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2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact.

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Presentation on theme: "2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact."— Presentation transcript:

1 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

2 Low Cost Cement replacement with PFA - also helps durability and workability. Cement replacement with GGBS - helps durability but may increase bleeding. Water (and cement) reduction with a water reducer - helps with durability. Cementitious content reduction with CSF - do not do it.

3 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

4 Light Weight Light weight aggregate - some strength reduction, good thermal properties. Foamed concrete - very low strength. No-fines concrete Fig Shows routes to producing light weight concrete and fig shows the achievable densities. Foamed concrete

5 Lightweight aggregates

6 Lightweight concrete and mortar

7 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

8 Heavy weight (for shielding) Heavy weight aggregate Steel shot - high cost and segregation.

9 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

10 Underwater concrete CSF - OK to use it for this - good cohesive mix. Non dispersal admixtures. Note that any concrete may be placed under water if precautions are used to avoid washout.

11 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

12 Ultra high Strength Superplasticisers (high range water reducers) CSF In-situ de-watering (for slabs) Must have strong aggregate

13 Ultra high performance concrete

14 Advantages of High Strength Concrete (HSC) High durability (e.g. abrasion and carbonation resistance) High strength to weight ratio, particularly for lightweight HSC High early strength allows faster construction and formwork reuse Increased elastic modulus and lower creep Very tall buildings become feasible Lower column costs for concrete and steel Smaller columns allow for more floor space Box girder and solid girder bridge spans may be increased and designs simplified

15 Disadvantages of HSC Increased cost per unit volume More stringent quality control of materials and construction needed CSF mixes may self-desiccate giving failure at day joints. Workability difficult to define and often declines rapidly with time after mixing Timing of concrete delivery and addition of admixtures becomes critical. High heat evolution may necessitate use of low heat binders (e.g. PFA) and cooling measures. Stiffness (modulus) does not increase in proportion to strength. More than 28 days may be required to reach specified strength Structural members may exhibit brittle failure. Use of HSC not covered by codes

16 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

17 Ultra durable concrete Ultra high strength with good curing Controlled permeability formwork Coated or stainless rebar Silanes or siloxanes (Glass fibre in surface)

18 Fragmentation resistance with glass fibre

19 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

20 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

21 Needs a feature to hide colour change

22 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

23 Exposed aggregate finish

24 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

25 Board finish

26 Patterned board finish

27 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

28 Brush Finish

29 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

30 Profiled (ribbed) finish

31 Profiles to hide day joints

32 Deep profiles on wall

33 Ribbed (profiled) finished spoiled by unevenly applied mould release oil.

34 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

35 Imprinted concrete

36 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

37 White concrete (being cleaned)

38 Pigmented Concrete

39 Concrete with good appearance (Architectural concrete) Avoid plain surfaces Exposed aggregate: Surface retarded, Bush hammered, Worked before final set, Hand placed aggregate Board finish Brush finish Ribbed finish Imprints etc. White cement, pigments etc. Note that a highly textured surface may collect dirt and moss.

40 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

41 Low noise concrete for roads Random grooves Exposed aggregate

42 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

43 Concrete with reduced environmental impact Cement replacements such as PFA or GGBS save 850kg of CO 2 for every tonne of portland cement saved No-fines concrete is also known as "pervious" concrete and can reduce or eliminate run-off from roads and prevent flooding and pollution. A bright white concrete surface with GGBS will reduce the "heat island" effect of cities in hot climates. Magnesia or Alumina Cements to replace calcium silicate

44 Placing pervious concrete

45 Concrete with reduced environmental impact Cement replacements such as PFA or GGBS save 850kg of CO 2 for every tonne of portland cement saved No-fines concrete is also known as "pervious" concrete and can reduce or eliminate run-off from roads and prevent flooding and pollution. A bright white concrete surface with GGBS will reduce the "heat island" effect of cities in hot climates. Magnesia or Alumina Cements to replace calcium silicate

46 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

47 Fast Setting Concrete for Precasting Superplasticisers to reduce the water content are often as effective as accelerators. High temperature curing - but this can cause delayed ettringite formation Autoclaved concrete (high temperature and pressure) for rapid production but the hydration products are very different.

48 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

49 Placing without formwork Shotcrete Often used with fibres.

50 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

51 Bulk Fill Foamed concrete Controlled Low Strength Material (CLSM) is a flowable fill Below about 1MPa it can be re-excavated with a hydraulic excavator Can be made without cement

52 CLSM. Waste gypsum and steel slag (no cement)

53 2.13 SPECIAL CONCRETES Low Cost Light Weight Heavy Weight Underwater Ultra High Strength Ultra Durable Architectural Low Noise Reduced environmental impact Fast setting Placing without formwork Bulk fill Self compacting

54 Self Compacting Concrete Requires viscosity modifier to prevent segregation Reduces labour required Reduces noise Reduces risk of white-finger Costs about £30/m 3 more


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