The reaction chemistry of the swelling and dissolution of disordered silica in alkali hydroxide solutions in the absence of calcium hydroxide is reasonably well understood. The alkali silica reaction mechanism catalysed by a soluble strong base as naoh or koh in the presence of caoh 2 alkalinity buffer present in the solid phase can be compared with the carbonation process of soda lime. Alkali silica reaction, minimising the risk of damage to concrete, guidance notes and recommended practice, c cement and concrete association of new zealand second edition incorporating amendment 1. Practices to mitigate alkalisilica reaction asr affected. Engineered for longterm durability, newcem slag cement helps structures achieve greater strength potential, reduced permeability, and increased resistance to sulfate attack and alkali silica reaction. Abstract identifying the susceptibility of an aggregate to alkali silica reaction asr before using it in concrete is one of the most efficient practices for preventing damage and failure. The method for identifying concrete containing gels formed by the alkali silica reaction as described in claim 1, further comprising the steps of contacting the surface of the concrete under investigation with a concentrated aqueous solution of rhodamine b for a chosen period of time, after said step of rinsing the concrete treated with the. This report summarizes the findings of an experimental evaluation into alkali silica reaction asr in cement free alkaliactivated slag and fly ash binder concrete. Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material. The term premature concrete deterioration pcd has been adopted to refer to problems associated with asr and def because it is often difficult to distinguish between them. Chemistry of alkalisilica reaction and testing of aggregates. Alkalisilica reaction in concrete with previously inert.
The factors involved are exceedingly complex, very interdependent and highly interactive. It occurs when the alkaline pore fluid and siliceous minerals in some aggregates react to form a calcium alkali silicate gel. Moreover, free expansion tests according to astm c1260 and. Pdf chemoplastic modelling of alkalisilica reaction asr. The alkali silica reaction in concrete swamy, r n on. Alkalisilica reaction in concrete containing glass. Alkalisilica reaction asr is a deleterious reaction between the alkaline pore solution of concrete and various metastable forms of silica contained in many natural and synthetic aggregates. Lon of this report does not necessarily indicate approval or endorsement by.
Alkali silica reaction article about alkali silica. Alkalisilica reaction and delayed ettringite formation. Cracking due to alkali silica reaction and its effect on durability properties of concrete acknowledments iii the author would like to express his gratitude to the thesis supervisors, prof. Alkali silica reaction asr and delayed ettringite formation def, or combinations of the two, have been found to be the main causes of these problems. Sand and gravel sources had to be tested using kansas test method ktmr23 1999, wetting and drying test of sand and sandgravel aggregate for concrete. In 1992 a first edition entitled the alkalisilica reaction in concrete, edited. This usually occurs between the highly alkaline portland cement and the various siliceous substances contained in the aggregate. Alkalisodium, potassium, and lithiumare generally introduced into concrete weakly bonded to hydroxyl ions, oh, by the cement. As part of a research project to develop draft specifications for glass in concrete, a major asr testing programme was undertaken to establish appropriate use of glass in concrete which avoided harmful asr. Activated silica solswater treatment 301 reaction of polysilicic acid with metal cations 303 references 304 4 colloidal silicaconcentrated sols 312 definition of colloidal silica and historical development 312 growth and stabilization of discrete particles 3 increasing particle size by adding active silica 3.
This is a short introduction to asr for more information, see the understanding cement bookebook. Specific reference is made to the differences between the formation of synthetic silica gels and of quartz and cristobalite. Some of these structures were considered structurally inadequate and have been replaced or repaired. Activated silica is frequently useful as a coagulation aid in water treatment. The effects of supplementary cementitious materials on alkali silica reaction. The aggregates varied their origin and mineralogical composition. The susceptibility of alkaliactivated fly ash and slag concrete binders to deleterious asr was evaluated in accordance with relevant astm standards.
The new zealand construction industry often refers to alkali aggregate reaction aar instead of alkali silica reaction asr. Alkali aggregate reactions publisher national bureau of standards collection nistir. Crystallization of silica gel in alkaline solutions at 100. There has been an enormous amount of literature about the background theory and cases of alkali silica reaction in concrete structures after its discovery by stanton in california, usa in 1940. When calcium hydroxide is present, dissolved silica reacts to form calcium silicate. Cases occur when changes in material properties lead to potentially reactive aggregates reacting with higher alkali cements.
