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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Article
  • Peer Reviewed
LBL Publications (2008)
    Cover page: Self-potential observations during hydraulic fracturing
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2010)
    The water-to-cement (w/c) ratio is one of the most important parameters determining the quality of cement-based materials. Currently, there is no practical way to accurately determine this ratio after all the ingredients of concrete have been mixed, posing a significant quality control problem for the construction industry. A new method has been developed to address this challenge whereby an electrical resistivity probe is immersed in fresh concrete, providing an instantaneous and accurate measure of a concrete’s water-to-cement ratio. Experiments were conducted on eight concrete mixtures designed according to the ACI 211.1 procedure, with varying w/c ratios (0.30, 0.40, 0.50, and 0.60) and fly ash percentages (0% and 25%). The results demonstrate a strong direct correlation between the resistivity of fresh concrete and the water-to-cement ratio. Average w/c ratio estimates based on measurements using the resistivity probe were within ±0.01 of the actual values for all mixes tested.
      Cover page: Instantaneous&nbsp;<em>In-Situ</em>&nbsp;Determination of Water-Cement&nbsp;Ratio of Fresh Concrete
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2004)

      We report here, for the first time, evolution of the streaming potential coupling coefficient as liquid carbon dioxide infiltrates Berea sandstone. Using 125 Omega-m tap water, the coupling coefficient determined before and after each CO2 flood of five samples averaged approximately -30 mV/0.1 MPa. After liquid CO2 passed through the specimens displacing all mobile pore water, trapped water remained and the coupling coefficient was approximately -3 mV/0.1 MPa. A bound water limit of the coupling coefficient for liquid CO2 flow was found using an air-dried sample to be -0.02 mV/0.1 MPa. For initially water-saturated samples, bulk resistivity varied during CO2 invasion from 330 Ohm-m, to 150 Ohm-m during CO2/water mixing, to a final value of 380 Ohm-m. Results suggest that trapped and bound water control electrical conduction and the electrokinetic response. Applications include monitoring CO2 injectate in subsurface reservoirs using the self potential method.

        Cover page: The streaming potential of liquid carbon dioxide in Berea sandstone
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