Qiu Yi Li

Hybrid Effect of Carbon Fiber on Piezoresistivity of Carbon Nanotube Cement-Based Composite

Cement-based nanocomposite filled with only 0.1 wt.% multi-wall carbon nanotube (MWNT) (MNFRC), or hybrid with 0.1 wt.% MWNT and 0.5 wt.% microsized short carbon fiber (SCF) (SF/MNFRC), were prepared employing surfactant ultrasonic dispersion and high-speed mixing process. The electrical resistivities (ρ), compressive stresses (σ), and longitudinal strains (εl) of these cured nanocomposites under cyclic uploading/unloading were simultaneously collected, to characterize their stress/strain-sensitive properties. There exists good piezoresisitivity and high strain sensitivity for MNFRC. The fractional change in ρ (Δρ) regularly descends or ascends following the σ, or the εl of MNFRC (the Δρ/εl sensitivity near 68). Hybrid of SCF is found to be more effective to improve the self-sensing repeatability and variation stability of the SF/MNFRC rather than the self-sensing sensitivity (the Δρ/εl sensitivity only about 64).

Effect of Multi-Wall Carbon Nanotube on Fracture Mechanical Property of Cement-Based Composite

Cementitious composites reinforced with multi-wall carbon nanotube (MWNT) (MWFRC) were prepared with surfactant dispersion, ultrasonication, and subsequently high-speed mixing process. Fracture mechanical performance of the cured MWFRC was characterized according to three-point bending method (ASTM 399). It is found that the addition of nanotubes significantly improve the flexural strength, the stress-intensity factor of the nanocomosites with dispersed MWNT fiber, the maximal enhancement amplitude is near to 45%, 80% with respect to the baseline, respectively. The superior fiber bridging capability of the dispersed MWNTs upon the micro-cracks contributes to the reinforcement to cement matrix.

Effect of Compressive Strain on Electrical Resistivity of Carbon Nanotube Cement-Based Composites

Multi-walled carbon nanotube (MWCNT) fiber reinforced cement-based composites (MWFRC) with 0.1 wt.% and 0.5 wt.% weight concentration of MWCNT (wcM)were prepared, associated with the reference. The electrical resistances and compressive strains of these cured nanocomposites under cyclic uploading/unloading were real-time collected, to explore their stress/strain-sensitive properties. Results reveal as follows, there is no self-sensing trait for the reference, but exists good piezoresisitivity and high strain sensitivity (above 110) for MWFRC; the fractional change in resistivity (Δρ) regularly descends or ascends following the compressive stress, or the longitudinal strain of MWFRC; the resistance caused by pore electrolyte polarization has obvious impact on the time-stability of the Δρ trendline of MWFRC with 0.1 wt.% wcM, similar to the reference, but negligible effect on that of MWFRC with 0.5 wt.% wcM.

Self-Sensing Property of Cementitious Nanocomposites Hybrid with Nanophase Carbon Nanotube and Carbon Black

Cementitious composite filled with only 0.1 wt% multi-walled carbon nanotube (MWCNT) (MNTCC), or hybrid with 0.1 wt% MWCNT and 0.5 wt% nanophase carbon black (NCB) (NB/MNTCC), were prepared employing surfactant ultrasonic dispersion and subsequently high-speed mixing process. The electrical resistivities (ρ), compressive stresses (σ), and longitudinal strains (εl) of these cured nanocomposites under cyclic loading (10 times) were simultaneously collected, to investigate their piezoresistivty properties. Results revealed that, hybrid of NCB is very effective for enhancement on the stress/strain sensitivity of NB/MNTCC (the strain sensitivity up to 107, much higher than that of MNTCC 67), but there is almost no improvement on the self-sensing repeatability and variation stability of the corresponding nanocomposite.

