Disclosed may be an intermediate surface for supporting a small paver, wherein the surface can also be used to exchange heat with the pavers. In one embodiment, the apparatus may be a tray defined by a frame with a lattice for supporting pavers. The tray preferably features a tubing track throughout the lattice to accommodate heat exchange tubing. In operation the tray may be positioned above a pedestal or directly on a subsurface. In embodiment, the tray may be outfitted with insulation and a metal plate so that heat may be exchanged with pedestals via fluid passing through tubing installed throughout the lattice. In a preferred embodiment, the tray features a slot in its corners for receiving a locking disk or locking slider.

One or more embodiments relates to a hot water storage system and a method for storing hot water, the system including at least one oversized diameter tube and at least one plumbing line diameter tube coupled to and in fluid communication with at least the at least one oversized diameter tube. The at least one oversized diameter tube is further coupled to and in fluid communication with a building hot water source.

A geopolymeric material is described having compressive strength at 28 days ranging from 15 to 100 N/mm.sup.2, obtainable by curing for 12 hours at a temperature ranging from 20 C. to 60 C., from a geopolymeric aqueous mixture comprising the following inorganic components in the following parts by dry mass: metakaolin 15-65 potassium silicate and/or sodium silicate 20-40 aggregates recycled from CDW (Construction and Demolition Waste) 5-300; said geopolymeric aqueous mixture is obtainable by mixing 20-175 parts by mass of water with said inorganic components, and has a viscosity at 23 C. between 100 and 10000 Pa.Math.s, wherein: i) the viscosity is measured via Brookfield methodology, ii) the aggregates recycled from CDW belong to one or more of the classes 17.01.01, 17.01.02, 17.01.03, 17.01.07 according to the European Waste Catalogue, iii) the aggregates recycled from CDW have a grain size less than or equal to 4 mm, preferably less than or equal to 2 mm.