What is concrete? Loved and loathed in equal measure, this building material, as soon as we try to define it, to specify it, to describe it, becomes, well, not very concrete at all, but rather fluid and surprisingly abstract! Concrete is a material which has been going through an interesting intellectual and practical renaissance in recent years, in no small part driven by the convergence of several different kinds of technology-driven manufacturing changes - ranging from computer aided manufacturing of formworks, to photograph etching, to engineering software, to nano- and bio-chemistry to 3D printing - which have opened up new worlds of realizable, expressive and performance optimised form. The demands posed by anthropogenic climate change, energy use, resource scarcity, and the environmental question more generally, have equally transformed the technologies and industries that are now feeding into developments in this material. On its own though, that is not enough to understand the revival in interest. In this paper I will argue that there are indeed profound relationships between capital, modernity and concrete. However, I will suggest that in order to really start to grasp these relations, we will need to explore some ways of thinking about concrete that have not been developed so far within the recent literature on the material. Notably I will develop an ecological approach to thinking about what concrete is, and in so doing redefine this material as a particular form of mud, or mudcrete: a material which is deployed by both human and non-human builders. I will note the ecological energetics and extended materialities of mudcrete, and will reflect upon the conceptual 'forms' or ‘patterns’ of this matter as a particular modality of the production of nature. Mudcretes always internalise in particularly interesting ways I argue, their external relations, the extended networks of materials, skills, labours and energies that go into their production. Mudcretes frequently stage fascinating bio-semiotic performances, whichever species or processes are dominant. But when the mudcretes in question are the product of human labour, they always act as social media.