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The alkali-silica reaction in concrete
72
Book reviews
less than 0.4. An explanation is provided as to why the 0.4 water-cement ratio is the dividing line between distinctly different concrete types with regard to microstructure and properties. The author suggests that, in the near future, both the demand for higher strength levels in concrete and the increasing use of precast concrete are expected to continue, and that concrete technologists should prepare themselves in advance to address the problems associated with these developments. The book is appropriately dedicated to the memeory of Robert Philleo who passed away in 1990. The authors of the chapters and the editors of the book deserve congratulations for putting together an outstanding collection of essays on various facets of concrete technology. Also, the publisher deserves a commendation for the good production qualities.
P. Kumar Mehta University of California, Berkeley, CA 94720, USA The Alkali-silica Reaction in Concrete. Edited by R. N. Swamy. The Blackie Publishing Group, Bishopbriggs, Scotland, 1991. ISBN 0-21692691-2. Price £65.00.
This book is the second written so far on the topic of alkali-silica reaction (ASR) in concrete. It is a welcome source of information in the current circumstances of increasing concern about this concrete deterioration process, and the editor is to be commended on his efforts in putting together experiences from several countries in this book. The first book was written by Dr D. W. Hobbs of the British Cement Association, and despite its acknowledged great value to researchers and practitioners in the field of concrete and ASR, it largely dealt with reactions involving aggregates of the type containing amorphous or cryptocrystalline silica such as opal and flint. The book under review contains much additional information gained in several countries with experiences pertaining to a great variety of rock types of various mineralogical compositions, giving the current book a broader base and applicability to the aggregate reactivity problem in most countries. The book is divided into 11 chapters, the first four dealing with the basics of ASR, and the latter seven dealing with experiences from seven dif-
ferent countries (UK, Denmark, Iceland, Canada, New Zealand, Japan and India). Chapter 1 is the 'Introduction to Alkali-aggregate reaction" and covers important aspects such as the historical background to the problem, the various types of AAR, reactive components in aggregate, the alkali and moisture requirements for AAR, the concept of pessiman effect, the various properties of gel products, observed effects of the reaction in structures, and a brief mention of tests used for the identification of reactive aggregates. A good deal of information is provided in the ~Introduction' which gives the reader excellent knowledge as a base for following the rest of the book. Areas of uncertainty, and those where more work is required, have been emphasised. Chapter 2 deals with the chemistry of A A R and covers important basic knowledge on the chemical and mineralogical features of aggregates, cement and blending materials: silica fume, flyash and blast furnace slag. Differences in the mineralogical and hydration properties of these materials have been described very clearly. The chemistry of pore fluid of concrete is dealt with in detail and in a readily understood manner, after which the chemical mechanism of A A R and control of alkali levels in concrete are covered. This section is very useful for those who may not have had much chemistry in their formal training, but are involved with cases of AAR. Chapter 3 is a review of new and conventional test methods for identifying alkali-reactive aggregates, giving detailed discussion of advantages and limitations of the ,~arious test methods. Although much valuable information has been provided in this chapter, it is to be recognised that the topic of 'testing' has been in a state of flux since the mid 1980s, due to an urgent need for development of more rapid and reliable test methods and more new information is becoming available. For instance, using a procedure similar to that of NBRI, South Africa (i.e., IM NaOH, 80°C), and using Australian aggregates expansion-time limits have been found that discriminate between reactive, slowly-reactive, and non-reactive aggregates, and the use of a single expansion-time limit has been found to be inappropriate. Also, a new microbar method, based on the Chinese autoclave test has been found to have wide applicability. In addition to the role of the laboratory tests, the applicability of expansion limits to design considerations has been highlighted, and it has been emphasised that expansive strain due to A A R is
Book reviews
not the only important factor, but that attention should be given also to the effects of A A R on other engineering properties of concrete such as flexural and tensile strengths. Much valuable information has been provided on non-destructive tests, and their applicability and limitations in assessment of deterioration of concrete due to ASR. It has been shown that measurements of pulse velocity and dynamic modulus of elasticity are both useful in monitoring the progress of ASR in concrete. Chapter 4 deals with the important topic of prevention of ASR by using mineral admixtures in the concrete mix. The confusion that exists in relation to the effectiveness of these materials (flyash, slag, silica fume) in mitigating ASR and its effects has been outlined. It has been emphasised that these materials have different rates of reaction and vary in their controlling effects on ASR expansion and cracking. Their effectiveness also depends on the reactivity of the aggregate and, for a given reactivity, on