The development and research of modified composite materials for reinforced concrete structures repairing by shotcrete method
Students Name: Pashkutskyi Andrii Bohdanovych
Qualification Level: magister
Speciality: Building Constructions, Products and Materials Technologies
Institute: Institute of Civil Engineering and Building Systems
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: англійська
Abstract: Pashkutskyi A.B., Kropyvnytska T.P. (supervisor). Development and research of modified composite materials for repair of reinforced concrete structures by shotcrete method. Master’s thesis, - Lviv Polytechnic National University, Lviv, 2022. The master’s thesis is devoted to the development and research of composite materials for the repair of reinforced concrete constructions by the shotcrete method by introducing an aluminum-containing accelerator, mineral additives, superplasticizer and fibers to obtain particularly strong concrete with improved construction and technical properties. The essence of shotcrete consists in applying a fast-hardening layer of repair solution or concrete under pressure and at a high intensity of supply to a previously prepared surface. The advantages of using such concrete are the high rate of restoration work and short hardening times. Concrete shotcrete provides a universal shape, high strength, durability, increased ability of the applied layer to connect with the base, and it is also easy to spray on the surface at high speed in hard-to-reach places. A complex combination of mineral additives (fly ash and zeolite), polycarboxylate superplasticizer and fibrous fibers in composite materials based on Portland cement with limestone with the additional introduction of fibrous fibers will allow to obtain highly mobile mixtures for the restoration or replacement of defective concrete and the protection of reinforcement, which is necessary to extend the service life of damaged reinforced concrete structures , which demonstrates deterioration of properties while ensuring technical and environmental effects. Study object - the processes of regulating the rheological and strength properties of modified composite materials for shotcrete in conditions of increased mobility. Scope of research - modified composite materials for repair of reinforced concrete structures by shotcrete method. The purpose of the work is to study the rheological and strength properties of modified composite materials and to develop shotcrete with increased construction and technical properties. Briefly put research results: - A review of literary sources was carried out regarding the features of shotcrete methods and materials for the production of shotcrete concrete. The characteristic properties of shotcrete are considered and the relevance of its use in construction is determined. - It was established that for the modified cementing system based on CEM II/A-LL with mineral additives, accelerator NaAl(OH)4) and superplasticizer PC has a conventional viscosity of 3.4, a Suttard spread of 360 mm. - Graphical interpretation of the data shows that the most optimal and effective compositions to ensure the necessary viscosity, mobility and strength are 10.0 wt.% fly ash, 5.0 wt.% zeolite, 1.5...2.5 wt.% accelerator NaAl(OH)4) and 1.5-2.0 wt.% PC. - It was established that modified composite materials with steel fiber for shotcrete are characterized by an average density of 2420 kg/m3, flexural and compressive strength after 1 and 2 days - 7.2 and 8.9 MPa and 29.6 and 60.1 MPa, deformations shrinkage is 0.9 mm/m, adhesion strength to the base is 3.2 MPa. Keywords - shotcrete concrete, composite materials, zeolite, fly ash, steel fiber, accelerator, polycarboxylate superplasticizer, viscosity, strength. References. 1. Sanytskyi M.A., Kropyvnytska T.P., Gev’yuk I.M. Rapid-hardening clinker-efficient cements and concretes: monograph. Lviv: "Prostir-M", 2021. 206 p. 2. Sinyakin D., Sopov V. Shotcrete concrete for construction and repair of engineering structures. Building materials and products. 2018. 1-2(97). 3. Kaminsky A. The use of an alkaline accelerator based on sodium aluminate in concrete technology. Theory and practice of construction. 2019. No. 912. C. 57–62.