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It is well known that the creep of concrete is influenced by the ambient relative humidity. But there is no sufficient information about the effects of moisture content in concrete specimens at the loading age on the creep behaviour and other mechanical properties. This experimental program was carried out to investigate the effects of moisture content on the strength and creep of concrete under uniaxial and triaxial (i.e. hydrostatic pressure) compressive stress at 30°C. And the dependence of moisture content on the visco-elasticity of concrete was discussed rheologically. The compression creep tests were performed under the following conditions; the moisture contents were 100% (wet), 68, 44, 14, 0 (dry) and -4% (over dry), and the creep stresses applied to the sealed concrete specimens were 100, 200 and 300 (kgf/cm2).The test results showed that the compressive strength, Fc and the elastic strain, ec of concrete decreased with increasing moisture content, φ. It was considered that the strength reduction may be due to the change of surface energy, γ in the hydrated cement gel, and the larger elastic strain at lower moisture content level was brought in as the result of growing of void and crack in concrete during drying procedure. On the other hand, the moisture dependency of creep strain, ec was greatly different from the case of elastic strain: the magnitude of creep strain increased rapidly with increasing moisture from 0% to 40%, and then became nearly constant in the range of 40% over. From these facts, it was considered that the refraction point at 40% moisture in the (φ-ec) curve was brought by the repulsiveforce disjoining pressure which acts among many gel particles.

Since the accelerated electron has by far a higher dose rate than gamma-rays, the electron polymerizing method is more suitable for the efficient fabrication of polymer-impregnated concrete (PIC) with a thin cross section. However, there are few published papers on the manufacturing process of PIC polymerized by electron beam.This experiment was carried out to investigate the effects of density of cement mortar, dose rate of electron beam (4MeV), total exposure dose and other factors which have influences upon the strength of MMA-PIC. The density of mortar, size of cross section of mortar specimens, dose rate of electron, total exposure dose and irradiating time interval were varied respectively as follow; ρ=1.55∼3.13g/cm3 (the kinds of aggregates in cement mortar used are perlite, artificial light weight aggregate, normal river sand and iron sand), t=3.5∼40mm in thickness, 0.55 or 1.10 Mrads/sec, 12.5∼100 Mrads per face, and 15∼60sec/cycle.The test results of mechanical strength of PIC show that the optimum total exposure dose is about 40Mrads at 0.55Mrads/sec rate and 50Mrads at 1.1Mrads/sec in the ordinary mortar. It is also shown that the impregnation depth from the surface of specimen has a linear relation with the density of cement mortar, and that its depth is about 1cm in conventional mortar.

It is well-known that the polymer impregnated concrete (PIC) has many excellent characteristics such as high compressive strength of over 1500kg/cm2, large elongation capacity, negligibly small water permeability and no-shrinkage. And it has also been reported by BNL and USBR that PIC shows good resistance to chemical attack. However, the chemical stability of PIC has been evaluated only form its weight loss, but scarecely from the loss of its mechanical strength.In this paper, the losses in weight and strength of a plain mortar, a mortar (PIC) impregnated with poly-methyl-methacrylate polymerized by thermal-catalyzer with BPO=5%, and a mortar impregnated with polypropylene fiber reinforced polymer were examined in order to obtain their resistance to chemical attack by 10%-HCl, 10%-MgSO4, 10%-CH3COOH and pure C6H6.The results showed that the weight loss of PIC (18.6%) was less than that of the plain mortar (24%), when attacked by 10%-HCl for 28 days. The losses in compressive strength of PIC and plain mortar after attacked by HCl were 67% and 97%, respectively; and after attacked by CH3COOH the losses were 26% and 57%, respectively. So, it can be said from the viewpoint of compressive strength that the chemical resistance of PIC is 23 times that of the plain mortar against HCl and 3.6 times against CH3COOH.

Although the polymer impregnated concrete (PIC) has such excellent characteristics as high strength, small water permeability, high corrosion resistance and no shrinkage, it has such weak points as low impact strength, no plastic range in strain and low toughness.In the present paper, the mechanical properties of fiber reinforced polymer impregnated concrete have been investigated by using several fibers, made of glass, polypropylene and metal, and MMA-and SM-monomers. The main results obtained are as follows:Among the five kinds of fiber examined, piano wire with 0.2mm diameter and 35mm length was most effective. The strengths of FPIC reinforced by the piano wire were 2003kg/cm2 for compressive, 536kg/cm2 for flexural, 195kg/cm2 for tensile, and 186kg/cm2 for Charpy's impact strength, whereas those of plain mortar cured in water were 593, 73, 36 and 8.7kg/cm2, respectively. And from the fact that the tensile maximum strain at the ultimate strength obtained in repeated bending test for PW-PIC beam 2500×10-6, it is deduced that FPIC-material has large toughness and has far more useful properties than PIC.