Low alkaline liquid state setting accelerator（LSA） for Portland cement was prepared in laboratory from aqueous solution of several inorganic sulfate salts and some organic chemical substances. Properties of cement w...Low alkaline liquid state setting accelerator（LSA） for Portland cement was prepared in laboratory from aqueous solution of several inorganic sulfate salts and some organic chemical substances. Properties of cement with addition of LSA relating to its setting time and strength development as well as its resistance to sulfate attack for short and long term exposure were experimentally examined. The experimental results showed that 5%-7% addition of LSA significantly accelerated the initial and final setting of Portland cement in the presence or absence of the blending of mineral admixtures, the initial and final setting time being less than 3 min and 6 min respectively. Meanwhile, the early 1 day curing age compressive strength increased remarkably by 20%, while the late 28 th day curing age compressive strength remained almost unchanged as compared with that of the reference accelerator free cement mortar specimen. Furthermore, mortar specimens of cement added with LSA and exposed to 5% Na2SO4 solution showed their excellent resistance to sulfate attack, with their short and long term curing age resistance coefficient to sulfate attack being around 1.04 to 1.17, all larger than 1.0. XRD analysis on hardened cement paste specimens at very early curing ages of several minutes disclosed the existence of more ettringite in specimens added with LSA than that of the reference specimens, meanwhile SEM observation also revealed the existence of well crystallized ettringite at very early hydration stage, suggesting that the accelerated setting of Portland cement can be attributed to the early and rapid formation of ettringite over the whole cement paste matrix due to the introduction of LSA. MIP measurement revealed that hardened cement paste specimens with the addition of LSA presented less medium diameter pores, more proportion of small pores and less proportion of large capillary pores, which is in a very good coincidence with the improvement of strength development of cement mortars added with LSA.展开更多
The dyeing behavior of cationic dyes to acrylic fiber with self-made low temperature dyeing accelerant was investigated in this study. Compared with conventional dyeing, the acrylic yarn was dyed with Cationic Turquoi...The dyeing behavior of cationic dyes to acrylic fiber with self-made low temperature dyeing accelerant was investigated in this study. Compared with conventional dyeing, the acrylic yarn was dyed with Cationic Turquoise Blue X-GB at 85℃ in the presence of accelerant and absence of accelerant, respectively. The influence of low temperature dyeing aceelerant on the dyeing mechanism of acrylic fiber dyed with cationic dye was analyzed through kinetics and thermodynamics study. The results show that adding dyeing accelerant ran heighten the equilibrium dye-uptake, dyeing rate constants, diffusion coefficients, and shorten half-dyeing time for acrylic fiber dyed with cationic dyes. Furthermore, the partition coefficient, the standard affinity, and the dye saturation value also increased in the dyeing at 85℃.展开更多
In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethyla...In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethylamine（Et_3N） and 1, 8-diazabicyclo [5.4.0]undec-7-ene（DBU） were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide（PI） films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 ℃, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 ℃ for 4 h.展开更多
The products of intertidal and super tidal(splash zone)corrosion on steel piles have been characterised at 3 UK sites with contrasting environmental conditions in order to determine corrosion reaction mechanism and if...The products of intertidal and super tidal(splash zone)corrosion on steel piles have been characterised at 3 UK sites with contrasting environmental conditions in order to determine corrosion reaction mechanism and if a common mechanism for accelerated low water corrosion occurs across sites.Intertidal corrosion samples at Shoreham and Newhaven ports show an internal composition of iron mono-and bi-sulphide,with intermediate sulphur oxidation state compounds,and an outer surface dominated by iron oxides and oxyhydroxides with a component of iron sulphates.The FTIR spectra are characteristic of sulphate green rust.In contrast,samples from Southend have all sulphur species below detection levels and are dominated by iron oxides and oxyhydroxides.Carbon binding energy spectra are consistent with the development of biofilms at all sites except for a splash zone sample at Southend.The results demonstrate a common mechanism for ALWC at Newhaven and Shoreham,involving the action of sulphate-reducing bacteria generating iron sulphides on the steel surface.These are subsequently oxidised to produce sulphate green rust,which may in turn oxidise to produce lepidocrocite.At Southend differences in environment are inferred to restrict the activity of sulphate reducing bacteria,resulting in direct oxidation of steel to generate iron oxyhydroxide gels,which subsequently recrystallise,dehydrate and oxidise to goethite,magnetite and ultimately hematite in both splash zone and intertidal samples.The multi-technique approach used here characterises the full range of corrosion products.展开更多
