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Ferrocement has attracted world-wide interest because of its proven suitability for marine structures as well as its potential as a repair material. The first part of the paper describes methodology for accelerated exposure of specimens to the marine environment simulated in the laboratory. The main features of this methodology were: the cyclic temperature and moisture environment, and the preloading of specimens up to the state of cracking before placing them in this environment. The second part reports and discussed the influence of the duration of load and the cyclic environment on the fatigue properties measured from tests performed under cyclic loading. These properties are compared with those of the specimens stored in a normal curing room. Fatigue results obtained from the ferrocement specimens are compared with those from the reinforcing wires tested in the air. The fatigue performance of reinforcement in the air was found to be considerably lower than that in the composite.

Fatigue characteristics of concrete beams were determined under water and in air. Significant differences were observed in the fatigue strengths between the beams tested in water and those in air. The failure pattern of a reinforced concrete beam tested in water occurs as a shear failure but as flexural failure in air. At the same upper load level, the fatigue life of the beam with web reinforcement was approximately 100 times that of the beam without it. The flexural crack width of the specimen in water was lower than that exposed to air. At the same upper load level, however, the deflection and the rate of propagation of the diagonal crack were larger in air.

The deterioration of concrete structures due to age, particularly in marine environments, has recently become a subject of great concern. In this study, the properties of 60-year-old concrete in a marine environment were examined. Taking the opportunity of the demolition of the northern breakwater of a port in Japan, samples were taken from the reinforced concrete caissons, from the upper concrete, and from the foot protection blocks. Tests for concrete strength, porosity, salt content, carbonation, and the corrosion status of the reinforcing bars were performed. The concrete seemed to have retained its strength even after sixty years of exposure to sea water environment. The pore sizes were generally smaller than those of ordinary concrete while the total porosity was the same. The salt content was high at approximately 0.3 to 0.6 percent near the surface of concrete. It reduced, however, to a constant value of about 0.1 percent at a depth of approximately 8 cm. As a result of the study, it was found that the concrete, which was made from blast furnace slag and volcanic ash and appeared to contain sea sand, had scarcely deteriorated at all even though it had been exposed to sea water environment for sixty years.

Report describes creep and expansion tests on concrete with various concrete mixes and stress levels in seawater and in lime-saturated water. The effect of seawater penetration is revealed by comparing the results with those obtained in lime-saturated water. It is shown that concrete made with portland cement and blast-furnace slag cement exhibits more creep in seawater than in lime-saturated water; this is especially true for portland cement concrete. No significant effect has so far been found with regard to concrete made with portland fly-ash cement. An increasing water-cement ratio leads to increasing (specific) creep, as expected. Expansion of concrete in seawater is greater than in lime water, especially for higher water-cement ratios. Blast-furnace slag cement expands less in seawater and more in lime water than portland cement does. The results do not support the superposition principle of linear creep and the superposition of creep and expansion (swelling).

Focus is the study of basic properties of the low water-absorption lightweight aggregate and the water-absorption reducing agent that were developed to make the pumping of lightweight concrete using non-presoaked lightweight aggregate possible. The water absorption of the low water-absorption aggregate was extremely small. The compressive strength and modulus of elasticity of the concrete were found to be considerably higher than those of the concrete using ordinary calcined expanded shale aggregate. The water-absorption reducing agent reduced water absorption under pressure considerably. The compressive strength and modulus of elasticity of the concrete using the aggregate that was treated with the agent were not significantly influenced by the agent. The concrete using the dry low water-absorption aggregate without presoaking that was treated with the agent was pumped through a pipeline with an equivalent horizontal length of 160 m. However, as the aggregate absorbed water, it showed a drop in slump, an increase in compressive strength, and a particular internal pressure distribution along the pipeline.