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The purpose of this study is to develop smart cementitious material by incorporating multi-walled carbon nanotubes (MWCNTs). Two different types of carbon nanotubes (CNT) were dispersed using probe ultrasonicator; (i) Pristine CNT (P-CNT), and (ii) Functionalized CNT through annealing (A-CNT). Percolation threshold and optimum content of CNTs were determined by measuring electrical resistivity, porosity, compressive and flexural strengths at various contents of CNTs (0, 0.5 %, 0.75 %, and 1 % with respect to mass of cement). Self-sensing study was also carried out on smart material by relating the electrical properties with cyclic compressive loading. For this purpose, the electrical response was recorded with Wheatstone Bridge (WSB) circuit. The effect of curing and saturation degree of specimens on the resistivity pattern was also discussed. The results of electrical resistivity and mechanical properties showed that the content of CNTs should be at least 0.75 % to develop smart cementitious materials with a significant sensitivity and without detrimental effect on the mechanical properties. Moreover, smart material incorporating pristine CNT provides better sensitivity of self-sensing response as compared to the annealed CNT. Self-sensing test results also showed that with the increase in the content of CNT, sensitivity and repeatability of the sensing response were improved.

The aim of this research work is to develop a corrosion resistant fiber-reinforced concrete for radioactive waste disposal structures. In the case of precast concrete, the use of fibers is a solution to reduce the amount of steel reinforcement while maintaining high mechanical performance and durability. Concrete has a low strain capacity and a limited tensile strength. Generally, reinforcing bars are used to ensure tensile strength. A fiber reinforcement can also help to overcome such a mechanical weakness. For this purpose, an amorphous metallic fiber (AMF), corrosion-resistant and suitable for application in severe environment conditions are used. The fresh and hardened properties of the self-compacting fiber reinforced concrete (SCFRC) are studied with volume fractions of AMF of 0% and 0.28% and with three different aspect ratios (82, 114 and 123). Flexural tensile tests according to European standard EN 14651 are conducted to quantify the contribution of the fiber reinforcement on the residual flexural tensile strength. Since these fibers are electrically conductive, they are also tested to design a smart concrete. For this purpose, electrical resistance of specimens submitted to cyclic flexural loadings are monitored using a Wheatstone bridge.

Calcium phosphate cement (CPC) is a multifunctional cement whose potential application depends on the reactants used to synthesise it. Just like many inorganic cements, the pure CPCs synthesised in all cases are very brittle and have low toughness values under loading. In this research, the CPC material is formed from the exothermic reaction between phosphoric acid and calcium silicate at controlled room temperature. Three fibre types, namely; macro polypropylene fibres, amorphous metallic fibres and recycled carbon fibres were chosen due to their corrosion resistance in acid to enhance the mechanical performance of this cement as a repair material. 1.5% by volume of each of these fibres were added to the CPC material and autogenously cured for 14 days at room temperature. Mechanical destructive and non-destructive tests were carried out on the resulting composites. The experimental results revealed that each type of fibre contributes to increase flexural strength, compressive strength, fracture energy and dynamic elastic modulus of CPC material. However, for this purpose the recycled carbon fibres have proven to be more efficient.

The purpose of this communication is to develop a self-sensing cement composite capable of detecting stress variation in concrete by monitoring its electrical property. The relationship between the electrical properties, i.e. electrical resistance of steel fiber reinforced concrete, and stress under loading as part of self-sensing study is presented in here. Amorphous metallic fibers (AMF) with two different lengths i.e. 10 mm and 30 mm are used as concrete reinforcement at a content of 40 kg/m3. A water to cement ratio of 0.39 was adopted for the mix proportions. Natural fine and coarse siliceous aggregates were used for this research. Superplasticizer was used to achieve the target of workability. The two-probe method is used for measuring electrical properties on cylinder specimens with diameter 100 mm and height 200 mm. The influence of different parameters such as fiber length, frequency of power input, maximum stress and variation of potential input on the sensitivity of the sensing are investigated. The results indicate that the electrical resistance of the concrete decreases reversibly during loading and increases reversibly during unloading. Good sensitivity obtained for the mix using 30 mm AMF length indicates that the addition of this type of fiber into concrete can be suitable to produce a self-sensing cement composite.