particle size, specific surface area, mineralogical composition, volume % used, source of alkali, and method of incorporation in concrete. In this chapter, the influence of reinforcement restraint on controlling expansion, cracking and hogging in concrete beams and slabs with and without mineral admixture has been discussed in detail. It has been shown that control of expansive strains by mineral admixtures, although important, cannot be the only criterion for effective control of ASR and its effects in a structure, but that other criteria including control of cracking, preservation of concrete strength and elastic modulus should also be considered. Chapter 5 deals with the UK experience with ASR. It contains a detailed history of ASR in the UK, and it is interesting to note the initial resistance of the concrete-related industry to the recognition of ASR as a problem (this is currently being repeated in other countries); it is now acknowledged as a problem of considerable significance. Some cases of ASR in the UK have been described. An important part of this chapter is the description of the work of Hawkin's Working Parties which was aimed at finding countermeasures to minimise the risk of ASR. Attempts at developing test methods for identifying reactive aggregates in the UK, diagnosis of ASR, monitoring and management of ASR affected structures are briefly reviewed. Chapter 6, the Danish experience, describes the phases of studies on ASR in this country. Fundamental studies leading to proposals for
73
reaction mechanisms and their confirmation are detailed. Prevention of ASR under Danish conditions is described, and it is interesting that aggregate is classified into three groups for using in different environments, and that the Danish Portland cement now contains flyash, which has been shown to be more effective than low-alkali cement in reducing A A R expansion in concrete. In Chapter 7, describing ASR experience in Iceland, where concrete is widely used in house building. Attention has been given to controlling ASR damage in structures such as housing units by limiting the moisture content of the concrete. The Icelandic experience with ASR in residential buildings may be unique. It arose because no precaution had been taken against it; it had been believed that buildings dry out quickly and were not susceptible to ASR. Results on full-scale repair projects using the various techniques (ventilated cladding, rendering applied on insulation, and impregnation with silanes and silicones) seem to be promising. As a preventive measure, the Icelandic cement now contains 7.5% silica fume. Chapter 8 contains the Canadian experience with ASR, dating back to 1953. An important part of this chapter is related to the development of Canadian standards for predicting alkaliaggregate reactivity, particularly the concrete prism test and its applicability to the various aggregate types found in Canada. Problems encountered with the standard test methods have been discussed. The effects of de-icing salt on ASR, and methods of counteracting ASR are briefly mentioned. Details are given of the distribution of reactive aggregates and ASR cases in Canada. Chapter 9 describes the New Zealand experience with ASR. Unlike many other countries, in New Zealand the chemical test (ASTM C289) and the mortar bar test (ASTM C227) have been found to be satisfactory for predicting ASR susceptibility, and the results correlate well with field behaviour. The various reactive N.Z. aggregates are described. The importance of adhering to the specification of low-alkali cement for the control of ASR has been emphasised. Chapter 10 gives details of the Japanese experience with ASR. This includes an outline of the basic studies on A A R in Japan: microstructural studies, effects of mineral admixtures and chemical admixtures, alkali and cement contents, temperature and environmental conditions. Many examples of concrete structures affected by ASR
74
Book reviews
have been shown, and the test methods used and the rapid methods developed in Japan are discussed. Of particular interest is the effect of repair systems on the prevention of further expansion and cracking of structures affected by ASR. Chapter 11 deals with the Indian experience with ASR. Two cases of ASR in dam structures have been described in detail, types of reactive aggregates and methodology for assessment of Indian aggregates have been given. Strained quartz has been found to play a role in ASR when present in sufficient amounts in the aggregate. The materials covered in the 11 Chapters make this book a valuable source of information, with ample references to the literature on ASR, for all those who deal with concrete. Researchers, students, concrete technologists, consulting engineers, aggregate producers, concrete users and specifiers will find this book of great interest. The authors of the chapters and the editor are to be congratulated for their fine efforts. Minor errors exist in the book which would easily be picked up by the readers without causing
misunderstanding. These are: Formula of ettringite on p. 6 should have 31 H20 and not 3H20. Formula for pH on p. 44 should have p before the L.H.S. or deleter p from RHS last line on p. 63, p is missing from 'expansions'. last line on p. 100 unsymmetrically~Asymmetrically. Fig. 7.13 on p. 22(I -- horizontal axis should be in month not %. Fig. 8.9 on p. 233 -- no letter markings on photographs as indicated in the caption. Fig. 8.10 on p. 234 -- in caption Fig. 1.6 should be Fig. 8.9. Fig. 8.11 on p. 235 -- no letter markings on photographs as indicated in the caption. Fig. 8.12 on p. 236 -- no letter markings on photographs as indicated in the caption. p. 320 line 12 from top than should read then. item (3) on p. 321 pigmetites should read pegmatites.
