Repairing a silage pit with sealants requires careful work. Carried out correctly, it will eliminate leaking of effluent and prolong the life of the pit. Last week, I attended a demonstration of repairs being made to a pit. It was on the farm of Brian Burgess, Lough Egish, Co Monaghan. The repairs were made with Botament sealants and I will be returning to look at the repaired surfaces over the next few years to see how the job turns out.

The pit was empty and Brian had it cleaned out and power-hosed in preparation. I cannot overemphasise the importance of proper cleaning of the surfaces. You must get back to sound concrete before attempting to apply coatings or sealants.

Grass silage in Ireland, compared with other countries, produces more effluent and the effluent is more acidic due to the higher moisture content of the ensiled material. The damage to silage bases and silage pit walls is more of a problem here than in other countries where wilting is more easily achieved. The silage pit used to demonstrate the products is a typical walled silage pit located beside a slatted unit. The pit is about 30m long by 11m wide (330m2) and the total length of the walls is about 70m. It is close to the public road and Lough Mourne, which is just over the road.

The silage pit was originally built in 1988 and the floor was resurfaced in 2005. The walls are structurally sound and the surface of the floor is not badly worn. The lower part of the wall is eaten away from the effects of effluent over the years.

There are a fair few cracks and joints in the floor, which need resealing in places. The wall floor joint has been sealed a few times and needs attention again. Joints were formed when the resurfacing took place but, since then, cracks have also appeared in parts of the surface. It’s hard to tell but these cracks may be due to cracks and movements in the original floor.

There is a tendency for cracks in the original floor to induce cracks just above them in the resurfaced floor. Joints are cracks that have been deliberately formed during construction and are straight and easy to seal whereas cracks appear where they are not supposed to and are not so easy to seal. In this pit, most of the joints and cracks are sealed but some stretches need resealing.

Botament manufactures a range of construction chemicals. These products have been used for silage pit repairs in Germany, France and other countries across Europe and Asia. The repair work on the Burgess pit was carried out by Jim Tierney, product manager and Fergal McGrath, technical manager for MC Chemicals/Botament, Castleblayney.

Role for repair materials

Ideally, these materials should be used on new silage pits – on walls at the wall floor joint and in channels and along the edges of channels. It would be best to use them as soon as the concrete is cured. However, if you can’t get around to it straight away, it can be done after a few years or at any stage as long as the pit is structurally sound, but obviously the sooner the better. By doing it in time, you are protecting your investment as silage structures are expensive; bases cost at least €25/m2 and walls more than €300 per linear metre.

The photos and descriptions below give an insight to the work done on Brian’s pit. More work has been done since these were taken last week and the joint/crack sealing also has to be attended to.

Picture one

During construction, the channel was formed under a sheet metal channel former and the channel former was left in situ, which is not usually the case.

Under a metal channel former, it can be very difficult to ensure that the concrete is properly compacted. It was decided to remove the channel former as it had loosened away along its edges and effluent was getting in around it. In this picture, we can see the channel after the metal channel former was removed. There were porous areas here and there, along the base of the channel.

There were three areas where the concrete was porous under the channel and a few places where the base of the channel came away stuck to the metal. A Botament repair mortar was used to repair the damaged and porous parts of the base and sides of the channel before it was brushed with the acid resistant protective coating (RD2).

Channels are essential for controlling effluent flow around silage pits, but if they contain weak points, honeycombing, cracks or porous patches, they can make matters worse.

Picture two

Jim brushes on the first coat of RD2 to the sides and base of the channel. Remnants of the bitumen coating are still present beside the channel. It would be good to coat a little of the floor at the pit side of the channel as this area, with free-flowing effluent, is almost as vulnerable as the channel itself.

Picture three

Sealing tape is placed at the wall floor joint and smoothed over the first coat of RD2. This will be brushed over with the second coat. The sealing tape, which is acid and rot resistant, will seal the wall floor joint and accommodate any normal movement. The tape costs €3 per linear metre. The wall surface along here is in good condition. More of the surface is eroded on other parts of the walls. These areas will have to be plastered with a repair mortar (cheaper than RD2) to build back the wall surface a bit and make the RD2 coverage go further.

Picture four

Here, we see Jim Tierney dampening the wall before applying the RD2. The imprint of the sealing tape can be seen at wall floor joint. Jim is available to supply and give advice on the use of the products.

Picture five

Fergal McGrath applies a layer of RD2 to replace some eroded concrete and repair surface damage. Using a steel float, it’s easy to apply it over the first brush-on layer. Applying RD2 like this will increase the cost versus a brush on coat. This is not necessary unless a smoother finish is desired. Where the surface needs building up quite a bit, a cheaper repair mortar should be used.

Note the darker cured initial coat versus the lighter colour of the freshly applied layer. This is because RD2 has visible curing control that lets you know when it’s cured and ready for a second coat.

If the surface is smooth, the second coat can be brushed on. The height of the repair is about 1m overall. The RD2 comes in 8kg and 20kg tubs. It is a two-part material half and half liquid and powder. They are mixed before use. The coverage of RD2 is about 2kg per m2 or about 10m2 per 20kg tub. This is for two coats on a fairly smooth wall but if the surface is rough, the coverage will be less. A 20kg tub costs €125, plus VAT, or about €12.5/m2.

Picture six

This shows the completed treatment of the channel after the porous and damaged areas were filled with the repair mortar and painted over with two coats of RD2. In the distance, this is how the silage wall looks after two coats of RD2.

Local TD and Minister for Arts, Heritage and the Gaeltacht, Heather Humphreys, visited the farm to see the work in progress. Minister Humphreys said: “Anything that helps farmers protect the environment as they go about their daily work is to be welcomed. I am pleased to see innovative ideas being developed that will help both farmers and the environment.”