To functionalize the cement-based materials, other networks except the cement hydration network were introduced to achieve the multi-functional properties. In this thesis, three other networks, including conductive network, polymer network and organic-inorganic composites network, were formed and investigated.

To form the conductive network in cement, different conductive components were tried, including conductive filler and conductive aggregate.

Carbon nanotubes (CNTs) are a hot topic in the last decades because of its excellent mechanical and electrical properties. It was added as conductive filler to fabricate the conductive cement-based material in this thesis. To ensure the conductive path can be formed in the cement-based material, high dosage with 1.5% weight of cement...[ Read more ]

To functionalize the cement-based materials, other networks except the cement hydration network were introduced to achieve the multi-functional properties. In this thesis, three other networks, including conductive network, polymer network and organic-inorganic composites network, were formed and investigated.

To form the conductive network in cement, different conductive components were tried, including conductive filler and conductive aggregate.

Carbon nanotubes (CNTs) are a hot topic in the last decades because of its excellent mechanical and electrical properties. It was added as conductive filler to fabricate the conductive cement-based material in this thesis. To ensure the conductive path can be formed in the cement-based material, high dosage with 1.5% weight of cement was chosen, and different dispersants were added to help disperse CNTs since CNTs are very easy to agglomerate. Three dispersants were selected in this study, which are Sodium Dodecyl Sulfonate (SDS), Tween-20 (T-20) and Triton x-100 (T-100). The effect of these three dispersants on hydration process, resistivity development and compressive strength was discussed, and Dynamic Light Scattering (DLS) test and Scanning electron microscopy (SEM) were conducted to evaluate the dispersion in solution and cement.

Conductive aggregate was another method to strengthen the conductive network in cement-based materials since aggregates occupy 50%-70% volume of concrete. Conductive aggregate was fabricated by pelletizing technology which consumes less energy. Carbon fiber and carbon black were ideal conductive filler for their low resistivity and price. Carbon fiber only was used as single filler and combined with carbon black as mixed filler in aggregate. Different contents of carbon fiber and carbon black were studied in this thesis. The influence of these fillers on resistivity, water absorption and crushing strength was recorded and SEM was adopted to analyze the micro-structure inside the conductive aggregate.

The second double network was in-situ polymerization generated polymer chain in cement hydration product. This was totally different from the conventional polymer concrete, in which the polymer was used as additive or binder. This innovative idea made polymerization and cement hydration took place at the same time, which would bring lots of benefits, including dense microstructure, ultra-high flexural strength. Mechanism behind these phenomena was also revealed. The whole reaction process could be described as follows: polymerization took place firstly and absorbed some water after that, cement started to hydrate and released ions, however, the released Ca2+ would be captured by sodium polyacrylate of polymer chain, retarded the cement hydration and led to a longer final setting of cement.

The third double network was formed by an organic-inorganic composite, called low heat releasing agent (LHRA). Organic-inorganic composites were synthetized by grafting method, which was a combination of suitable nano inorganic particles and organic functional groups. During the selection of inorganic and organic materials, impact of these materials on cement hydration was well studied. Relevant mechanical properties were tested and showed a promising result. Temperature rising of a concrete with and without LHRA was evaluated, which exhibited remarkable effect of LHRA in delaying the temperature rising and decreasing temperature gradient from center to surface of concrete specimen. Moreover, the inclusion of nano inorganic particles showed the effect in keeping the compressive strength development in LHRA modified concrete same level with reference concrete.