Nanotechnology in concrete – A review

Graphene oxide (GO) is the product of chemical exfoliation of graphite. Due to its good dispersibility in water, high aspect ratio and excellent mechanical properties, GO is a potential candidate for use as nanoreinforcements in cement-based materials. In this paper, GO was used to enhance the mechanical properties of ordinary Portland cement paste. The introduction of 0.05 wt% GO can increase the GO-cement composite compressive strength by 15-33% and the flexural strength by 41-59%, respectively. Scanning electron microscope imaging of the GO-cement composite shows the high crack tortuosity, indicating that the two-dimensional GO sheet may form a barrier to crack propagation. Consequently, the GO-cement composite shows a broader stress-strain curve within the post-peak zone, leading to a less sudden failure. The addition of GO also increases the surface area of the GO-cement composite. This is attributed to increasing the production of calcium silicate hydrate. The results obtained in this investigation suggest that GO has potential for being used as nano-reinforcements in cement-based composite materials.

Mechanical properties and microstructure of a graphene oxide-cement composite

Effect of nano-silica on rheology and fresh properties of cement pastes and mortars

Nano reinforced cement and concrete composites and new perspective from graphene oxide

Beneficial role of nanosilica in cement based materials – A review

Characteristics of cement mortar with nano-SiO2 particles

The amorphous or glassy silica, which is the major component of a pozzolan, reacts with calcium hydroxide formed from calcium silicate hydration. The rate of the pozzolanic reaction is proportional to the amount of surface area available for reaction. Therefore, it is plausible to add nano-SiO 2 particles (NS) to make high-performance concrete. The compressive strengths of cement mortar were evaluated at various water-cementitious material ratios (w/cm). Five different w/cm were used, including 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of NS, 3, 6, 9, and 12% by weight of cement. The compressive strengths of cement mortar with the addition of silica fume were also evaluated at a w/cm of 0.35 to compare with mortar containing nano-SiO 2 particles and three contents of silica fume were: 5, 10, and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with NS were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzes some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH) 2 , and the rate of heat evolution. The results of the examinations indicate that the SiO 2 in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.

The nano scale of particles can result in dramatically improved or different properties from conventional grain-size materials of the same chemical composition. Therefore, it is practical to add nano-silica in particle form with 99.9% of SiO2 in nano scale to improve the characteristics of cement mortar. The compressive strengths of cement mortar were evaluated at various water-cementitious ratio. Five different water-cementitious ratios were used including, 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of nano-SiO2 particles, 3%, 6%, 9%, and 12% by weight of cement. The compressive strength of cement mortar with the addition of silica fume were also evaluated at w/cm ratio of 0.48 to compare with mortar containing nano-SiO2 particles and three contents of silica fume were: 5%, 10% and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with nano-SiO2 particles were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzed some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH)2 and the rate of heat evolution. The results of the examinations indicate that the SiO2 in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.

Investigations on the development of powder concrete with nano-SiO2 particles

Uniaxial creep behavior and prediction of recycled-PET polymer concrete

This paper presents the wind characteristics of an existing long span bridge based on the measured wind data. The wind data obtained from the two measuring stations on the Seohae bridge are processed and statistically analyzed. The Weibull distribution is used to model the wind speed on the bridge. The parameters of the Weibull distribution,k andc are estimated using two methods, the that the two methods give a good fit to the distribution of the measured wind speed data on the bridge. The dominant wind directions on the FCM bridge are northwest and east. The wind rose diagram shows that strong winds usually come from the northwest. From the Weibull distribution for each direction, it can be known that the parameters ofk andc are quite different according to the wind direction.

Chang-Hyun Kim

Papers

Characteristics of cement mortar with nano-SiO2 particles

Characteristics of cement mortar with nano-SiO2 particles

Investigations on the development of powder concrete with nano-SiO2 particles

Uniaxial creep behavior and prediction of recycled-PET polymer concrete

Wind Characteristics of Existing Long Span Bridge Based on Measured Data