“FA-sand” for concrete was the fine aggregate mixed previously with flyash (FA). However, the study about concrete with FA-sand is extremely few, and the further investigation toward to the widespread use is needed. From the above backgrounds, this study investigated the heat of hydration (simplified adiabatic temperature rise tests), the compressive strength, and the durability (chloride penetration depth, carbonation depth) of concrete with FA-sand. That is, concrete whose water cement ratio was 55% and unit water content was 175kg/m³, was made for all cases. After that, the performances of concrete with FA-sand and concrete mixed with FA in the concrete mixing time as the replacement for the fine aggregates were compared. Also the influences of the type and the manufacture method of FA-sand on the performances of concrete were evaluated. The conclusions were as follows; (1) the heat of hydration and the hardened properties of concrete with FA-sand were equal to those mixed with FA in the mixing time. (2) The stored period of FA-sand, the plant and sampling period of FA, the mixer type manufactured FA-sand were not affected on the heat of hydration and the hardened properties of concrete.

There has been a great demand of using the recycled aggregate and fly ash in the concrete structure. It is known that the compressive strength will increase in the early age when the mineral fine powder, such as fly ash, is mixed into the concrete with a part of the fine aggregate, under the condition of constant unit cement content. However, its mechanism has not been clearly understood until now. In this paper, we made experiments to explain the mechanism of the early strength development by using recycled aggregate mortar. In addition, we examined the influence of the mineral fine powder, which is mixed into the mortar, which extended the strength development of the recycled aggregate mortar from 3 days to 180 days. From the results obtained, we found that in response to the influence of calcium hydroxide in the adhesion cement paste of recycled aggregate, the fly ash had brought forward the early pozzolanic reaction for 28 days. However unlike the pozzolanic reaction of the usual fly ash, the early pozzolanic reaction did not contribute to strength development. By mixing the mineral fine powder, the early strength development had strongly influenced the filler effect of physical action. The mixture of the recycled aggregate mortar using the mineral fine powder as a part of the fine aggregate had brought much larger strength increment ratio than the normal aggregate mortar. The results indicate that the combination of fly ash and recycled aggregate would have a good affinity.

The S-phases (_γN-phases) of SUS304 steel were prepared using direct current plasma nitriding (DCPN) and active screen plasma nitriding (ASPN). Furthermore, diamond-like carbon (DLC) films on these S-phases were prepared using plasma chemical vapor deposition (PCVD). The nitride layers included the _γ'Fe₄N phase. The X-ray stress constant K of the nitride layers were evaluated using _γN (200)+_γ'Fe₄N(200) diffraction with CrKα characteristic X-rays. The _γN (200)+_γ'Fe₄N(200) diffraction angle 2θ of DCPN powder and ASPN powder were 73.49° and 72.98°, respectively. The X-ray stress constants of the _γN (200)+_γ'Fe₄N(200) phase nitrided using DCPN and ASPN, E / (1+ν) , were 202 GPa and 153 GPa, respectively. The X-ray stress constant K of the _γN (200)+_γ'Fe₄N(200) phase nitrided using DCPN and ASPN were -2,365 MPa/deg and -1,809 MPa/deg, respectively. The X-ray residual stress of these S-phases prepared using DCPN and ASPN were approximately -5.3 GPa and -2.6 GPa, respectively. On the other hand, Raman microprobe spectroscopy was used for residual stress measurements of the DLC films deposited on these S-phases. The Raman spectra of the DLC films were classified into the disorder (D') peak at 1,150 cm^-1, D peak, and graphite (G) peak. The residual stresses in the DLC films on these S-phases as estimated from the Raman shift of the G peak for DCPN and ASPN were -3.2 GPa and -3.0 GPa, respectively. The hardness of the DLC films as determined using the nano-indentation method was very large. It is possible that increases in compressive residual stresses in the DLC films caused decreases in the contact areas and the indentation depth of the indenter, which appeared to cause increases in the Young's modulus and hardness of the DLC films.