The present invention provides a bidirectional energy-transfer system comprising: a thermally and/or electrically conductive concrete, disposed in a structural object; a location of energy supply or demand that is physically isolated from, but in thermodynamic and/or electromagnetic communication with, the thermally and/or electrically conductive concrete; and a means of transferring energy between the structural object and the location of energy supply or demand. The system can be a single node in a neural network. The thermally and/or electrically conductive concrete includes a conductive, shock-absorbing material, such as graphite. Preferred compositions are disclosed for the thermally and/or electrically conductive concrete. The bidirectional energy-transfer system may be present in a solar-energy collection system, a grade beam, an indoor radiant flooring system, a structural wall or ceiling, a bridge, a roadway, a driveway, a parking lot, a commercial aviation runway, a military runway, a grain silo, or pavers, for example.

A modular nuclear shield wall construction block /1, 40 )comprising a framework (30) formed from a basalt fibre reinforced polymer composite and concrete interspersed within the framework, wherein the block is configured to interlock with a corresponding block in one or more dimensions. A method (500) of forming a modular construction block (1, 40); and a method (600) of forming a modular structure are also disclosed.