Polymers in concrete: a vision for the 21st century☆
Introduction
Polymers in concrete have received significant publicity over the past 25 years. Many optimistic projections were made as to the future widespread use of polymer-impregnated concrete (PIC), polymer concrete (PC), and polymer-modified concrete (PMC). As the end of the 20th century approaches, a review of the past and future is in order. A discussion of the use of these materials will be presented followed by a projection of the realistic uses of these materials in the future.
Section snippets
Historical perspectives
PMC and PC came into use in the 1950s, although the uses were very limited. It was only in the 1970s, after PIC was developed that concrete-polymer materials received significant publicity. American Concrete Institute Committee 548, Polymers in Concrete, was formed and in 1975 the first International Congress on Polymer in Concrete (ICPIC) was held in London. Later RILEM committees were formed to address specific areas in concrete polymer composites. Regular ACI Symposia and ICPIC conferences
PIC
PIC first became widely known after researchers at Brookhaven National Laboratory and the Bureau of Reclamation in the US performed extensive research on the material in the 1960s, although USSR researchers claimed to have invented it earlier. PIC was produced by impregnating hydrated portland cement concrete with a low viscosity monomer, usually methyl methacrylate, which was subsequently polymerized by radiation or thermal catalytic techniques. PIC typically developed compressive strengths
PC
PC was used as early as 1958 in the US to produce building cladding. PC consists of aggregate with a polymer binder and contains no portland cement or water. Polyester–styrene, acrylics and epoxies have been the most widely used monomers/resins, but vinyl ester, furan, and urethane, have also been used. Sulphur is also considered to be a polymer and sulphur concrete has been used for applications requiring high acid resistance.
In addition to the use of PC for precast cladding, it was most
PMC
PMC using latexes has been in use since the 1950s. PMC consists of portland cement concrete with a polymer modifier such as acrylic or styrene–butadiene latex (SBR), polyvinyl acetate, and ethylene vinyl acetate. From a construction standpoint PMC has the desirable attribute of being very similar to conventional portland cement concrete technology. The amount of polymer is usually in the range of 10–20% of the portland cement binder. There are only a few polymers suitable for adding to
Bonding agents
A fourth use of polymers is to seal cracks in concrete. Cracking is perhaps the most well known and most common distress in concrete. Repairing cracks has been a difficult problem. Epoxy injection was developed to provide a structural repair, but has the disadvantage of being very expensive and slow. The development of high molecular weight methacrylate (HMWM) in the early 1980s for sealing cracks was a major development. The HMWM can be mopped, brushed, broomed, or sprayed onto a surface and
Limitations
Polymers in concrete have made tremendous strides over the past 30–40 years. Are these materials a passing fad, or do they represent a significant, important materials technology?
First, it should be understood that one of the primary limitations of concrete-polymer materials is cost. The cost of polymers can range from 10 to 100 times that of portland cement, and even considering that the specific gravity of cement is about 2 times that of polymer, the cost per unit volume of polymer
The vision for the future
Where will polymers in concrete be successful for the future? Some insight can be found from looking at past history; current and projected developments can also give a view of the future. A brief summary of potential developments follows.
Conclusions
PIC, PC, and PMC have received considerable attention over the past 25 years. These materials have been used for repair of concrete, overlays, and precast components. Limitations include cost, odor, toxicity, and flammability. New and improved materials, applications, and uses are projected.
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Paper presented at the Sheffield Infrastructure Conf., 1999, and reviewed according to Journal procedures.