If you have an old concrete trough, the best option is likely to replace it with a new model from our quality selection. You can attempt to repair the trough if you wish with a sealant such as Bondex. Mix Bondex with sharp sand and cement to make a strong repair mortar that may be applied in 6mm thicknesses. If you want to do extremely thin repairs, use a formula of 1:1 Bondex to Polycote Kiln dried Sand and Cement. This may be blended as wet as you wish and poured/scraped over the surface of a trough to create a temporary repair.