scholarly journals Effects of CNT Dosages in Cement Composites on the Mechanical Properties and Hydration Reaction with Low Water-to-Binder Ratio

2019 ◽  
Vol 9 (21) ◽  
pp. 4630 ◽  
Author(s):  
Sang-Hwa Jung ◽  
Sungwoo Oh ◽  
Sung-Wook Kim ◽  
Jae-Heum Moon
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Construction Material ◽  
Isothermal Calorimetry ◽  
Strength Development ◽  
Hydration Reaction ◽  
Cement Composites ◽  
Gravimetric Analysis ◽  
Binder Ratio ◽  
Water To Binder Ratio

This study aimed to investigate the potential use of carbon nanotubes (CNTs), which are an innovative construction material preferred by many researchers. Long-term microstructure enhancement and on-site application are major reasons to conduct research on CNT-cement composites; thus, a study on mechanical properties as well as the thermal conductivity of CNT-cement composites was carried out. As the CNT content increased, the thermal conductivity of CNT-cement composites was also enhanced. In addition, a couple of microstructure analyses such as isothermal calorimetry, thermal gravimetric analysis and SEM-EDS (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) for observing hydration reaction rate and types of hydration products were conducted to establish the advantage of CNT use in cement composites. Strength development of CNT-cement composites at early ages was slow, although eventually CNTs containing water developed equivalent level of strengths at last as internal curing effects.

Experimental and Modeling Studies on Thermal Conductivity of Cement Composites Containing Nanosilica

2014 ◽  
Vol 979 ◽  
pp. 119-123
Author(s):  
Pongsak Jittabut ◽  
Prinya Chindaprasirt ◽  
Supree Pinitsoontorn
Keyword(s):  
Thermal Conductivity ◽  
Cement Paste ◽  
Building Energy ◽  
Cement Composites ◽  
Building Energy Efficiency ◽  
Cement Pastes ◽  
Research Article ◽  
Binder Ratio ◽  
Nanosilica Particle ◽  
Water To Binder Ratio

This research article was presented the thermal conductivity of cement pastes containing nanosilica. The effects of nanosilica particle size and concentration determined by mixing three nanosilica particle sizes of 12, 50 and 150 nm, using nanosilica were of 1-5 wt%. The water to binder ratio of 0.5 was used. The thermal properties test were subsequently measured in terms of thermal conductivity coefficient using ISOMET 2114. The thermal conductivities of cement paste is thus numerically calculated and the predictions are compared with the existing experimental data. A unifying equation for four fundamental effective thermal conductivity structural models (Series, Parallel, one-dimensional heat flow, Maxwell’s model) was derived. The best prediction was provided by a composite model that combined the Maxwell’s model. Consequently, applications of nanosilica cement paste in building constructions may be an interesting solution in order to improve sustainability and building energy efficiency.

Thermo-Mechanical Behaviour of an Innovant Straw Lime Composite for Thermal Insulation Applications

2013 ◽  
Vol 390 ◽  
pp. 542-546 ◽  
Author(s):  
Naima Belayachi ◽  
Marwen Bouasker ◽  
Dashnor Hoxha ◽  
Muzahim Al-Mukhtar
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Construction Material ◽  
Barley Straw ◽  
Mechanical And Thermal Properties ◽  
Fiber Types ◽  
Cereal Straw ◽  
Lime Water ◽  
Binder Ratio ◽  
Water To Binder Ratio

This paper presents an investigation on the use of new light-weight construction material, composed of lime, water and cereal straw fiber. Two types of fibers were used: wheat and barley straw. The influence of some parameters such as fiber types, binder types (lime and/ or lime-cement), fiber to binder ratio (F/B) and Water to Binder ratio (W/B) on the mechanical and thermal properties is studied. Compressive strength, thermal conductivity and density of the material were investigated. The results indicated that the thermal conductivity of the straw-lime composites decreased with increasing straw content. The result comparisons also revealed that the composite reinforced by wheat straw fibres has the highest compressive strength.

scholarly journals Bond Strength between Glass Fiber Fabrics and Low Water-to-Binder Ratio Mortar: Experimental Characterization

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Daniel Bohling ◽  
Andrzej Cwirzen ◽  
Karin Habermehl-Cwirzen
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Bond Strength ◽  
Glass Fiber ◽  
Penetration Depth ◽  
Pullout Strength ◽  
Lap Shear Strength ◽  
Lap Shear ◽  
Binder Ratio ◽  
Water To Binder Ratio

Full utilization of mechanical properties of glass fiber fabric-reinforced cement composites is very limited due to a low bond strength between fibers and the binder matrix. An experimental setup was developed and evaluated to correlate the mortar penetration depth with several key parameters. The studied parameters included fresh mortar properties, compressive and flexural strengths of mortar, the fabric/mortar bond strength, fabric pullout strength, and a single-lap shear strength. Results showed that an average penetration of mortar did not exceed 100 µm even at a higher water-to-binder ratio. The maximum particle size of the used fillers should be below an average spacing of single glass fibers, which in this case was less than 20 µm to avoid the sieving effect, preventing effective penetration. The pullout strength was strongly affected by the penetration depth, while the single-lap shear strength was also additionally affected by the mechanical properties of the mortar.

