Effect of Rice Straw on Tensile Properties of Tailings Cemented Paste Backfill

It is important and difficult to improve the tensile strength of backfill material to ensure the stability of goafs. In this study, rice straw (RS) in fiber form is used to improve the tensile properties of cemented paste backfill (CPB). An orthogonal experiment was designed, Brazilian indirect tensile strength tests were conducted to test the tensile performance of RS fiber-reinforced cemented paste backfill (RSCPB) under different fiber content (1, 2, 3 kg/m3) and fiber length (0.8~1, 1~3, 3~5 cm), and the microstructure of RSCPB was analyzed with scanning electron microscopy (SEM). The results showed that, compared with the conventional cemented paste backfill (CCPB), the increase in tensile strength of RSCPB ranged from 115.38% to 300.00% at 3 days curing age, 40.91% to 346.15% at 7 days, and −38.10% to 28.00% at 28 days., and the strain was slightly reduced during the curing period. The tensile strength, strain, and percentage increase of the RSCPB compared to the CCBP did not show a monotonic pattern of variation with the RS fiber content and length during the curing period. The RSCPB samples fractured under peak stress, showing obvious brittle failure. In addition, sulfate generated from S2− in the tailings inhibits the hydration reaction, and generates swelling products that form weak structural surfaces, which, in turn, lead to a 28-day tensile strength and strain of RSCPB lower than those at 7 days.

A Disposable DNA Analysis Chip with a Powerless Actuator

A non-instrumented, single-use, affordable, and fully- yet safely-disposable DNA analysis system for Point Of Care (POC) diagnostic process has been proposed by integrating (1) a hydration-reactive mixture for a portable heating element as a powerless actuator, (2) commercially available optical adhesive films as valves, and (3) an exothermic reaction-based recombinant polymerase amplification (RPA) process for non-instrumented DNA amplification. The operational error tolerance of the adhesive valves was evaluated by gas production and long-lasting ability, and the amplification performance of the RPA device was validated by gel electrophoresis. Finally, a DNA analysis device was fabricated and tested based on a hydration reaction with a DNA extraction microfluidic channel and an exothermic reaction-based RPA device. In the DNA extraction process, dimethyl adipimidate (DMA) solution was used to eliminate some required injection steps from the extraction process. The integrated system's functionality was successfully demonstrated, and the suggested system could become a foundation for the ultimate total solution for POC DNA analysis.

Zr-Catalyzed Microwave Assisted Functionalization of Alkyne and Nitroalkene

Water and zirconium(IV) as catalyst were found to be effective in the transformation of terminal aromatic alkyne to aromatic methyl ketone in the microwave. This terminal alkyne hydration reaction proceeded in excellent yield with Zr(cp)2Cl2. The reaction was moved efficiently in presence of electron donating or electron withdrawing substituent on aromatic ring. An eco-friendly synthesis of aldehyde by oxidative cleavage of nitroalkene was developed with Zr(cp)2Cl2 catalyst and water in microwave.

Formulation of Non-Fired Bricks Made from Secondary Aluminum Ash

The secondary aluminum ash is the black slag left after the primary aluminum ash is extracted from the metal aluminum. To address the environmental pollution and resource waste caused by the accumulation and landfill of aluminum ash, this study fabricated non-fired bricks by using secondary aluminum ash as the principal raw material, which was supplemented by cement, slaked lime, gypsum and engineering sand. The effects of mix proportions of various admixtures on the mechanical properties of non-fired bricks were investigated, and on this basis, the hydration mechanism was analyzed. The results showed that the mix proportions were 68.3% aluminum ash, 11.4% cement, 6.4% slaked lime, 4.2% gypsum and 9.7% engineering sand. The compressive strength of the fabricated bricks reached 22.19 MPa, and their quality indicators were in line with the MU20 requirements for Non-fired Rubbish Gangue Bricks. Evident hydration reaction occurred inside the non-fired bricks, with main products being calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH) and ettringite (AFt). Besides, a dense structure was formed, which enhanced the brick strength.

Very high volume fly ash concrete utilizing microash and hydrated lime, with silica fume

The incorporation of high volume fly ash, up to 80%, in concrete without compromising the mechanical and durability properties is potentially very advantageous to the concrete industry in enabling the delivery of economic, social and environmental benefits. To assess this, two high volume fly ash mix designs incorporating 80% class F ultra-fine fly ash, known as microash and hydrated lime, with 10% silica fume and 0 % silica fume have been investigated. Properties investigated are compressive strength, carbonation, chloride ion penetration, water absorption and permeability. The specimens were cured for a maximum period of 90 days to optimize completion of the hydration reaction. The results show that the concrete manufactured with 80% microash exhibited compressive strength in excess of 40 MPa at 28 days and over 70 MPa at 90 days. The material also displayed excellent durability properties compared to the normal Portland cement concrete and other high volume fly ash concretes. The addition of silica fume improved the strength and durability properties of the material.

Effect of Nano-Si3N4 on the Mechanical Properties of Cement-Based Materials

In this paper, in order to improve the wear resistance of road cement, nano-Si3N4 (NSN) was incorporated into cement, and the effect of NSN on compressive strength and wear resistance of road cement was investigated. The main variable of the experimental investigation was the dosage of NSN. The experimental results showed that the addition of NSN could significantly improve the compressive strength and wear resistance of cement paste. Compared with the reference group, the wear resistance can be improved by 46.5% and the compressive strength of cement paste can be improved by 12.3% when the addition of NSN is 0.16% by weight. In addition, the improvement mechanisms of NSN on cement paste were revealed by hydration heat, XRD, DTA-TG, nanoindentation, nitrogen adsorption, and SEM for microscopic phase tests. Through the microscopic analysis, the addition of NSN can accelerate the hydration reaction and promote the hydration degree, optimize the pore structure, and make the cement paste more compact. Additionally, NSN can improve the performance of the interface transition zone (ITZ) and increase the content of HD C-S-H gel. The action mechanism of NSN is mainly dominated by the surface effect, filling effect, and larger surface energy of NSN thereby improving the mechanical properties of cement-based materials. These research results have guiding significance for the design of the high wear resistance and high compressive strength of cement-based materials.

High-magnitude stresses induced by mineral-hydration reactions

Fluid-rock interactions play a critical role in Earth’s lithosphere and in engineered subsurface systems. In the absence of chemical mass transport, mineral-hydration reactions will be accompanied by a solid-volume increase that may induce differential stresses and associated reaction-induced deformation processes, such as dilatant fracturing to increase fluid permeability. However, the magnitudes of stresses that manifest in natural systems remain poorly constrained. Here we show that the simplest hydration reaction in nature MgO + H2O⇔ Mg(OH)2 can induce stresses of several hundred megapascals, with local stresses up to ∼1.5 GPa. We demonstrate that these stresses are dissipated not only by fracturing but also induce plastic deformationwith dislocation densities (10^15m−2) exceeding those typical of tectonically deformedrocks. If these reaction-induced stresses can be transmitted across larger length scales they may influence the bulk stress state of reacting regions. Moreover, the structural damage induced may be the first step towards catastrophic rock failure, triggering crustal seismicity.

Ergodic Algorithmic Model (EAM), with Water as Implicit Solvent, in Chemical, Biochemical, and Biological Processes

For many years, we have devoted our research to the study of the thermodynamic properties of hydrophobic hydration processes in water, and we have proposed the Ergodic Algorithmic Model (EAM) for maintaining the thermodynamic properties of any hydrophobic hydration reaction at a constant pressure from the experimental determination of an equilibrium constant (or other potential functions) as a function of temperature. The model has been successfully validated by the statistical analysis of the information elements provided by the EAM model for about fifty compounds. The binding functions are convoluted functions, RlnKeq = {f(1/T)* g(T)} and RTlnKeq = {f(T)* g(lnT)}, where the primary linear functions f(1/T) and f(T) are modified and transformed into parabolic curves by the secondary functions g(T) and g(lnT), respectively. Convoluted functions are consistent with biphasic dual-structure partition function, {DS-PF} = {M-PF} ∙ {T-PF} ∙ {ζw}, composed by ({M-PF} (Density Entropy), {T-PF}) (Intensity Entropy), and {ζw} (implicit solvent). In the present paper, after recalling the essential aspects of the model, we outline the importance of considering the solvent as “implicit” in chemical and biochemical reactions. Moreover, we compare the information obtained by computer simulations using the models till now proposed with “explicit” solvent, showing the mess of information lost without considering the experimental approach of the EAM model.