Master's thesis in the field of structural engineering
Abstract:
In this study, the effect of some effective parameters on the strength of polymer concrete based on epoxy resin, including hardener, filler and solvent, has been investigated. Rice husk ash and broom stalk ash were used as fillers and acetone-toluene mixture with a ratio of 50-50% was used as a solvent in making the samples. According to the results of the tests, adding appropriate amounts of filler improves the compressive, bending and chemical resistance of polymer concrete. In samples containing 18.4% of polymer, adding rice husk ash with a filler-material ratio of 0.075 causes a 21% increase in compressive strength. Samples containing broom stalk ash, with a filler-material ratio of 0.09 and 18.4% of polymer, showed a 27% improvement in flexural strength compared to the sample without filler. The results of the tests on the solvent show that adding optimal amounts of solvent improves the efficiency and increases the compressive and bending strengths of concrete, but the use of large amounts of solvent may have a negative effect on polymer concrete due to the possibility of reducing polymer adhesion. Also, changing the type of hardener and the mixing ratio of hardener-resin has caused a change in the resistance properties of polymer concrete. The amine hardener with a lower equivalent weight has led to 27 and 13% improvement in the compressive and bending resistances, as well as an increase in the modulus of elasticity of the samples compared to the samples containing the amine hardener with a higher equivalent weight.
Key words: polymer concrete, epoxy resin, filler, solvent, hardener
1- Chapter 1: Introduction
Concrete is one of the most widely used construction materials, which is widely used due to its low price, easy use and ability to respond to the required conditions. From the time of the use of concrete by the Romans until 1824 and the manufacture of Portland cement by Joseph Spadin, especially in recent centuries, people sought to improve the properties of concrete, and used different adhesives, additives and stone materials to achieve their goals. Today, there is a wide range of materials and methods to improve the properties of cement concrete (Portland cement concrete) or to replace the use of cement in concrete, depending on the required mechanical and chemical resistance. And structural issues and existing conditions are selected according to the costs. Improving the properties of concrete in two general ways: 1- Reinforcing concrete using fibers and rebar, which is mainly used to improve the bending strength and plasticity of concrete 2- Improving the quality of concrete itself through the addition of chemicals, pozzolans and fillers.
Polymer as an option to achieve this goal (improvement of concrete properties) has been considered for several decades. Polymer materials are used in both ways to improve the properties of concrete. Solid and hardened polymer materials in the form of fibers (such as polypropylene) or FRP rebars [1] reinforce concrete. The process of polymerization and hardening is carried out in manufacturing factories, and materials with specific characteristics are provided to the user. Boron, carbon, glass and polyamide are the most important materials from which fibers are made. Carbon FRP (CFRP[2]) and glass (GFRP[3]) rebars are made of fibers with a matrix of polymeric materials (such as epoxy). In addition to the use of fibers (polymer composites) in civil engineering, fibers (polymer composites) are used in other fields such as aerospace engineering (making shuttles), transportation (making cars and planes), sports goods (making rackets and ski sticks), machines and tools (turbine blades, gears), etc. These materials harden during concrete processing and improve the resistance properties of concrete by forming networks intertwined with the cement network. Injection polymer concrete (PIC[4]) and cement-polymer concrete (PCC[5]) are among these. The type of polymer and its mixing percentage are very effective on the final strength of concrete. Active research and development of concrete-polymer composites in Germany, America, England, Japan and Russia began approximately 80 years ago, and now they are widely used in various applications. For example, the volume of polymer used only in polymer-cement mortar (PCC) in Japan at the end of the 20th century has reached more than 100,000 tons per year [2]..
In general, the reasons for expanding the use of composite structures are:
1- Efficiency, which causes beautiful architecture to arise in the building
2- Resistance to atmospheric conditions
3- Resistance to corrosion in corrosive environments
4- Buildings where the use of metal is not allowed.
Polymer concrete (PC [6]) is one of the non-solid uses of polymer. It is in concrete that does not improve the quality of concrete (cement), but it has a sticky polymer binder that replaces cement and keeps stone materials together after hardening. Polymer concrete has much higher resistance properties than cement concrete and can be a good substitute for it if concrete (cement) is unable to provide the necessary resistance. Application in structural members with high compressive and especially tensile strength, as well as low permeability and high chemical resistance makes it a suitable option for building structures on coasts, cold regions, water and sewage channels, water and chemical tanks. Having high damping (about four times that of steel) has led to its use in making a bed for mechanical devices and machines with high vibration. In addition to the above advantages, having impact and abrasion resistance, etc., brings many practical fields, including in road construction and bridge covering for concrete and polymer materials. However, the expensiveness of polymer materials, weakness against high temperatures, being toxic to some extent, or having environmental problems for some polymers or processing agents (hardeners or hardeners) or additives can be considered as its disadvantages and weaknesses.
Due to the earthquake-proneness and high cost and time of construction in our country, the use of prefabricated and light materials is strongly felt in the construction industry. Technology that has been used for years in advanced countries, especially America. Lightness, high mechanical and chemical resistance, low processing time are the effects of using polymer materials in these products. The use of polystyrene foams in block beam ceilings and prefabricated walls is a growing trend in Iran.
Polymers have different types and characteristics and are divided into two groups: thermoset (hard heat) and thermoplastic (soft heat). Usually, thermoset polymers are used in making polymer concrete. But most of the polymers used in concrete are thermoplastic polymer-cement. Criteria such as hardening at room temperature, fire resistance, environmental issues and economic issues are placed next to mechanical properties and guide consumers to choose a polymer from among all types of polymers [3]. According to extensive tests and research conducted by researchers on polymer concrete, depending on the type and amount of polymer materials (resin and hardener) and additives, there are wide changes in the amount of strength and salient features of polymer concrete. For example, the value of compressive strength in polymer concrete can be between 50 and 160 megapascals. Therefore, in this thesis, it has been tried to study the factors affecting the strength of polymer concrete (especially the compressive and bending strengths). For this purpose, three classifications have been used: the residue on the grade 16 sieve, past the grade 16 sieve, the combination of 60% of the material passed through the grade 16 sieve with 40% remaining on the sieve (by weight). 5 different mixing ratios: 10%, 13%, 16%, 19%, 22% were used in making the samples. The mixing ratio suggested by the manufacturer is 16%.
Showing the effect of the type of hardener on the strength of polymer concrete: two types of amine hardeners were used for three different percentages of resin.
Investigation of the effect of two types of rice husk ash and broom stalk ash fillers obtained from agricultural residues on the strength properties of polymer concrete: samples in three different percentages of polymer (13, 18.4, 23) and They were made with different percentages of filler.
Investigating the effect of solvent on the compressive and bending strength of polymer concrete: Acetone-toluene solvent (50%-50%) was used to reduce the viscosity of the polymer. The samples were made from two different types of epoxy resin and from two different percentages of polymer (8 and 10).
1-2 Thesis structure
In the first chapter, an introduction of the generalities and necessities of research and materials for basic familiarity with polymer materials were presented.
In the second chapter, explanations about polymers, especially epoxy resin, as well as the properties of polymer-containing concretes are provided.