Quality Concrete

Concrete Mix Design, Quality Control and Specification

Ken Day 3rd edition 2006, ISBN: 9780415393133, 391 pages

This book first came out in 1995, was revised in 1999 and is now up to its third edition. The writer became aware of this text in 1996 and has tracked its development over the past 13 years.

It is the only Australian book of its kind that covers concrete mix design in great detail. Whilst primarily relating to Australian concrete mix processes, it has been used successfully by many overseas concrete technologists. Previous Australian publications on concrete technology whilst very good (e.g. ‘Concrete Technology & Practice’ by Taylor; ‘Australian Concrete Technology’ by Ryan & Antill; and ‘Concrete Technology’ by Orchard) have not gone into the great depth of concrete mix design that this book had achieved. Not even the well known books such as the UK publication ‘Properties of Concrete’ by Adam Neville, nor the US publication ‘Concrete’ by Mehta, nor the South African publication ‘Concrete Technology’ by Fulton, addresses concrete mix design to the extent as this book.

The writer of this review has met Ken Day on several occasions and is always amazed by his knowledge in the subject and his enthusiasm for anything relating to concrete. When the writer was working for CSR Readymix (now Cemex) in 2002-2003, Ken’s software program was used for all the mix designs produced by that supplier as well as the mixes supplied by one of their competitors, Pioneer Concrete (now Hanson).

This third edition combines the wealth of knowledge aggregated in the first and second edition but now adds new information on concrete due to the changing scene in the concrete marketplace. Topics such as polycarboxylate ether admixtures and geopolymers have been included in the book as these products are now forming part of the new landscape of concrete mix design.

This edition also draws upon the expertise of many other practitioners in the marketplace who have held technical manager roles in various cement and concrete supplier companies both in Australia and overseas. The writer has also interacted on a personal level with the people mentioned in this text and also values their technical expertise in concrete technology and mix design.

With regards to the content of the book there are 13 chapters in all with a multitude of useful tables and figures. The first two chapters address basic quality control and the basic properties of concrete e.g. strength, water cement ratio, slump heat generation (due to hydration), durability as well as the up-to-date topics of self compacting concrete (also referred to as self consolidating concrete).

Chapter 3 is for those who have little understanding of concrete mix design and as such this section addresses the basics via simple mix design processes using simple assumptions and calculations. Quality control is revisited in Chapter 4 but this time in more detail addressing topics such as strength distributions, standard deviations, safety margins, batch control and CUSUM charts (short for ‘cumulative sum’ – which are the differences between each successive result and mix target value). These charts are particularly useful in graphically highlighting a declining trend in concrete strengths over many subsequent mixes. This chapter also addresses the ConAd system in detail (short for Concrete Advice – a software program written by Ken Day on concrete mix design and mix database management).

Chapter 5 addresses mix design from a ‘futuristic’ perspective such as ‘Just in Time’ mixes (i.e. testing concrete at the same time testing of the ‘material’ that goes into the concrete being tested as in order to speed up the process). Particular attention to self compacting concrete mixes is also addressed in this chapter. These types of mixes are the latest innovation in mix design i.e. producing a mix that flows freely without any need of additional vibration, effort (or more importantly water) to move it along. These mixes (and their proper design) will ensure that this special class concrete will get in and around congested reinforcement and intricate formwork.

Chapters 7, 8 and 9 all address the materials aspect of concrete i.e. the important parameters that are required to produce good quality concrete. These include the various types of cements and cementitious products in the marketplace today. The writer has given many presentations to engineers over the past few years and has been surprised that many do not realise materials such as flyash, slag, silica fume, metakaolin, polycarboxylate superplasticisers, viscosity modifying admixtures (to name a few) are added to a multitude of concrete mixes being supplied to many building projects today. Ken Day’s book provides a simple insight into the key properties requirements and standard dosages of these materials.

Chapter 10 will be of particular interest to those readers who wish to understand the ‘statistics’ behind the mix design process. Standard deviations, COV’s and testing errors are all explained with realistic values quoted.

Chapter 11 was of particular interest to the writer as it outlined many of the tests that are carried out on concrete e.g. the new J ring test on self compacting concrete. Correlation equations have been provided for cylinder compression tests (relevant to the Australian and US market) vs cube tests (relevant to European, South African and many Asian countries). Maturity vs Equivalent age relationships and equations are also provided. These should be of particular importance to engineers involved in the prestressed/post tensioned concrete field as cable stressing and early age strength are key criteria that need to be understood so that minimum strengths in the required time frame are achieved on site.

The remaining chapters and Appendix provide an array of other notable topics in the field of concrete technology e.g. cracks in concrete, fire, polymers and so on.

