THESIS
2015
vi leaves, vii-xxi, 114 pages : illustrations (some color) ; 30 cm
Abstract
In this study, interactions between inorganic and organic materials in
cement/polymer composites have been investigated. Firstly we have simultaneously
studied the interactions between superplasticizers and common inorganic fillers such
as calcium carbonate and silica fume. The superplasticizer used in this study was
polycarboxylate-ether plasticizer (PCE). The PCE used was a comb-like copolymer
containing a sodium polymethacrylate (PMA) backbone partially esterified with
polyethyleneglycol (PEG) side chains. A series of suspensions were fabricated by
dispersing calcium carbonate (CaCO
3), cement and silica fume into a PCE/water
solution. Sedimentation and optical microscopy tests indicated that both CaCO
3 and
cement could form homogeneous suspensions. The crystallization behavi...[
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In this study, interactions between inorganic and organic materials in
cement/polymer composites have been investigated. Firstly we have simultaneously
studied the interactions between superplasticizers and common inorganic fillers such
as calcium carbonate and silica fume. The superplasticizer used in this study was
polycarboxylate-ether plasticizer (PCE). The PCE used was a comb-like copolymer
containing a sodium polymethacrylate (PMA) backbone partially esterified with
polyethyleneglycol (PEG) side chains. A series of suspensions were fabricated by
dispersing calcium carbonate (CaCO
3), cement and silica fume into a PCE/water
solution. Sedimentation and optical microscopy tests indicated that both CaCO
3 and
cement could form homogeneous suspensions. The crystallization behavior of the
PEG side chains revealed that PEG had stronger interactions with CaCO
3 than with
cement and silica fume particles, which were further confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A detailed
time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested
that PEG were mainly located on the surfaces of the CaCO
3, and the PMA backbones
were mainly located on the surfaces of the cement and silica fume, respectively. The
different interactions between copolymer and inorganic particles were associated with
their interfacial tensions and had remarkable influence on the paste fluidity. The
findings in this part of study would have some potential application in the selection of
inorganic fillers for a certain superplasticizer environment. Secondly, we have
investigated the interactions in mechanical behavior between inorganic and organic
materials in a series of cement/polymer composites. One group of cementitious
composites was obtained by melt-dispersing ultra-high molecular weight polyethylene
(UHMWPE) into cement matrix followed by water immersion. The structure and
chemical composition of the composites were characterized by scanning electron
microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). Three point
bending tests showed that the flexural strength and flexural toughness of the
composite were improved dramatically with the presence of UHMWPE, and further
enhancement could be obtained by incorporating only 0.1 vol% oriented Vectran
fibers. An adhesive test revealed that the interfacial binding force between polymer
and fiber was much stronger than that between cement and fiber, which made the fiber
much effective in the enhancement of mechanical strength. Our findings provide a
simple and effective way for using thermoplastic polymer to improve the interface
between polyester fibers and cement matrix, and achieve dramatically increased
flexural strength and flexural toughness of the composite. Similar phenomena were
observed for UHNWPE-MPC (magnesium phosphate cement) composites.
Tricalcium silicate (C
3S), the most predominant component in cement, was
used together with polymer hydrogel to form a composite for study. Because there were hydroxide groups in the hydration products of C
3S, they could act as a crosslinker of polyacrylamide (PAM) hydrogel. The crosslinkers had significantly improved mechanical strength, ultimate tensile strain, and elastic range of the
hydrogel composite.
The study has demonstrated that the interaction between inorganic and organic materials in cement-polymer composites can benefit the composite properties chemically, physically or mechanically if the composites are carefully designed with
the sound mechanism. The composites developed in this study have a great potential to be applied in engineering field.
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