摘要
早强型外加剂的研究主要集中在水泥基材料强度发展早期阶段的水化速率变化、产物变化、液相离子变化等方面,但对其作用机理和效果等缺乏系统性的总结。本文归纳了三类早强剂(无机、有机和复合)的早强机理及在各水化阶段的作用,得出以下结论:无机系早强剂通过提高体系碱度、压缩双电层、提供晶核以降低成核势垒等作用,破坏了水化阻滞膜或液相离解平衡,从而加速离解期的离解速率、增大液相中的离子浓度;此外,还通过加速诱导期水化产物的消耗,破坏水化反应平衡以加快水化产物钙矾石或钙铝水滑石形成,提高早强固相体积含量和体系致密度,从而提高早期强度。有机早强剂主要通过分散作用来促进离解速率,通过络合作用或水化作用破坏反应平衡,但掺量影响其早强效果和凝结速度。复合早强剂则协调多种机理来加快水化的整体进程,需注意避免新产物的生成阻碍原有活性组分正常的水化进程。总而言之,早强剂的选择应与胶凝材料体系相匹配,结合其作用机理促进各水化阶段强度发展。为满足尽可能早强的需求,阴离子宜选择硫酸系和硅酸系,阳离子宜选用Ca^(2+)、Al^(3+),或较高活性成分且无耐久性隐患的Li^(+),有机系早强剂宜考虑该物质的分散作用和络合作用,但应注意避免长期性能的降低,以及它们对应的促凝和缓凝阈值。
Research on early strengthening agent has mainly focused on the changes of hydration rate,product and liquid-phase ions in the early stage of strength development of cement-based materials.However,a systematic summary of its mechanism and effects is lacking.In this paper,therefore,the early strengthening mechanisms of three types of early strengthening agents(inorganic,organic and composite)and their functions in each hydration stage are reviewed.The following conclusions are summarized.The inorganic early strengthening agents destroy hydration-blocking film or liquid dissociation equilibrium by increasing the alkalinity of the system,compressing the double layer,and providing a crystal nucleus to reduce the nucleation barrier,so as to accelerate the dissociation rate during the dissociation period and increase the ion concentration in the liquid phase.Furthermore,the early strength will be improved during the induction period by accelerating the formation of ettringite or calcium alumina hydrotalcite,and by improving the volume content of the early strengthening solid phase and the density of the system through the consumption of hydration products and the destruction of the equilibrium of the hydration reaction.Organic early strengthening agents mainly promote the dissociation rate through dispersion or destroy the reaction equilibrium through complexation and hydration.The dosage,however,affects the early strength and setting rate.Compound early strengthening agents coordinate multiple mechanisms to accelerate the ove-rall hydration process,but more attention should be paid to avoiding the formation of new products which will the normal hydration process of the original active components.As the following suggestions proposed,the selection of early strengthening agents should match the binder and coordinate the early strengthening mechanism to promote the strength development of each hydration stage.To meet the demand of high early strength as early as possible,sulfuric acid and silicate are selected as anions,
作者
庞超明
唐志远
杨志远
黄鹏
PANG Chaoming;TANG Zhiyuan;YANG Zhiyuan;HUANG Peng(Jiangsu Key Laboratory of Civil Engineering Materials,School of Materials Science and Engineering,Southeast University Nanjing 211189,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2023年第9期76-86,共11页
Materials Reports
基金
国家重点研发计划(2021YFB3802000,2021YFB3802004)。
关键词
水泥基材料
水化进程
早强技术
作用机理
复合早强剂
cementitious material
hydration process
early strengthening technology
function mechanism
compound early strengthening agent
