Presentation at OWICS Symposium in Singapore, August 2009

1. FUTURECRETE The Future of Concrete in a Greener World Ken W. Day

2. The Task Ahead In 1981 my paper “Concrete in 1991” to OWICS was easy to write I even suggested it may be suitable for presentation in 1991 as “Concrete in 2001” due to excessive conservatism in the industry and professions Today it is much more difficult to look 10, or even 5, years into the future

4. Concrete can be self-consolidating or roller compacted, have a strength of more than 200MPa, be pumped to 600 metres height and claims are made of 100year durability.

5. Several organisations are either making or investigating concrete made with no Portland cement whatever;

7. Cement Cement production is a major source of CO2 But concrete is a desirable construction material,: having low embodied energy, high thermal mass, potentially high durability Cement production is one of world’s major businesses so there is: Significant cost and inertia in any change And the cement industry has a significant voice in government policy

8. Cement So the task confronting us is to minimise the usage of cement without reducing the production of concrete (and, if possible, with minimum disruption of the cement industry) Is Geopolymer a solution?

9. Geopolymer One current producer has said that it is easy to make geopolymer and almost anyone can do it. However to make large quantities of GPC, with acceptable properties, at a competitive price, is a very different matter.

10. . Certainly potentially cost-competitive GPC is possible, and indeed is already in limited production, in Europe by Joseph Davidovits (the original discoverer of GPC) in Australia by Jannie van Deventer and Peter Duxon. However such GPC needs to reach full industrial scale to be fully cost-competitive -see Duxon’s appendix to written paper.

11. GPC at Zeobond

12. Zeobond GPC Plant, Melbourne

13. Zeobond GPC Plant, Melbourne

17. Cement replacement materials So, if we cannot rely solely on GPC, what can we replace cement with?

18. Cement replacement materials Fly Ash (PFA) Slag (ggbfc) Silica Fume Metakaolin Rice Hull Ash (RHA) Superfine Calcium Carbonate (CaCO3)

19. Ex Boudewijn Piscaer Estimated availability & CO2 reduction in Millions of Tons

20. Cement It is clear that there will in the future be very little use of OPC as the sole cementing material. Professor Swami of Sheffield University, UK, has written: “No concrete should be made without incorporating mineral admixtures or other pozzolanic cement replacement materials. Indeed, if one uses Portland cement alone in the cementitious system, then it should be (i.e. needs to be) justified”

22. but need also to consider reduction through better mix design and QC and better admixtures.

23. A major problem in USA is the continued use of prescription specifications,

26. as has been done for 30 years in Australia

27. will have huge consequences.

28. It will mean that additional profit can be made by having a high class laboratory and top class personnel.

29. Many producers will be unable to compete so that, as in Australia for many years, Most RMC plants will be owned by a few major organisations

31. Staff

32. Procedures

33. Record keeping and verification

36. One approach, still persisting amongst ignorant specifiers, was to specify a minimum cement content.

37. Then it became apparent that, at a given W/C ratio, more water was more deleterious than less cement.

39. A recent paper has shown that the introduction of ggbfs (ground, granulated, blast furnace slag) can have distinctly more effect on durability/permeability than a 25% reduction in W/C

41. A great deal of work is being done on this:

42. RCP used in USA and elsewhere

43. VPV (Fred.Andrews-Phaedonos@roads.vic.gov.au)

44. Mark Alexander at Capetown Uni. South Africa

45. James Aldred’s 260page PhD thesis

46. Accepting such a criterion would allow the producer to determine which replacement material and/or admixture provides the best value in his area

48. But several years ago, Harrison in Australia has shown that a large proportion of magnesia (magnesium oxide) gives a substantial improvement in durability and other properties by supplementing Portlandite with Brucite (Mg(OH)2) in otherwise normal concrete, while reducing CO2 generation in production and continuing to absorb it after placing.

49. Imperial College UK have started working on “Novacem”, entirely replacing Portland Cement with magnesia

51. Nearly every Quarry is surrounded by discarded mountains or filled pits of “dust”.

53. So suitable crusher fines can be used as the sole fine aggregate

54. And coarser crusher fines can be used in conjunction with an excessively fine sand

55. And finer crusher fines with an excessively coarse sand

57. For more than 30 years I have been designing cost competitive mixes, overseas and “over the telephone”, with no trial mixes and no more information than a sand grading and verbal description of coarse aggregate.

58. The likelihood that such a procedure would still yield an optimum mix, capable of competing with a higher tech assessment and investigation, is perhaps now remote.

60. Surface finish requirements are becoming more demanding and may require self-compacting concrete in special formwork

61. Such concrete can be obtained by oversanded and over-cemented ordinary concrete heavily dosed with admixture

63. They are being used to reduce water content; improve workability; entrain air; accelerate or retard setting and strength development; and to reduce permeability, shrinkage or bleeding

64. It used to be that the purpose of admixtures was to save cost by reducing cement content, but the new high range water-reducers cost distinctly more than the cement they replace

65. So the cost justification was saving labour content

66. But they took hold faster in cheap labour countries,

67. Because the big justification was saving skill

74. RMC will be produced under strict QC (by Producers) to meet limits of strength, workability, pumpability, durability, and shrinkage, often using crusher fines and always at least one cement replacement material.

75. As much as 30 to 40% will be self compacting.

76. Another substantial % will be for RCC roads,

77. Permeable concrete will be more widely used

79. Geopolymer concrete likely to be quite widely used but cannot amount to a substantial proportion of concrete in the near future (also note that it uses fly ash and ggbfc).

80. Fly ash, ggbfc, silica fume, rice hull ash, metakaolin and especially superfine calcium carbonate, will be widely used – all concrete will contain at least one of these and there will be competition for available supplies of them.

82. required to use natural sand of specified grading

83. produced (and specified) by a company having no knowledge of concrete technology or QC and having no laboratory facilities or effective control system

86. if you always require your selected expert to back his recommendation with actual test data from a recognized laboratory