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The strength mechanisms of two kinds of cement-asphalt (CA) mortar, which vary principally in their strength and elastic modulus, were investigated by environmental scanning electron microscopy, calorimetry, and strength tests. The results showed that the asphalt emulsion delayed the early hydration of the cement and the asphalt membrane had a negative effect on the further hydration of the cement, to some extent. The cement products could impale the asphalt membrane, and the cement could hydrate adequately because of the sufficient water supply in the CA mortar. The framework formed by the hardened cement paste was the primary structure skeleton in the CA mortar with a high elastic modulus and the asphalt phase, exhibiting as a filling phase, increased the weak phase of the structure system. For CA mortar with a low elastic modulus, the asphalt phase exhibited as a dominant phase. Two weak structure skeletons, formed by the asphalt membrane and the hardened cement paste, respectively, were responsible fo...

High frequency coherent acoustic-phonons are excited in Fe/Si film by using femtosecond pump-probe technique. The dynamics of coherent acoustic-phonons can be fitted well to a classical damped harmonic function. The frequency and the dephasing time of the observed acoustic-phonons are 0.25 THz and 12 ps, respectively, which are independent of pumping photo-energy and fluence. Moreover, the amplitude of the coherent acoustic-phonons is linearly proportional to the fluence. The critical parameter (12e-ph/T) is calculated to be about 0.6, which indicates that the electron pressure might play a significant role in driving coherent acoustic phonons. The thickness and the mass density of the film are required to determine the out-of-plane elastic constant C～283 GPa of the Fe/Si film.