A. Shayan
Book reviews
less than 0.4. An explanation is provided as to why the 0.4 water-cement ratio is the dividing line between distinctly different concrete types with regard to microstructure and properties. The author suggests that, in the near future, both the demand for higher strength levels in concrete and the increasing use of precast concrete are expected to continue, and that concrete technologists should prepare themselves in advance to address the problems associated with these developments. The book is appropriately dedicated to the memeory of Robert Philleo who passed away in 1990. The authors of the chapters and the editors of the book deserve congratulations for putting together an outstanding collection of essays on various facets of concrete technology. Also, the publisher deserves a commendation for the good production qualities.
P. Kumar Mehta University of California, Berkeley, CA 94720, USA The Alkali-silica Reaction in Concrete. Edited by R. N. Swamy. The Blackie Publishing Group, Bishopbriggs, Scotland, 1991. ISBN 0-21692691-2. Price £65.00.
This book is the second written so far on the topic of alkali-silica reaction (ASR) in concrete. It is a welcome source of information in the current circumstances of increasing concern about this concrete deterioration process, and the editor is to be commended on his efforts in putting together experiences from several countries in this book. The first book was written by Dr D. W. Hobbs of the British Cement Association, and despite its acknowledged great value to researchers and practitioners in the field of concrete and ASR, it largely dealt with reactions involving aggregates of the type containing amorphous or cryptocrystalline silica such as opal and flint. The book under review contains much additional information gained in several countries with experiences pertaining to a great variety of rock types of various mineralogical compositions, giving the current book a broader base and applicability to the aggregate reactivity problem in most countries. The book is divided into 11 chapters, the first four dealing with the basics of ASR, and the latter seven dealing with experiences from seven dif-
ferent countries (UK, Denmark, Iceland, Canada, New Zealand, Japan and India). Chapter 1 is the 'Introduction to Alkali-aggregate reaction" and covers important aspects such as the historical background to the problem, the various types of AAR, reactive components in aggregate, the alkali and moisture requirements for AAR, the concept of pessiman effect, the various properties of gel products, observed effects of the reaction in structures, and a brief mention of tests used for the identification of reactive aggregates. A good deal of information is provided in the ~Introduction' which gives the reader excellent knowledge as a base for following the rest of the book. Areas of uncertainty, and those where more work is required, have been emphasised. Chapter 2 deals with the chemistry of A A R and covers important basic knowledge on the chemical and mineralogical features of aggregates, cement and blending materials: silica fume, flyash and blast furnace slag. Differences in the mineralogical and hydration properties of these materials have been described very clearly. The chemistry of pore fluid of concrete is dealt with in detail and in a readily understood manner, after which the chemical mechanism of A A R and control of alkali levels in concrete are covered. This section is very useful for those who may not have had much chemistry in their formal training, but are involved with cases of AAR. Chapter 3 is a review of new and conventional test methods for identifying alkali-reactive aggregates, giving detailed discussion of advantages and limitations of the ,~arious test methods. Although much valuable information has been provided in this chapter, it is to be recognised that the topic of 'testing' has been in a state of flux since the mid 1980s, due to an urgent need for development of more rapid and reliable test methods and more new information is becoming available. For instance, using a procedure similar to that of NBRI, South Africa (i.e., IM NaOH, 80°C), and using Australian aggregates expansion-time limits have been found that discriminate between reactive, slowly-reactive, and non-reactive aggregates, and the use of a single expansion-time limit has been found to be inappropriate. Also, a new microbar method, based on the Chinese autoclave test has been found to have wide applicability. In addition to the role of the laboratory tests, the applicability of expansion limits to design considerations has been highlighted, and it has been emphasised that expansive strain due to A A R is
Book reviews
not the only important factor, but that attention should be given also to the effects of A A R on other engineering properties of concrete such as flexural and tensile strengths. Much valuable information has been provided on non-destructive tests, and their applicability and limitations in assessment of deterioration of concrete due to ASR. It has been shown that measurements of pulse velocity and dynamic modulus of elasticity are both useful in monitoring the progress of ASR in concrete. Chapter 4 deals with the important topic of prevention of ASR by using mineral admixtures in the concrete mix. The confusion that exists in relation to the effectiveness of these materials (flyash, slag, silica fume) in mitigating ASR and its effects has been outlined. It has been emphasised that these materials have different rates of reaction and vary in their controlling effects on ASR expansion and cracking. Their effectiveness also depends on the reactivity of the aggregate and, for a given reactivity, on particle size, specific surface area, mineralogical composition, volume % used, source of alkali, and method of incorporation in concrete. In this chapter, the influence of reinforcement restraint on controlling expansion, cracking and hogging in concrete beams and slabs with and without mineral admixture has been discussed in detail. It has been shown that control of expansive strains by mineral admixtures, although important, cannot be the only criterion for effective control of ASR and its effects in a structure, but that other criteria including control of cracking, preservation of concrete strength and elastic modulus should also be considered. Chapter 5 deals with the UK experience with ASR. It contains a detailed history of ASR in the UK, and it is interesting to note the initial resistance of the concrete-related industry to the recognition of ASR as a problem (this is currently being repeated in other countries); it is now acknowledged as a problem of considerable significance. Some cases of ASR in the UK have been described. An important part of this chapter is the description of the work of Hawkin's Working Parties which was aimed at finding countermeasures to minimise the risk of ASR. Attempts at developing test methods for identifying reactive aggregates in the UK, diagnosis of ASR, monitoring and management of ASR affected structures are briefly reviewed. Chapter 6, the Danish experience, describes the phases of studies on ASR in this country. Fundamental studies leading to proposals for
73
reaction mechanisms and their confirmation are detailed. Prevention of ASR under Danish conditions is described, and it is interesting that aggregate is classified into three groups for using in different environments, and that the Danish Portland cement now contains flyash, which has been shown to be more effective than low-alkali cement in reducing A A R expansion in concrete. In Chapter 7, describing ASR experience in Iceland, where concrete is widely used in house building. Attention has been given to controlling ASR damage in structures such as housing units by limiting the moisture content of the concrete. The Icelandic experience with ASR in residential buildings may be unique. It arose because no precaution had been taken against it; it had been believed that buildings dry out quickly and were not susceptible to ASR. Results on full-scale repair projects using the various techniques (ventilated cladding, rendering applied on insulation, and impregnation with silanes and silicones) seem to be promising. As a preventive measure, the Icelandic cement now contains 7.5% silica fume. Chapter 8 contains the Canadian experience with ASR, dating back to 1953. An important part of this chapter is related to the development of Canadian standards for predicting alkaliaggregate reactivity, particularly the concrete prism test and its applicability to the various aggregate types found in Canada. Problems encountered with the standard test methods have been discussed. The effects of de-icing salt on ASR, and methods of counteracting ASR are briefly mentioned. Details are given of the distribution of reactive aggregates and ASR cases in Canada. Chapter 9 describes the New Zealand experience with ASR. Unlike many other countries, in New Zealand the chemical test (ASTM C289) and the mortar bar test (ASTM C227) have been found to be satisfactory for predicting ASR susceptibility, and the results correlate well with field behaviour. The various reactive N.Z. aggregates are described. The importance of adhering to the specification of low-alkali cement for the control of ASR has been emphasised. Chapter 10 gives details of the Japanese experience with ASR. This includes an outline of the basic studies on A A R in Japan: microstructural studies, effects of mineral admixtures and chemical admixtures, alkali and cement contents, temperature and environmental conditions. Many examples of concrete structures affected by ASR
74
Book reviews
have been shown, and the test methods used and the rapid methods developed in Japan are discussed. Of particular interest is the effect of repair systems on the prevention of further expansion and cracking of structures affected by ASR. Chapter 11 deals with the Indian experience with ASR. Two cases of ASR in dam structures have been described in detail, types of reactive aggregates and methodology for assessment of Indian aggregates have been given. Strained quartz has been found to play a role in ASR when present in sufficient amounts in the aggregate. The materials covered in the 11 Chapters make this book a valuable source of information, with ample references to the literature on ASR, for all those who deal with concrete. Researchers, students, concrete technologists, consulting engineers, aggregate producers, concrete users and specifiers will find this book of great interest. The authors of the chapters and the editor are to be congratulated for their fine efforts. Minor errors exist in the book which would easily be picked up by the readers without causing
misunderstanding. These are: Formula of ettringite on p. 6 should have 31 H20 and not 3H20. Formula for pH on p. 44 should have p before the L.H.S. or deleter p from RHS last line on p. 63, p is missing from 'expansions'. last line on p. 100 unsymmetrically~Asymmetrically. Fig. 7.13 on p. 22(I -- horizontal axis should be in month not %. Fig. 8.9 on p. 233 -- no letter markings on photographs as indicated in the caption. Fig. 8.10 on p. 234 -- in caption Fig. 1.6 should be Fig. 8.9. Fig. 8.11 on p. 235 -- no letter markings on photographs as indicated in the caption. Fig. 8.12 on p. 236 -- no letter markings on photographs as indicated in the caption. p. 320 line 12 from top than should read then. item (3) on p. 321 pigmetites should read pegmatites.
A. Shayan