Effects of pore water-rock reaction on heat extraction from the karst geothermal reservoirs: Based on the dual media model

Fractures and caves are the main flow and storage channels for the karst geothermal reservoirs, and the water-rock reaction within them significantly affects the thermal performance. Most previous studies concentrated on the fractures, disregarding the impact of the pore water-rock reaction. The objective of this study is to explore the...

Influence of pore property and alkalinity on the bio-deposition treatment efficiency of recycled aggregates

Microbial induced calcium carbonate precipitation (MICP) technology has been successfully used to enhance the properties of recycled concrete aggregates. However, the complex source and varied physical and chemical properties of recycled aggregates may have influence on the modification efficiency since microbes are often sensitive to the...

A novel lattice model to predict chloride diffusion coefficient of unsaturated cementitious materials based on multi-typed pore structure characteristics

This paper develops a novel lattice diffusive model to quantitatively study the chloride diffusion coefficient in unsaturated cementitious materials, in which the pore voxels are redistributed to make a better representation of a real microstructure of hardened cement paste. Considering the hierarchical microstructure and different drying...

Carbonation Rate of Alkali-Activated Concretes: Effects of Compositional Parameters and Carbonation Conditions

The current ability to predict the carbonation resistance of alkali-activated materials (AAMs) is incomplete, partly because of widely varying AAM chemistries and variable testing conditions. To identify general correlations between mix design parameters and the carbonation rate of AAMs, RILEM TC 281-CCC Working Group 6 compiled and analysed...

Numerical study of interactive ingress of calcium leaching, chloride transport and multi-ions coupling in concrete

In circumstances with wastewater and seawater, the behavior of multi-ions including calcium, chloride and others in concrete attracts attention. The present study investigated the multiple mechanisms that could happen under the special field situation above, including calcium leaching, chloride transport and multi-ion coupling. To realize the...

Influence of liquid-binder ratio on the performance of alkali-activated slag mortar with superabsorbent polymer

The influences of liquid-binder ratio and mixing sequence on the performance of superabsorbent polymer (SAP)-containing alkali-activated slag (AAS) mortar are investigated in this study. It is found that the SAP absorbs much less liquid in upper supernatant of AAS than in water. Mixing SAP with liquid first induces a larger absorption...

Chloride diffusion of alkali-activated fly ash/slag concrete

The widespread application of alkali-activated fly ash/slag (AAFS) concrete requires satisfaction of a series of performance criteria both from its early age properties (e.g. workability, strength) and long-term stability. In this study, long-term (till 180 days) natural chloride diffusion tests were conducted to evaluate the chloride diffusion...

Effect of reactive aggregate on the early age reaction of water-glass activated slag/fly ash mortars

Alkali activated materials (AAMs) have received worldwide attention due to its lower embodied energy and environmental impact than that of traditional cementitious materials. However, the activators with high alkalinity may raise the risk of alkali silica reaction (ASR) induced deterioration when reactive aggregates are used, which thereby...

Effect of reactive aggregate on the early age reaction of water-glass activated slag/fly ash mortars

Alkali activated materials (AAMs) have received worldwide attention due to its lower embodied energy and environmental impact than that of traditional cementitious materials. However, the activators with high alkalinity may raise the risk of alkali silica reaction (ASR) induced deterioration when reactive aggregates are used, which thereby...

New insights into long-term chloride transport in unsaturated cementitious materials: Role of degree of water saturation

Concrete is rarely saturated. Reliable durability design of marine concrete structures requires a solid understanding of the long-term chloride transport in unsaturated concretes. This paper presents a critical analysis of the time-dependent chloride diffusion coefficient in unsaturated cementitious materials exposed to marine environment....

Dependence of unsaturated chloride diffusion on the pore structure in cementitious materials

Conceptual analysis is performed to examine the effects of pore features on the water continuity in unsaturated porous systems. The roles of pore features in relative chloride diffusion coefficient (D_rc) of mortar specimens at various degrees of water saturation (S_w) were studied based on mercury intrusion porosimetry...

A model for predicting the relative chloride diffusion coefficient in unsaturated cementitious materials

An analytical model for predicting the relative chloride diffusion coefficient in cementitious materials at different degrees of water saturation is presented in this paper. The model is developed based on the Nernst-Einstein equation and conductivity of cementitious electrolyte, as well as on moisture distribution in the pore structure. Good...

Non-saturated Chloride Diffusion in Sustainable Cementitious Materials

Chloride-induced reinforcement corrosion, caused by chloride diffusion in the unsaturated concrete cover, is a major durability problem of concrete structures. Current concepts for concrete mixture design and for service life prediction are generally based on the understanding of the chloride diffusion coefficient of saturated concrete. This...

Effect of admixture on the pore structure refinement and enhanced performance of alkali-activated fly ash-slag concrete

This paper investigates the influence of a plasticizing admixture on the pore structure refinement of alkali-activated concrete and paste mixtures and the consequently enhanced performance. Alkali-activated fly ash-slag concrete and paste are designed using a polycarboxylate-based admixture with different dosages. The pore structure and...

Effect of natural carbonation on the pore structure and elastic modulus of the alkali-activated fly ash and slag pastes

The aim of this paper was to investigate the effect of natural carbonation on the pore structure, and elastic modulus (E_m) of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes after one year of exposure in the natural laboratory conditions. The chemical changes due to carbonation were examined by...

Relationship between the size of the samples and the interpretation of the mercury intrusion results of an artificial sandstone

Mercury intrusion porosimetry (MIP) measurements are widely used to determine pore throat size distribution (PSD) curves of porous materials. The pore throat size of porous materials has been used to estimate their compressive strength and air permeability. However, the effect of sample size on the determined PSD curves is often overlooked....

Experimental study of chloride diffusivity in unsaturated ordinary Portland cement mortar

Experiments are carried out to investigate the chloride diffusivity in partially saturated ordinary Portland cement mortars with water-to-cement (w/c) ratios of 0.4, 0.5 and 0.6. Based on resistivity measurement and Nernst-Einstein equation, the chloride diffusivities of cement mortars at various water saturations are estimated. The pore...