The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated...The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated. Results indicate that the porous concrete with a cement dosage only 150 kg/m^3 has high strength and satisfying permeability when the aggregate has a passing percentage of 4.75 mm around 10% to 15%, with the increase of the maximum size of the aggregate, the strength of the porous concrete decreases and the permeability increases. When the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate is about 20%, there are no interference among the particles by Weymouth theory, the strength of the pervious porous concrete reaches the peak value. The optimum continues gradation limit of the aggregate for porous concrete pervious road base material is recommended according to the theoretical calculation and experimental results.展开更多
An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved des...An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.展开更多
The mechanical properties of recycled aggregates concrete from demolition have been studied for several years. It has been documented that rheological properties of these concrete are generally affected by use of recy...The mechanical properties of recycled aggregates concrete from demolition have been studied for several years. It has been documented that rheological properties of these concrete are generally affected by use of recycled aggregates. They could present mechanical properties less affected by the presence of recycled aggregates if the initial concrete were of good quality. However, manufacturing problems, mainly attributed to the angular character of these aggregates and to the granulometry of recycled sand, limit their industrial use. The worth point of this study consists in the optimization of the concrete formulation using specific admixture, adapted to this aggregates in order to facilitate its manufacturing. It shows that the new generation of superplasticizers containing some copolymer polycarboxylate makes it possible to significantly improve the fluidity of the recycled aggregates concrete in its fresh state. The aim of this research is to control rheologica] properties of fresh recycled aggregates concrete with fine and coarse recycled aggregates to limit the negative influence of aggregates on mechanical properties of concrete.展开更多
Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA),a low-density core-shell NLA(CNLA) was developed.Moreover,two types of porous lightweight aggregate concrete (PLAC) for wallbo...Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA),a low-density core-shell NLA(CNLA) was developed.Moreover,two types of porous lightweight aggregate concrete (PLAC) for wallboard were designed,using both foam and lightweight aggregates.The effects of LA on lightweight concrete workability,compressive strength,dry shrinkage,and thermal conductivity were studied and compared.The bulk density of CNLA can be lowered to 500 kg/m^(3),and its cylinder crushing strength is 1.6 MPa.PLACs also have compressive strengths ranging from 7.8 to 11.8 MPa,as well as thermal conductivity coefficients ranging from 0.193 to 0.219 W/(m·K^(-1)).The CNLA bonds better to the paste matrix at the interface transition zone,and CNLA concrete has a superior pore structure than SLA concrete,resulting in a 20% improvement in fluidity,a 10% increase in strength,a 6% reduction in heat conductivity,and an 11% decrease in drying shrinkage.展开更多
基金Funded by the Opening Fund of the Key Laboratory of Silicate Material Science and Engineering,Ministry of Education(No.YSJJ2004-13)
文摘The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated. Results indicate that the porous concrete with a cement dosage only 150 kg/m^3 has high strength and satisfying permeability when the aggregate has a passing percentage of 4.75 mm around 10% to 15%, with the increase of the maximum size of the aggregate, the strength of the porous concrete decreases and the permeability increases. When the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate is about 20%, there are no interference among the particles by Weymouth theory, the strength of the pervious porous concrete reaches the peak value. The optimum continues gradation limit of the aggregate for porous concrete pervious road base material is recommended according to the theoretical calculation and experimental results.
基金Projects(51978346,51778302)supported by the National Natural Science Foundation of ChinaProject(202002N3117)supported by the Ningbo Science and Technology Project,China。
文摘An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.
文摘The mechanical properties of recycled aggregates concrete from demolition have been studied for several years. It has been documented that rheological properties of these concrete are generally affected by use of recycled aggregates. They could present mechanical properties less affected by the presence of recycled aggregates if the initial concrete were of good quality. However, manufacturing problems, mainly attributed to the angular character of these aggregates and to the granulometry of recycled sand, limit their industrial use. The worth point of this study consists in the optimization of the concrete formulation using specific admixture, adapted to this aggregates in order to facilitate its manufacturing. It shows that the new generation of superplasticizers containing some copolymer polycarboxylate makes it possible to significantly improve the fluidity of the recycled aggregates concrete in its fresh state. The aim of this research is to control rheologica] properties of fresh recycled aggregates concrete with fine and coarse recycled aggregates to limit the negative influence of aggregates on mechanical properties of concrete.
基金Funded by the National Key R&D Programs of China (Nos. 2016YFC0701907, 2021YFB3802000 and 2021YFB3802004)。
文摘Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA),a low-density core-shell NLA(CNLA) was developed.Moreover,two types of porous lightweight aggregate concrete (PLAC) for wallboard were designed,using both foam and lightweight aggregates.The effects of LA on lightweight concrete workability,compressive strength,dry shrinkage,and thermal conductivity were studied and compared.The bulk density of CNLA can be lowered to 500 kg/m^(3),and its cylinder crushing strength is 1.6 MPa.PLACs also have compressive strengths ranging from 7.8 to 11.8 MPa,as well as thermal conductivity coefficients ranging from 0.193 to 0.219 W/(m·K^(-1)).The CNLA bonds better to the paste matrix at the interface transition zone,and CNLA concrete has a superior pore structure than SLA concrete,resulting in a 20% improvement in fluidity,a 10% increase in strength,a 6% reduction in heat conductivity,and an 11% decrease in drying shrinkage.
