Sprayed concrete has been a very effective technique for structural facing for over 100 years. It can be used on many applications such as stabilising rock faces, masonry structures, bored pile retaining walls and concrete repairs.

Gunite, the term applied to a dry mix, is a blend of pre-mixed sand and cement that is carried through a high-velocity compressed air stream from the machine to the nozzle, where the cement is hydrated as it is deposited. The process bonds the gunite to clean concrete, brick or stone. Gunite will also bond to other materials that have similar coefficient rates of expansion and contraction. Typical uses are bridge and harbour repairs, to provide a facing to loose rock faces, and providing a facing to contig and secant retaining walls - both as temporary or permanent works.

Shotcrete, the term generally applied to wet mix, involves pumping of a previously prepared concrete, typically ready-mixed concrete, to the nozzle. Compressed air is introduced at the nozzle to impel the mixture onto the receiving surface. The wet-process procedure generally produces less rebound and therefore waste and dust compared to the dry-mix process. The greatest advantage of the wet-mix process is that all the constituents are mixed with the water and required additives prior to application resulting in more predictable results. Also, larger volumes can be placed in less time than the dry spray process.

Advantages of sprayed concrete:
• Little requirement for expensive formwork
• High strength and compaction therefore low permeability and excellent durability
• Low water/cement ratio
• Gains strength very quickly
• Excellent adhesion and bond strength
• Material can be pumped over 200m to point of application

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Quinn Piling Limited is a limited company registered in Northern Ireland. Company Registration No. NI041458
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