TY - JOUR

T1 - Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates

A1 - Lindgreen,Holger

A1 - Geiker,Mette Rica

A1 - Krøyer,Hanne

A1 - Springer,Niels

A1 - Skibsted,Jørgen

AU - Lindgreen,Holger

AU - Geiker,Mette Rica

AU - Krøyer,Hanne

AU - Springer,Niels

AU - Skibsted,Jørgen

PB - Pergamon

PY - 2008

Y1 - 2008

N2 - Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates), surface charge, and size (micron and nano). The structure of the resulting cement pastes and mortars has been investigated by atomic force microscopy (AFM), helium porosimetry, nitrogen adsorption (specific surface area and porosity), low-temperature calorimetry (LTC) and thermal analysis. The main result is that the cement paste structure and porosity can be engineered by addition of selected layer silicates having specific particle shapes and surface properties (e.g., charge and specific surface area). This seems to be due to the growth of calcium-silicate hydrates (C-S-H) on the clay particle surfaces, and the nano-structure of the C-S-H depends on type of layer silicate. The effect of layer silicate addition is most pronounced for palygorskite and smectite having the largest surface area and negative charges on the particle surfaces. The cement pastes containing palygorskite and bentonite have, in comparison to the pure cement pasta and the paste containing kaolinite, a more open pore structure consisting of fine pores. Silica fume paste contains a significant amount of closed pores. As a secondary result, it is demonstrated that both the degree and duration of sample drying strongly modifies the structure of the cementitious materials under investigation.

AB - Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates), surface charge, and size (micron and nano). The structure of the resulting cement pastes and mortars has been investigated by atomic force microscopy (AFM), helium porosimetry, nitrogen adsorption (specific surface area and porosity), low-temperature calorimetry (LTC) and thermal analysis. The main result is that the cement paste structure and porosity can be engineered by addition of selected layer silicates having specific particle shapes and surface properties (e.g., charge and specific surface area). This seems to be due to the growth of calcium-silicate hydrates (C-S-H) on the clay particle surfaces, and the nano-structure of the C-S-H depends on type of layer silicate. The effect of layer silicate addition is most pronounced for palygorskite and smectite having the largest surface area and negative charges on the particle surfaces. The cement pastes containing palygorskite and bentonite have, in comparison to the pure cement pasta and the paste containing kaolinite, a more open pore structure consisting of fine pores. Silica fume paste contains a significant amount of closed pores. As a secondary result, it is demonstrated that both the degree and duration of sample drying strongly modifies the structure of the cementitious materials under investigation.

KW - Paste

KW - Clay

KW - Layer Silicate

KW - Cement

KW - Mortar

KW - atomic force microscopy

KW - Nano

KW - structure engineering

KW - Additives

KW - porosity

KW - Silica Fume

U2 - 10.1016/j.cemconcomp.2008.05.003

DO - 10.1016/j.cemconcomp.2008.05.003

JO - Cement and Concrete Composites

JF - Cement and Concrete Composites

SN - 0958-9465

IS - 8

VL - 30

SP - 686

EP - 699

ER -