Early hydration and viscoelastic properties of tricalcium aluminate pastes influenced by soluble sodium salts

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research Pub Date : 2025-01-30 DOI:10.1016/j.cemconres.2025.107788

Daniel Axthammer , Tobias Lange , Joachim Dengler , Torben Gädt

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引用次数: 0

Abstract

During the early hydration of ordinary Portland cement (OPC), tricalcium aluminate (C₃A) exhibits the highest reactivity among the clinker phases. Consequently, C₃A significantly influences the early rheological properties of OPC-based materials, thereby linking rheology with C₃A reactivity. The reactivity of C₃A is affected by temperature, calcium sulfates, admixtures, and ionic strength. Calcium sulfate phases such as gypsum, bassanite, or anhydrite are used in technical Portland cement to control the early reactivity of C₃A.

This work investigates the impact of three sodium salts — sodium chloride (NaCl), sodium nitrate (NaNO₃), and sodium sulfate (Na₂SO₄) — on the hydration of C₃A. We study model suspensions composed of 10% cubic C₃A and 90% quartz by weight with in-situ isothermal calorimetry. The C₃A suspensions were mixed inside the calorimeter with a water-to-solid ratio of 0.8. Increasing concentrations, i.e., 400, 1000, and 2000 µmol g⁻¹, of the sodium salts mentioned above lead to characteristically decreased C₃A reactivities. Combined with small amplitude oscillatory shear (SAOS) rheology experiments, we show that the addition of Na₂SO₄ significantly reduces the heat flow and the initial storage modulus. In contrast, NaNO₃ and NaCl had less pronounced effects on both storage modulus and reaction heat.

The differences in structure development are attributed to the formation of different hydrate phases. Specifically, Na₂SO₄ leads to ettringite formation, whereas the presence of nitrate and chloride ions favors the precipitation of AFm phases. The study concludes that introducing various sodium salts can modulate the kinetics of C₃A hydration and alter the reaction pathway, forming different hydrate phases.

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可溶性钠盐对铝酸三钙膏体早期水化及粘弹性的影响

在普通硅酸盐水泥（OPC）水化初期，铝酸三钙（C3A）在熟料相中表现出最高的反应活性。因此，C3A显著影响opc基材料的早期流变特性，从而将流变学与C3A反应性联系起来。C3A的反应性受温度、硫酸钙、外加剂和离子强度的影响。硫酸钙相如石膏、玄武石或硬石膏用于技术硅酸盐水泥中，以控制C3A的早期反应性。本文研究了氯化钠（NaCl）、硝酸钠（NaNO3）和硫酸钠（Na2SO4）三种钠盐对C3A水化反应的影响。我们用原位等温量热法研究了由10%立方C3A和90%重量石英组成的模型悬浮液。C3A悬浮液在量热计内混合，水固比为0.8。增加上述钠盐的浓度，即400、1000和2000µmol g−1，导致C3A反应活性明显降低。结合小振幅振荡剪切（SAOS）流变学实验，我们发现Na2SO4的加入显著降低了热流和初始存储模量。相比之下，NaNO3和NaCl对储存模量和反应热的影响较小。结构发育的差异主要是由于不同水合物相的形成。具体来说，Na2SO4导致钙矾石的形成，而硝酸盐和氯离子的存在有利于AFm相的沉淀。研究认为，引入不同的钠盐可以调节C3A水化反应动力学，改变反应途径，形成不同的水合物相。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Cement and Concrete Research 工程技术-材料科学：综合

CiteScore

20.90

自引率

12.30%

发文量

318

审稿时长

53 days

期刊介绍： Cement and Concrete Research is dedicated to publishing top-notch research on the materials science and engineering of cement, cement composites, mortars, concrete, and related materials incorporating cement or other mineral binders. The journal prioritizes reporting significant findings in research on the properties and performance of cementitious materials. It also covers novel experimental techniques, the latest analytical and modeling methods, examination and diagnosis of actual cement and concrete structures, and the exploration of potential improvements in materials.