The contractor laid this firebrick with typical masonry mortar and topped the face with refractory mortar. The brick must be laid in refractory mortar, with joints no larger than 1/4".
Incorrect MortarGallery: GalleryDescription: The contractor laid this firebrick with typical masonry mortar and topped the face with refractory mortar. The brick must be laid in refractory mortar, with joints no larger than 1/4".