石膏种类对掺减水剂水泥浆体流动行为的影响  

Effect of Gypsum Type on Flowability of Cement Pastes with Superplasticizer

作　　者：舒鑫 张倩倩 杨勇 冉千平 SHU Xin;ZHANG Qianqian;YANG Yong;RAN Qianping(State Key Laboratory of High-Performance Civil Engineering Materials,Jiangsu Sobute New materials Co.,Ltd.,Nanjing 210008,China;School of Materials Science and Engineering,Southeast University,Nanjing 210096,China)

机构地区：[1]江苏苏博特新材料股份有限公司,高性能土木工程材料国家重点实验室,南京211103 [2]东南大学材料科学与工程学院,南京211189

出　　处：《硅酸盐学报》2025年第3期497-504,共8页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金面上项目(52178215)。

摘　　要：为探明混凝土拌合早期流动性剧烈变化的本质,从石膏种类出发,采用熟料与不同石膏(二水石膏、半水石膏)制备了5种水泥,聚焦其前1 h浆体流动性经时变化,考察减水剂吸附、矿物相溶解、水化产物析出等过程,从而揭示浆体早期流动性经时变化内在机制。结果表明:矿物相溶解以及水化产物析出、生长是引起浆体早期流动度复杂多样的关键因素。对于二水石膏体系,钙矾石形成导致体系比表面积大幅增加,引起浆体流动度经时损失;对于半水石膏体系,除了钙矾石外,析出的大尺寸二水石膏加速了浆体流动度早期损失,但间隙液中SO_(4)^(2-)浓度逐渐降低有利于减水剂吸附,从而导致浆体流动度出现反增长。Introduction Appropriate workability is a key to ensuring the smooth pouring,building of concrete,and quality of the project.However,in practical applications,the workability of concrete often undergoes unexpected drastic changes in the early mixing stage,such as rapid loss of flowability,false set and so on.The change of flowability of cement paste overtime in the early stage is mainly related to the early hydration of cement and the adsorption behavior of superplasticizer.Cement pastes with different mineral compositions can exhibit different change rules overtime.In the early stage of hydration,especially in the first hour,the hydration reaction of tricalcium aluminate(C_(3)A)mainly occurs.Since the reaction of C_(3)A with water is extremely rapid,a large amount of calcium sulfate is incorporated into cement,and gypsum dihydrate(G,CaSO_(4)·2H_(2)O)is usually the most important source of calcium sulfate.Although the existing studies focus on the influence of gypsum types on the hydration of C_(3)A,the fundamental reasons are still need to be explored.In this paper,the effect of gypsum types was considered to elucidate the fundamental reasons behind the drastic changes in early flowability of fresh concrete.Five cements were prepared using clinker combined with different types of gypsum(i.e.,G,gypsum dihydrate and H,hemihydrate gypsum).The study focused on the time-dependent changes in the flowability of pastes within the first hour,and examined the processes such as adsorption of superplasticizer,dissolution of mineral phase and precipitation of hydration products,thus analyzing the intrinsic mechanisms behind the time-dependent changes in flowability.Methods Based on the content of C_(3)A in the clinker,four types of cements with a single gypsum type were prepared via adding G and H,respectively,at two molar ratios of SO_(4)^(2-)to C_(3)A of 0.5 and 1.5,and one type of cement with mixed gypsum was prepared at a molar ratio of SO_(4)^(2-)to C_(3)A of 1.5 and a molar ratio of G to H of 2.In the test,the water b

关 键 词：流动性 半水石膏 铝酸三钙 减水剂 钙矾石 

分 类 号：TU528[建筑科学—建筑技术科学]