By using the uptodate temperatuer-stress testing machine, the thermal expansion coefficient of concrete at early ages was studied and indicative conclusions were achieved ： temperature rising due to hydration heat is...By using the uptodate temperatuer-stress testing machine, the thermal expansion coefficient of concrete at early ages was studied and indicative conclusions were achieved ： temperature rising due to hydration heat is not directly correlated with cracking, but the temperature and stress evolation process should be taken into consideration in the same time. Proper chemical admixtures and mineral cornpasitions can improve the mechanical properties of concrete such as thermal expansion coefficient, which is very indicative in practice.展开更多
In order to compare the compensation effect of expansive materials with different mineral sources on the temperature stress of concrete,we investigated the temperature stress of concrete when adding calcium sulfoalumi...In order to compare the compensation effect of expansive materials with different mineral sources on the temperature stress of concrete,we investigated the temperature stress of concrete when adding calcium sulfoaluminate type expansive materials(CSA)or CaO and calcium sulfoaluminate mixed type expansive materials(HCSA)at different temperatures by temperature-stress testing machine(TSTM)considering the influence of temperature history on the expansion.The experimental results show that the expansion characteristics of the two kinds of expansive materials with different mineral sources significantly vary.When adding expansive materials,the growth rate of compressive stress during the heating stage increases obviously,the maximum compressive stress is higher,while the decline rate of tensile stress in the late cooling stage becomes slow,and finally cracking temperature decreases.It is proved that concrete with HCSA has lower cracking temperatures and better temperature shrinkage compensation effect.Therefore,it is rational to choose HCSA when preparing concrete with high expansion energy to reduce thermal cracking.展开更多
In order to improve the early-age cracking resistance of concrete, different types of superplasticizers are used. Two types of polycarboxlic salt/acid superplasticizers and one retarding naphthalene superplasticizer a...In order to improve the early-age cracking resistance of concrete, different types of superplasticizers are used. Two types of polycarboxlic salt/acid superplasticizers and one retarding naphthalene superplasticizer are selected to investigate the influence of superplasticizers on the early-age cracking resistance of the concrete by using the slab test and the temperature-stress test. The results show that the polycarboxlic salt/acid superplasticizer cannot always improve the cracking resistance capacity of the concrete compared with the naphthalene superplasticizer, which is related to the chemical structure of the polycarboxlic salt/acid superplasticizer. High plastic tensile strength and dynamic elastic modulus at the early stage are beneficial to avoid cracking, and low hydration heat is also helpful. The evolutions of the drying shrilakage stress and the hydration heat temperature stress varying with time can be comprehensively evaluated by means of the slab test and the temperature stress test.展开更多
目的:探讨石榴籽油对小鼠抗抑郁作用的影响。方法:120只小鼠随机分为3组,每组各40只。每组小鼠随机分为对照组、模型组、石榴籽油高剂量组及石榴籽油低剂量组,每组各10只。石榴籽油高剂量组、石榴籽油低剂量组灌胃剂量分别为0.03 m L...目的:探讨石榴籽油对小鼠抗抑郁作用的影响。方法:120只小鼠随机分为3组,每组各40只。每组小鼠随机分为对照组、模型组、石榴籽油高剂量组及石榴籽油低剂量组,每组各10只。石榴籽油高剂量组、石榴籽油低剂量组灌胃剂量分别为0.03 m L·g-1、0.015 m L·g-1,对照组给予盐酸多塞平片,50 mg·kg-1,模型组每日给予等量生理盐水灌胃。给药后分别用于小鼠悬尾绝望实验(TST)、强迫游泳实验(FST)和利血平诱发的小鼠体温降低实验,观察石榴籽油对小鼠游泳不动时间和体温的影响。结果:石榴籽油高剂量组、低剂量组在一定程度可减少小鼠游泳不动时间,与模型组比较,差异具有统计学意义(P<0.05);石榴籽油高剂量组、低剂量组可减少小鼠悬尾不动时间,与模型组比较,有显著性差异(P<0.05);石榴籽油高剂量组、低剂量组与模型组比较,具有明显拮抗小鼠体温下降的作用,差异具有统计学意义(P<0.05)。结论:石榴籽油具有抗抑郁作用。展开更多
基金Founded by Hubei Key Loboratory of Roadway Bridge and Struc-ture Engineering( Wuhan University of Technology)
文摘By using the uptodate temperatuer-stress testing machine, the thermal expansion coefficient of concrete at early ages was studied and indicative conclusions were achieved ： temperature rising due to hydration heat is not directly correlated with cracking, but the temperature and stress evolation process should be taken into consideration in the same time. Proper chemical admixtures and mineral cornpasitions can improve the mechanical properties of concrete such as thermal expansion coefficient, which is very indicative in practice.
