硅酸盐学报

水泥砂浆抗压强度与其饱水孔结构特征关系模型

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梁华明 ¹ , 乔晶 ¹ , 卢艺菲 ¹ , 王捷 ² , 周春圣 ¹

硅酸盐学报 | 研究论文 2025,53(2): 304-312

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硅酸盐学报 |研究论文 2025 , 53 (2) : 304 -312

水泥砂浆抗压强度与其饱水孔结构特征关系模型

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梁华明¹, 乔晶¹, 卢艺菲¹, 王捷², 周春圣¹

作者信息

^1．哈尔滨工业大学土木工程学院，哈尔滨 150090

^2．中铁科研院文化遗产保护研究院，成都 610036

通讯作者:

周春圣（1983—），男，博士，教授。

作者简介:

梁华明（1998—），男，博士研究生。

Relationships Between Compressive Strength of Cement Mortars and Pore Structure Characteristics at Water-Saturation

Huaming LIANG¹, Jing QIAO¹, Yifei LU¹, Jie WANG², Chunsheng ZHOU¹

Affiliations

^1.School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China

^2.Cultural Heritage Rehabilitation Institute of China Railway Academy, Chengdu 610036, China

Corresponding Author:

ZHOU Chunsheng (1983-), male, Ph.D., Professor. E-mail: C_S_Zhou@hit.edu.cn

LIANG Huaming (1998-), male, Doctoral candidate. E-mail: LianghuamingHIT@outlook.com

出版时间: 2025-02-20 doi: 10.14062/j.issn.0454-5648.20240425

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摘要

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水泥基材料孔结构对其抗压性能具有决定性影响。为准确描述水泥基材料抗压强度与孔结构的重要关联，利用低场磁共振弛豫技术，对掺引气剂的饱和水泥砂浆进行原状、无损测试，结合抗压强度测量结果，验证并改进抗压强度与孔结构特征间的关系模型。结果表明：低场磁共振技术能准确获取饱和砂浆的孔结构特征，以总孔隙率或分级孔隙率为变量的经验模型拟合效果一般，模型拟合所得经验参数不够稳定，模型的适用性差。基于孔径分布曲线，假设不同孔隙对抗压强度的影响权重与其对数孔径线性相关，所得改进经验模型形式简洁、拟合精度显著提高且能准确反映试件组内差异。此外，基于Griffith断裂理论，以总孔隙率及对数平均半径为自变量的理论模型表达式复杂且预测精度不高。若将半径大于10 nm的孔隙视为缺陷，其影响采用Griffith断裂理论解释；将半径小于10 nm的孔隙视作凝胶内部孔隙，它对基体强度的影响近似采用Powers提出的模型描述，所得修正Griffith断裂理论模型的预测精度极高且稳定性、可解释性强，能准确反映孔结构细微区别导致抗压强度差异。引气剂的掺入主要大幅增加半径10 nm以上的毛细孔隙，但同时也会小幅减少半径10 nm以下的基体孔隙，低场磁共振技术能获取水泥砂浆全尺度孔隙结构，进而协助解析孔结构特征与抗压强度的根本关联。

关键词

孔结构 / 抗压强度 / 水泥砂浆 / 引气 / 低场磁共振技术

Abstract

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Introduction

The pore structure of cement-based materials significantly influences their compressive strength. Studies have shown that the nanoscale pore structure significantly changes with variations in water content. Traditional pore measurement methods like mercury intrusion porosimetry and gas adsorption require the drying of specimens, potentially altering or even destroying the pore structure. The accuracy and representativeness of the compressive strength-pore structure relationship model established on this basis are therefore questionable. To accurately describe the important correlation between compressive strength and pore structure of cement-based materials, low-field magnetic resonance relaxation technique is utilized to carry out in-situ, nondestructive testing of saturated cement mortar doped with air-entraining agent. This is then combined with compressive strength measurement results to validate and refine the model describing the relationship between compressive strength and pore structure characteristics.

Methods

(1) Specimen preparation To avoid the ambiguous effects of ferromagnetic substances when using by low-field nuclear magnetic resonance (LF-NMR) technique, white Portland cement with low Fe₂O₃ content was used to prepare cement mortars with water-to-cement ratio of 0.4. Cement to sand ratio is 1∶2. And air-entraining agents (SJ-2 type) were incorporated. Chemical composition of white cement were 0.50% Fe₂O₃, 64.60% CaO, 21.71% SiO₂, 4.60% Al₂O₃, 2.80% SO₃, 2.43% MgO, 0.48% R₂O. The mass ratio of air-entraining agents to cement was 0%, 0.05%, 0.10%, and 0.15%. Considering different mass ratios, they are named as WP-BLK, WP-SJ05, WP-WP-SJ10, and WP-SJ15, respectively.

