From Worms Knowledge Base
When selected, your worm puts on his trusty yellow hat and pulls out a cement mixer. Time to fill in that ugly pot-hole.
On activation, the cement mixer is tipped and cement pours out into the terrain. It moves over the terrain like a fluid, filling cracks and holes, generally flowing down slopes until it reaches a container. It does not directly damage worms it comes into contact with, or actually affect any of the objects on the terrain. But when all the cement has settled, it solidifies into solid terrain, encasing any worms unlucky enough to be in the way.
These worms will have to escape by teleportation, or drilling tools such as the blowtorch.
The cement is no harder to destroy than standard terrain, but an alternative variation sees the cement as being a harder substance. Varying strengths of land have been discussed and generally seen as a positive idea.
For this weapon to work, Worms must be programmed with primitive fluid dynamics. I am not sure how exactly they would operate but in two dimensions it can't be too challenging.
Worms have a tendancy to end up at the bottom of a pit, or stuck in a trench, after being knocked about a bit, so it would come as no surprise to see this construction tool over-used, and many players may get frustrated to see their worms continually getting encased in cement. Still, this tool can be used for other things, such as disabling a mine's threat or by blocking the entrance/exit to a suitably formed tunnel.
So far, the Girder is the only weapon capable of creating land in Worms. Unless you count the Long Bow, but that's not an effective building-tool. More options for creating land are needed, but it's hard to come up with things that don't resemble a Girder. Cement, however, despite not being as versatile as a Girder, provides more opportunities for land creation.