The study of the modified Portland cement compositions with rubber crumb additive
Students Name: Polishchuk Yurii Mykhailovych
Qualification Level: magister
Speciality: Building Constructions, Products and Materials Technologies
Institute: Institute of Civil Engineering and Building Systems
Mode of Study: full
Academic Year: 2023-2024 н.р.
Language of Defence: англійська
Abstract: Polishchuk Y., Marushchak U. (supervisor). Study of modified portland cement compositions with rubber crumb additive. Master’s thesis. – Lviv Polytechnic National University, Lviv, 2023. Extended abstract. Over the past few years, the construction industry has been responding to the challenge of incorporating sustainable development principles into production processes, whether by using solid waste as aggregates in concrete or by seeking more environmentally friendly raw materials. In Europe, about 2 million tons of used car tires are produced annually. The total volume of their processing does not exceed 30%. Waste tire rubber is a serious global problem due to the lack of landfills for its disposal and the health hazards associated with these landfills and health hazards [1]. Recycling and utilization of rubber waste as a substitute for natural aggregate in concrete is a promising environmentally friendly solution. Rubber-based aggregates can be used to improve concrete properties such as impact resistance, energy absorption, and strength [2, 3]. The introduction of rubber crumb, which is characterized by elastic properties, makes it possible to change the nature of its destruction from brittle to plastic due to the redistribution of stresses between the matrix and rubber grains. At the same time, when rubber crumb is introduced, the bending and compressive strength decreases. To solve the problem of reducing the rheological and physico-mechanical parameters of concrete with the introduction of rubber crumb, it is promising to introduce complex organic and mineral additives containing a polycarboxylate superplasticizer and an active mineral additive [4, 5]. The master’s thesis presents the results of research on Portland cement compositions modified with a complex organic and mineral additive based on microsilica in combination with highly effective polycarboxylate superplasticizer and rubber crumb. The object of the study is physical and mechanical properties of modified Portland cement compositions with the addition of rubber crumb. The subject of research is modified cementing systems with the addition of crumb rubber. The purpose of the study: study of modified cementitious compositions with the addition of rubber crumb for concrete with increased physical and mechanical properties. The results of tests of cement stone based on Portland cement modified with a polycarboxylate superplasticizer indicate a decrease in its strength by 32-42% with the introduction of 5% by weight of rubber crumb. Using the method of mathematical planning of the experiment, the influence of the amount of rubber crumb and microsilica with a stabilized amount of superplasticizer on the indicators of strength, average density, and water absorption was studied. It is shown that the use of a complex organo-mineral modifier based on microsilica and a highly effective polycarboxylate plasticizer in combination with rubber crumb in the amount corresponding to the main level of variation provides an increase in strength by 10-33%, compared to a stone without microsilica. The introduction of ultra-dispersed microsilica and highly effective polycarboxylate superplasticizer results in the compaction of the stone structure. Class C 32/40 concrete was designed using modified Portland cement systems with the addition of crumb rubber for use in floor covering of the warehouse. A technological scheme for the production of concrete using modified cementing systems with the addition of rubber crumb has been developed. The economic expediency of using modified rubber concrete in the arrangement of the industrial floor of the warehouse is calculated. Key words: modified Portland cement composition, rubber crumb, superplasticizer, microsilica, compressive strength.