Yield stress of aerated cement paste is studied. Samples are prepared by mixing aqueous foam with cement paste, which allows controlling bubble size, gas volume fraction and yield stress of the cement paste. Two distinct behaviors are observed depending on the surfactant used to prepare the precursor aqueous foam: (i) For a surfactant with low adsorption ability with respect to cement grains, bubbles tend to decrease the yield stress of the paste with magnitude governed by the Bingham capillary number, which accounts for bubble deformability. (ii) For a surfactant with high adsorption ability, bubbles increase significantly the yield stress. This behavior is shown to result from the surfactant-induced hydrophobization of the cement grains, which adsorb at the surface of the bubbles and tend to rigidify them. Within this regime, the effect of air incorporation is comparable to the effect of added solid particles.

中文翻译：

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加气水泥浆的屈服应力

研究了加气水泥浆体的屈服应力。通过将含水泡沫与水泥浆混合来制备样品，这允许控制水泥浆的气泡大小、气体体积分数和屈服应力。根据用于制备前体水性泡沫的表面活性剂，观察到两种不同的行为：（i）对于相对于水泥颗粒具有低吸附能力的表面活性剂，气泡倾向于降低浆体的屈服应力，其幅度受宾汉毛细管控制数字，这说明了气泡的变形能力。(ii) 对于具有高吸附能力的表面活性剂，气泡显着增加屈服应力。这种行为被证明是由表面活性剂引起的水泥颗粒疏水化造成的，水泥颗粒吸附在气泡表面并趋于使它们硬化。在这个制度下，