The effect of undrained heating on a fluid-saturated hardened cement paste

Abstract

Ghabezloo et al. (2008): The effect of undrained heating on a fluid-saturated hardened cement paste 150The effect of undrained heating on a fluid-saturated hardened cement paste AbstractThe effect of undrained heating on volume change and induced pore pressure increase is an important point to properly understand the behaviour and evaluate the integrity of an oil well cement sheath submitted to rapid temperature changes. This thermal pressurization of the pore fluid is due to the discrepancy between the thermal expansion coefficients of the pore fluid and of the solid matrix. The equations governing the undrained thermo-hydro-mechanical response of a porous material are presented and the effect of undrained heating is studied experimentally for a saturated hardened cement paste. The measured value of the thermal pressurization coefficient is equal to 0.6MPa/°C. The drained and undrained thermal expansion coefficients of the hardened cement paste are also measured in the heating tests.The anomalous thermal behaviour of cement paste pore fluid is back analysed from the results of the undrained heating test.

Micromechanics analysis of thermal expansion and thermal pressurization of a hardened cement paste

“…In accordance with results of Valenza and Scherer [3], the analysis of the undrained heating test revealed that the thermal expansion coefficient of cement paste pore fluid is anomalously higher than the one of pure bulk water. This experimental study was a part of a larger study on the thermo-poro-mechanical behaviour of a hardened cement paste [1] [4][5] [6]. The experimental program consisted by drained, undrained and unjacketed compression tests, as well as drained and undrained heating tests and permeability evaluation tests.…”

“…The predictive capacity of the micromechanics model is verified by comparing the parameters with some experimental results from literature. In the continuity of the approach used in [7], the micromechanics model is used here in association with the results of drained and undrained heating tests presented in [1]. The model has been already calibrated in [7] for the poroelastic parameters, but a second calibration step should be performed for the thermal behaviour.…”

Effect of porosity on the thermal expansion coefficient: A discussion of the paper ‘Effects of mineral admixtures on the thermal expansion properties of hardened cement paste’ by Z.H. Shui, R. Zhang, W. Chen, D. Xuan, Constr. Build. Mater. 24 (9) (2010) 1761–1767

“…φ is the porosity, B is the Skempton coefficient, f α is the pore fluid thermal expansion coefficient and φ α is the pore volume thermal expansion coefficient [2].…”

“…The variation of the drained thermal expansion with porosity is related to the variations of this parameter with the stress state using the following relation [2][6]:…”

“…Moreover in the discussion of the experimental results in section 3.2 of [1], these authors mention that "… more porous materials have lower CTE, because the void could accommodate the internal thermal expansion of material". For both mentioned arguments a paper published by our group, Ghabezloo et al [2], is cited. But the mentioned argument about the effect of porosity on the thermal expansion coefficient is not given in our paper and it is not clear how the authors could obtain it from the presented results.…”