Influence of Water Repellent Surface Impregnation on Water Absorption Properties of Recycled Aggregate Concrete

This paper aimed to investigate the influence of using silane surface water repellent treatment on the capillary water absorption properties of recycled aggregate concrete. In this study, two types of coarse aggregate, natural aggregates and recycled aggregates were used, and the surface water repellent treatment of concrete was produced by brushing 100g/m2 and 200g/m2 of paste. It was found that the silane impregnation depth of recycled concrete was deeper than that of natural concrete, and the surface treatment was more effective in the improvement of capillary water absorption properties of recycled aggregate concrete than the natural aggregate concrete.

Cement-Based Composite with Carbon Nanotubes Reinforcement Tailored for Structural Damping

Cement-based composites filled with some multi-walled carbon nanotubes (MWNTs) (MWNT/CC) were fabricated using surfactant enwrapping, ultrasonic treatment, and subsequently intensive shear mixing. The damping capacities of the cured nanocomposites were characterized with forced vibration testing and half-power bandwidth identification method. Results show that, the MWNTs can greatly enhance the structural damping capacity of the MWNT/CC beam with balanced strength reinforcement. There exists 44.5%, 10% increase in the damping ratio, and fundamental frequency of the MWNT/CC with 1.0 wt% MWNTs addition, along with strength reinforcement, as compared to the reference, respectively.

Influence of Preparation Process on the Performance of Strain Hardening Cementitious Composite

The modification of matrix is an important method to improve the mechanical properties of strain hardening cementitious composite (SHCC). The influence of the properties of the matrix water binder ratio (W/B) and fresh state rheology on SHCC tensile behaviors are useful for the SHCC design. The W/B influences only on tensile strength, but not the stain capacity, if the fresh state workability remains uniform. On the other hand, the workability has a significant influence on SHCC strain capacity through its influence on the fiber distribution. Consequently, it is important to cast SHCC carefully and make sure the even fiber distribution to insure the bridging function and mechanical properties of SHCC.

Influence of Physical Strengthening Technology on the Properties of Recycled Coarse Aggregate

This paper studied the properties improvement of recycled coarse aggregate by the physical strengthening technology (particle-shaping method). Through the analysis for obtained properties which consist of density, crush index, bulk density and water absorption. etc of recycled coarse aggregates in different strengthening technologies, the categories of recycled coarse aggregate could be assessed and determined. The results showed that ordinary recycled coarse aggregates that was handled twice by using particle shaping equipment can achieve the standard of class Iaggregates and its water absorption ratio at 24h was 1.2%, the apparent density reached 2575kg/m3, crush index value was 9%, the void ratio was 45%, all property parameters were close to those of natural coarse aggregate.

Research on Antiseptic and Corrosion-Inhibiting Admixture for Concrete

Concrete buildings in coastal area are dual attacked by chloride and sulfate easily. The erosions make great damage to buildings. This research develops a new type of antiseptic and corrosion-inhibiting admixture for concrete. It is a kind of inner-adding inorganic powder and made up by compaction component, corrosion-inhibiting component and sodium nitrite. The test results show that this admixture has the ability to resistant chloride and sulfate erosion, the admixture also can prolong service life of buildings which are exposed to high concentration of chloride and sulfate.

Experimental Research on Making Aerated Concrete by Petroleum Coke Desulfuration Residue

Petroleum coke desulfuration residue, from combustion desulfuration of high sulfur petroleum coke, presents drying powdery and a favorable cementing performance. Lime and gypsum are replaced by petroleum coke desulfuration residue to produce aerated concrete in this research. The experimental results indicate that products made of high-sulfur petroleum coke desulfuration residue satisfy the requirements in national code of autoclaved aerated concrete [1] (GB11968-2006) and has better performance than traditional lime aerated concrete products. Consequently, the application of high-sulfur petroleum coke desulfuration residue in aerated concrete broadens the resourcelized utilization of petroleum coke desulfuration residue, and solves the scarcity of building materials resources. It ought to have expansive application prospect because of remarkable economic, social, and environmental benefits.