This invention is intended to provide a high strength porous concrete structure which is preferably applied to a water permeable pavement, a draining pavement, a sound insulating board, a sound-proofing barrier, a sound absorbing block for acoustic, a block for plants, a riverbed block, a water purifying matrix, a gas absorbing matrix, a decorative board for building, a fish reef, a block for fish reef or a block for breeding algae and to provide a method of manufacturing the high strength porous concrete structure. The high strength porous concrete structure 1 having an arrangement in which a plurality of lumps 2 whose configuration is rough aggregates are integrally formed with the same concrete tissue and a gap 3 formed between the lumps 2 is through to a back side 2a of the lump 2 is manufactured by putting a thermoplastic material 8 into contact with a surface of a porous concrete structure 6 using rough aggregates 10 so as to form a form 9 and placing mortar or concrete 13 which does not include rough aggregates into the form 9.

A self locking stirrup mat for providing supplemental support for wire cage concrete reinforcement comprises a stirrup mat formed of a grid of interconnected wires preferably with manually formable tie wires, stirrup elements projecting from the grid, and a self-locking attachment mechanism for attaching the stirrup mat to a wire cage. The self-locking attachment mechanism comprises a plurality of clips fixed at spaced locations on the grid. The clips are shaped and positioned to receive cage wires therein through inlets that are engaged by moving the stirrup mat on the surface of the cage. The clips have one-way inlets that resist removal of the cage wires from the inlets with considerably more force than needed to insert the cage wire into the inlets. In one aspect of the invention, the clips are formed of flat elongated resilient steel loops welded to the tie wires at inclined angles. The clips have inclined elongated internal openings with cam surfaces that draw the stirrup mat securely against a cage when the stirrup mat is slid in a predetermined direction, downwardly on a vertical cage, after the cage wires have been engaged in the clips. In another aspect of the invention resilient clips having one-way inlets are attached to outer ends of the stirrup elements for attachment to a second wire cage. The clips may have enlarged outer loops that serve as spacers.

A clip-on stirrup mat for a concrete reinforcement cage comprises at least one and preferably a plurality of resilient clips attached to the stirrup mat and extending outwardly therefrom in the direction of application of a mat to a cage. The clip has a relatively narrow outer end that fits between adjacent wires in the cage and has inwardly extending, diverging first and second legs that lead to more widely spaced distal ends that form an inner end of the clip. The first leg is attached to the mat adjacent a distal end of the leg, and the second leg is resiliently deflectable toward the first leg. The clip and legs are shaped and positioned on the mat such that, as the mat is attached to the cage, the outer end of the clip fits through adjacent wires in the cage and the second leg engages and is deflected toward the first leg by one of the adjacent cage wires. The second leg includes a gripping surface thereon, which may be convolutions, that engages a wire on the cage as the mat is installed on the cage. The gripping surface resists the removal of the clip and mat from the wire cage once the mat has been installed. Clips are preferably mounted at regular intervals on stirrup mat element wires and are spaced so that the clips fit on single and double wrapped cages.

An attachable spacer for maintaining a spaced relationship between first and second wire mesh concrete reinforcing cages is formed of a length of wire and has an elongated central portion adapted to extend between the cages and first and second attachment clips on first and second outer ends of the central portion for attaching the ends of the spacer to the first and second cages. The first attachment clip has a fastener that hooks on a wire of one of the cages so as to resist movement of the spacer in a direction perpendicular to a plane of the cage or transverse to the wire to which the hook is attached. The second attachment clip comprises first and second spaced hooks interconnected by an arm that extends laterally from the second end of the central portion, the hooks being spaced and shaped to fit over and resiliently engage adjacent spaced parallel wires in the second cage so as to restrain the second end of the central portion from movement transverse to the axis of the wires to which the second attachment means is attached. The resilient engagement of the hooks serves to restrain the spacer from rotation about an axis of the central section, locking both ends of the spacer on the spaced cages and restraining the spacer from sliding along the cage wires.