According to the designed proportions, the white cement, sand, air-entraining agents and water were mixed and casted into prisms of size 20 mm×20 mm×50 mm. After demounting at 24 h, they were all cured in saturated lime water at (20±2) ℃ for 180 d. After reaching the specified age, ten specimens were taken from each group of mortar and put into the high-pressure water saturation equipment for 3 d to ensure that the specimens were completely saturated and set aside.

(2) Pore structure test The pore structure of saturated mortars were tested by LF-NMR technology. Utilising a 2 MHz NMR analyser manufactured by Limecho Ltd., China, transverse relaxation test was performed through the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence at controlled room temperature about 20 ℃. In detail, the echo time τ_e (s) was adopted as short as 60 μs to detect the water confined in nanoscale pores of fast relaxation. Preliminary experimental tests had revealed that echo time τ_e ≤100 μs was short enough to make the contribution of diffusion relaxation negligible due to the controlled low concentration of Fe₂O₃ in white cement pastes. Moreover, A long sequence of N = 40 000-60 000 echoes generated at time τ= nτ_e (n=1, 2, …, N) (s) was recorded to capture the water stored in large capillary pores and even air voids with long relaxation time. 256-1024 scans with enough long repetition time 5-15 s were averaged. Except for the echo time, the rest of the parameters were flexibly adjusted according to water content of specimen. One can see detailed steps for testing pore structure by low-field magnetic resonance techniques in the relevant literature. (3) compressive strength test The compressive strength test of specimens were carried out by YAW-300 microcomputer automatic cement folding testing machine, which was produced by Jinan Hengruijin Testing Machine Co., Ltd., with a maximum capacity of 100 kN. The size of the compression surface of the specimen is 20 mm×50 mm, and the loading rate is fixed at 0.2 kN/s.

Results and discussion

LF-NMR technology accurately captures the pore structure characteristics of saturated mortar. Empirical models using total porosity or graded porosity as variables are generally effective, but the empirical parameters obtained from model fitting are not stable enough, limiting the model's applicability. An improved empirical model, based on the pore size distribution curve and assuming a linear relationship between the weights of different pores on compressive strength and their logarithmic pore sizes, offers a concise form, significantly improves fitting accuracy, and accurately reflects the differences within the specimen groups. Furthermore, building on Griffith's fracture theory, the theoretical model, which uses total porosity and logarithmic mean radius as independent variables, exhibits complex expressions and low predictive accuracy. If pores with a radius above 10 nm are regarded as defects, their influence can be explained by Griffith's fracture theory. Meanwhile, pores with a radius of 10 nm or less are regarded as internal pores of the gel, and its effect on the strength of the matrix is approximated using the model description proposed by Powers. The resulting modified Griffith fracture theory model is very high in prediction accuracy, stable, and interpretable, accurately reflecting how minor differences in pore structure lead to small changes in compressive strength.

Conclusions

The incorporation of air-entraining agents mainly increases the capillary pores above 10 nm in radius but also decreases the matrix pores below 10 nm in radius. LF-NMR technology can obtain the full-scale pore structure of cement mortar, aiding in the description of the fundamental correlation between pore structure characteristics and compressive strength.

Key words

pore structure / compressive strength / cement mortar / air-entraining / low-field nuclear magnetic resonance technique

引用本文

梁华明, 乔晶, 卢艺菲, 王捷, 周春圣. 水泥砂浆抗压强度与其饱水孔结构特征关系模型. 硅酸盐学报, 2025 , 53 (2) : 304 -312 . DOI: 10.14062/j.issn.0454-5648.20240425

Huaming LIANG, Jing QIAO, Yifei LU, Jie WANG, Chunsheng ZHOU. Relationships Between Compressive Strength of Cement Mortars and Pore Structure Characteristics at Water-Saturation[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (2) : 304 -312 . DOI: 10.14062/j.issn.0454-5648.20240425

基金

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国家自然科学基金(52078172)
中国中铁股份有限公司重大课题：近现代特色民族工业遗产保护与活化利用研究(科研院2023-重大-02)

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2025年第53卷第2期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240425

接收时间：2024-06-26
首发时间：2026-10-22
出版时间：2025-02-20

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收稿日期：2024-06-26
修回日期：2024-07-26

基金

国家自然科学基金(52078172)

中国中铁股份有限公司重大课题：近现代特色民族工业遗产保护与活化利用研究(科研院2023-重大-02)

作者信息

^1．哈尔滨工业大学土木工程学院，哈尔滨 150090

^2．中铁科研院文化遗产保护研究院，成都 610036

通讯作者:

周春圣（1983—），男，博士，教授。

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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