Readymix concrete producers employ a standard mix designation which should be used when ordering. The initial figures in Table II indicate the strength grade and the latter figures indicate the maximum size of aggregate. For example, the silage pit mix recommended indicates concrete with a crushing strength of 40 Newtons per square millimetre after 28 days and a maximum aggregate size of 20mm. Adequate durability is achieved by specifying a cement content appropriate to the demands made on the concrete. This is particularly important for silage pits and milking parlour floors.

Concrete must be fully compacted. The presence of entrapped air in hardened concrete reduces strength and critically affects durability. While hand tamping is appropriate in some cases, it is easier to achieve full compaction using mechanical methods. These include vibrating screeds for yards and floors and poker vibrators for walls, silos and for the edges of slabs. The timing of the final brushed, tamped or trowelled finish is very important. Premature finishing draws excess water and cement to the surface and this invariably leads to rapid surface deterioration and poor resistance to wear. Unnecessarily wet mixes greatly delay the work of finishing and inevitably cause serious and unnecessary difficulties. Concrete needs to be protected to prevent moisture loss especially for the first week after placing. The interval between final finishing and the start of curing should be kept to a minimum to avoid damage to the surface. The more usual methods for curing include covering with damp sacking, damp sand or polythene sheet or spraying continuously with water. In cold weather polythene sheet covered with straw provides protection against frost.   Use Irish Cement which has been stored in dry conditions. Use only clean sand and gravel. Select the right mix for the job and always keep a strict control on the addition of water. Compact concrete with a minimum of delay, particularly in warm weather. Protect freshly placed concrete from rapidly drying out and from frost. The readymixed supplier is responsible for providing material as ordered. Do not add extra water as this weakens the concrete and may invalidate the supplier’s guarantee. Advisory Engineers are always available to help solve problems related to the use of concrete on the farm.