Stimulated infrared emission from rocks: assessing a stress indicator

International audienceTo study the effect of stress-activated positive hole (p-hole) charge carriers on the infrared (IR) emission from rocks, we subjected a portion (~10 vol.%) of a large (30×60×7.5 cm3) block of anorthosite, a nearly monomineralic (Ca-rich feldspar) igneous rock, to uniaxial deviatory stress up to failure. We measured the IR emission from a flat surface ?40 cm from the stressed rock volume over the 800?1300 cm?1 (7.7?12.5 ?m) range. Instantly, upon loading, the emission spectrum and intensity change. At first narrow bands appear at 930 cm?1 (10.75 ?m), 880 cm?1 (11.36 ?m), 820 cm?1 (12.4 ?m) plus additional narrow bands in the 1000?1300 cm?1 (7.7?10.0 ?m) range. The 10.75?12.4 ?m bands are thought to arise from vibrationally excited O-O stretching modes, which form when p-hole charge carriers, which spread from the stressed rock volume into the unstressed rock, recombine at the surface. They radiatively decay, giving rise to "hot" bands due to transitions between excited states. Before failure the broad emission bands at 1170 cm?1 and 1030 cm?1 (8.7 and 9.7 ?m) also increase slightly in intensity, suggesting a small increase in temperature due to thermalization of the energy deposited into the surface through p-hole recombination. Stimulated IR emission due to hole-hole recombination and its follow-on effects may help understand the enhanced IR emission seen in night-time satellite images of the land surface before major earthquakes known as "thermal anomalies"

Stimulated infrared emission from rocks: assessing a stress indicator

International audienceTo study the effect of stress-activated positive hole (p-hole) charge carriers on the infrared (IR) emission from rocks, we subjected a portion (~10 vol.%) of a large (60×30×7.5 cm3) block of anorthosite, a nearly monomineralic (Ca-rich feldspar) igneous rock, to uniaxial deviatory stress up to failure. We measured the IR emission from a flat surface ?40 cm from the stressed rock volume over the 800?1300 cm?1 (7.7?12.5 ?m) range. Upon loading, the intensity and spectrum of the IR emission change. Narrow bands near instantly appear at 930 cm?1 (10.75 ?m), 880 cm?1 (11.36 ?m), 820 cm?1 (12.4 ?m) plus additional bands in the 1000?1300 cm?1 (10.0?7.7 ?m) range. Upon further loading the bands broaden and shift. Their intensities increase but also fluctuate. Near the emission maxima at 300 K, at 1150 cm?1 and 1030 cm?1 (8.7 and 9 ?m), barely any intensity increase occurs suggesting that the temperature of the surface does not actually increase. We propose that the observed narrow IR emission bands arise from vibrationally excited O-O stretching modes which form when p-hole charge carriers (activated in the stressed rock) spread into the unstressed portion of the rock to the surface, where they recombine and radiatively decay. The effect, stimulated IR emission due to hole-hole recombination, may help explain the enhanced IR emission seen in night-time satellite images of the land surface before major earthquakes known as "thermal anomalies''

Determination of In-Situ Compressive Strength of Precast Concrete Girders

Verification of field compressive strength of precast concrete girders from 52 bridges in seven counties in California are presented. Nondestructive Testing (NDT) methods used are Proceq\u2019s Silver Schmidt Rebound Hammer and Ultrasonic Pulse Velocity (UPV) and James Instruments\u2019 Windsor Pin and Windsor Probe Systems. NDT tests were performed on concrete walls, slabs, and cylinders constructed under ambient and laboratory curing conditions at San Jose State University. Data from the laboratory testing in combination with data supplied by the manufacturer of the NDT equipment were utilized to develop strength prediction charts for the different bridge girders. Concrete cores from five selected bridges were taken, and compressive strength and NDT tests were performed and analyzed. Results obtained from the cores with the bridge prediction data were compared to verify accuracy of the predictions. The America Concrete Institute (ACI) 209 equation was utilized, and modified equations are proposed for more accurate bridge strength predictions

Effect of Thermoplastic Aggregates Incorporation on Physical, Mechanical and Transfer Behaviour of Cementitious Materials

International audienc