alkali aggregate reaction ppt

alkali aggregate reaction ppt

Repair of Reinforced Concrete Beams Damaged by Alkali ...

alkali-aggregate reaction. There are three types of alkali-aggregate reactions, namely the alkali-silica, alkali-silicate and akali-carbonate reactions. Deterioration due to the alkali-silica reaction is more common and this paper refers to this aspect. The alkali-silica reaction was first recognized as a problem in North American in 1940, in

Alkali aggregate reaction - LinkedIn SlideShare

Alkali-aggregate reaction (AAR) is a reaction between the alkali hydroxides present in the pore solution of concrete and certain constituents of some aggregates; under certain conditions the reaction may produce deleterious expansion and cracking of the concrete. There are two distinct types of alkali-aggregate reaction in concrete; these are ...

Alkali-Aggregate Reaction (AAR) of Concrete Structures

Alkali Content of Concrete Mix Water and Aggregates Introduction Alkali silica reaction (ASR) is a chemical reaction between some types of aggregate and the highly alkaline pore water present in all Portland cement concretes. When the concrete contains sufficient moisture, alkalis and reactive aggregate the reaction produces

Alkali Aggregate Reaction in Concrete

Sep 25, 2006· tom which confirms the occurrence of the alkali-aggregate reaction is the presence of the reaction products (alkali silicate gel) in the concrete. Keywords: alkali-silica reaction, test methods, SEM. 1. Introduction The varying aggregate properties, in particular those related to the rate of the alkali reaction, make it necessary

Alkali-carbonate reaction in concrete and its implications ...

Alkali aggregate reaction • Alkali aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non crystalline silicon dioxide, which is found in many common aggregates. • This reaction can cause expansion of the altered aggregate, leading to spalling and loss of strength of the concrete.

Alkali–silica reaction - Wikipedia

Alkali-Aggregate Reaction in Concrete: A World Review is unique in providing authoritative and up to date expert information on the causes and effects of Alkali-Aggregate Reaction (AAR) in concrete structures worldwide. In 1992 a first edition entitled The Alkali-Silica Reaction in Concrete, edited by Professor Narayan Swamy, was published in a first attempt to cover this concrete problem from ...

Alkali Aggregate Reaction Topic - concrete

The alkali–silica reaction (ASR), more commonly known as "concrete cancer", is a swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive non-crystalline silica found in many common aggregates, given sufficient moisture.. This reaction causes the expansion of the altered aggregate by the formation of a soluble and viscous gel of sodium ...

The Impact of Expansion due to Alkali-Carbonate Reaction ...

Alkali-aggregate reaction (ASR) in concrete is one of the least dealt with concrete degradation mechanism in Finland. It is a common belief that it does not occur due to the exceptional quality of Finland's granitic rock. However, over 50 cases have been identified in the past 15 years in concrete structures, raising uncertainty in this ...

Diagnosis and Control of Alkali-Aggregate Reactions in ...

"The Static and Dynamic Behaviour of Reinforced Concrete Beams with Cracks Due to Alkali-Silica Reaction," Proceedings of the Seventh International Conference, Concrete Alkali-Aggregate Reactions ...

Alkali Silica Reaction - Proactive Avoidance

alkali content of concrete, use of low alkali cement, include PFA, GGBS, etc. M2: Avoid the presence of a critical amount of reactive silica, e.g. identify non-reactive aggregate M3: reduce the access of moisture and maintain the concrete in a sufficiently dry state, e.g. use external cladding or tanking

Alkali-silica reaction in concrete

The Impact of Expansion due to Alkali-Carbonate Reaction on Engineering Properties of Concrete

Aggregate Reaction - an overview | ScienceDirect Topics

Sep 25, 2006· tom which confirms the occurrence of the alkali-aggregate reaction is the presence of the reaction products (alkali silicate gel) in the concrete. Keywords: alkali-silica reaction, test methods, SEM. 1. Introduction The varying aggregate properties, in particular those related to the rate of the alkali reaction, make it necessary

Alkali Content of Concrete Mix Water and Aggregates

A chemo-damage model is presented for anisotropic swelling analysis of concrete arch dams affected by alkali-aggregate reaction (AAR). The model combines the AAR kinetics and the plastic-damage model, and the chemical and mechanical phases are coupled. A redistributing weight function, determined by the applied stresses in the concrete, is ...

