THE BEAUTY OF NO-CEMENT CONCRETE

David M.J. Ball, David Ball Group PLC, United Kingdom

37th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 29 - 31 August 2012, Singapore

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37th Conference on Our World in Concrete & Structures

29-31 August 2012, Singapore

__________________________________

2President of the Concrete Society

THE BEAUTY OF NO-CEMENT CONCRETE

David M.J. Ball1,2

1David Ball Group PLC

Huntingdon Road, Bar Hill, Cambridge CB23 8HN, United Kingdom

e-mail: <chairman@davidballgroup.com> webpage: http//www.davidballgroup.com

Keywords: New, no-cement concrete, performance, appearance and benefits

Abstract. The paper with the title of “The Beauty of no-cement concrete” will begin by explaining the problems of Ordinary Portland Cement concrete, the poorly understood early age performance and explain why the discovery of cement-free concrete will enable the industry to produce zero-carbon structural concrete. It will show that even with a very low water cement ratio, remarkable rheology and easy handling is possible. The presentation will include examples of very high, cement replacement projects and the consequent benefits. It will propose a radical re-think and recommend a significant reduction in both cement and reinforcement steel to achieve sustainability benefits. It will also explain how high-flow concrete will make construction times faster and give outstanding surface finish. It will conclude that doing more with less can lead to maintenance-free structural concrete assets. 1. INTRODUCTION As outgoing President of the Concrete Society and visiting lecturer at Cambridge University as well as a member of the Technical Committee to BSI and a Council Member of the Bahrain Society of Engineers, I am delighted to present to you today. I bring greetings from the Concrete Society and the Institute of Concrete Technology, our sister organisation that we help to manage. The UK and Cambridge in particular, have a special affinity and association with Singapore. We both identify with hard work and success. My wife was born here. She was taught to swim at the Tanglin Club and to this day it is delightful to watch her move in the water. I could be biased of course, I know that, but Singapore gave her a wonderful start in life and for that I am grateful. It is good to be back at OWIC again. I gave the Committee the title ‘The Beauty of No-Cement Concrete’ at the end of last year’s Conference. It is a title that I am pleased to explain, for the first time, here in Singapore at this Conference, this year. To many, it will be a case of ‘Disruptive Technology’ and to others it will be counter-intuitive; it should not work. To me, it has been an amazing voyage of discovery which, for the first time, I am able to announce at OWIC at Singapore.

David M.J. Ball

2. WHAT WE ARE ABOUT TO DISCOVER

Whilst I shall take you through the history of the Company and the role which we play in the industry and the achievements made particularly in waterproofed, corrosion-resistant concrete, I will explain the extraordinary role that ultra-low carbon concrete can play in the world’s drive for sustainable construction. Since the Kyoto protocol in 1998 set the global agenda to reduce greenhouse gas emissions to the level of 1990 as a bench mark, progress has been made. However, in spite of vast sums of money spent on reducing emissions and energy efficient equipment and vehicles coming on stream, there has been virtually no effect on global CO

2 output due mainly to population growth and

developing countries expansion. National governments are increasingly realising that tough decisions on carbon pricing and hard targets on actual CO

2 emissions are needed to force companies and

individuals to take action. The Danish government recently, for example, has set a 50% reduction in CO

2 output to be achieved by 2025 - only 13 years from now.

3. THE ISSUES FACING US

Coming to the heart of the issues facing us, it is well to remember that the industry has done well not only at the cement manufacturing, entry level, by improving production, using waste in fuels, reducing sulphur and CO

2 emissions. If I were to leave you with one overriding strap line to this year’s

Conference it would be DOING MORE WITH LESS. However, less material does not mean the structures will look cheap or nasty. I will show that what we make in the future will be beautiful, for a number of different reasons.

For the benefit of overseas delegates let me advise you what the UK cement industry has achieved since 1998.

• Dust emissions are down by 70%

• Oxides of nitrogen reduced by 50%

• Sulphur Dioxide emissions are down by a massive 75% This is a significant environmental achievement. And on energy savings, the percentage of fuel-including waste is steadily climbing to almost 30% to a figure of 1.4m tonnes of waste per year replacing fossil fuels and this is targeted to reach 50% by 2020. In the cement industry in the UK, by 2008 the CO

2 emissions were 3.7m tonnes lower than the 1998

level achieved by major investment in new plant and technology and the use of waste-derived fuels. How all of this can continue to be delivered and improved on will require technical innovation, capital investment and accurate monitoring. Only passionate commitment will make this happen and it begins with every single one of us taking personal responsibility.