In summary the writer would strongly recommend this text to engineers and other technical staff in the concrete marketplace who wish to gain a better understanding of the theory and practice of proper concrete mix design. Ken Day has dedicated his professional career in accumulating a vast knowledge on concrete mix design, quality control and specification and his experience and expertise both in Australia and abroad have been documented in this text for all future generation of engineers, technicians and concrete suppliers (and customers) to reference. If you use concrete regularly, you should have this book on your shelf!!

Concrete Mix Design, Quality Control and Specification was reviewed by Paul UnoBE MBdgSc MIE(Aust) CPEng. Paul is Director of Cement & Concrete Services, he has 30 years experience in the concrete engineering and building industry.

WIND LOADING OF STRUCTURES

Wind Loading of Structures, 2 e.
John D Holmes
2007, 9780415409469, 392pp, $198

When it was announced that Dr J Dean Holmes was to spend the Fall 2001 semester at Louisiana State University* he was described as “one of the leading authorities on Wind Engineering in the world”. The content and quality of this book is consistent with that assessment of his standing. The book provides a comprehensive, practical examination of wind loading of structures.

The text is structured as follows:

• An introductory chapter considers meteorological aspects and wind-induced damage.
• Chapters 2-7 cover basic aspects of wind loading common to most structures – wind speed prediction, wind characteristics, bluff-body aerodynamics, dynamic response, internal pressures, wind-tunnel techniques.
• Chapters 8-14 deal with wind loading for particular types of structures – buildings (low-rise, tall, large roofs and sports stadiums), slender vertical structures (towers, chimneys, masts), long-span bridges, transmission lines & system risks, miscellaneous other structures (walls, hoardings, free-standing roofs, antennas, building appendages).
• Chapter 15 reviews the provisions of six major standards for wind loading, including AS/NZS 1170.2-2002.
• Six appendices cover terminology, symbols, probability distributions relevant to wind loading, a world survey of extreme wind climates (74 countries), approximate formulae for natural frequencies, an application of the effective static load method to a simple structure.

This structure is unchanged from the first edition but there have been changes to almost every chapter and appendix. Chapter 15 has been completely re-written because of the extensive revisions to most of the codes reviewed.

Features that add considerably to the appeal of the book include:

• Each chapter has a careful, thoughtful introduction and a brief concluding summary.
• Each chapter has an extensive reference list; including all the references you would expect to find (with the possible exception – for an Australian author – of the major report on Tracy) and giving due weight to the significant historical developments, unlike some recent authors who seem unaware that much happened before the advent of the Internet. Australian researchers are well represented in the lists.
• Many firms are working on overseas projects and the survey in Appendix D provides a convenient first look at the likely wind loading requirements.
• Chapter 7 will assist the structural or other engineer to prepare an appropriate brief for the wind-tunnel specialist and will aid in the interpretation of the test results.

The impressive cover image portrays some interesting aspects of failure and warranted identification and a brief discussion.

All engineers should be seeking to improve and increase their understanding of the processes they deal with rather than simply following codes and standards. For structural engineers concerned with wind loading of structures this book will assist them greatly in this endeavour.

* hurricane.lsu.edu/newsarchives.htm

Review by Bill Boyce FIEAust CPEng, 2004 John Connell Gold Medallist.Formerly Reader in Civil Engineering at University of Queensland & Technical Advisor Structural at Kellogg Brown & Root.

PROLONG THE LIFE OF STRUCTURES

Corrosion of Steel in Concrete, 2e,
John P Broomfield

2007, ISBN: 9780415334044, 296pp, $243

In an age when engineers are being expected to prolong the life of deteriorating structures,  provide designs and specifications that are sustainable this book provides an excellent reference to any engineer involved with corrosion and corrosion prevention of reinforced concrete.

All 11 chapters present the corrosion of reinforced concrete in a methodical manner clearly explaining the science and technology used and applied in the industry. The author draws on his well recognised global and respected experience to give examples to enhance the topics covered.

Chapters progress through corrosion fundamentals of steel in concrete, mechanisms of corrosion, condition evaluation, corrosion monitoring, repair and rehabilitation techniques, modelling deterioration, life cycle costs, designing for durability and future developments all having text well presented. Consideration could be given to having future editions with coloured photos as close as possible to the text reference to further assist inexperienced engineers visualising what could be expected in the field.

Even without any coloured graphics this entire book is considered to be a valuable and comprehensive guide and reference to both experienced and inexperienced engineers.

Reviewed by Brad Dockrill, Engineers Australia – Structural College Board Chairperson