I just made a mod I hope you will add.
It adds concrete that you can pour and cure. Now we can form up, pour, and cure concrete slabs, houses, etc.
The concrete liquid is very viscous and slow moving. It has a slump of 4 nodes. Every 30 seconds it hardens into cured concrete. Cured concrete has no craft, but you can mine the blocks and make concrete stairs.
Because it is the number of concrete nodes that could be made equals the number of nodes the liquid could flow in 30 seconds, I have made the recipe for the batch of wet concrete expensive in nodes. 12 compressed cobble and 1 water bucket makes one wet concrete source (a batch of concrete). The empty bucket is returned. That means that you need 12*9 = 108 cobblestone nodes to make one concrete source. Typically, a single source node will generate far fewer nodes than 108, however, if placed in the air, if you happen to place it such that you get most of the 30 seconds cure time before the abm cures it, and the concrete liquid falls, 120 or so nodes may be generated. I thought that requiring 108 cobble was a good compromise, since most uses will generate no more than 60 nodes or so, often much less.
This makes an easy way to pour concrete roads. Dig the form, then place concrete sources every so often in the void, and it will form up and cure. Interesting experiments could be made with pouring concrete houses, though you have to be careful not to leave voids when every 30 seconds the wet concrete cures.
Here is the minetest forum post: