Concrete silos lose strength, fall over

At least two concrete silos have toppled onto dairy barns in one year

Nelson Zandbergen
Farmers Forum

SOUTH DUNDAS — At least two Ontario dairy farms picked up the pieces after concrete tower silos fell over and destroyed their barns for reasons unrelated to weather, sources familiar with both situations have told Farmers Forum. One silo collapse occurred this past spring in Perth County, preceded by a similar event in Dundas County in 2022.

Both operations are rebuilding while their cows are being milked on other farms. The Dairy Farmers of Ontario, citing confidentiality, won’t say how many milk producers are rebuilding due to silo collapse or any other type of catastrophe.

Nonetheless, the frequency of silo collapse has increased in recent years, OMAFRA says, and these serious events have been known to kill farmers, farm employees and livestock.

Silage acids get the blame for causing the deterioration of both poured concrete and precast concrete stave silos. When these acids touch the concrete silo walls, they react with the Portland cement matrix and cause a gradual loss of strength.

The rate and severity of the damage depends on silo size, excessive moisture in the stored feed and the amount of preventative coatings — gunite, aka sprayed concrete — applied to the structures to maintain them. For more details, see the online Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) fact sheet.

Silo collapse often “happens because they don’t regularly ‘gunite’ the inside or outside of the lower 10 feet on a concrete silo,” retired Ottawa Valley Harvestore sales rep Henk Huizenga observed. While Huizenga specialized in Harvestore’s blue steel silos, he’s well versed about the ins and outs of concrete silos. He said he’s seen lots of concrete silo collapses in his career, most often the precast type that go up in sections or staves.

OMAFRA recommends using high-quality concrete when building new silos and to add an acid-resistant coating to the bottom ¼ to ⅓ of the structure. If possible, remove all silage from the silo once a year to allow the lower silo walls to dry out.

Cracking of the concrete walls is the only warning sign of impending silo failure. Farmers are advised to visually scan for cracks in silo walls at lease once a year. Contact an engineer before emptying a silo showing signs of distress, the OMAFRA fact sheet says.