Research On Leaching Behavior Of Plastic Concrete Based On Electrochemical Accelerating Mechanism

Plastic concrete cutoff walls have been widely used in water conservancy and hydropower projects, for low elastic modulus, big extreme limit strain and well impermeability. The environment of hydraulic concrete worked is envolved in water circumstance, whatever the leaching behavior of plastic concrete can't be ignored. In this paper, the effects about the water-cement ratio and amount of bentonite and clay were studied which mainly focus on the work performance and mechanical behavior of the plastic concrete; through the Electrochemical Accelerate Leaching Method, the change of the plastic concrete during the process of dissolution has been studied. The main results include that:With regard to the single factor, with increase of water-cement ratio and the amount of bentonite and clay, the compressive strength and elastic modulus of plastic concrete decreased, and the relevant permeability coefficient increased.The plastic concrete have been tested by means of Electrochemical Accelerating Leaching Method. The results show that pH value of the anode shows relatively acidic, and the pH value of the cathode seems to be alkaline. Ca²⁺ precipitates from the plastic concrete gradually in the leaching period. At the beginning the dissolution amount of Ca²⁺ is higher, after that the dissolution rate leveled off. The greater the bentonite content, the less amount of Ca²⁺. When the total content of cementitious material is a fixed amount, the dissolution amount of Ca²⁺ of specimen mixed with bentonite and clay will be less than that of ones mixed with bentionite. The quality of plastic concrete decreased slightly, ultrasonic propagation time increased and the resistivity decreased after the dissolution which has indicated that the concrete density decreased and the porosity increased simultaneously. The internal structure of the dissolved specimen after 25th freeze-thaw cycles were damaged seriously, which has been accelerated by the leaching process.The micro-analysis on dissolved and non-dissolved specimen was conducted by Scanning Electron Microscopy(SEM) and spectroscopy tests. The results show that while the content of Ca(OH)₂ decreased, the concentration of Calcium and the density of the concrete decreased but the porosity increased.