Thermal, mechanical, and surface properties of poly(vinyl alcohol) (PVA) polymer modified cementitious composites for sustainable development

Thermal conductivity of cement paste containing waste glass powder, metakaolin and limestone filler as supplementary cementitious material

Linde and Shell team up to commercialise lower-carbon technology for ethylene

The influence of sulfonated asphalt on the mechanical properties and microstructure of oil well cement paste

Investigation of thermal conductivity and related parameters of early-age cement paste

Fly ash (FA), silica fume (SF), and ground blast furnace slag (GBFS) were used as the supplementary cementitious materials (SCMs) in cement paste. The autogenous shrinkage (AS) and the shrinkage cracks of cement paste with SCMs were experimentally investigated in this study, and the relationship of AS, tensile strength, and crack area of cement paste were analyzed. The test results show that FA decreases the AS of cement paste and SF increases the AS. Both the AS and the crack area of cement paste decrease with the increase of the water-binder (W/B) ratio. When W/B ratios of different cement pastes are kept the same, the tensile strength of cement paste is not influenced by the AS if the specimens can shrink freely. Equations are established to describe the relationship among AS, tensile strength, and crack area of the cement paste with SCMs.

Effects of graphene oxide aggregates on hydration degree, sorptivity, and tensile splitting strength of cement paste

Surface properties of UV-irradiated poly(vinyl alcohol) films containing small amount of collagen

A multi-scale analysis framework is used to efficiently identify the correlation between the microstructure and tensile strength of slag blended cement paste in this study.This framework confirms that the tensile strength of cement paste can be predicted by considering the effect of microstructure.The framework is applied to cement paste specimens containing blast furnace slag.The tensile strength of the slag blended cement paste is evaluated by experiment and simulation.The slag blended cement paste is observed using micro-CT (computed tomography), which is subjected to a splitting test to measure the tensile strength.The micro-CT images are reconstructed into virtual 3D microstructures to be used as a simulation model.The virtual 3D microstructures are employed to simulate the splitting test through a finite element analysis, with a phase-field fracture model applied to identify the crack patterns within the microstructure.The input parameters required for the simulation are obtained from nanoindentation correlated with characteristics from micro-CT.The framework is subsequently utilized to evaluate the tensile strength of slag blended cement paste and compared with experimental results.This study demonstrates the feasibility of extending the multi-scale framework to cement paste with admixtures.

Abstract: Carbon nanotubes (CNTs) are potential candidates to enhance the heat balance of concrete, reducing internal stresses caused by differential heating in massive concrete elements. The higher the aspect ratio (AR) and content of CNTs, the greater the expected thermal conductivity (TC). However, high AR may impair the proper dispersion of CNTs in cementitious matrix, potentially harming the workability and mechanical strength of the composite. This work evaluated the effect of the AR (35, 250, 900, and 3500) and content (0.05% and 0.10%) of CNTs on the TC, rheology (squeeze flow), and mechanical strength of cement paste. Results showed that 0.05% CNT increased the TC of paste by up to 15% for AR of 250, but further increasing AR progressively reduced the TC of the composite. In turn, 0.10% CNT incorporation did not result in significant TC gains. The yield stress and viscosity of the mixes progressively increased as CNTs content and AR increased, by up to 119% compared with plain cement paste. No significant differences were observed in 28-day compressive strength with 0.05% CNT incorporation, while 0.10% CNT led to slight strength reductions for some mixes. Regarding flexural strength, 0.05% incorporation of either CNT decreased the strength of the mixes while 0.10% incorporation generally compensated this reduction, except for the lowest aspect ratio. Overall, CNTs with intermediate AR (around 250) was effective in improving the thermal conductivity of cement paste, increasing it by 15% with relatively low content (0.05%) while did not significantly impair the fresh and mechanical performance of the composite.

Thermal conductivity plays a significant role in controlling thermal cracking of cement-based materials. In this study, the thermal conductivity of cement paste at an early age was measured by the hot plate method. The test results showed that the thermal conductivity of cement paste decreased with the increase of water/cement ratio and curing age. Meanwhile, a multiphase model for the thermal conductivity of cement paste was proposed and used to study the influence of saturation and curing temperature on the thermal conductivity of cement paste. To determine the parameters involved in this model, the thermal conductivity of each phase in cement paste was calculated by the molecular dynamic simulation method, and the hydration of cement was simulated by the Virtual Cement and Concrete Testing Laboratory. The inversion results showed that the relative error between experimental and simulation results lay between 1.1% and 6.5%. The thermal conductivity of paste in the saturated condition was 14.9–32.3% higher than that in the dry state. With the curing temperature increasing from 10 °C to 60 °C, the thermal conductivity of cement paste decreased by 3.9–4.9% depending on the water/cement ratio.

Summary: In this paper we have tried to find the relationship of thermal and mechanical properties i. e. thermal conductivity, tensile strength and Young's Modulus of the composite material. Two systems were selected; poly(vinyl alcohol)/sodium sulphate composite, and poly(vinyl alcohol)/lithium sulphate composite. Various concentrations of these salts were used to make composites of poly(vinyl alcohol). Films were grown, dried at room temperature and were subjected to mechanical, structural and thermal characterization. Thermal conductivity was determined at room temperature using polyethylene, silicon and quartz as reference. It was found out that the thermal conductivity of both the systems is highly dependent on the nature and the concentration of added salt in the polymeric composite. Thermal conductivity of the poly vinyl alcohol/ sodium sulphate composite, and poly vinyl alcohol/lithium sulphate composite, decreased with concentration of the salts in the polymer composite. These composites were also analyzed by XRD. Observed roperties were explained on the bases of their structure. Machenical properties such as tensile strength and Young's Modulus were also found out to be a function of the compostion of the composite

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)–graphene (GA)–nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA–CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA–GA–CNF hydrogel. PVA–GA–CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer–Emmett–Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA–GA–CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA–GA–CNF ternary composite aerogel has potential application in thermal insulation.

Thermal properties of carbon nanofibers enhanced lightweight cementitious composite under high temperature

Thermal conductivity of cementitious composites containing microencapsulated phase change materials

Development of thermal insulation packaging film based on poly(vinyl alcohol) incorporated with silica aerogel for food packaging application