International Concrete Abstracts Portal

The purpose of this paper is to develop pre-casting permanent forms which are effective in improving the durability and appearance of concrete structure, conserving wood and modernizing cast-in-place concrete work. The influences of various materials used and accelerated curing methods on the properties of PCM(polymer cement mortar) applied to the forms were investigated. In these experiments, polymer dispersions composed of SA(styrene-acryl), PAE(polyacrylic ester), EVA(ethylene-vinyl acetate) and SBR(styrene-butadiene rubber) were used. Mixtures contained aggregate ; crushed silica and ferro-nickel slag sand, cement ; normal Portland, high-early strength portland and white portland cement, and color pigment ; red, green, yellow and black color pigment, were used. Steam curing and oven-dry curing were carried out. The fluidity, compressive strength, flexural strength, resistance to abrasion, chloride ion penetration, carbonation and sulfate, and surface color of PCM were examined. From these investigations, the following conclusions can be obtained. The use of SA type polymer, ferro-nickel slag sand, high-early strength portland cement and color pigments were effective in getting PCM with high fluidity, mechanical strength, durability and tinting strength. Additionally, steam curing and oven-dry curing are practical for the early-age strength development of PCM.

Automated production of precast polymer concrete construction components is presented. Both batchwise and continuous production are discussed, and examples of both techniques are shown. Automated on-site application and execution systems allow benefits to be taken of the specific features of polymer-cement concrete. Automated execution of overlays, tunnels, porous polymer-cement concrete pavements and polymer-cement shotcrete are presented as examples.

In this program, the performance of concrete masonry pavers is examined under freezing and thawing conditions of ASTM C 1262-95. The 100 x 200 x 60 mm solid rectangular pavers of eight different mixture proportions were manufactured in a commercial plant and tested to determine their physical and inherent characteristics. Mass loss and surface condition under various freezing and thawing cycles, density, absorption, compressive strength, and tensile-splitting resistance were compared in order to assess the potential of each mixture proportion as a measure of field durability and quality control. The results obtained under C 1262 also enabled comparison with the degree of severity experienced by the same group of pavers under the other ASTM and Canadian freezing and thawing (with or without deicing salt) tests.

One method of confirming in a laboratory the resistance of concrete to frost damage is freezing and thawing testing. The Japan Society of Civil Engineers established a standard method, JSCE G 501, in line with ASTM C 666 Procedure A. However, whether this method accurately evaluates the resistance of actual concrete structures to frost damage should be open to further discussion. The test method needs modifications particularly for lightweight aggregate concrete. With aggregate being prewetted in the production process, lightweight aggregate concrete in Japan is doomed to be evaluated as having low durability by the JSCE-specified laboratory tests, as such concrete tends to break up during testing by the freezing expansion of water in critically saturated aggregate. However, a number of actual structures, such as bridge decks where drying proceeds after placing, have exhibited sufficient durability. The authors verify the durability of lightweight aggregate concrete against frost damage by freezing and thawing tests on specimens containing lightweight aggregate with the degree of saturation being modified by drying, as well as by the measurement of the degree of drying and frost resistance of concrete specimens exposed to an outdoor environment in winter.

This paper investigates the effects of various curing methods in cold weather conditions on the compressive strength of concrete incorporating ground granulated blast-furnace slag ( GGBS). The specific surface area of GGBS ( 4000, 6000, and 8OOOcm*/g) was varied and the replacement level of cement by GGBS ( 50, 60, 70, and 80%). Mortar specimens were prepared for the experiment. The specimens were cured at 5°C constant and 20°C constant respectively by atmospheric curing, water curing, and sealed curing. Compressive strength test results were performed at various ages. Furthermore, the effects of applying heat curing at 30°C constant at early age to GGBS-concrete on the strength development were also examined. Results show the concrete incorporating the GGBS with the specific surface area of 8OOOcm*/g would have no strength development problem even though it were cured at 5°C by sealed curing. However, heat curing may have a bad influence on the strength development particularly at later ages. On the other hand, GGBS-concrete with the specific surface area of 4000cm*/g would require heat curing in order to improve the compressive strength at early ages. Finally, based on the data derived from this experiment, the relationship between the compressive strength of concrete incorporating GGBS and maturity is discussed.