Cellulose Fibres as a Reinforcing Element in Building Materials

2017 ◽  
Author(s):  
Viola Hospodarova ◽  
Nadezda Stevulova ◽  
Vojtech Vaclavik ◽  
Tomas Dvorsky ◽  
Jaroslav Briancin
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Building Materials ◽  
Reference Sample ◽  
Physical And Mechanical Properties ◽  
Natural Fibre ◽  
Cement Composites ◽  
Cellulose Fibres ◽  
Cellulosic Fibres

Nowadays, construction sector is focusing in developing sustainable, green and eco-friendly building materials. Natural fibre is growingly being used in composite materials. This paper provides utilization of cellulose fibres as reinforcing agent into cement composites/plasters. Provided cellulosic fibres coming from various sources as bleached wood pulp and recycled waste paper fibres. Differences between cellulosic fibres are given by their physical characterization, chemical composition and SEM micrographs. Physical and mechanical properties of fibre-cement composites with fibre contents 0.2; 0.3and 0.5% by weight of filler and binder were investigated. Reference sample without fibres was also produced. The aim of this work is to investigate the effects of cellulose fibres on the final properties (density, water absorbability, coefficient of thermal conductivity and compressive strength) of the fibrecement plasters after 28 days of hardening. Testing of plasters with varying amount of cellulose fibres (0.2, 0.3 and 0.5 wt. %) has shown that the resulting physical and mechanical properties depend on the amount, the nature and structure of the used fibres. Linear dependences of compressive strength and thermal conductivity on density for plasters with cellulosic fibres adding were observed.

scholarly journals The role of shrinkage reducing admixtures and supplementary cementitious materials in volume stability and strength development

2019 ◽  
Vol 289 ◽  
pp. 02005
Author(s):  
Ioanna Papayianni ◽  
Fotini Kesikidou ◽  
Philip Henes Alt
Keyword(s):  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Strength Development ◽  
Capillary Absorption ◽  
Volume Stability ◽  
Cement Mortars ◽  
Shrinkage Reducing Admixture ◽  
Binder Ratio ◽  
Shrinkage Reducing Admixtures ◽  
Water To Binder Ratio

Shrinkage is one of the main reasons for mortar and concrete failures like curling, crack formation and de-bonding. It is a complex phenomenon due to many factors involved, such as the type and amount of cement, water to binder ratio, binder to aggregates ratio and the type and granulometry of the aggregates, relative humidity, air temperature and the temperature of concrete. To reduce this phenomenon, Shrinkage Reducing Admixtures (SRAs) have been studied over the last 30 years. On the other hand, investigation in the field of Supplementary Cementitious Materials (SCMs) has indicated that their use in concrete may improve its volume stability depending on their percentage and the type of the material. In this paper, the addition of a Shrinkage Reducing Admixture and Supplementary Cementitious Materials like ladle furnace slag, calcareous fly ash and limestone filler, were investigated. Their influence, separately and in combination, in volume stability and strength development of cement mortars was identified. Capillary absorption and open porosity were also determined.

Microscopic Analysis and Study of High-Performance Seawater All-Coral Concrete

2019 ◽  
Vol 815 ◽  
pp. 216-222
Author(s):  
Chao Chen ◽  
Jin Ming Liu ◽  
Yang Yang ◽  
Zhi Guo Guo
Keyword(s):  
Mechanical Properties ◽  
Natural Environment ◽  
High Performance ◽  
Work Performance ◽  
Room Temperature ◽  
Microscopic Analysis ◽  
Internal Curing ◽  
Mix Design ◽  
Binder Ratio ◽  
Water To Binder Ratio

The ocean islands are far from inland and the concrete sandstone aggregates are scarce. In this paper, high-performance seawater all-coral concrete was developed by seawater mixing and room temperature maintenance design, and by optimizing the water-to-binder ratio, regulating internal curing, changing auxiliary cementing materials and blending ratio, incorporating expansion agent, adjusting fiber blending, etc. Combined with the consideration of work performance and mechanical properties, the concrete self-shrinkage is adjusted to further optimize the mix design. The mechanical properties of the optimized high-performance seawater all-coral concrete were studied, and the relevant durability tests were carried out according to the natural environment characteristics of the island. This is of great significance to the construction of island projects, repair and construction, and construction of protective projects [1].

scholarly journals Effect of Graphene Oxide on Mechanical Properties of Cement Mortar and its Strengthening Mechanism

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3753 ◽  
Author(s):  
Yahui Wang ◽  
Jiawen Yang ◽  
Dong Ouyang
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Cement Hydration ◽  
Strengthening Mechanism ◽  
Cement Composites ◽  
Working Mechanism ◽  
Cement Pastes ◽  
Cement Mortars ◽  
Binder Ratio ◽  
Growth Space

