Durability and Curing of Shotcrete - saimm：耐久性和固化的喷浆及.pptVIP

Durability Curing North American Specifications Moist curing for a minimum of 7 days is a recommended norm Durability Curing A current perspective The benefits of curing newly placed structural concrete are well understood in the civil engineering industry Moist conditions are necessary to ensure that complete hydration is achieved which in turn will ensure optimum strength gain and minimise shrinkage Durability Curing A current perspective When it comes to sprayed concrete it often appears that the above mentioned benefits are not fully appreciated Perhaps this stems from the fact that when first introduced in tunnelling work shotcrete was used as a temporary expedient Durability Curing A current perspective The expected service life in mining is often a lot less than in the civil industry This simply reinforces an attitude that shotcrete is a temporary expedient and that proper QC is not required Durability Curing A current perspective The expected service life in mining is often a lot less than in the civil industry This simply reinforces an attitude that shotcrete is a temporary expedient and that proper QC is unecessary Durability Curing A current perspective What seems to be overlooked is that poor QC of the whole process of producing and placing shotcrete (includng curing) can lead to mix designs being used that contain excessive quantities of cement – resulting in unnecessary expense …… Durability Curing A current perspective ………… and resulting in undesirable effects such as shrinkage Durability Curing Methods of curing Water-spraying at suitable intervals – but there are difficulties in ensuring this is actually done Maintaining an humidity RH of 80% or more – not always a practical solution Curing membranes – but NOK where multiple layers are required Durability Curing Methods of curing Internal curing by using special additives, eg Meyco TCC 735 Internal curing by using sintered lightweight aggregates – available in the US – but maybe not