Alkali–aggregate reaction - Wikipedia

For alkali-silica reaction to occur, three conditions must be present: • reactive forms of silica in the aggregate • high-alkali (pH) pore solution • sufficient moisture The amount of gel formed in the concrete depends on the amount and type of reactive silica, and the alkali hydroxide concentration in the con-crete pore solution.

Alkali Aggregate Reaction | Materials | Chemical Compounds ...

The pozzolanic reaction mechanism is believed to be a process in which silicate anions are detached from the reactive aggregate by hydroxyl ions in the pore fluid. Sodium and potassium ions are the ions most readily-available to balance the silicate anions and an alkali-silicate gel is formed.

What is Alkali Aggregate Reaction in Concrete? [Civil Planets]

13. Alkali Aggregate Reaction. Alkali-aggregate reaction or alkali-silica reaction, takes place between alkali content of cement and silica content of aggregates is also a major factor effecting durability of concrete. Due to this reaction, Concrete expansion occurs which finally lead to severe cracking and concrete gets deteriorated.

Alkali-Silica Reactivity of High Density Aggregates for ...

Alkali aggregate reaction is one of them where the chemical reaction happens between the aggregates, which leads the concrete to lose its strength and smooth appearance. Alkali-Aggregate Reaction The chemical reaction between the concrete aggregates and alkali hydroxide with the help of environmental moisture that leads to cracks on the ...

PPT – Alkali-Silica Reaction: PowerPoint presentation ...

2.2.2 Alkali Aggregate Reaction (AAR) When a highly basic fluid which consist of alkali hydroxides ions like (K +, Na + ـــــ OH – ) fill the pores in concrete and the aggregate in concrete are chemically unstable in the high pH environment, the concrete encounter with distresses such as cracking, losing serviceability ...

TESTING ALKALI-REACTIVITY OF SELECTED CONCRETE …

Jul 16, 2019· Alkali aggregate reactions (AAR) occur when aggregates in concrete react with the alkali hydroxides in concrete producing a hygroscopic gel which, in the presence of moisture, absorbs water and causes expansion and cracking over a period of many years. This alkali-aggregate reaction has two forms, namely: Alkali-silica reaction (ASR) and Alkali-carbonate reaction (ACR).

Alkali-Aggregate Reaction - Portland Cement Association

Less reactive aggregates often expensive or difficult to find ... exerting a force against surrounding concrete. Creation of alkali-silica gel ... – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow - id: ZDc1Z

Alkali-Aggregate Reaction in Concrete: A World Review

Jan 15, 2014· According to Katayama, the alkali-aggregate reaction of carbonate rocks can be subdivided into three categories: (1) the ACR of dolomitic limestone that results in dedolomitisation, (2) the ACR of non-dolomitic limestone that produces reaction rims and (3) the alkali-silica reaction (ASR) of various carbonate rocks.

PPT – Alkali-Silica Reaction: PowerPoint presentation ...

Alkali-aggregate reaction is the expansive reaction that takes place in PCC between alkali (contained in the cement paste) and elements within an aggregate. The most common is an alkali-silica reaction. This reaction, which occurs to some extent in most PCC, can result in map or pattern cracking (see Figure 1), surface popouts and spalling if ...

Effects of alkali–aggregate reaction on concrete and ...

If a highly reactive aggregate has been used in the concrete, only a small amount of alkali is required to initiate the reaction. (Farny and Kosmatka, 1997) ASR may also occur in a low-alkali cement concrete if the structure experiences wetting and drying cycles.

NPTEL :: Civil Engineering - Concrete Engineering and ...

Lecture-24 Alkali – aggregate reaction (Part 1 of 2) Lecture-25 Alkali – aggregate reaction (Part 2 of 2) Lecture-26 Reinforcement corrosion in concrete ; Lecture-27 Chloride penetration in concrete ; Lecture-28 Using epoxy-coated bars in concrete structures; Lecture-29 Using FRP as reinforcement in concrete structures (Part 1 of 2)