Wenzhong Zhu - Academia.edu (original) (raw)

Papers by Wenzhong Zhu

Mineralogical Magazine, 2008

Calcium carbonate biominerals are frequently analysed in materials science due to their abundance... more Calcium carbonate biominerals are frequently analysed in materials science due to their abundance, diversity and unique material properties. Aragonite nacre is intensively studied, but less information is available about the material properties of biogenic calcite, despite its occurrence in a wide range of structures in different organisms. In particular, there is insufficient knowledge about how preferential crystallographic orientations influence these material properties. Here, we study the influence of crystallography on material properties in calcite semi-nacre and fibres of brachiopod shells using nanoindentation and electron backscatter diffraction (EBSD). The nano-indentation results show that calcite semi-nacre is a harder and stiffer (H ≈ 3—5 GPa; E = 50–85 GPa) biomineral structure than calcite fibres (H = 0.4—3 GPa; E = 30—60 GPa). The integration of EBSD to these studies has revealed a relationship between the crystallography and material properties at high spatial reso...

Cement and Concrete Composites, 2017

Advanced Engineering Materials, 2018

Organisms exert exquisite control on mineral formation by tuning structural and material properti... more Organisms exert exquisite control on mineral formation by tuning structural and material properties to meet functional requirements. Brachiopods are sessile marine organisms that filter feed via a large lophophore which is supported by a delicate calcite loop that grows from the inner surface of the shell. How does the loop support the weight of the large lophophore? Electron backscatter diffraction (EBSD) and nanoindentation analyses of the loop as it emerges from the shell of Laqueus rubellus reveal that calcite fiber crystallography generates asymmetry in the material properties of the structure. In the core of the emergent loop, the fibers are short and kernel‐like. Either side of the core, the long fibers have a different crystallographic orientation and resultant material properties. fibers on the anterior, load‐bearing side, are harder (H = 3.76 ± 0.24 GPa) and less stiff (E = 76.87 ± 4.87 GPa) than the posterior (H = 3.48 ± 0.31 GPa, E = 81.79 ± 5.33 GPa). As a consequence o...

The study is related to the EU 7 Framework Programme CODICE (COmputationally Driven design of Inn... more The study is related to the EU 7 Framework Programme CODICE (COmputationally Driven design of Innovative CEment-based materials). The main aim of the project is the development of a multi-scale model for the computer based simulation of mechanical and durability performance of cementitious materials. This paper reports results of nanoindentation testing on fully calcium leached cement paste in relation with the prediction from the latest computer model developed in the CODICE research project. Using the statistical nanoindentation technique, intrinsic properties of different hydrate phases after leaching has been studied. In order to perform reliable nanoindentation experiments a very smooth and flat sample surface is required. Due to the very porous and weak microstructure of fully-leached cement paste resin impregnation has to be used to produce satisfactory and representative specimens for the nanoindentation experiments. Extensive trials with different low stiffness resins (Youn...

Cement and Concrete Composites, 2017

Construction and Building Materials, 2015

ABSTRACT The present study explores the viability of reusing mixed recycled aggregate from constr... more ABSTRACT The present study explores the viability of reusing mixed recycled aggregate from construction and demolition waste as a partial (25 and 50 wt%) replacement for natural coarse aggregate in the manufacture of concretes with a compressive strength of 30 MPa. It further analyses the effect of some of the constituents (asphalt, clay-based materials, floating particles and fines) of these recycled aggregates on the properties of recycled concretes. Despite the high asphalt and floating particle content of the recycled aggregate used, came from waste management plant at Glasgow, it was found to have no adverse effect on the workability of the new concretes. Hardened concrete density and compressive strength were observed to decline with increasing replacement ratios, at a variable rate depending on the components of the recycled aggregate mix and the thickness of their ITZs (the thicker the weaker). While concrete with 25% recycled aggregate exhibited lower sorptivity than the reference concrete, absorption was higher when the replacement ratio was 50%. The findings showed that this type of recycled aggregate can be used in concrete manufactured for housing applications and confirmed the importance of good construction and demolition waste management to deliver high quality recycled aggregate.

