Hydraulic transport properties of unsaturated cementitious composites with spheroidal aggregates

Author(s):  
Jinyang Jiang ◽  
Fengjuan Wang ◽  
Weiqi Guo ◽  
Wenxiang Xu
Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 458
Author(s):  
Sascha Frank ◽  
Thomas Heinze ◽  
Mona Ribbers ◽  
Stefan Wohnlich

Flow and transport processes in fractured systems are not yet fully understood, and it is challenging to determine the respective parameters experimentally. Studies on 10 samples of 2 different sandstones were used to evaluate the reproducibility of tracer tests and the calculation of hydraulic transport properties under identical boundary conditions. The transport parameters were determined using the advection–dispersion equation (ADE) and the continuous time random walk (CTRW) method. In addition, the fracture surface morphology and the effective fracture aperture width was quantified. The hydraulic parameters and their variations were studied for samples within one rock type and between both rock types to quantify the natural variability of transport parameters as well as their experimental reproducibility. Transport processes dominated by the influence of fracture surface morphology experienced a larger spread in the determined transport parameters between repeated measurements. Grain size, effective hydraulic aperture and dispersivity were identified as the most important parameters to evaluate this effect, as with increasing fracture aperture the effect of surface roughness vanishes and the experimental reproducibility increases. Increasing roughness is often associated with the larger effective hydraulic aperture canceling out the expected increased influence of the fracture surface morphology.


Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2385
Author(s):  
Dong Cui ◽  
Hao Wei ◽  
Xiaobao Zuo ◽  
Keren Zheng ◽  
Qiannan Wang

Nanomaterials have received increased concentration in the field of civil engineering, as their incorporation can effectively modify the mechanical and transport properties of cementitious composites. In this study, to understand the effect of graphene oxide (GO) nanoparticles on the durability and mechanical properties of cementitious composites serving underwater, mortars incorporated with GO were taken for study. To match the real circumstance, all specimens were immersed directly in a flowing river for three years, and their transport properties, mechanical properties and microstructure before, and after, river experience were studied separately. The results showed that the incorporation of GO could reduce both early-age permeation coefficient and later-age chloride migration coefficient of mortar specimens. The average porosities of mortars could be reduced by the range of 3.37–11% with GO incorporation. Moreover, through a novel dual-scan method, GO incorporation was confirmed effective in enhancing both the leaching and cracking resistance. Furthermore, the compressive strengths, flexural strengths and splitting tensile strengths could be improved by the range of 4.37–9.82%, 7.78–22.33%, 8.14–28.73%, respectively with GO incorporation, and the tested mechanical strengths for GO-incorporated mortar after three-year river experience could be retained to a higher extent. Finally, based on durability and mechanical properties, the optimum mix proportion of GO was determined to be 0.06 wt.% in this study. The work presented here is of high reference value for the designing of marine infrastructure and can help promote the application of nanomaterials in civil engineering.


2017 ◽  
Vol 7 ◽  
pp. 184798041774230 ◽  
Author(s):  
Qiaofeng Zheng ◽  
Baoguo Han ◽  
Xia Cui ◽  
Xun Yu ◽  
Jinping Ou

Graphene, a two-dimensional monoatomic thick building block of a carbon allotrope, has emerged as nano-inclusions in cementitious materials due to its distinguished mechanical, electrical, thermal, and transport properties. Graphene nanoplatelet and its oxidized derivative graphene oxide were found to be able to reinforce and modify the cementitious materials from atomic scale to macroscale, and thereby endow them with excellent mechanical properties, durability, and multifunctionality. This article reviews the progress of fabrication, properties, mechanisms, and applications of graphene-based cementitious composites.


2012 ◽  
Vol 19 (4) ◽  
pp. 415-421 ◽  
Author(s):  
Mostafa Jalal

AbstractIn this paper, transport properties of high-performance self-compacting concrete (SCC), as one of the important cementitious composites incorporating micro and nano silica (NS) (SiO2) into the binder, have been investigated. For this purpose, different mixtures were designed with different amounts of silica fume (SF) and NS admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resistivity tests. Water absorption and capillary absorption were also measured as other durability related properties. The results showed that water absorption, capillary absorption, and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially the blend of SF and NS. By addition of the admixtures, resistivity of the SCC mixtures increased, which can lead to reduction of corrosion probability.


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