旋转黏度计测定水泥浆体静态屈服应力和黏弹性研究

采用旋转黏度计进行了恒定剪切速率、应力松弛、蠕变试验,研究了水泥浆体的静态屈服应力和黏弹性.结果表明:新拌水泥浆体属于带有屈服应力的黏弹性流体,其静态屈服应力为弹性向黏性转变时所对应的剪切应力;恒定剪切速率、应力松弛、蠕变试验均能测试出水泥浆体屈服应力和黏弹性.在恒定剪切速率试验中,新拌水泥浆体的屈服应力测试依赖于测试时剪切速率的选择,剪切速率过小,水泥浆体不出现静态屈服应力,剪切速率过大,测试的静态屈服应力较小;在应力松弛和蠕变试验中,测试出的水泥浆体静态屈服应力较恒定剪切速率试验的精确.对于一个静态屈服应力未知的新拌水泥浆体,可先采用恒定剪切速率试验粗略选择剪切速率和剪切应力范围,之后采用应力松弛或蠕变试验进行精确测试其静态屈服应力.

Static Yield Stress and Viscoelasticity of Fresh Cement Paste Measured by Rotational Viscometer

The static shear rate, stress relaxation and creep tests were carried out by using rotational viscometer to investigate the static yield stress and viscoelasticity of cement paste.The results show that the fresh cement paste is a viscoelastic fluid with yield stress, and its static yield stress is the shear stress corresponding to the transformation of elasticity to viscosity;Yield stress and viscoelasticity of paste can be measured by the constant shear rate, stress relaxation and creep.In the constant shear rate test, the yield stress test of the fresh cement paste depends on the choice of the shear rate during the test, the cement slurry does not exhibit static yield stress when the shear rate is too low, and the static yield stress is small when the shear rate is too high;in the stress relaxation and creep tests, the measured static yield stress of the cement paste is more accurate than the constant shear rate test.For fresh cement paste with its static yield stress unknown, it's better to select the shear rate and the shear stress range roughly through a constant shear rate test and then accurately test the static yield stress by stress relaxation or creep test.