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 (CaCO₃), cement and silica fume into a PCE/water solution. Sedimentation and optical microscopy tests indicated that both CaCO₃ and cement could form homogeneous suspensions. The crystallization behavi...[ Read more ]

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 (CaCO₃), cement and silica fume into a PCE/water solution. Sedimentation and optical microscopy tests indicated that both CaCO₃ and cement could form homogeneous suspensions. The crystallization behavior of the PEG side chains revealed that PEG had stronger interactions with CaCO₃ 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 CaCO₃, 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 (C₃S), 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 C₃S, 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.