The effects of the water–binder ratio and different graphene oxide (GO) sizes on the mechanical properties of GO-cement composites were systematically studied by preparing GO-cement mortars. The scanning electron microscopy observation (SEM) of the surface and fracture surface of cement pastes was carried out to study the morphology of cement hydration crystals in GO-cement systems under different space conditions. It was found that GO nanosheets significantly improved the compressive, flexural, and tensile strengths of cement mortars. When the dosage of GO nanosheets was 0.03% by weight of cement, the compressive, flexural, and tensile strengths at 28 days increased by 21.37%, 39.62%, and 53.77%, respectively, but GO was not found to be able to regulate the formation of flower-like cement hydration crystals. It was only shown that the growth space had an important influence on the morphology of hydrates. A possible working mechanism was proposed by which GO nanosheets prevented the expansion of microcracks in the cement pastes via a shield effect, thus enhancing the strength and toughness of the cement composites.

Investigation on the Effect of Hydroxyapatite Nanorod on Cement Hydration and Strength Development

2021 ◽  
Vol 21 (3) ◽  
pp. 1578-1589
Author(s):  
Han Yan ◽  
Qianping Ran ◽  
Yong Yang ◽  
Xin Shu ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Isothermal Calorimetry ◽  
Superior Performance ◽  
Strength Development ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Early Hydration ◽  
Cement Pastes ◽  
Supplementary Cementitious Material ◽  
Acceleration Period

This work investigated the effect of hydroxyapatite (HA) nanorods on the strength development and hydration of cement. Undispersed HA nanorods (HA-UD) and dispersed HA nanorods (HA-DN) were prepared by atom-efficient neutralization. The strength of mortars modified by HA nanorods was tested, as well as their compatibility with supplementary cementitious material. The hydration of HA-modified cement pastes was characterized via in situ X-ray diffraction, isothermal calorimetry and scanning electron microscopy. As the results suggest, the undispersed HA-DN caused a considerable increase in superplasticizer demand to achieve the same level of flow. Both HA nanorods showed a significant accelerating effect on early hydration, with approximately 100% strength enhancement at 12 h at 2.0% dosage. The effect on early strength of the nanorods is retained in systems with up to 30% fly ash in the binder mass. According to the characterizations, the rate of the hydration reaction in the acceleration period was enhanced by HA nanorods, and C3S consumption was also increased. In all of the testing situations, HA-DN showed superior performance, likely due to improved spatial distribution of the hydroxyapatites. The results suggest that proper dispersion of the nanorods is necessary to optimize its performance.

Experiment and Micro-Mechanism Study on Mechanical Properties and Durability of High-Calcium Fly Ash Concrete

2011 ◽  
Vol 480-481 ◽  
pp. 59-65
Author(s):  
Shuang Xi Li ◽  
Tuan She Yang ◽  
Zhi Ming Wang ◽  
Quan Hu
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Frost Resistance ◽  
Strength Development ◽  
Hydration Reaction ◽  
Optimal Dosage ◽  
Fly Ash Concrete ◽  
Low Calcium ◽  
High Calcium ◽  
High Calcium Fly Ash

Low-calcium fly ash is paid much attention for its wide use in engineering, the research and application technology of it are very mature, but as to high-calcium fly ash concrete, the researches on stability, mechanical property and durability of it are very less , The existing researches are still inadequate for practice of engineering. As to this problem, using small shek kip hydropower project as example, the volume stability of high-calcium fly ash concretes with different fly ash dosages are tested, then the optimal dosage of the high-calcium fly ash is determined; based on this, the impacts of high-calcium fly ash on the performance of mechanical properties , impermeability and frost resistance of concrete are studied; Finally, macro performance is analyzed from a micro-mechanism point of view through taking the electron micrograph. As the study shows, the optimal dosage of high-calcium fly ash should be taken as 20% -25%; for the concrete with special requirements, the dosage can be relaxed to 30% when the high-calcium fly ash achieves high quality. The compressive strength of high-calcium fly ash concrete is higher than the low-calcium fly ash concrete. Strength development advantage of high-calcium fly ash concrete reflects at the early age, this advantage takes the trend of weakening as the development of age. Concrete mixed with high-calcium fly ash has good performance in impermeability. The high-calcium fly ash has high activity, the high-calcium fly ash and secondary hydration reaction products can be filled into the pore capillary and cracks of the concrete structure, improving the pore structure, thereby increasing the density of cement paste. High-calcium fly ash concrete has good performance in frost resistance. The destructive effects of freeze-thaw cycles on cement structure has connection with the microstructure of cement and impermeability , the improvement of impermeability avoids the water entering into the concrete, reduces the risk of destruction caused by frost heave.The study on micro-mechanism proves well the macro-phenomena above.

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