Abstract
The capillary absorption capacity exerts an important effect on the durability of cement-based materials and is closely related to the pore structure. In this study, a variety of cement-based specimens were examined. The capillary water absorption and pore structure of the samples were determined using a gravimetric method and mercury intrusion porosimetry (MIP), respectively. The capillary water absorption coefficients for different water–binder ratios, diverse types and dosages of mineral admixtures, and various preloads were measured. The experimental results were analyzed and compared with data available in the current literature. The test results showed that the capillary water absorption performance of cement-based materials increased with an increasing water–binder ratio, first decreased and then increased with an increasing fly ash dosage, decreased with an increasing mineral power dosage, and decreased when the preload was less than a critical value and increased rapidly when the preload was greater than the critical value. The relationship between the capillary absorption coefficient and porosity was nearly linear. Water absorption by cement-based materials mainly correlated with pore diameters in the range of 10~1000 nm. The capillary water absorption coefficient increased continuously with the increase of pore fractal dimension.
Highlights
With the development of national infrastructure, cement-based materials are being used in increasingly harsh environments that impose increasing demands on their durability
The capillary water absorption characteristics are closely related to the pore structure [11], and Oltulu et al [12] found a statistically significant relationship between the pore size distribution obtained using mercury intrusion porosimetry (MIP) and Brunauer–Emmett–Teller (BET) tests and the capillary water absorption coefficient of mortar
This paper describes the results of capillary water absorption tests and previous research and investigates the capillary water absorption coefficients of cement-based materials with different water–binder ratios, types and dosages of mineral admixtures, preloads, and different porosities
Summary
With the development of national infrastructure, cement-based materials are being used in increasingly harsh environments that impose increasing demands on their durability. The capillary absorption test is the most common method used to study water transport within concrete, and the capillary absorption coefficient was selected to characterize the rate of water entry into the interior of porous materials [9]. Studies of the water transport of cement-based materials by performing capillary water absorption tests are very important to evaluate the performance of cement-based materials, predict their service life, and improve the level of durability design [10]. Mobili et al [13] and Gao et al [14] concluded that with the increasing use of recycled aggregates and external loading, the porosity of cement-based materials increases, and the capillary water absorption coefficient increases . Shi et al [17] and Huang [18] applied the fractal dimension to study the pore structure of concrete, and their results showed that the smaller the fractal dimension, the smaller the corresponding porosity of the specimen, and the permeability of specimens was related to their porosity, fractal dimension, and average pore size
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