International Concrete Abstracts Portal

Polymer concrete (PC) 3-in. x V-in. (75-mm x 300-mm) cylinders were loaded in uniaxial compression stress-strength ratios of 0.3, 0.4 and 0.5 for one year to investigate creep behavior. The PC was made with methyl methacrylate (MMA). The results indicate that the creep in PC is approximately one to two times higher than that of portland cement concrete. However, the specific. creep for both is about the same. The creep in-creases with an increase in the stress-strength ratio; but no linear relationship exists between the two variables. More than 20 percent of the final creep took place within the first day, and nearly 50 percent during the first five days. The static strength of PC was not significantly affected by the long-term creep loading. The high creep strain and the low sustained strength of PC could be the two major obstacles in its structural application. Plain PC 6 x 6 x 36-in. (150-mm x 150.-mm x 900-mm) beams made with MMA were tested to evaluate the flexural fatigue strength of PC subjected to different stress levels and stress ranges. The flexural behavior during the test period was observed. Beams were tested as simply supported beams with a 30-in. (750-mm) span and symmetrically loaded at third points. Beams were cyclically loaded at a constant rate of five cycles per second up to two million cycles or failure of the beam. Similar to port-land cement concrete, the applied stress is the most important factor influencing the fatigue life of PC. As the applied stress increases, the fatigue life decreases. The effect of the range between the maximum and the minimum applied stress was also significant; the wider the stress range, the shorter the fatigue life. Although the PC beam failed in a sudden, brittle mode, an increase in deflection was always noticed as the fatigue life was approached. The test results indicate that PC beams are superior to portland cement concrete beams in fatigue strength.

Recently powdered emulsions of improved quality have, been developed and commercialized as cement modifiers. Mixed in a powder form with cement mortars, they are re-emulsified and modify the mortars. The purpose of this study is to evaluate the quality of the commercial powdered emulsions for cement modifiers. Polymer-modified mortars using powdered emulsions were prepared with variation in polymer-cement ratio, and tested for strength, adhesion, waterproofness, length change and water resistance. Their properties were also compared with those of ordinary polymer-modified mortar using styrene-butadiene rubber latex. It is concluded from the test results that the powdered emulsion- modified mortars can be used in the same manner as ordinary polymer-modified mortar in practical applications, in consideration of their drying shrinkage.

The testing program of reinforced concrete joints con-sisted of six beam column joints with varying strength cementing agents in the joint region: 1) normal strength concrete (fc' = 4,000 psi); 2) high strength concrete (fc' = 10,000 psi); and 3) polymer concrete (fc' = 12,000 psi). Half of these joints con-tained l-l/2 percent by volume of hooked end fibers. The polymer used in the joint region was Sika Stix 350. The fibers used were dramix fibers (30 mm. long by .50 mm. in diameter). From the test series on joints of this investigation, information on the following will be described: strength, ductility, energy absorp-tion and dissipation, mechanisms of failure, and mechanisms of stiffness and energy dissipation under cyclic loading. From the analysis of the results, it can be concluded that the polymer concrete used in the joint region provided: 1) better bond; 2) better confinement of the joint region; 3) a stiffer mem-ber; 4) a higher moment capacity; 5) higher shear strength; 6) more ductility; 7) far less cracking; and 8) significant improve-ment in the energy dissipation capacity than did the 4,000 psi and 10,000 psi portland cement concrete used in the joint area. The addition of fibers helped to strengthen the joint region, and improve the energy absorption and dissipation capacity of the joints with normal and high strength concrete. Also, the addi-tion of fibers to the beam column with polymer in the joint re-gion made made the joint area act elastically while the inelastic region was formed a distance 10 inches from the face of the col-umn in the normal strength concrete beam. The benefits and disadvantages of using a polymer concrete instead of high strength or normal concrete in seismic construc-tion of a joint will be described.

The quality deterioration of underwater concretes may be caused mainly by the washout of the cement from the concrete. The addition of an acryl-type polymer to concrete was found to be effective to prevent such deterioration. With the increase of the polymer content, the resistance of the concrete to be sepa-rated in water improved. This polymer did not affect the hydra-tion of the cement. A dialdehyde-type auxiliary agent was found to be effective to improve the function of the polymer at a dosage of only 1% of the polymer when it was added to the con-crete after the addition of the polymer. Due to the high vis-cosity of the concrete containing the polymer, the cleaning operation of equipment such as concrete pumps and mixers tends to be time-consuming. To avoid this, an alminum compound was found to be useful when it was added to the equipment together with water. Through the action of the alminum compound the concrete left in the equipment lost its viscosity immediately, flocculated and precipitated. By the field test in which concretes contain-ing polymer were applied to a underwater concrete structure, the performance of the polymer was confirmed.

At the Ruhr-University Bochum, West Germany, experimental work has been carried out in the last three years dealing with polymer modified concrete, which is appropriate for the shotcreting process. The tests carried out are dealing with alteration of properties of both, fresh and hardened concrete, compared with a concrete of the same mix proportions, however, without any resin. Experience has shown that polymer modified concretes of different mix proportions can only be compared, if all concretes in question have the same binder volume. The binder volume consists of portland cement, water, epoxy resin and hardener. In all tests the epoxy contents were variied between 0 and 25% of the binder volume. The compressive and bending tests on hardened concrete do not only refer to strength and other mechanical data; in addition an alternating water-air-storage up to a maximum of 500 cycles was considered. These tests were extended to answer the question, if different properties of polymer and hardened cement paste do effect the formation of internal cracks due to

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.

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.

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.

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.

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.