隧道管片混凝土蒸养工艺参数的研究

Study on the technology parameters of steam-curing for tunnel lining segments

在蒸汽养护制度下,隧道管片混凝土脱模强度与蒸汽养护制度关系密切。根据工程实际施工需要,隧道管片蒸汽养护时间不宜超过12小时。制备大断面隧道管片,蒸汽养护恒温温度应控制在55～65℃,春秋季升温时间采用3-3-3-2方式,而冬季施工蒸汽养护升温时间适宜采用5-5-3-2方式;混凝土水灰比可控制在0.32～0.34,坍落度可控制在30～70 mm,蒸养后脱模强度≥23 MPa;在55℃和65℃蒸汽养护制度下,试样XRD图谱同时出现AFt衍射峰和AFm衍射峰,在外界条件的变化下,由于晶型转换而发生延迟AFt现象。采用MPG矿物添加剂,能减少Ca(OH)2结晶生成并促进C-S-H胶凝的大量生成,对蒸汽养护混凝土早期脱模强度有明显改善作用。

Strength of concrete of tunnel segments during stripping is closely dependent on the steam-curing regime. Time for steam-curing is recommended to be less than 12 hours according to the requirements of construction. For fabricating segments with large cross-section, constant temperature for steam-curing should be controlled within 55 ℃ -65 ℃ ; during spring and autumn in the period for temperature increasing it is suitable to adopt 3-3-3-2 mode, while during winter to adopt 5-5-3-2 mode; water-cement ration can be controlled within 0.32～0.24, slump within 30-70mm; strength after stripping≥23 MPa; under the regime of 55 and 65℃ steam-curing, in XRD spectrum of specimen will appear AFt and AFm diffraction peaks at the same time; due to the variation of external conditions, delay of AFt may occur by the transform of crystal types. Adopting MPG mineral admixture can diminish the formation of Ca （OH）2 crystal and enhance the formation of C-S-H gel in big amount and promote the strength of concrete during early stripping.