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P.C. (MMA) systems have been in use for over 20 years and have become one of the most promising materials for the rapid repair of concrete, especially bridge deck repairs. The major bridge applications include joint and spa11 repairs, thin bonded overlays, and deck impregnation. The latest design concept utilizing P.C. (MMA) is for modular bridge deck replacement using the P.C. (MMA) for bearing pads, for joining individual panels and for contraction joint pours. Pre-packaged systems consist of two components, a pre-mixed powder that contains fine aggregates coated with polymers, initiators and pigments and a liquid monomer component (Methyl Methacrylate). The practical success of the systems have been due to the application technology developed through applied research by commercial firms. Repair work with P.C.(MMA) is similar to work using Portland Cement Concrete and proper surface preparation is essential to the successful use of P.C. (MMA) for rehabilitation. P.C. (MMA), has many advantages over conventional concrete, including among others, rapid setting, ease of use, usability in hot and cold temperatures and water and salt resistance. P.C. (MMA) can also be feathered to "zero". There are several different P.C. (MMA) systems, each ideally suited for a particular application (i.e. thin overlays, spa11 repairs, etc.) and any questions related to its use should always be checked with the manufac-turer.

A PIG of 2400 kg/cm 2 compressive strength is obtained by use of an ordinary cement mortar of 600 kg/cm2 compressive strength (W/C = 0.5, S/C = 2.5 : 1 by wt.) as matrix and MMA as its impregnant with impregnation and thermal catalytic polymerization under high pressure up to 200 atmospheres. Using the same materials, the compressive strength of the PIC obtained with ordinary impregnation is only 1600 kg/cm2. The polymer loadings of the former and the latter PIC are 9.2% and 7.5% respectively. The following contribute to the super-high compressive strength of this PIC: (1) Minimizing the effect of residural air; (2) Overcoming the airblock effect due to ink-bottle-shaped pores during impregnation; (3) Reducing the effect of shrinkage of impregnant during polymerization; and (4) Increasing the interfacial area and adhesive power between matrix and polymer.

The tensile-splitting stress distribution for partially polymer-impregnated concrete is mathematically predicted from the viewpoint of theory of elasticity, and the results are confirmed by experiments. It is shown that tensile-splitting load to par-tially polymer-impregnated concrete cylinders can be predicted by the proposed failure mode and compressive strength can be adapted to the law of mixtures for composite materials. Furthermore the experimental equation proposed by Knudsen for the relation between strength and porosity for a porous brittle crystal body is examined. The obtained strengths for partially polymer-impreg-nated concrete can be evaluated more exactly than those heretofore in use.

The work presented is a portion of a larger investiga-tion concerning the improvement of durability of concrete structures in seawater. Therefore, as an introduction, the deterioration of reinforced concrete in corrosive environment is discussed followed by a description of two types of polymer modification of concrete. This latter means the addition of a liquid polymer of polymerizable system to the fresh concrete. The major portion of the paper presents a new investigation concerning the effects of epoxy modification on the properties of concrete, primarily strength. It is demonstrated that the addition of a suitable epoxy to the fresh concrete can increase the concrete strength significantly. This strength improvement can be further increased by the simultaneous use of a compatible superplasticizer, or an accelerator, or both.

In the past a few years, greater interest has been focussed on the use of silica fume as a concrete admixture, which is a by-product in the manufacturing process of ferrosilicon and metallic silicon. The purpose of this study is to find appro-priate process conditions for developing superhigh strength concrete by the application of both silica fume addition and polymer impregnation. Base concrete was mixed by use of the silica fume and polyalkyl aryl sulfonate-type water-reducing agent, and cured in autoclave or hot water. The cured base concrete was dried, and impregnated with polymethyl methacrylate by thermal polymerization in hot water. The strength properties of such superhigh strength concrete were tested. The reproduci-bility of its strength development was examined. It is concluded that superhigh strength concrete having a compressive strength of 2370 to 2600 kg/cm2 is obtained by the above process with good reproducibility.