Development of phenolic concrete mixes and structural behaviour of phenolic concrete components

Abstract

This work relates to the development of a method of preparing a filled phenolic resin, for use particularly, but not exclusively, in building materials. The method includes mixing filler and micro-filler, a catalyst, resin and a hetrocyclic alcohol (i.e. furfuryl alcohol) at a stable temperature, compacting the mixture and allowing the mixture to set and cure. The condition for setting may be with heat and pressure, with heat and/or pressure, or at ambient temperature and pressure. To design a particular grading from the various numbers of filler components available, a computer program was produced permitting up to 14 components of known grading to be combined into the closest possible approximation to a defined target grading. This was compared to the grading obtained using a combination of trial and error and graphical procedures. In developing the Phenolic Concrete mixes, initially, the cold set resol phenolic systems were used which resulted in products with low strength as a result of insufficient bond development between the inert granular or powder like materials (fillers) and the resin. Consequently, modified resins were developed which resulted in the production of high strength Phenolic Concrete systems. The determination of the Phenolic Concrete properties was used in describing the indicative inter-relation between the mix constituents, mix proportioning, and criteria of both strength and economy. In addition, Phenolic Concrete mixes were designed with optimization of the mix matrix resin in developing highly fillable media and defining its macro- properties affecting the strength of the end product. Its material properties as a function of its microstructure was investigated using fracture mechanics. The maximum mix ratio devised was 9:1 weight by weight of filler to resin. Maximum compressive cylinder strength obtained was 88.3 N/mrn(^2) and maximum disc tensile strength was 8.85 N/mm(^2) with maximum flexural strength being 30.5 N/mm(^2). The unit weights ranged from 2.08 to 2.28 g/cm(^3), modulus of elasticity ranged from 14.64 X 10(^9) to 19.6 X 10(^9) N/m(^2) and flexural modulus ranged from 17.4 x 10(^9) to 32.4 X 10(^9) N/m(^2). Maximum fracture toughness obtained was 2.12 N/m(^3/2), and maximum fracture energy was 220.7 J/m(^2). The development, construction techniques and properties of various phenolic resin concretes were investigated and described. Using the modified resin systems and the techniques developed here, filled phenolic resin concrete was produced cheaply without sacrificing strength and stiffness. The use of wet or dry fibre glass laminates as primary reinforcement resulted in exceptionally strong composite systems. Alternatively, or in addition, the filled phenolic resin systems were combined with further reinforcing materials such as profiled high yield steel bars. These were then used in manufacturing box beams, bridge deck panels, (and subsequently, access floor tiles). The technique by which these components were constructed proved to be reliable and repeatable. The structural behaviour of these Phenolic Concrete components was studied and proved to be predictable applying elastic theory and ultimate load analysis.