2nd International RILEM Symposium on Advances in Concrete through Science and Engineering, 2006

Special Publication, 2004

Materiales de Construcción, 2011

The textural and mechanical characterization of C-S-H gels formed from the hydration of pure T1-C... more The textural and mechanical characterization of C-S-H gels formed from the hydration of pure T1-C 3 S, β-C 2 S and their blends are studied by Nitrogen sorption and nanoindentation experiments. The surface area and nanoporosity of C-S-H gels formed from the hydration of β-C 2 S and the 30-70 (T1-C 3 S and β-C 2 S mixture) are higher than those from hydration of T1-C 3 S, and 70-30, with the difference decreasing with hydration age. Such changes are well supported by findings of nanoindentation study, which shows the greater relative volume of C-S-H phases with lower densities in the β-C 2 S and the 30-70 pastes. With the increase in hydration age, the relative volume of C-S-H phases with higher densities increased at the expenses of those with lower density. Important quantitative correlations were found among these textural characteristics and the mean chain length, determined from 29 Si magic-angle-spinning (MAS) NMR, of the C-S-H gels.

Journal of The Royal Society Interface, 2014

Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening th... more Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis , was cultured at projected levels of p CO 2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus ( E ), hardness ( H ) and toughness ( K IC ) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more bri...

Special Publication, 2004

Nanotechnology in Construction 3, 2009

This paper reports results of micro/nano-scale mechanical characterisation of the cement-based ma... more This paper reports results of micro/nano-scale mechanical characterisation of the cement-based materials at micro/nano-scale using various available mapping techniques. Two new techniques: Express Nanoindentation Test option by Agilent Technologies and PeakForce QNM by Bruker were applied to mapping mechanical properties of cement-based materials, together with the use of conventional nanoindentation technique. Preliminary test results as well as advantages and limitations for the different techniques were discussed.

Mineralogical Magazine, 2008

Calcium carbonate biominerals are frequently analysed in materials science due to their abundance... more Calcium carbonate biominerals are frequently analysed in materials science due to their abundance, diversity and unique material properties. Aragonite nacre is intensively studied, but less information is available about the material properties of biogenic calcite, despite its occurrence in a wide range of structures in different organisms. In particular, there is insufficient knowledge about how preferential crystallographic orientations influence these material properties. Here, we study the influence of crystallography on material properties in calcite semi-nacre and fibres of brachiopod shells using nanoindentation and electron backscatter diffraction (EBSD). The nano-indentation results show that calcite semi-nacre is a harder and stiffer (H ≈ 3—5 GPa; E = 50–85 GPa) biomineral structure than calcite fibres (H = 0.4—3 GPa; E = 30—60 GPa). The integration of EBSD to these studies has revealed a relationship between the crystallography and material properties at high spatial reso...

Cement and Concrete Composites, 2017

Advanced Engineering Materials, 2018

Organisms exert exquisite control on mineral formation by tuning structural and material properti... more Organisms exert exquisite control on mineral formation by tuning structural and material properties to meet functional requirements. Brachiopods are sessile marine organisms that filter feed via a large lophophore which is supported by a delicate calcite loop that grows from the inner surface of the shell. How does the loop support the weight of the large lophophore? Electron backscatter diffraction (EBSD) and nanoindentation analyses of the loop as it emerges from the shell of Laqueus rubellus reveal that calcite fiber crystallography generates asymmetry in the material properties of the structure. In the core of the emergent loop, the fibers are short and kernel‐like. Either side of the core, the long fibers have a different crystallographic orientation and resultant material properties. fibers on the anterior, load‐bearing side, are harder (H = 3.76 ± 0.24 GPa) and less stiff (E = 76.87 ± 4.87 GPa) than the posterior (H = 3.48 ± 0.31 GPa, E = 81.79 ± 5.33 GPa). As a consequence o...