Download a pdf of practices to mitigate alkalisilica reaction asr affected. Alkalisilicareaction asr is a result of reaction between the alkalinepore solution and reactive silica in the aggregate. The minimum level of silica fume as a percentage of material content is calculated on the basis of the alkali content of the concrete expressed as kgm 3 na 2 o e, but in cases where silica fume is the only scm to be used, the silica fume content should be 7. Silica dissolution related to the alkalisilica reaction. Alkalisilica reaction and microstructure of concrete. Sposito the effects of potassium and rubidium hydroxide on the alkali silica reaction, cement and concrete research, volume. These w ill be discussed below in separate paragraphs. This reaction produces a hygroscopic gel, which absorbs water and swells, causing cracking to occur as tension builds in the concrete structure.
Apr 19, 2019 the activation reaction is believed to be the neutralization of sodium silicate, leading to polymerization of silicate ions. Asr is the specific type of alkali aggregate reaction that is of concern in new zealand. The chemical reaction can result in abnormal expansion and cracking of concrete. Effect of alkali silica reaction on the mechanical properties of aging. The alkali silica reaction though not true is described as a concrete cancer. Alkalisilica reaction takes place between alkalis na 2 o and k 2 o from cement or other sources and certain reactive silica minerals present in the coarse or fine aggregates. Alkali silica reaction article about alkali silica reaction. The effects of supplementary cementitious materials on alkali. Chapter 2 alkalisilica reaction guidelines for the use of. Usually a i 5cm3 bottle was used, and metal oxides, and alkalimetal salts on the crystallization 0. The alkali silica reaction asr, alkaline reaction or concrete cancer is a chemical reaction between silicon dioxide in concrete aggregates and alkali hydroxide in the concrete pore solution. The process acidifies the silicate and uses caustic material to raise the ph to less than 12 to stabilize the activated silica. I searched the whole internet for the pdf and i couldnt find one so i bought the book and decided to take a picture for each page and compiled all pictures to a pdf file to share with every poor student.
Thomas, diego lazama, sulapha peethamparon clarkson university utrc, the city college of new york 7th street and convent ave. 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 noncrystalline 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. Alkali silica reaction asr is a deleterious reaction between the alkaline pore solution of concrete and various metastable forms of silica contained in many natural and synthetic aggregates. It has been accepted for inclusion in all theses by an authorized administrator of tigerprints. The silicic acid h 2 sio 3 or sio 2 is simply replaced in the reaction by the carbonic acid h 2 co 3 or co 2. Alkaliaggregate reaction aar of concrete structures.
The use of surplus waste glass in concrete has been avoided on the grounds that it is known to undergo harmful alkali silica reaction asr. This report gathers the stateoftheart in alkali silica reaction asr in concrete, and asr mitigation techniques, in preparation for a more detailed study to be submitted to congress in response to public law 106398 hr 4205. If you are a student and obliged to buy this book, feel free to download this book. Alkalisilica reactivity surveying and tracking guidelines, which can be downloaded. Article information, pdf download for effect of alkali silica reaction on the. A detailed explanation of the most important properties of natural and synthetic silica and silica gels is given. Provides a comprehensive account of the silica chemistry involved in a wide range of research and development activities, and a wealth of information on production and production control. The alkalisilica reaction in concrete swamy, r n on. Alkalisilica reaction article about alkalisilica reaction.
Chemoplastic modelling of alkalisilica reaction asr conference paper pdf available march 2014. Under adverse conditions, the volume of the alkali silicate gel may gradually expand to such an extent as to cause localised swelling pressure. Alkali silica reaction asr can cause serious expansion and cracking in concrete, resulting in major structural problems and sometimes necessitating demolition. Bhupinder singh, in waste and supplementary cementitious materials in concrete, 2018.
Alkali silica reaction an overview sciencedirect topics. The effect of monovalent and bivalent cations on the surface charge of opal, cement and concrete research, 933934, 2003. No concreted structure or part of a concrete structure any where in the world has collapsed due to alkali silica reaction alone. Testing methods and mitigation alternatives by wissam touma, ph. T he first guidance documents on ways of minimising the risk of damage due to alkalisilica reaction in concrete were published in the early 1980s by the concrete society technical report 304 and bre digest 330.
