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TYPE GB FLYASH BLEND CEMENT |
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Type GB Flyash Blend Cement is a general purpose blended cement containing a nominal 25% flyash. It complies with AS 3972 Type GB and is available in bulk as well as in 40kg and 20kg bags as Builders Cement.
Type GB Flyash Blend Cement is an economical alternative to Type GP and can be used in many situations where workability or durability considerations dictate the use of a blended cement. Because of the extended setting time of concrete using blended cements it is essential that appropriate curing be employed to allow the concrete to develop its full capacity. Flyash is a very fine material with a spherical particle shape and when incorporated into a concrete mix can be expected to provide the the following benefits:
Type GB Flyash Blend Cement is also suitable for use in Road Stabilisation where the delayed setting time results in increased working time available for contractors to form pavements. Strength Development. Under standard conditions of moisture and temperature the rate of gain in compressive strength of concrete made from Type GB Flyash Blend cement can be expected to be marginally less than that made with Type GP Portland cement.However, with continued availability of moisture, concrete made with Type GB Flyash Blend cement can be expected to exhibit greater strengths at 90 days and beyond.
Effect of excess water. Use only the minimum amount of water to mix and place concrete. The following graph shows the reduction in compressive strength of concrete with increased water addition.
The porosity of concrete made with excess water is also increased resulting a structure with less resistance to chemical attack. Other factors which effect the strength and durability of concrete containing Type GB Flyash Blend cement manufactured by Sunstate Cement Ltd are:
The cement content for each grade of concrete will be dependent on the nominated target strengths. AS 3600 “Concrete Structures” recommends minimum strengths to achieve adequate concrete durability for various exposure classifications. AS 1379 “ The Specification and Manufacture of Concrete” is the relevant Standard for the production and ordering of concrete. For site mixed concrete the following mix proportions are suggested. Mix Proportions by Volume
Mixing. AS 1379 gives requirements for material quality and mixing procedures for premixed concrete. Recycled water may only be used where testing can demonstrate compliance with this code. Dissolved salts and organic matter may adversely affect the strength, durability and appearance of the concrete. Sand contaminated by the above will have a similar effect.
Curing. A minimum curing period of seven days is recommended for all exposure classifications. Concrete should be maintained in a moist condition where practicable. Water sprays, wet sand or moisture retaining techniques such as polyethylene sheets or curing compounds have been used successfully. Curing should begin as soon as the selected technique allows. In hot conditions aliphatic alcohol is recommended as a technique to avoid plastic shrinkage cracking, but is not a substitute for a proper curing regime. For normal concrete curing can produce a compressive strength 80 to 100% greater than concrete not subject to curing. Curing can also effect other concrete properties including:
Variations in the duration of curing or uses of different curing methods may effect the initial colour of concrete. The following table provides examples of some typical cement properties of Type GB Flyash Blend manufactured by Sunstate Cement Ltd.
WORKING INSTRUCTIONS Storage. Contact with air and moisture will cause hydration of the cement and alter the cement properties. The ‘shelf life’ of Type GB Flyash Blend Cement is therefore dependent on the storage conditions. Bagged product should be stored off the ground and stacked to allow free circulation of air. Please note that bags are not waterproof.It is recommended that cement be retested prior to use if its age exceeds three months. Handling. A Material Safety Data Sheet can be obtained here.
Concrete Properties |
Concrete Mix | Mix Proportions |
Cement Properties |
Compatibility |
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© Sunstate Cement Ltd. All Rights Reserved |
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Sunstate Cement manufactures Type GB Flyash Blend Cement by
grinding Portland Cement clinker with flyash collected from coal-fired power
stations and complying with AS 3582.1. The flyash is added during the milling
process to ensure a thorough mixing of the components.
Placing. AS 3600 gives requirements for handling, placing
and finishing concrete. Minimum cover to reinforcement is 20mm for the lowest
exposure classification.