International Concrete Abstracts Portal

Conventional portland cement concrete and concretes with latex and epoxy additives were prepared and tested for their microstructure characteristics using the scanning electron microscope (SEM). The chloride-ion penetration profiles were also studied on 10-cm concrete cubes that were immersed in 15 percent NaCl solution for 21 days. Following the 21-day soaking period and a subsequent 21-day air-drying period, concrete powder samples were removed by drilling at depth intervals of 0 to 12, 12 to 25, 25 to 38, and 38 to 50 mm and tested for acid-soluble chloride-ion content using a potentiometric titration procedure. The results of these investigations and typical micrographs are presented.

Polymer concrete is a composite material that is often a viable alternative to portland cement concrete. The mechanical and durability properties of three high-molecular weight methacrylate polymer concrete systems using different monomers are discussed. Properties discussed include compressive strength, flexural bond testing, modulus of elasticity, coefficient of thermal expansion, shrinkage, freeze thaw, freeze-thaw shear bond, water absorption, chemical resistance, and crack repair. The monomers themselves were shown to be very effective in sealing cracks with widths as narrow as 0.5 mm while restoring flexural strength.

A furfuryl alcohol-based polymer concrete (FA-PC) has been developed for use as an all-weather repair material for concrete and asphalt surfaces. For this application, the following criteria were established: high-strength at an age of one hour, placement of the materials possible during heavy precipitation over temperatures ranging from -32 to 52 C, and the chemical constituents low in cost with long-term stability when contained in a maximum of three packages during storage. A formulation consisting of furfuryl alcohol monomer (FA), à,à,à-trichlorotulene, pyridine, silane, zinc chloride, silica filler, and coarse aggregate meets these requirements. Optimized formulations were established for use with premixed and percolation placement methods. The premixed formulation meets essentially all of the property and storage criteria and is compatible with moisture contents up to 4 percent by weight of the total mass, which stimulates placement in a 2.54 cm/hr rainfall. The working time for the FA-PC slurry can be controlled at ñ15 min over the operating temperature range -20 to 52 C by simply varying the à,à,à-trichlorotoluene catalyst concentration while holding all the other constituents constant. Below -20 C, slight increases in FA and ZnCl2 concentrations are needed to yield optimum properties. Prototype equipment for the mixing and placement of FA-PC was constructed and used in a series of tests up to a size of 6 x 6 x 0.15 m. The equipment consisted of a concrete transit mix supply of mixed aggregate, a hopper-fed volumetric feed screw that supplied aggregate at a known rate to a mixing screw, and a monomer pump and spray nozzle. The unit mixed and delivered FA-PC at ÷ 182 kg/min. The practicability of using equipment currently employed for the continuous placement of conventional portland cement concrete was proven. Field tests were performed under rainfall and dry conditions at temperatures ranging from -15 to 35 C. In all of these tests, the mixing and placement equipment performed well and the FA-PC slurries exhibited self-leveling characteristics. Test results from proxy samples prepared during the placement of the patches and cores taken after simulated aircraft trafficking indicated that the property requirements at an age of one hour were attained.

Polymer-modified concretes have been subjected to various climate conditions over seven years to find out differences in their hardening characteristics and in particular, the influence of temperature and moisture on the development of strength and elasticity. Generally, the resistance of concrete to long-time exposure conditions is clearly improved by the investigated dispersions, regardless of their generic types. This could be recognized more by the change in the dynamic modulus than by the compression test, which may pretend sound materials while the dynamic modulus points out structural defects. To compare dynamic moduli, the content of moisture has to be taken into account. A special correlation between moisture content, density, and the change of dynamic modulus of elasticity has been given.

Lightweight polymer concrete composites have been developed with excellent insulating properties. The composites consist of lightweight aggregates such as expanded perlites, multicellular glass nodules, or hollow alumina silicate microspheres bound together with unsaturated polyester or epoxy resins. These composites, known as insulating polymer concrete (IPC), have thermal conductivities from 0.09 to 0.19 Btu/hr-ft-F. Compressive strengths, depending on the aggregates used, range from 1000 to 6000 psi. These materials can be precast or cast-in-place on concrete substrates. Recently, it has been demonstrated that these materials can also by sprayed onto concrete and other substrates. An overlay application of IPC is currently underway as dike insulation at an LNG storage tank facility. The composites have numerous potentials in the construction industry, such as insulating building blocks or prefabricated insulating wall panels.