The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,...The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,including the Na_(2)O concentration and SiO_(2)/Na_(2)O(S/N)molar ratio,on the rheological behavior of alkali-activated slag fly ash pastes were investigated.The small amplitude oscillatory shear(SAOS)and shear test were used to evaluate the structural build-up and flowability of pastes.Besides,zeta potential measurement,calorimetric test and thermogravimetric analysis(TGA)were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes.It was found that high Na_(2)O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste.Moreover,the structural build-up of alkali-activated slag-fly ash pastes consists of two stages,which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels,respectively.展开更多
The effects of unoiled polyvinyl alcohol(PVA)fiber with four different volume fractions of 0%,1.0%,1.5%and 2.0%on the bending properties of alkali-activated slag(AAS)mortar plates were studied.Meanwhile,the acoustic e...The effects of unoiled polyvinyl alcohol(PVA)fiber with four different volume fractions of 0%,1.0%,1.5%and 2.0%on the bending properties of alkali-activated slag(AAS)mortar plates were studied.Meanwhile,the acoustic emission(AE)technique and a high-speed camera were utilized to detect the crack development over the complete damage process,and the scanning electronic microscopy(SEM)was used to observe the fiber-matrix interface.Test results show that PVA fibers play a significant role in the toughness improvement of AAS plates.However,the enhancing effect of PVA fibers on the bending behaviour of AAS plates at 120 d is not as remarkable as at early ages.It is observed that the failure process of the PVA fiber-reinforced alkali-activated slag plate can be divided into three stages:elastic stage,main crack formation stage and post-peak load stage.Observations on the fracture surface of specimens indicate that the deterioration process of specimens under bending changed from fiber pull-out at 3 and 28 d to fiber fracture at 120 d.展开更多
基金Project(2017 YFB 0310100)supported by National Key R&D Program of ChinaProjects(51778629,51922109)supported by the National Natural Science Foundation of ChinaProjects(2020 zzts 617,2020 CX 011)supported by the Innovation-Driven Project of Central South University,China。
文摘The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,including the Na_(2)O concentration and SiO_(2)/Na_(2)O(S/N)molar ratio,on the rheological behavior of alkali-activated slag fly ash pastes were investigated.The small amplitude oscillatory shear(SAOS)and shear test were used to evaluate the structural build-up and flowability of pastes.Besides,zeta potential measurement,calorimetric test and thermogravimetric analysis(TGA)were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes.It was found that high Na_(2)O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste.Moreover,the structural build-up of alkali-activated slag-fly ash pastes consists of two stages,which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels,respectively.
基金The National Basic Research Program of China(973Program)(No.2015CB655100)the National Natural Science Foundation of China(No.51378115)
文摘The effects of unoiled polyvinyl alcohol(PVA)fiber with four different volume fractions of 0%,1.0%,1.5%and 2.0%on the bending properties of alkali-activated slag(AAS)mortar plates were studied.Meanwhile,the acoustic emission(AE)technique and a high-speed camera were utilized to detect the crack development over the complete damage process,and the scanning electronic microscopy(SEM)was used to observe the fiber-matrix interface.Test results show that PVA fibers play a significant role in the toughness improvement of AAS plates.However,the enhancing effect of PVA fibers on the bending behaviour of AAS plates at 120 d is not as remarkable as at early ages.It is observed that the failure process of the PVA fiber-reinforced alkali-activated slag plate can be divided into three stages:elastic stage,main crack formation stage and post-peak load stage.Observations on the fracture surface of specimens indicate that the deterioration process of specimens under bending changed from fiber pull-out at 3 and 28 d to fiber fracture at 120 d.
