Gen_11:3, "slime had they for morter": chemer. Hot bitumen was used for cement in the walls of Babylon (Herodotus i. 179). At It, now Heets, eight days' journey from Babylon, the bitumen was obtained. Layard says the cement is so tenacious that it is almost impossible to detach one brick from another. Stubble or straw among the Egyptians, as hair or wool among us, was added to mud or moist clay to increase tenacity.
If this were omitted, or if the sand, ashes, and lime in the proportion 1, 2, 3, were insufficiently mixed, there would be "untempered mortar," tapheel Arabic tapal, pipe-clay like, detritus of felspar (Eze_13:10). The absence of the true uniting cement answers to the false prophet's lie, "thus saith Jehovah, when He had not spoken" (Eze_22:28), false assurances of peace to flatter the people into non-submission to Nebuehadnezzar (Eze_21:29; Jer_6:14; Jer_23:16-17). 'aaphaar "dust" also is used for mortar (Lev_14:41-42).
Fausset's Bible Dictionary
By Andrew Robert Fausset, co-Author of Jamieson, Fausset and Brown's 1888.