The study is related to the EU 7 Framework Programme CODICE (COmputationally Driven design of Inn... more The study is related to the EU 7 Framework Programme CODICE (COmputationally Driven design of Innovative CEment-based materials). The main aim of the project is the development of a multi-scale model for the computer based simulation of mechanical and durability performance of cementitious materials. This paper reports results of nanoindentation testing on fully calcium leached cement paste in relation with the prediction from the latest computer model developed in the CODICE research project. Using the statistical nanoindentation technique, intrinsic properties of different hydrate phases after leaching has been studied. In order to perform reliable nanoindentation experiments a very smooth and flat sample surface is required. Due to the very porous and weak microstructure of fully-leached cement paste resin impregnation has to be used to produce satisfactory and representative specimens for the nanoindentation experiments. Extensive trials with different low stiffness resins (Youn...

Cement and Concrete Composites, 2017

Construction and Building Materials, 2015

ABSTRACT The present study explores the viability of reusing mixed recycled aggregate from constr... more ABSTRACT The present study explores the viability of reusing mixed recycled aggregate from construction and demolition waste as a partial (25 and 50 wt%) replacement for natural coarse aggregate in the manufacture of concretes with a compressive strength of 30 MPa. It further analyses the effect of some of the constituents (asphalt, clay-based materials, floating particles and fines) of these recycled aggregates on the properties of recycled concretes. Despite the high asphalt and floating particle content of the recycled aggregate used, came from waste management plant at Glasgow, it was found to have no adverse effect on the workability of the new concretes. Hardened concrete density and compressive strength were observed to decline with increasing replacement ratios, at a variable rate depending on the components of the recycled aggregate mix and the thickness of their ITZs (the thicker the weaker). While concrete with 25% recycled aggregate exhibited lower sorptivity than the reference concrete, absorption was higher when the replacement ratio was 50%. The findings showed that this type of recycled aggregate can be used in concrete manufactured for housing applications and confirmed the importance of good construction and demolition waste management to deliver high quality recycled aggregate.

2nd International RILEM Symposium on Advances in Concrete through Science and Engineering, 2006

Special Publication, 2004

Materiales de Construcción, 2011

The textural and mechanical characterization of C-S-H gels formed from the hydration of pure T1-C... more The textural and mechanical characterization of C-S-H gels formed from the hydration of pure T1-C 3 S, β-C 2 S and their blends are studied by Nitrogen sorption and nanoindentation experiments. The surface area and nanoporosity of C-S-H gels formed from the hydration of β-C 2 S and the 30-70 (T1-C 3 S and β-C 2 S mixture) are higher than those from hydration of T1-C 3 S, and 70-30, with the difference decreasing with hydration age. Such changes are well supported by findings of nanoindentation study, which shows the greater relative volume of C-S-H phases with lower densities in the β-C 2 S and the 30-70 pastes. With the increase in hydration age, the relative volume of C-S-H phases with higher densities increased at the expenses of those with lower density. Important quantitative correlations were found among these textural characteristics and the mean chain length, determined from 29 Si magic-angle-spinning (MAS) NMR, of the C-S-H gels.

Journal of The Royal Society Interface, 2014

Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening th... more Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis , was cultured at projected levels of p CO 2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus ( E ), hardness ( H ) and toughness ( K IC ) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more bri...

Special Publication, 2004

Nanotechnology in Construction 3, 2009

This paper reports results of micro/nano-scale mechanical characterisation of the cement-based ma... more This paper reports results of micro/nano-scale mechanical characterisation of the cement-based materials at micro/nano-scale using various available mapping techniques. Two new techniques: Express Nanoindentation Test option by Agilent Technologies and PeakForce QNM by Bruker were applied to mapping mechanical properties of cement-based materials, together with the use of conventional nanoindentation technique. Preliminary test results as well as advantages and limitations for the different techniques were discussed.