西安建筑科技大学学报(自然科学版)

根据工程实践惯例与高原自然环境特点,模拟了低压低湿耦合作用下的典型养护模式,研究了各养护模式下水泥水化进程与水泥浆体内部孔结构发展特点.水泥水化的进程由硬化浆体中化学结合水的含量表征,通过高温灼烧测得.水泥净浆的孔结构发展通过压汞法和氮吸附法进行分析,得到的孔结构特点同时也是评价水泥水化进程的重要依据.最后以混凝土的抗压强度试验验证上述对水泥净浆在化学与物理层面的分析.结果表明:同样的相对湿度下,低压养护的水泥净浆化学结合水比常压养护的少,凝胶孔发展也不如常压养护的充分,即水化进程有一定程度的滞后.若过早停止保湿养护进入低压低湿环境,28 d时水泥净浆中将残留更多的毛细孔.试验各组混凝土均能达到设计强度等级,但当浸水养护只有7 d,养护气压低至61 kPa且相对湿度低至30%时,强度富余非常有限.

Typical curing modes considering low air pressure and low relative humidity were designed based on normal engineering practice and physico-geographical environment of plateau regions. Cement paste specimens were cured in these designed modes and subsequently experienced a series of tests to investigate the hydration level and pore structure development. The level of cement hydration was characterized by the content of chemically-combined water, which was tested by the loss on ignition. Pore structure development of hardened cement paste was analyzed by both mercury intrusion and nitrogen absorption. The pore structure provided extra basis for cement hydration evaluation. Finally, compressive strength test of concrete was conducted to verify the above chemical and physical analyses on hardened cement paste. Results show that in the same relative humidity, the hydration level of cement paste cured in low air pressure is lower than that in ordinary air pressure, presenting as lower content of chemically-combined water and less gel pores. More capillary pores would remain at 28 d age if moisture retention untimely discontinues to make the cement paste expose to an environment with low air pressure and low humidity. Moreover, although all tested concrete groups satisfy the anticipated strength grade, there is a very limited surplus for concrete cured in 61 kPa & RH 30% after only 7 d water immersion.

引言
1 材料与方法
2 结果与分析
3 讨论
4 结论

表1 养护条件分组<br/>Tab.1 Grouping of curing conditions

表1 养护条件分组
Tab.1 Grouping of curing conditions

图1 低压罐内的湿度调节方法<br/>Fig.1 Methods for humidity control in the low-pressure tank

图1 低压罐内的湿度调节方法
Fig.1 Methods for humidity control in the low-pressure tank

图2 不同养护条件下硬化水泥净浆的烧失量<br/>Fig.2 LOI of hardened cement paste cured in different conditions

图2 不同养护条件下硬化水泥净浆的烧失量
Fig.2 LOI of hardened cement paste cured in different conditions

图3 不同养护条件下硬化水泥净浆孔隙率与平均半径(MIP)<br/>Fig.3 Porosity and average pore radius of hardened cement paste cured in different conditions(MIP)

图3 不同养护条件下硬化水泥净浆孔隙率与平均半径(MIP)
Fig.3 Porosity and average pore radius of hardened cement paste cured in different conditions(MIP)

图4 不同养护条件下硬化水泥净浆的孔半径分布(压汞法)<br/>Fig.4 Pore radius distribution of hardened cement paste cured in different conditions(MIP)

图4 不同养护条件下硬化水泥净浆的孔半径分布(压汞法)
Fig.4 Pore radius distribution of hardened cement paste cured in different conditions(MIP)

图5 不同养护条件下硬化水泥净浆孔体积与平均直径(氮吸附法)<br/>Fig.5 Pore volume and average diameter of hardened cement paste cured in different conditions(NAP)

图5 不同养护条件下硬化水泥净浆孔体积与平均直径(氮吸附法)
Fig.5 Pore volume and average diameter of hardened cement paste cured in different conditions(NAP)

图6 不同养护条件下硬化水泥净浆的孔径分布(氮吸附法)<br/>Fig.6 Pore diameter distribution of hardened cement paste cured in different conditions(NAP)

图6 不同养护条件下硬化水泥净浆的孔径分布(氮吸附法)
Fig.6 Pore diameter distribution of hardened cement paste cured in different conditions(NAP)

图7 不同养护条件下混凝土的抗压强度<br/>Fig.7 Compressive strength of concrete cured in different conditions

图7 不同养护条件下混凝土的抗压强度
Fig.7 Compressive strength of concrete cured in different conditions

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备注

引言

1 材料与方法

2 结果与分析

3 讨论

4 结论

期刊信息