基金Funded by the National Key R&D Program of China(2017YFB0310102)。
文摘In order to compare the compensation effect of expansive materials with different mineral sources on the temperature stress of concrete,we investigated the temperature stress of concrete when adding calcium sulfoaluminate type expansive materials(CSA)or CaO and calcium sulfoaluminate mixed type expansive materials(HCSA)at different temperatures by temperature-stress testing machine(TSTM)considering the influence of temperature history on the expansion.The experimental results show that the expansion characteristics of the two kinds of expansive materials with different mineral sources significantly vary.When adding expansive materials,the growth rate of compressive stress during the heating stage increases obviously,the maximum compressive stress is higher,while the decline rate of tensile stress in the late cooling stage becomes slow,and finally cracking temperature decreases.It is proved that concrete with HCSA has lower cracking temperatures and better temperature shrinkage compensation effect.Therefore,it is rational to choose HCSA when preparing concrete with high expansion energy to reduce thermal cracking.
基金International Collaborative Research Project of Sika Technology AG of Switzerland,the Traffic Scientific Research Project in Jiangsu Province (No. 2010Y01)
文摘In order to improve the early-age cracking resistance of concrete, different types of superplasticizers are used. Two types of polycarboxlic salt/acid superplasticizers and one retarding naphthalene superplasticizer are selected to investigate the influence of superplasticizers on the early-age cracking resistance of the concrete by using the slab test and the temperature-stress test. The results show that the polycarboxlic salt/acid superplasticizer cannot always improve the cracking resistance capacity of the concrete compared with the naphthalene superplasticizer, which is related to the chemical structure of the polycarboxlic salt/acid superplasticizer. High plastic tensile strength and dynamic elastic modulus at the early stage are beneficial to avoid cracking, and low hydration heat is also helpful. The evolutions of the drying shrilakage stress and the hydration heat temperature stress varying with time can be comprehensively evaluated by means of the slab test and the temperature stress test.
文摘目的:探讨石榴籽油对小鼠抗抑郁作用的影响。方法:120只小鼠随机分为3组,每组各40只。每组小鼠随机分为对照组、模型组、石榴籽油高剂量组及石榴籽油低剂量组,每组各10只。石榴籽油高剂量组、石榴籽油低剂量组灌胃剂量分别为0.03 m L·g-1、0.015 m L·g-1,对照组给予盐酸多塞平片,50 mg·kg-1,模型组每日给予等量生理盐水灌胃。给药后分别用于小鼠悬尾绝望实验(TST)、强迫游泳实验(FST)和利血平诱发的小鼠体温降低实验,观察石榴籽油对小鼠游泳不动时间和体温的影响。结果:石榴籽油高剂量组、低剂量组在一定程度可减少小鼠游泳不动时间,与模型组比较,差异具有统计学意义(P<0.05);石榴籽油高剂量组、低剂量组可减少小鼠悬尾不动时间,与模型组比较,有显著性差异(P<0.05);石榴籽油高剂量组、低剂量组与模型组比较,具有明显拮抗小鼠体温下降的作用,差异具有统计学意义(P<0.05)。结论:石榴籽油具有抗抑郁作用。
