Precast concrete materials, manufacture, properties and usage - Chapter 9 ppt

... knowledge, ‘know-how’ and ‘alchemy’, and if one does not know what the variables are doing at any one time control is lost. One can list the factors and control variables one would use in precast manufacture ... all procedures in the manufacture and/ or testing (Assessors and Company). 4. Keeping Record Cards on all machinery, equipment, etc. (Company and Assessors). (See Chapte...

Ngày tải lên: 08/08/2014, 10:23

... accurate and consistent quantity of concrete into the mould. In some precast processes tilting tables are used both to cast the concrete and lift the mould and concrete into the near-vertical ... 240V or three-phase supply under closely supervised nominally dry conditions. 13. Re-vibration of concrete is beneficial if the concrete is re-vibratable and the cost of double ha...

Ngày tải lên: 08/08/2014, 10:23

... required and the hand process is time- consuming. After the trowelling or rolling-in, the unit is subjected to a wash-off, sand-blast or other suitable technique to expose the aggregate. Fig. 6.6. Precast ... process a 4- or 8-drop would take place about every 15 seconds. 6.6.3 Wet and earth-moist mix presses In the production of floor tiles the wet and earth-moist mix mentioned fo...

Ngày tải lên: 08/08/2014, 10:23

... the maximum temperature and the early and late strengths. (c) Exceeding 90 °C concrete temperature causes loss in both the 24 hour and 28 day strengths due to the concrete becoming too hot and losing water. (d) ... up and gains strength slowly; a warm-starting concrete, say 25°C, warms up and gains strength more quickly; and a concrete starting at, say 40°C, can be handl...

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... 0-2 0 3-4 90 5 7-6 Master e-book ISBN ISBN 0-2 0 3-7 98 8 1-3 (Adobe eReader Format) ISBN 0-8 533 4 -9 9 4-0 (Print Edition) WITH 40 TABLES AND 1 09 ILLUSTRATIONS © APPLIED SCIENCE PUBLISHERS LTD 198 2 All ... Publishers Ltd 198 2 PRECAST CONCRETE Materials, Manufacture, Properties and Usage M.LEVITT ARCS, BSc, DIC, PhD Head—Materials Sci...

Ngày tải lên: 08/08/2014, 10:23

... relevant to precast concrete manufacture leaving mix design to Chapters 5 and 6. 1.5.1 Cement types The most common cements used are ordinary and rapid-hardening Portland (including white), sulphate-resisting ... Publishers Ltd 198 2 synthetic aggregates need to be pre-wetted prior to mixing with the cement and additional water. Some limestones and sandstones have a slower absorpt...

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... as Copyright Applied Science Publishers Ltd 198 2 2 ADMIXTURES This chapter covers the range of admixtures used in precast concrete products and mortars used with precast masonry. They are all used ... Vibrated reinforced and unreinforced concretes (reinforced units only if permitted by regulations). 2.2 (a) and (c) as 2.1 and pressed and extruded products. 2.2 (b) ready...

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... concrete colour Both the desk-top 100mm square sample and the 300mm square hand- portable samples are misleading in the case of unpigmented materials, and for coloured concretes and mortars they seldom ... agents should be water-in-oil emulsion creams or chemical release agents. Ordinary mineral mould oils and oil-in- water emulsions promote streaking and staining. (c) Pan-type...

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... series of works-manufactured, laboratory-tested pneumatic-hammer-compacted precast concrete kerbs. The results may be related to any hand machine or mass machine process where earth-moist mix designs ... the user, and in this respect vibrated concrete can only take a few per cent of ash and it is hardly economic to set up a second silo in a precast concrete factory to handle suc...

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... defective concrete in toto and replace with good quality concrete. Most of the experience with alkali-aggregate reaction is that the defect manifests itself after the steel has corroded and the concrete ... Publishers Ltd 198 2 organic growth areas so treated should be left for a few days before cleaning and scrubbing the surface. 8.4 SITE HANDLING AND USAGE With a good deal...

Ngày tải lên: 08/08/2014, 10:23