This article sets out to analyze how concrete is implicated in the transformation of public space in provincial Peru. While concrete enhances a state's capacity to produce reliable, predictable structures, there are also significant limits in relation to its connective capacity in both the material and social domains. Ethnographic attention to the relational dynamics of concrete reveals how its promise to operate as a generic, homogeneous, and above all predictable material is constantly challenged by the instability and heterogeneity of the terrains to which it is applied. The image of power that concrete affords is thus a compromised one, as the stability and predictability of this substance is secure only insofar as it is surrounded by and embedded in specific relationships of care. © Berghahn Journals.