Innovative self-compacting fiber-reinforced concrete with compensated shrinkage for machinery steel anchors grouting

    Innovations, Vol. 9 (2021), Issue 3, pg(s) 105-107

    The technical design of ETEM factory (Sofia) requires the specialized conveyor stretching machine to be monolithic fitted by using of system of steel anchor rods with a diameter of 30 and 40 mm and different lengths (600-700 mm), which have to be grouted in pre-left holes with a diameter of about 150 mm in steel-reinforced concrete foundation slab.
    The technically determined anchoring depth determines the total thickness of the anchor layer within 700-800 mm, reaching the “lower edge of the steel support plate”. The company’s produced grouting compositions generally have significant limitations in terms of the maximum allowable thickness of a single layer – usually up to 30-40 mm, which implies multi-stroke implementation to fill the entire anchoring depth.
    Given the above, and mainly, taking into account the conditions of laying and the specifics of the operating mode of the facility, thepossibility to use concrete batching plant produced high-strength self-compacting fiber-reinforced concrete with compensated shrinkage (to some degree of self-stressing) is estimated as an attractive alternative from a technical and financial point of view.
    After the innovative mix design of that an innovative composition of concrete and its casting in real production conditions, specialized laboratory tests were conducted to prove its strength-deformation characteristics – compressive strength, tensile strength in bending, modulus of elastic deformation and shrinkage characteristics. The obtained results prove that the required high technical and technological characteristics of the concrete mix and the hardened concrete are completely achieved precise for the specific application ca se.


    Innovative hybrid fiber-reinforced shotcrete for thin repairing overlays – long term mechanical and structural characteristics

    Innovations, Vol. 9 (2021), Issue 2, pg(s) 66-68

    Solvay Sodi JSC, Devnya, Bulgaria, is the biggest calcinated soda production plant in Europe. It is built in 1974 and it works in three-shift production regime up to present days. The exploitation environment is highly influenced by numerous factors, act ing corrosively on main reinforced concrete structures – active atmospheric processes (in continental type moderate climate), sea water born chlorideaerosols, as well chemical attack caused by carbon dioxide and nitric acid, presented in the air in form of evaporation. The most reinforced concrete structures need urgent remedial measures to restore the load-bearing capacity of its components.
    The “light soda” silos are reinforced concrete facilities (cylindrical shells) which repair has to be executed dur ing continuous production process. The options for repair of these structures and restoration of their load bearing ability by specially designed innovative high-tech hybrid reinforced sprayed concrete, containing capillary crystalline admixture, are discussed in the report.
    It is well known that two basic methods of shotcrete exist – “dry” and “wet” ones.
    The report discusses the main advantages of the specially designed innovative hybrid fiber-reinforced “wet” shotcrete for thin repairing overlays, compared to industrially made “dry” one. By purposeful using of standard and direct physical test methods the basic long -term mechanical and structural characteristics of two composites are presented and discussed. The effectiveness of the proposed “wet” method is based to real possibilities to involve in concrete mix design different chemical innovative admixtures – ultra high range water reducing (HRWRA), shrinkage compensating (ShCA), internal crystallization one, etc. The mechanical properties of “wet” one dramatically exceeded respective ones of the “dry” one. The mechanical test results fully correspond to the respective long -term structural characteristics, obtained by using of X-Ray, DTA, SEM and BET-methods.
    It could be concluded that the innovative hybrid fiber-reinforced “wet” shotcrete is preferable for high-performance thin repairing overlays
    for structural strengthening of damaged concrete structures.