基金Funded by the Major State Basic Research Development Program of China(No.2011CB013800)
文摘Low alkaline liquid state setting accelerator（LSA） for Portland cement was prepared in laboratory from aqueous solution of several inorganic sulfate salts and some organic chemical substances. Properties of cement with addition of LSA relating to its setting time and strength development as well as its resistance to sulfate attack for short and long term exposure were experimentally examined. The experimental results showed that 5%-7% addition of LSA significantly accelerated the initial and final setting of Portland cement in the presence or absence of the blending of mineral admixtures, the initial and final setting time being less than 3 min and 6 min respectively. Meanwhile, the early 1 day curing age compressive strength increased remarkably by 20%, while the late 28 th day curing age compressive strength remained almost unchanged as compared with that of the reference accelerator free cement mortar specimen. Furthermore, mortar specimens of cement added with LSA and exposed to 5% Na2SO4 solution showed their excellent resistance to sulfate attack, with their short and long term curing age resistance coefficient to sulfate attack being around 1.04 to 1.17, all larger than 1.0. XRD analysis on hardened cement paste specimens at very early curing ages of several minutes disclosed the existence of more ettringite in specimens added with LSA than that of the reference specimens, meanwhile SEM observation also revealed the existence of well crystallized ettringite at very early hydration stage, suggesting that the accelerated setting of Portland cement can be attributed to the early and rapid formation of ettringite over the whole cement paste matrix due to the introduction of LSA. MIP measurement revealed that hardened cement paste specimens with the addition of LSA presented less medium diameter pores, more proportion of small pores and less proportion of large capillary pores, which is in a very good coincidence with the improvement of strength development of cement mortars added with LSA.
基金Science and Technology Department of Zhejiang Province,China (No. 2008C01069-4)
文摘The dyeing behavior of cationic dyes to acrylic fiber with self-made low temperature dyeing accelerant was investigated in this study. Compared with conventional dyeing, the acrylic yarn was dyed with Cationic Turquoise Blue X-GB at 85℃ in the presence of accelerant and absence of accelerant, respectively. The influence of low temperature dyeing aceelerant on the dyeing mechanism of acrylic fiber dyed with cationic dye was analyzed through kinetics and thermodynamics study. The results show that adding dyeing accelerant ran heighten the equilibrium dye-uptake, dyeing rate constants, diffusion coefficients, and shorten half-dyeing time for acrylic fiber dyed with cationic dyes. Furthermore, the partition coefficient, the standard affinity, and the dye saturation value also increased in the dyeing at 85℃.
文摘In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethylamine（Et_3N） and 1, 8-diazabicyclo [5.4.0]undec-7-ene（DBU） were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide（PI） films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 ℃, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 ℃ for 4 h.
基金financially supported by the EU-RDF INTERREG 2SEAS Project SOCORRO2:Seeking out corrosion
文摘The products of intertidal and super tidal(splash zone)corrosion on steel piles have been characterised at 3 UK sites with contrasting environmental conditions in order to determine corrosion reaction mechanism and if a common mechanism for accelerated low water corrosion occurs across sites.Intertidal corrosion samples at Shoreham and Newhaven ports show an internal composition of iron mono-and bi-sulphide,with intermediate sulphur oxidation state compounds,and an outer surface dominated by iron oxides and oxyhydroxides with a component of iron sulphates.The FTIR spectra are characteristic of sulphate green rust.In contrast,samples from Southend have all sulphur species below detection levels and are dominated by iron oxides and oxyhydroxides.Carbon binding energy spectra are consistent with the development of biofilms at all sites except for a splash zone sample at Southend.The results demonstrate a common mechanism for ALWC at Newhaven and Shoreham,involving the action of sulphate-reducing bacteria generating iron sulphides on the steel surface.These are subsequently oxidised to produce sulphate green rust,which may in turn oxidise to produce lepidocrocite.At Southend differences in environment are inferred to restrict the activity of sulphate reducing bacteria,resulting in direct oxidation of steel to generate iron oxyhydroxide gels,which subsequently recrystallise,dehydrate and oxidise to goethite,magnetite and ultimately hematite in both splash zone and intertidal samples.The multi-technique approach used here characterises the full range of corrosion products.
