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Proposals for the repair and waterproofing of iron-concrete structures cable tunnel
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As preparation for repair should be made in conditions of closed space the use of sand-jet working is not acceptable because of some reasons:
because of the close space the dust which has nowhere to get dispersed will create zero visibility;
even ensuring of the autonomic air supply system so that workers breathe will not allow creating safe conditions for executing work;
removal of used sand and removed concrete in amount 250 - 300 t from the tunnel has not found its reflection in the work volume list, though the volume of these works is tremendous and presents a self-standing task that requires financing.
Taking into account the above-indicated we suggest that preparation of surface is executed by a hydro-abrasive-jet or hydro-jet device with pressure 500 - 1000 bar. This will ensure the minimal amount of hard waste and more qualitative preparation of concrete surface. Taking into consideration our principal approach towards repairs and water-proofing of the tunnel dedusting of concrete surface as a separate operation is not needed since after cleansing of concrete surface moisturizing for on-bringing of repair and water-proofing compositions is done.
Repair and water-proofing of the cable tunnel.The tunnel represents a structure mounted of iron-concrete section of box type which are welded between themselves through input pieces and monolithed by concrete - the main reason of concrete destruction is moisture penetration through concrete (reason - bad water proofing layer) and cold touches (monolithic spots). The penetrating moisture exposes structure's metallic elements (armed and input pieces) to corrosion which leads in consequence to concrete destruction. The suggested repair is effective when a penetrating organic cover finds itself from the side of moisture penetration, then it impedes the concrete from getting wet through and water does not get to metal, but absolutely another effect is observed at covering by these materials from the inside-impeding moisture evaporation, that accumulates in concrete the cover accelerates the metal corrosion process starts getting separated (shot) off armature because of the pressure created by metal corrosion products. Besides, sews hermetisation from the inside is not much effective for the same reason-water will accumulate in sews the strengthening metal corrosion process.
Our proposal consists in the following:
The first thing to do is to effectuate injecting of cold sews by hydro-reactive polyurethane tar, which foaming inside the sew (foam brevity is chosen depending on the breadth of the sew opening from 1:3 to 1:25) shuts down the way of getting moisture beyond concrete edge (tar's life underground up to 100 years), afterwards a deepening is made (depending on the sew opening from 10 to 20 mm, up to 50 mm deep), deepening's bottom is worked by mineral water-proofing composition of penetrating type like penetron (penetron, acvamatpenetrat and so on), afterwards a cord of hydro-widening polyurethane is sticked to the bottom's opening (by getting moisture it enhances up to 300% of the initial size), then a becker (the cord of foamed polyethylene) is hammered in the open into the deepening and the deepening is culminated by the polyurethane hermetizer HYPERSIAL 25 LM: after hermetization of the sews one gets down to the repairs and water-proofing of the concrete. All metallic sections are covered by anticorrosive composition FERROSIL and then by repair composition on polymer-cement basis. After restoring the protective layer above armature and restoring the original geometrical parameters of iron-concrete structure the whole concrete surface is moisturized and a solution of mineral hydro-isolating action lice PENETRON is brought on in 2 layers (consumption 1,5 kG/m2).
Comments:Water-proofing of penetrating action like PENETRON (the stuff of the American firm PENETRON) allows to prevent the moisture penetration through the concrete's body even at presence of high hydro-static pressure because of formation of undeluted in water crystal-hydrates, thanks to special chemical additions moving with forces of back osmos through capillary towards water they stop water circulation in concrete completely. And as growth of crystal-hydrates takes place in time, active additions manage to penetrate into concrete to such an extent, that they allow to protect armature from water's bad influence, to increase concrete's frost resistance and to make the concrete withstand aggressive factors - drained waters, chlorides, carbonates, sulfates, nitrates etc., to increase water penetrability of the concrete up to W 12, to increase durability indicators and even the ability to cure the cracks in concrete up to opening's width 0,4 mm. In such a way PENETRON acts as "concrete doctor" protecting it all time of exploiting.