dormant period occurs, it is th e case for gluconate addition. During hydration a. complex calcium-gluconate adsorbs on first C-S-H nuclei and prevents them from growing. - …

What is hydration of cement and heat of hydration - Civil Sir

2) dormant phase ( zone 2):- it is known as dormancy period of heat of hydration in which the evolution of heat gradually slow down and dramatically in this stage. And the dormancy period of concrete can last from 1 to 3 hours. during in this period concrete is in plastic stage which allows the concrete to transport and placed without any major ...

Multiscale Numerical Simulation of Expansion Response of ...

Expansion of concrete caused by external sulfate attack (ESA) is a multiscale chemomechanical response, mainly including internal stress evolution at the dormant period and significant cracking expansion for a detrimental duration in hardened cement paste (HCP).

Monitoring Concrete Temperature in Extreme Weather Conditions

During this period fresh concrete is transported and placed. At this time, the concrete has not yet hardened and is still workable (plastic and fluid). The length of the dormant period has been shown to vary depending on multiple factors (cement type, admixtures, w/cm, etc.). The end of the dormant period is typically characterized by the ...

SURFACE RETARDER FOR CONCRETE

This is called the dormant, or induction period (Stage II). The first part of the dormant period, up to perhaps half-way through, corresponds to when concrete can be placed. As the dormant period...

Concrete: Scientific Principles

The dormancy period can last from one to three hours. During this period, the concrete is in a plastic state which allows the concrete to be transported and placed without any major difficulty. This is particularly important for the construction trade …

Dormant Companies and Their Filing Obligations in ...

IRAS' definition of a dormant company. IRAS defines a dormant company as a company which has not conducted any business and has not received any income over a 12-month period. For example, if a company has not conducted any business and has received no income in 2019, IRAS will identify it as a dormant company in Year of Assessment (YA) 2020.

Chemical Reactions in Pozzolanic Concrete

Then for the next 2 to 4 hours follows a relative inactivity, known as induction/dormant period (stage 2). Portland cement concrete remains in the plastic state for several hours due to this prolonged phase of inactivity. At the end of the induction period tricalcium silicate continues to rapidly hydrate and by 4 to 8 hours it has reached its ...

A review on the potential of filamentous fungi for ...

After placing the concrete samples in an equimolar urea-calcium solution for 3 days followed by a drying period of 3 days, complete filling of the cracks and crack bridging was witnessed for the samples with a crack width of 0.3 mm . The study of bacteria-based self-healing of concrete has gone beyond lab-scale experiments.

Types of Admixtures of Concrete & Cement | Chemical, Mineral

This is called the dormant period when the concrete is plastic and can be placed. At the end of the dormant period, the hydration rate increases and a lot of calcium silicate hydrate and calcium hydroxide is formed relatively quickly. This corresponds to the setting time of the concrete. Retarding admixtures delay the end of the dormant period ...