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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Understanding geopolymer binder-aggregate interfacial characteristics at molecular level

The interfacial characteristics of geopolymer binder to aggregate composites are poorly understood, especially at molecular level. Herein, molecular models are developed to study, for the first time, the geopolymer-aggregate interface. Chemically, various forms of interfacial bonding are characterized, including Al-O-Si bonding through condensation reactions, NaO and H-bonding. An atomic-level interfacial transition zone (ITZ) is identified, attributed to the concentration of –OH groups. Increasing the Si/Al ratio of geopolymer is found to decrease the ITZ density, but have limited effect on the ITZ width. A heterogeneous diffusion characteristic occurs in geopolymer, due to the weak interfacial interaction. Mechanically, lowering the Si/Al ratio promotes the interfacial strength due to the stronger interfacial interaction and higher cross-linking degree in geopolymer. Under loading the interfacial fracture undergoes three stages: crack propagation, chain bridging (including aluminosilicate and ionic bridging) and breakage. The above atomic-level findings may facilitate a better design of geopolymer concrete in engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2SiO5 by Materials Project

Al2SiO5 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra, corners with four equivalent AlO5 trigonal bipyramids, and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–2.11 Å. In the second Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with four equivalent AlO6 octahedra, corners with four equivalent SiO4 tetrahedra, and an edgeedge with one AlO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 49–58°. There are a spread of Al–O bond distances ranging from 1.83–1.91 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four equivalent AlO6 octahedra and corners with four equivalent AlO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 55–69°. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to two Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2SiO5 by Materials Project

Al2SiO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four equivalent AlO4 tetrahedra, corners with four equivalent SiO4 tetrahedra, and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.98 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent AlO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–62°. There are a spread of Al–O bond distances ranging from 1.72–1.81 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four equivalent AlO6 octahedra and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 50–55°. There are a spread of Si–O bond distances ranging from 1.59–1.66 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to two Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2SiO5 by Materials Project

Al2SiO5 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with five SiO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.02 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO6 octahedra, corners with three SiO4 tetrahedra, and edges with five AlO6 octahedra. The corner-sharing octahedra tilt angles range from 16–19°. There are a spread of Al–O bond distances ranging from 1.88–2.01 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO6 octahedra, corners with four SiO4 tetrahedra, and edges with four AlO6 octahedra. The corner-sharing octahedra tilt angles range from 16–19°. There are a spread of Al–O bond distances ranging from 1.90–1.96 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four SiO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.01 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–54°. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Al3+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a see-saw-like geometry to four Al3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2Si4O11 by Materials Project

Al2Si4O11 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Al2Si4O11 sheet oriented in the (0, 0, 1) direction. Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with four SiO4 tetrahedra, a cornercorner with one AlO5 trigonal bipyramid, and edges with two equivalent AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.68–1.97 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent SiO4 tetrahedra and corners with two equivalent AlO5 trigonal bipyramids. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent SiO4 tetrahedra and corners with two equivalent AlO5 trigonal bipyramids. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al8SiO14 by Materials Project

Al8SiO14 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are seven inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent SiO4 tetrahedra, corners with six AlO4 tetrahedra, and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–2.00 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four AlO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–64°. There is three shorter (1.76 Å) and one longer (1.87 Å) Al–O bond length. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four AlO6 octahedra, a cornercorner with one SiO4 tetrahedra, and corners with three AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–64°. There are a spread of Al–O bond distances ranging from 1.73–1.96 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four AlO6 octahedra, corners with two AlO4 tetrahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of Al–O bond distances ranging from 1.76–1.81 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one SiO4 tetrahedra, corners with seven AlO4 tetrahedra, and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.09 Å. In the sixth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent AlO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.73–1.82 Å. In the seventh Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent AlO6 octahedra, a cornercorner with one SiO4 tetrahedra, and corners with three AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–61°. There is three shorter (1.74 Å) and one longer (1.89 Å) Al–O bond length. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra and corners with four AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Si–O bond distances ranging from 1.65–1.69 Å. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to two Al3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Al3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Al3+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the tenth O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2SiO5 by Materials Project

Al2SiO5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Al3+ is bonded to six O2- atoms to form distorted AlO6 octahedra that share corners with three equivalent SiO6 octahedra, corners with four equivalent AlO6 octahedra, an edgeedge with one AlO6 octahedra, edges with two equivalent SiO6 octahedra, and a faceface with one AlO6 octahedra. The corner-sharing octahedra tilt angles range from 42–59°. There are a spread of Al–O bond distances ranging from 1.80–2.09 Å. Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with two equivalent SiO6 octahedra, corners with six equivalent AlO6 octahedra, and edges with four equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 42–56°. There are a spread of Si–O bond distances ranging from 1.76–1.90 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Al3+ and two equivalent Si4+ atoms to form distorted OAl2Si2 trigonal pyramids that share corners with four OAl2Si2 trigonal pyramids and edges with four equivalent OAl3Si trigonal pyramids. In the second O2- site, O2- is bonded to three equivalent Al3+ and one Si4+ atom to form a mixture of distorted corner and edge-sharing OAl3Si trigonal pyramids. In the third O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Al3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2SiO5 by Materials Project

Al2SiO5 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Al3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.83–2.19 Å. Si4+ is bonded to six O2- atoms to form corner-sharing SiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are a spread of Si–O bond distances ranging from 1.70–1.89 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Al3+ and one Si4+ atom to form distorted OAl3Si trigonal pyramids that share a cornercorner with one OAl2Si2 tetrahedra, corners with three equivalent OAl3Si trigonal pyramids, edges with two equivalent OAl2Si2 tetrahedra, and edges with two equivalent OAl3Si trigonal pyramids. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded to two equivalent Al3+ and two equivalent Si4+ atoms to form distorted OAl2Si2 tetrahedra that share corners with two equivalent OAl2Si2 tetrahedra, corners with two equivalent OAl3Si trigonal pyramids, and edges with four equivalent OAl3Si trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2Si2O11 by Materials Project

(AlO3)2Si2O5 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of one AlO3 sheet oriented in the (0, 0, 1) direction and one Si2O5 sheet oriented in the (0, 0, 1) direction. In the AlO3 sheet, Al is bonded to six O atoms to form distorted edge-sharing AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–1.89 Å. There are four inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the second O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the third O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the fourth O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the Si2O5 sheet, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are three inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the third O site, O is bonded in a single-bond geometry to one Si atom.

36 MATERIALS SCIENCE↗