Mechanical properties of alkali activated slag concrete with ultra fine dredged sand from Yangtze River
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摘要: 分析了长江下游航道超细疏浚砂的理化性质,并以超细疏浚砂为原料,设计了5种不同疏浚砂掺量的碱激发矿渣混凝土(AASC)配合比,研究了其流动性、抗压强度、劈拉强度和吸水率的变化。通过SEM、XRD和压汞(MIP)技术,分析了AASC的物相组成和微观结构。研究表明:长江下游航道的超细疏浚砂颗粒细度模数在0.1~0.5之间。随着超细疏浚砂掺量的提升,试件的抗压强度和劈拉强度呈先上升后降低的趋势,而其流动性持续下降。在疏浚砂掺量(疏浚砂与细骨料的质量比)为50%时,AASC具有较好的力学性能和工作性能。试件的吸水率、密度测试以及SEM和MIP观察表明,适当掺入疏浚砂能够增加混凝土密实度,改善混凝土界面过渡区的结构,但过量疏浚砂导致混凝土流动性降低,且混凝土内的多害孔隙增加。Abstract: The physical and chemical properties of ultra-fine dredged sand in the lower reaches of the Yangtze River were analyzed. Five kinds of alkali activated slag concrete (AASC) mix proportions with different contents of ultra-fine dredged sand were designed. The fluidity, compressive strength, splitting tensile strength, density and water absorption were studied. The microstructure and phase composition of AASC were analyzed by SEM, XRD and mercury intrusion porosimetry (MIP). The results show that the fineness modulus of the ultra-fine dredged sand is between 0.1 and 0.5. With the increase of ultra-fine dredged sand content, the compressive strength and splitting tensile strength first increase and then decrease, while the fluidity continues to decline. When the dredged sand content (mass ratio to fine aggregate) reaches 50%, AASC obtains proper mechanical properties and workability. The results of water absorption, density test, SEM observation and MIP test show that the appropriate addition of dredged sand can increase the compactness of concrete and improve the structure of interface transition zone, but excessive dredged sand can reduce the fluidity of concrete and increase the porosity of concrete.
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表 1 矿渣化学成分
Table 1. Chemical composition of slag
Component CaO SiO2 Al2O3 MgO TiO2 S Na2O K2O Ratio/wt% 39.42 33.04 15.64 7.80 1.28 1.05 0.61 0.39 表 2 长江疏浚砂具体物理性能参数
Table 2. Physical properties of dredged sand from Yangtze River
Apparent density/
(kg·m−3)Bulk density/
(kg·m−3)Higher feed density/
(kg·m−3)Water
content/wt%Clay
content/wt%Porosity/
vol%Fineness
modulus2686-2695 1331-1404 2400-2800 11.4-17.8 1.9-3.2 9.7-18.5 0.1-0.5 表 3 不同疏浚砂掺量的碱激发矿渣混凝土(AASC)配合比 WD
Table 3. Mix proportion of alkali activated slag concrete (AASC) with different dredged sand contents
$ {{W}}_{\rm{D}} $ (kg·m−3) Group Stone Dredged sand River sand Fly ash Slag Sodium silicate Water Water reducer AASC0 1125 0 606 150 350 140 155 0.87 AASC25 1125 151.5 454 150 350 140 155 0.87 AASC50 1125 189 189 150 350 140 155 0.87 AASC75 1125 454 151.5 150 350 140 155 0.87 AASC100 1125 606 0 150 350 140 155 0.87 -
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