Permeability of Concrete and Correlation with Microstructure Parameters Determined by 1H NMR

Yurong Zhang,Junzhi Zhang,Zhaofeng Fang,Shengxuan Xu,Chaojun Mao

doi:10.1155/2020/4969680

Yurong Zhang, Junzhi Zhang + Show 3 more

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https://doi.org/10.1155/2020/4969680

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Abstract

Water and gas permeability coefficients of concrete with different water-binder (w/b) ratios and admixtures were measured by a self-designed test device based on the steady-state flow method for liquid and the method of differential pressure in stability for gas, respectively. In addition, the micropore structure of concrete was determined by 1H nuclear magnetic resonance (NMR). Results indicated that there are good correlations between water and gas permeability of concrete with different w/b ratios, with correlation coefficient greater than 0.90. Better correlations between water permeability and segmental contributive porosity ranged from 10 to 100 nm and 100 to 1000 nm can be identified, but the gas permeability is more relevant to the segmental contributive porosity ranging from 100 to 1000 nm. Moreover, the correlation between water permeability and contributive porosity for each pore diameter is always better than that of gas permeability. The influence of admixtures on the relationship between permeability and pore size distribution of concrete is significant. Moreover, water permeability coefficient is one or two orders of magnitude lower than the gas permeability coefficient.

Highlights

Water and gas permeability are considered reliable indicators to evaluate the durability of concrete [1]
Substituting the boundary condition of water penetration test into equation (2) and the equation for water permeability coefficient can be obtained: Qh where μw is the dynamic viscosity of water (10−6kPa · s), Q is the average flow through the concrete (m3/s), h is the height of the specimen (m), A is the cross-sectional area of water (m2), and ΔP is the difference value of water pressure between upper and lower surfaces of test samples (MPa)
It is worth noting that the values of water and gas permeability coefficients are the average value after eliminating abnormal numbers with the Grubbs method [34]

Summary

Introduction

Water and gas permeability are considered reliable indicators to evaluate the durability of concrete [1]. Chen et al [15] used limestone powder as a cement substitute to evaluate the water resistance of concrete and found a significant linear correlation between permeable porosity and water penetration depth, as well as sorptivity coefficient. Water and gas permeability coefficients of the test concrete were measured with a self-designed test device based on the method of differential pressure in stability for gas [24] and the steady-state flow method for liquid. E microstructure parameters such as porosity and pore size distribution of the test concrete were tested by NMR. The reasons and influence factors causing a difference between water and gas permeability coefficients were attempted to be identified, and the influences of w/b ratio and admixture on the microstructure parameters of concrete and its macropermeability were discussed. The degree of correlation between water and gas permeability and segmental contributive porosity with different pore diameters was analyzed

Materials and Proportions of Concrete

Experimental Procedure and Methods

Results and Analysis

A7 A8 A9 A10

Conclusions e conclusions of this work can be summarized as follows: