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To address the problem that traditional cement-based slurry materials cannot meet the actual demand for grouting and reinforcement of large deformation roadways in coal mines, some high-performance composite slurry materials are obtained by modifying ordinary Portland cement with nano-silica sol, ethylene-vinyl acetate copolymer (EVA) and fly ash. The orthogonal test and extreme difference analysis are used to systematically study the variation of the physical and mechanical properties of the composite slurries, determine the optimal ratio, and further analyze the difference in the physical properties between the optimal ratio of composite slurries and pure cement, construct the hydration reaction mechanism model of the composite slurries, and elucidate the mechanical properties of the composite slurries for reinforcing broken rocks. The results of the study show that the optimum proportion of composite slurry is 0.7 water-cement ratio, 15% fly ash, 2% silica sol and 7.5% EVA. Compared with pure cement, the rheology of composite slurry is slightly decreased, but the stability and mechanical properties of the slurry are significantly improved, with the initial setting time shortened by 38.9%, the final setting time shortened by 53.8%, the precipitation rate reduced by 60%, the stone rate increased by 3.3%, the uniaxial compressive strength increased by 39.1%, the tensile strength increased by 97.2%, and the tensile/compression ratio increased by 41.7%. Silica sol and fly ash undergo volcanic ash reaction with Ca(OH)2 to generate more calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) at different times, which promotes the hydration reaction of the composite slurry and accelerates the film formation of EVA to make the stone body more dense. The injection volume of the composite grout and the uniaxial compressive strength of the bonded body both increase with the increasing grouting pressure. With the increase in the Talbot index, the compressive strength first increases and then decreases. The failure mode is often characterized by bulging, and shear dilation deformation is pronounced. When the grouting pressure exceeds 2 MPa and the Talbot index is 0.5, the bond strength of the grout is higher, and the damage is reduced. This study provides a feasible way for early strength and toughening modification of ce-mentitious composite pastes.

In view of the problems of low early strength and weak deformation resistance of ordinary cement-based materials, the cement-based materials were modified by nano-silica sol. The nano-silica sol was charasterized by means of electro-hydraulic servo universal testing, X-ray diffraction, and scanning electron microscopy. The fluidity, stone rate, uniaxial compressive strength, elastic modulus, hydration products, and microstructure of cement-based materials with different water-cement ratios were evaluated. The results show that when the content of silica sol is within 0.5% and the water-cement ratio is less than 1.0, the fluidity of cement slurry can be significantly improved, and the maximum increase is 20.24%. The stone formation rate increases with the increase of nano-silica sol admixture, and the silica sol increases the stone formation rate of slurry with water-cement ratio greater than 0.7 significantly, with a maximum increase of 24.49%. When the content of silica sol is 2%, the compressive strength of the stone body increases the most. The effect of increasing the strength gradually weakens. The incorporation of nano-silica sol promotes the early hydration reaction of cementitious, and reacts with the hydration products to produce hydrated calcium silicate gel (C—S—H) and makes the microscopic morphology more dense, so that the early compressive strength and elastic modulus of the stone body are significantly increased. Nano-silica sol promotes the hydration reaction by shortening the induction period and providing nucleation sites for C—S—H in the particle voids, which improves the performance of cementitious materials.

Fosthiazate is a common insecticide for root‐knot nematode control, but it has a short shelf life and is prone to decomposition. In order to improve the stability and prolong the release time, this experiment used the ionic gel method to cross‐link chitosan with sodium tripolyphosphate and added nano‐silica sol to prepare microcapsules suspensions. The optimal preparation parameters for the preparation of chitosan/sodium tripolyphosphate@nano‐silica sol microcapsulated suspensions were optimized by single factor experiments and response surface analysis, and the encapsulation efficiency reached 61.3%. The highest control effect in greenhouse pots can reach 84.1%, and the optimal concentration was 2 g/m2 mixed with soil, which increased stem length, root length and fresh weight by 81.1%, 47.7% and 62.5%. The study showed that the microcapsules of chitosan cross‐linked with sodium tripolyphosphate and added with nano‐silica sol could significantly prolong the release of Fosthiazate, which also provided a positive effect on soybean cyst nematode control. [ABSTRACT FROM AUTHOR]

How good dispersion of nano-SiO2 (NS) plays a great influence on how strong reinforcing efficiency to cement-based materials. In this study, a novel nanohybrid of polycarboxylate ether (PCE) grafted nano-silica sol (PCE@NSS) was prepared by sol–gel methods to chemically adsorb PCE onto NSS. The developed nanohybrid showed a higher ultraviolet–visible (UV–Vis) absorbance and slower sedimentation in alkaline solutions, indicating the better dispersion and stability of PCE@NSS than that of untreated NSS. By this way, only 0.05 wt.% addition of PCE@NSS was helpful to refine the capillary pore size and reduce the total porosity of cement mortar, which in turn improved the compressive and flexural strength of cement mortar by 18.34% and 10.5% at 28 days, respectively. In addition, a reinforcing index (R index) with the ratio of strength enhancement % to dosage % was proposed, indicating that the R index of PCE@NSS showed 10 times higher than that of other NS-based nanomaterials reported in literatures, addressing the highly reinforcing efficiency of PCE@NSS to cement mortar. Furthermore, water absorption coefficient of cement mortar was therefore reduced by 12.7% with 0.2 wt.% addition of PCE@NSS. In conclusion, such an ultra-low dosage of PCE@NSS with better dispersion and stability exhibited great potential to reinforce cement-based materials with highly efficiency, lower cost and reduced carbon emissions.

The dilemma of insufficient wood resources and poor properties of fast-growing wood necessitates a breakthrough in the expansion and efficient utilization of wood resources to meet the real needs. With the aim of enhancing the properties of fast-growing poplar wood, a combination of PVA and nano-silica sol impregnation treatment was carried out to develop a novel functional wood material with good dimensional stability, compressive strength and thermal stability, while fully exploiting the unique structural properties of the wood itself. In this work, PVA-nano-silica sol composite wood was prepared by in-situ impregnation of poplar fast-growing wood via ultrasound-assisted and vacuum impregnation methods. Firstly, the effects of different treatments on the impregnation effect and strengthening effect of modified wood were explored. The results showed that the PVA-nano-silica sol dispersion system had no negative effect on the impregnation modification, and the compressive strength of modified wood was obviously improved compared with natural wood. Among them, the most effective modification was achieved under the condition of vacuum-assisted impregnation. The effect of compound impregnation modification on the structure of poplar fast-growing wood was analyzed by FTIR, XRD, SEM, and EDS, in which PVA and nano-silica sol can form a certain cross-linking system and form chemical bonds such as Si-O-C and Si-O-Si, enabling them to enter the structure of wood and react with wood cell walls effectively. The compressive strength of modified poplar wood was increased by 72.29% compared with natural poplar wood. According to the thermogravimetric analysis, the thermal stability of the modified poplar wood was improved to some extent. In view of all the results, the method proposed in this study provides an opportunity for the high value utilization of low quality wood, and this modified wood can be considered as a candidate for new lightweight and high performance materials in the construction field. [ABSTRACT FROM AUTHOR]

Nano-silica sol (NSS) is an aqueous liquid containing colloidal nano-silica in dispersed state. It has been reported to offer better effects to the cement-based materials compared with nano-silica powder, which is by far the most widely studied nanomaterial for concrete applications. To identify the optimal type of NSS (acidic/ neutral/ alkaline) for use in cement-based materials, its effects on the performances and the influence mechanisms, a three-staged research program for testing the workability, strength, durability and chemo-physical properties of mixes with various types and contents of NSS at various ages has been completed. Generally, the addition of NSS decreased the workability and increased the strength and durability of concrete. It was found that alkaline NSS was the desirable type from the viewpoint of highest workability and strength. X-ray diffraction patterns, wet packing density, scanning electronic microscope images and mercury intrusion porosimetry tests verified the pozzolanic reaction effect, nucleation effect, densification effect and pore modification effect brought about by NSS. In-depth analysis revealed that the NSS induced nucleation effect at early age and pozzolanic reaction effect at later age, densified the microstructure and reduced both volume and size of pores. These effects explained the improvement of strength and durability of concrete by using NSS. • Performance and influence mechanisms of nano-silica sol (NSS) are studied. • Alkaline NSS is the desirable type for highest workability and strength. • X-ray diffraction patterns and scanning electronic microscope images are captured. • Wet packing density and mercury intrusion porosimetry tests are carried out. • Pozzolanicity, nucleation, densification, pore modification effects are verified. [ABSTRACT FROM AUTHOR]

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A series of novel addition cured polydimethylsiloxane ( PDMS) nanocomposites with various amounts of nano-silica sol were prepared via hydrosilylation for the first time. The influence of various amounts of nano-silica sol on the morphology, thermal behavior, mechanical and optical properties of these PDMS nanocomposites was studied in detail. It was found that with an increment in the amount of nano-silica sol the reinforcing effect of the nano-silica sol on the thermal and mechanical properties of the PDMS nanocomposites was very noticeable compared with the reference material. The prominent improvements in resistance to thermal degradation and mechanical properties can probably be attributed to the strong interaction of PDMS chains and uniformly dispersed particles resulting from the nano-silica sol. However, the transparency of the PDMS nanocomposites slightly decreased with an increment in weight fraction of nano-silica, compared with that of PDMS composite without nano-silica (Sol-0), which can probably be ascribed to an increasing size of the aggregated particles in the PDMS nanocomposites. The optimum amount of nano-silica sol for preparing novel addition curing PDMS nanocomposites was about 15 wt%. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: A novel waterborne epoxy acrylate (WEA) was synthesized using bisphenol A epoxy resin as basic resin (E-44), acrylic acid (AA) and maleic anhydride (MA) as modification agent. Nano-silica sol was synthesized by a sol–gel method using tetraethyl orthosilicate (TEOS) as precursor. The UV curable waterborne epoxy acrylate/silica sol hybrid materials were prepared by UV radiation, in which the synthesized WEA served as an organic polymer phase, and the nano-silica sol as an inorganic phase. 3-Trimethoxysilyl-propyl methacrylate (TMSPM) was selected as a coupling agent between the organic polymer phase and the inorganic phase. The influence of the photoinitiator amount and the curing time on the curing degree of the mixture system was investigated, and both the WEA coated film and the hybrid material coated film were characterized by Fourier transform infrared (FT-IR) spectra and thermogravimetry (TG) analysis. The experimental results showed that the maximum curing degree achieved was 88% gel content, the optimal photoinitiator amount was 3.5%, and curing time was 40s. FT-IR analysis implied that WEA/silica sol hybrid materials were formed for the hybrid between WEA and TMSPM modification silica sol. TG analysis indicated that the decomposition temperature of WEA/silica sol hybrid material coated film was 33°C higher than that of WEA coated film, which indicated that the addition of nano-silica sol improved the thermal stability of waterborne epoxy acrylate (WEA). [Copyright &y& Elsevier]