膨胀剂提升混凝土抗塑性开裂能力研究
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摘要
采用平板受限法和图像法,研究了膨胀剂提升混凝土抗塑性开裂的能力。研究结果表明,吹风加速混凝土表面失水条件下,不同水胶比(0.21～0.43)的混凝土均会发生塑性开裂,且随着水胶比的降低,混凝土的塑性开裂状况加剧;膨胀剂提升混凝土抗塑性开裂的能力与混凝土的水胶比有关,膨胀剂提升混凝土抗塑性开裂的效果随着水胶比的降低而减小,甚至出现负作用。同时,研究结果表明,吹风加速表面失水对诱导混凝土产生塑性开裂有显著作用,因此,对浇筑成型的混凝土结构进行及时的养护,在避免和减缓混凝土结构的塑性开裂方面具有重要作用。
Using plastic shrinkage cracking measuring apparatus and image analysis method,influence of expansive agent on the plastic cracking resistance ability of concrete was studied.Experiment results show that with surface wind blow,concrete with different water-to-binder ratio(0.21～0.43)resulted in plastic cracking inevitably,and along with the decrease of water-to-binder ratio,the status of plastic cracking of concrete was aggravated.The ability of expansive agent for improving the plastic cracking resistance of concreteis water-to-binder ratio related,the plastic cracking resistance of concrete decreased with the decrease of water-to-binder ratio of expansive introduced concrete,and even resulted in the negative result.Meanwhile,experiment results show that surface wind blow is a significant factor which promotes plastic cracking tendency of concrete.So,the guarantee of prompt curing of concrete structure after casting is of crucial importance for preventing and mitigating the plastic cracking of concrete.
Using plastic shrinkage cracking measuring apparatus and image analysis method,influence of expansive agent on the plastic cracking resistance ability of concrete was studied.Experiment results show that with surface wind blow,concrete with different water-to-binder ratio(0.21～0.43)resulted in plastic cracking inevitably,and along with the decrease of water-to-binder ratio,the status of plastic cracking of concrete was aggravated.The ability of expansive agent for improving the plastic cracking resistance of concreteis water-to-binder ratio related,the plastic cracking resistance of concrete decreased with the decrease of water-to-binder ratio of expansive introduced concrete,and even resulted in the negative result.Meanwhile,experiment results show that surface wind blow is a significant factor which promotes plastic cracking tendency of concrete.So,the guarantee of prompt curing of concrete structure after casting is of crucial importance for preventing and mitigating the plastic cracking of concrete.
引文
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[2]FERNANDO P,NETO,SANTOS A B D S,LA R H L,et al.Effect of the addition of synthetic fibers to concrete thin slabs on plastic shrinkage cracking[J].Construction and Building Materials,2010,24(11):2171-2176.
[3]OZGR E,KHALED M.Effect of steel fibers on plastic shrinkage cracking of normal and high strength concretes[J].Materials Research,2010,13(2):135-141.
[4]ZIAD B,MARC M.Application of fibrillated polypropylene fibers for restraint of plastic shrinkage cracking in silica fume concrete[J].ACIMaterials Journal,2001,99(4):337-344.
[5]American Concrete Institute.Hot weather concreting.In ACI Manual of Concrete Practice.ACI,Detroit,1999,ACI Committee 305.
[6]Australian pre-mixd concrete association.Cracks in concrete due to plastic shrinkage and plastic settlement.Technical Bulletin,1995,95(1):20-32.
[7]KWAK H G,HA S J.Plastic shrinkage cracking in concrete slabs.Part I:a numerical model[J].Magazine of Concrete Research,2006,58(8):505-516.
[8]SAMAN T A,MIRZAW H,WAFA F F.Plastic shrinkage cracking of normal and high-strength concrete:a comparative study[J].ACIMaterials Journal,1996,93(1):36-40.
[9]UNO P J.Plastic shrinkage cracking and evaporation formulas[J].ACIMaterials Journal,1998,95(4):35-375.