4. WHY IS THIS IMPORTANT?

As everyone knows, every tonne of Ordinary Portland Cement produced puts 1 tonne of CO2 into the

atmosphere. OPC has given the construction industry a terrible problem since its invention in 1825. The problem lies with its hydration: it causes an exothermic reaction. It has a high adiabatic temperature rise during hydration which leads to 99% of all cracking problems with concrete. Either, early-age thermal or the related early restraint cracking is caused by expansion and subsequent contraction while the concrete is still relatively green. Specifically, compressive strength in OPC based concretes is achieved relatively quickly whilst the tensile strain capacity (flexural strength) develops more slowly. The rate at which the concrete is allowed to cool back to ambient temperature is not often understood by contractors. This lack of knowledge leads to statements by both consultants and contractors that ‘all concrete cracks’. That is simply untrue. However, it does get both the consultant and the contractor ‘off the hook’ and the asset owner, the client, just has to put up with the industry’s verdict - ‘what did you expect, all concrete cracks?’ or even worse, ‘there is no such thing as a dry concrete box in the ground’. Not only does this get concrete a poor reputation as a building material and plays right into the hands of the steel industry, it is scientifically wrong. I will seek to show today, for the first time in history, that we can deliver highly sustainable, ultra-low carbon, leak-free, maintenance free, concrete structures TODAY. We can also deliver ultra-low

David M.J. Ball

carbon concrete structures with less materials, greater durability characteristics and better finishes and appearances than has ever been achieved before. 5. THE STATE OF THE NATION

It is important to evaluate to where we are now, and to that extent these international conferences and the papers being delivered, provide a current global snapshot of how concrete construction and research is a constant evolving process. By sharing design ideas, construction methods and showing state-of-the-art projects, we can work together on a global basis to achieve sustainable, high-durability concrete assets. 6. DOING MORE WITH LESS I have hinted in the text above that it is my proposition here today that we could do so much more with less materials. After water, concrete is the most used material on earth. It is my personal opinion that a great deal more could be done to deliver more sustainable, high durability concrete structures with less cement and steel. Design codes largely ignore (or at least take far too long to catch up with) the improving properties of concrete. Indeed, designers seem to assume that they will always have low quality concrete on site and that delay (of the Codes of Practice) and that mind set means we are over designing and wasting valuable resources. We are also damaging the environment and behaving irresponsibly. That is not a criticism of Singapore designers I hasten to add. It is a global problem and a very serious issue. Let me set a challenge. If we were able to take out crack control steel reinforcement by careful concrete design and reduce the cement content by specifying performance-based strengths, we could remove up to 30% of both cement and steel and still achieve high durability, low maintenance structural concrete assets. A combination of aggregates of low thermal expansion co-efficients, low water cement ratios using polycarboxylate ether superplasticisers together with high cement replacement (GGBS in particular) delivers a concrete, when placed and cured correctly, does not shrink or crack. Let me give you a recent up-to-date example. The Shard building in London, currently the tallest in Europe at 1,016ft high, has a basement slab comprising 5,600m

3 of concrete

containing 80% GGBS cement replacement. It was cast over a weekend on a continuous delivery programme with NO construction joints. The heat of hydration was carefully monitored using thermo-couples and the maximum heat was to within 1 degree of the predicted levels. This is an example of using low heat of hydration to allow joint-free construction and taking out all early-age thermal cracking. It is predicted to shrink by 5mm around the perimeter. Since the basement walls are steel sheet welded piles and will be under lateral compression due to shear forces, the 5 mm predicted long-term creep will close automatically during the lifetime of the building. If we focus on the microstructure of concrete and concentrate on producing highly durable concrete, the thickness or depth of concrete cover could be reduced. Euro Code 2 1992 : 1-1 : 2004 clause 4.4.1.3 states that a 10mm reduction in cover can be made ‘if the accuracy of the steel fixing can be verified’. Good quality control on site can easily overcome this issue. On a large project that can mean a significant reduction in materials used. It is also another sustainability plus point. It will automatically reduce the project’s embedded carbon. However, doing more with less is just the start. Let me take you a whole new, game change and describe the features. 7. INTRODUCING ULTRA-LOW CARBON CONCRETE

