Ultrasonic determination of elastic moduli in cement during hydrostatic loading to 1 GPa

An ultrasonic methodology has been developed for determination of the elast ic constants of porous, cementitious materials as a function of applied hyd rostatic pressures up to 1 GPa. The methodology can be performed upon bulk samples and in a fashion, which is more controlled than traditional impact (shock wave) testing. In-addition, data can be acquired during both the app lication; and release of the pressure. The data for mortar and cement paste samples, with porosity ranging from 13.7 to 24.1% by volume, indicate that during the initial application of pressure there is an irreversible, appro ximately linear, increase in the elastic moduli associated with the compact ion of the pores. During subsequent cycling of the pressure, a slight 'hyst eresis' was observed, with sound wave velocities and elastic moduli being s lightly lower during the application of the pressure than during the releas e of the pressure. This effect was observed to be reproducible, and is cons istent with a weak bonding between crack or pore faces forced into contact by the applied pressure. Use of the proposed ultrasonic methodology for qua ntification of the effects of pressure on the elastic moduli in cement-base d materials will provide the foundation for accurate modeling of the behavi or of cementitious materials during a broad range of high-strain inducing c onditions such as ballistic impact (military) or geological instability (ci vilian). (C) 2000 Elsevier Science S.A. All Fights reserved.