Alkalickokremicita reakce dvorakovo nabrezie ba 2018. The effects of supplementary cementitious materials on. The problem stems from a lack of standardized testing of aggregates. Alkali silica reaction is a reaction in which certain aggregates react with the alkaline pore solution of concrete and manifests itself in extreme cases in the form of deterioration and distress in concrete. The reactionleads to the formation of a gel which absorbs water and expandsleading to damaging expansions and cracking in the concrete. But please support the author if you find this book useful.
Topics on alkalisilica reaction development bureau. The key point in the al kali silica reaction is the hydrous dissolution of silica in the presence of dissolved na andor k at high ph, commonly obtaining in opc concrete. Discusses the solubility of different forms of silica and the factors that influence dissolution and deposition, comparing and recommending analytical methods. Alkali silica reaction under the influence of chloride based. 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. Under stress free conditions, the internal swelling pressure. Civil engineering department the university of texas at austin david fowler, ph. This thesis is brought to you for free and open access by the theses at tigerprints. The properties and qualities of the silica and its environment may affect its solubility under the given conditions. Alkali silica reaction under the influence of chloride. Alkalisilica reaction and high performance concrete.
Alkali silica reactivity is the process in which certain minerals mostly glass type silica in the presence of moisture are broken down by the highly alkaline environment of concrete producing a gel that expands creating tensile forces in the concrete matrix which cause cracking of the concrete. Asr is the most common form of alkali aggregate reaction aar in concrete. The term premature concrete deterioration pcd has been adopted to refer to problems associated with asr and def because it. The microscopic examination was carried out on concrete. Civil engineering department the university of texas at austin and ramon carrasquillo, ph.
Asr causes microcracks in concrete which may lead to inserviceability of. Reactants of alkalisilica reaction and the composition of reaction products to understand the reaction between an aggregate and alkaline pore solution it is necessary to know the nature of the aggregate, the reaction environment including the type of ions present and their concentrations, temperature and the composition of the reaction products. Alkali silica reaction asr is a persistent issue and has evaded eradication for nearly 80 years. Alkali silica reaction asr in cement free alkali 121916 activated sustainable concrete zihui li, robert j. This gel absorbs water, producing a volume expansion which can disrupt the concrete. However, it is known that concrete expansion, due to alkali silica reaction, could be suppressed by using sufficient quantity of a pozzolan even when the concrete is exposed to a strong alkaline solution.
High replacement levels of slag cement in properly proportioned mixes also help control shrinkage, creep and thermal cracking in mass concrete structures. Activated silica solswater treatment 301 reaction of polysilicic acid with metal cations 303 references 304 4 colloidal silica concentrated sols 312 definition of colloidal silica and historical development 312 growth and stabilization of discrete particles 3 increasing particle size by adding active silica 3. Alkali silica reaction asr is the most common form of alkaliaggregate reaction. Recommended citation desai, purvi, alkali silica reaction under the influence of chloride based deicers. Jan 20, 2009 the use of surplus waste glass in concrete has been avoided on the grounds that it is known to undergo harmful alkali silica reaction asr. Apr 02, 2017 alkali silica reaction asr is a persistent issue and has evaded eradication for nearly 80 years.
Accelerated laboratory testing for alkalisilica reaction using. The kansas department of transportation kdot has controlled alkali silica reaction asr for more than 70 years through the use of selected aggregates. The resulting alkali silicate gel has an expanding effect and can lead to concrete damage. A human cancer, if untreated is terminal, whereas the alkali silica reaction and the expansion it induces, if untreated, eventually stops. Avoid the presence of a critical amount of reactive. The alkali silica reaction is an unusual and unpredictable phenomenon which occurs worldwide. Alkali silica reaction in portland cement concrete 16.
The main criticism of astm c 1260 is that the high temperature combined with the high concentration of free hydroxides creates a very harsh condition. The applications of activated silica depend mainly on the size, charge and shape of the. Enter your mobile number or email address below and well send you a link to download the free kindle app. Activated silica is a substance or material usually formed from the reaction of a dilute silicate solution with a dilute acid. High replacement levels of slag cement in properly proportioned mixes also help control shrinkage, creep and thermal cracking in mass concrete.
43 1286 1204 80 1415 1483 1369 866 1175 603 65 185 317 335 250 537 27 356 467 1024 582 827 1435 1036 651 769 404 357 836 20 54 380 1476 270 1224 392 1077 166 453