What if we could produce high strength, ultra-low carbon, maintenance-free concrete structures today? What would you say if we could produce a concrete that:

• Used no OPC cement

• Had a zero carbon rating

• Was acid, chloride and sulphate resistant

• Was an ‘off-white’, not grey in colour

David M.J. Ball

• Had self-compacting properties when being placed

• Had ultra-low shrinkage due to an increased density leading to significantly greater dimensional stability

• Used 30% less water

• Needed 30% less reinforcement steel as crack-control steel is not needed 8. CONCLUSION As a humble manufacturer, if that is not a contradiction in terms, it may surprise you to hear that I am a great believer in and supporter of fundamental, knowledge-driven research and development. There is no ‘quick-fix route’ to sustainable, low-carbon concrete construction, but given that after water, it is the most ubiquitous material used on the planet, it is surprising how little is spent on research and development. It is my conviction that a number of practical changes, being made collectively, at the same time, backed by academic, objective and independent institutions like NUS here in Singapore could help humanity achieve a better world. Let us listen, learn together and apply. We owe this much to our children.

David M.J. Ball

Appendix 1 DURABILITY DATA OF CEMFREE CONCRETE Compressive strength Compressive strength tested according to BS EN 12390-3:2009 reached (at 20°C) 10 MPa at 1 day, 30 MPa at 7 days, 44 MPa at 28 days (strength development is shown in Figure 1). ** Such concretes surpass the GGBS concretes standard BS 6246: 1996 requirements state “greater than 12 MPa at 7 days and greater than 32 MPa at 28 days”.

Figure 1 Compressive strength of CEMFREE concrete. Setting time Setting time measured according to BS EN 13294:2002 at ambient laboratory temperature (20°C), initial, 6 hours final, 9 hours

David M.J. Ball

Durability Data Durability is a long term and an on-going issue. However, the results to date indicate that CEMFREE concretes, mortars and renders are as durable and even more so than the OPC based equivalents. Dimensional stability Drying shrinkage and wetting expansion tests, determined according to BS EN 12617-4:2002, are shown in Figures 2 and 3, respectively, showed that the drying shrinkage after 56 days was of the order of 0.6 mm/m (600 microstrains). The wetting expansion was 0.2 mm/m (200 microstrains) after the same period.

Figure 2 Drying shrinkage of CEMFREE

Figure 3 Wetting expansion of CEMFREE

Initial surface absorption test (ISAT) and water permeability Initial surface absorption determined according to BS 1881-208:1996 with the following results: 10 minutes – 0.05 ml/m

2·s

30 minutes – 0.04 ml/m2·s

1 hour – 0.03 ml/m2·s

David M.J. Ball

These results according to the Concrete Society Report TR 31 indicates a very high quality concrete. Water permeability was measured following BS EN 12390-8:2009. The depth of penetration after 72 hours was measured as zero, classifying the concrete as very impermeable. Chloride and oxygen penetration test The chloride penetration test is an important parameter for the protection of reinforcing steel. The parameter was determined using ASTM 1202-12. It was found that the passed charge was 196 Coulombs which corresponds to a very high resistance of the concrete to penetration by the chloride ion as shown in Table 1 reproduced from the abovementioned standard. This suggests a very good environment for the protection of the reinforcing steel.

Passed charge (Coulombs)

Chloride ion penetrability

>4000 High

2000-4000 Moderate

1000-2000 Low

100-1000 Very Low

<100 Negligible

Table 1 Interpretation of passed charge values in terms of chloride ion penetrability. Reproduced from ASTM C1202-12. Alkalinity level (pH) The pH of typical DBG-XYZ concretes is between 11.5-12.0 which is sufficient for the protection of steel. It is also low enough to prevent alkali silica reaction problems.

Three Examples of CEMFREE Polished Concrete

Example 1

David M.J. Ball

Example 2

Example 3