Due to the existence of the attached mortar,the performance of the recycled concrete aggregate(RCA)is inferior to the natural aggregate,which significantly limits its wide application in industry.In this study,five ki...Due to the existence of the attached mortar,the performance of the recycled concrete aggregate(RCA)is inferior to the natural aggregate,which significantly limits its wide application in industry.In this study,five kinds of modified solutions were used to modify the surface of RCA,and the modification effects were compared.The results showed that sodium silicate,nano-silica(NS),Bacillus pasteurii and soybean powder had relatively good modification effects on RCA,which could reduce the crushing value and water absorption,and increase apparent density.The composite solution(15%sodium silicate and 2%NS)and soybean powder solution had better modification effect.The 28 d compressive strength and splitting tensile strength of recycled aggregate concrete(RAC)prepared by RCA modified by soybean powder solution were 4.6%and 5.2%higher than those prepared by RCA modified by composite solution,respectively.This indicates that among the five kinds of modified solutions,soybean powder solution has the best modification effect on RCA,and the optimal soaking time of soybean powder solution is 8 h.At this time,the crushing value,water absorption and apparent density of RCA are 12.8%,5.3%,and 2653 kg/m^(3),respectively.The research results of this study provide a reference for the modification of RCA and its efficient utilization.展开更多
Microbially induced carbonate precipitation(MICP)is a promising technique for the autonomous healing of concrete cracks.In this study,the effect of pH on MICP was investigated.The results indicate that the MICP proces...Microbially induced carbonate precipitation(MICP)is a promising technique for the autonomous healing of concrete cracks.In this study,the effect of pH on MICP was investigated.The results indicate that the MICP process was inhibited when the pH was higher than 11.Both vaterite and calcite were produced when the pH was<8,whereas only calcite was produced when the pH was>8.Recycled concrete aggregates(RCA)coated with sodium silicate have been proposed as protective carriers for microbial healing agents.Although the presence of the coated RCA resulted in a loss of the splitting tension strength of the concrete,the loaded healing agents were highly efficient in self-healing cracks.Concrete incorporated with 20%RCA loaded with healing agents exhibited the best self-healing performance.When the initial crack widths were between 0.3 and 0.4 mm,the 7-d mean healing rate was approximately 90%.At 28 d,the crack area filling ratio was 86.4%,while its water tightness recovery ratio was 74.4%and 29.8%,respectively,for rapid and slow absorption.This study suggests that RCA coated with sodium silicate is an effective method for packaging microbial healing agents and has great potential for developing cost-effective self-healing concrete.展开更多
The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites.Concrete reinforcement with fibers has a long history.Nowadays,many ...The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites.Concrete reinforcement with fibers has a long history.Nowadays,many new fibers associated with high performance and possessing eco-environmental characteristics,such as basalt fibers and plant fibers,have received much attention from researchers.In addition,nanomaterials are considered as a core material in the modification of cement composites,specifically in the enhancement of the strength and durability of composites.This paper provides an overview of the recent research progress on cement composites reinforced with fibers and nanomaterials.The influences of fibers and nanomaterials on the fresh and hardened properties of cement composites are summarized.Moreover,future trends in the application of these fibers or of nanomaterial-reinforced cement composites are proposed.展开更多
Dear colleagues,Welcome to the inaugural issue of Low-carbon Materials and Green Construction(LMGC).This journal is a new international journal concerned with the materials and construction in civil engineering to cop...Dear colleagues,Welcome to the inaugural issue of Low-carbon Materials and Green Construction(LMGC).This journal is a new international journal concerned with the materials and construction in civil engineering to cope with the challenges raised by climate change,together with resources and energy consumption,which is dedicated to the widest dissemination of high-quality original research and insights.展开更多
基金the financial support of National Key R&D Program of China(No.2019YFC1906200)the National Natural Science Foundation of China(Nos.51879093,51009057 and 52108206)+1 种基金Jiangsu Science and Technology Department of China(No.BE2015706)Science and Technology Project of Nanjing Water Authority(No.201802).
文摘Due to the existence of the attached mortar,the performance of the recycled concrete aggregate(RCA)is inferior to the natural aggregate,which significantly limits its wide application in industry.In this study,five kinds of modified solutions were used to modify the surface of RCA,and the modification effects were compared.The results showed that sodium silicate,nano-silica(NS),Bacillus pasteurii and soybean powder had relatively good modification effects on RCA,which could reduce the crushing value and water absorption,and increase apparent density.The composite solution(15%sodium silicate and 2%NS)and soybean powder solution had better modification effect.The 28 d compressive strength and splitting tensile strength of recycled aggregate concrete(RAC)prepared by RCA modified by soybean powder solution were 4.6%and 5.2%higher than those prepared by RCA modified by composite solution,respectively.This indicates that among the five kinds of modified solutions,soybean powder solution has the best modification effect on RCA,and the optimal soaking time of soybean powder solution is 8 h.At this time,the crushing value,water absorption and apparent density of RCA are 12.8%,5.3%,and 2653 kg/m^(3),respectively.The research results of this study provide a reference for the modification of RCA and its efficient utilization.
基金financial support provided by the National Key Research and Development Program of China(2019YFC1906203).
文摘Microbially induced carbonate precipitation(MICP)is a promising technique for the autonomous healing of concrete cracks.In this study,the effect of pH on MICP was investigated.The results indicate that the MICP process was inhibited when the pH was higher than 11.Both vaterite and calcite were produced when the pH was<8,whereas only calcite was produced when the pH was>8.Recycled concrete aggregates(RCA)coated with sodium silicate have been proposed as protective carriers for microbial healing agents.Although the presence of the coated RCA resulted in a loss of the splitting tension strength of the concrete,the loaded healing agents were highly efficient in self-healing cracks.Concrete incorporated with 20%RCA loaded with healing agents exhibited the best self-healing performance.When the initial crack widths were between 0.3 and 0.4 mm,the 7-d mean healing rate was approximately 90%.At 28 d,the crack area filling ratio was 86.4%,while its water tightness recovery ratio was 74.4%and 29.8%,respectively,for rapid and slow absorption.This study suggests that RCA coated with sodium silicate is an effective method for packaging microbial healing agents and has great potential for developing cost-effective self-healing concrete.
基金Financial support from the National Science Fund for Distinguished Young Scholars of China(Nos.51325802 and 11625210)is highly acknowledged.The authors declare that there are no conflicts of interest.
文摘The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites.Concrete reinforcement with fibers has a long history.Nowadays,many new fibers associated with high performance and possessing eco-environmental characteristics,such as basalt fibers and plant fibers,have received much attention from researchers.In addition,nanomaterials are considered as a core material in the modification of cement composites,specifically in the enhancement of the strength and durability of composites.This paper provides an overview of the recent research progress on cement composites reinforced with fibers and nanomaterials.The influences of fibers and nanomaterials on the fresh and hardened properties of cement composites are summarized.Moreover,future trends in the application of these fibers or of nanomaterial-reinforced cement composites are proposed.
文摘Dear colleagues,Welcome to the inaugural issue of Low-carbon Materials and Green Construction(LMGC).This journal is a new international journal concerned with the materials and construction in civil engineering to cope with the challenges raised by climate change,together with resources and energy consumption,which is dedicated to the widest dissemination of high-quality original research and insights.
