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SHRINKAGE LIMITING CEMENT |
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Type SL Shrinkage Limiting Cement is a normal portland cement complying with AS 3972.
Type SL should be specified where the performance of a structure would benefit from reduced concrete shrinkage, with examples being:
Strength Development. Under standard conditions of moisture and temperature the rate of gain in compressive strength of concrete made from Type SL cement can be expected to be marginally less than that made with Type GP Portland cement. However, with an appropriate curing regime, concrete made with Type SL cement can be expected to exhibit similar strengths at 90 days and beyond.
Water/cement ratio = 0.66, Cement content = 320kg/m3 Slump = 80mm, Total water = 210litres/m3 Effect of excess water. Use only the minimum amount of water
to mix and place concrete.
The porosity of concrete made with excess water is also increased resulting in a structure with less resistance to chemical attack. Other factors which effect the strength and durability of concrete containing Type SL 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.
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 mitigate 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 SL manufactured by Sunstate Cement Ltd.
Type SL may be blended with other cements complying with AS 3972 and with blast furnace slag or flyash complying with AS 3582. However this could be detrimental to the shrinkage characteristics. It is also compatible with admixtures complying with AS 1478. WORKING INSTRUCTIONS Storage. Contact with air and moisture will cause hydration of the cement and alter the cement properties. The ‘shelf life’ of Type SL is therefore dependent on the storage conditions.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 / Proportions |
Cement Properties |
Compatibility |
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© Sunstate Cement Ltd. All Rights Reserved |
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Sunstate Cement manufactures Type SL from portland cement
clinker but with a lower particle fineness compared to Type GP. This lower
fineness results in slightly slower early strength development but reduces the
amount of drying shrinkage. Other factors such as aggregate type, water content
and curing practices will also have a significant effect on the overall
shrinkage performance of the concrete.
Placing. AS 3600 gives requirements for
handling, placing and finishing concrete. Minimum cover to reinforcement is 20mm
for the lowest exposure classification.