Water-solid Ratio Research Articles

Green Protective Geopolymer Coatings: Interface Characterization, Modification and Life-Cycle Analysis.

In the interest of solving the resource and environmental problems of the construction industry, low-carbon geopolymer coating ensures great durability and extends the service life of existing infrastructure. This paper presents a multidisciplinary assessment of the protective performance and environmental impacts of geopolymer coating. Various parameters, such as main substance, water-solid (W/S) ratio, activator type and curing time, were investigated for their effects on interface characterization in terms of contact angle, surface energy, mechanical properties and microstructure. These parameters had negligible effects on the amounts and types of hydrophilic functional groups of geopolymer surfaces. A combination of organic surface modifiers and geopolymer coatings was shown to ensure hydrophobic surface conditions and great durability. Silicon-based modifiers exhibited better wetting performance than capillary crystalline surfactants by eliminating hydroxyl groups and maintaining structural backbone Si-O-T (Si, Al) on geopolymers’ surfaces. Finally, life-cycle analysis was conducted to investigate the environmental performance. Geopolymer coating yielded substantially lower environmental impacts (50–80% lower in most impact categories) than ordinary Portland cement (OPC) coating. Silicon-based modifiers had negligible influence due to their minimal usage. Increasing the W/S ratio diluted the geopolymer coating and decreased the environmental impacts, and slag-based geopolymer coating achieved lower environmental impacts than FA-based and MK-based varietie.

Effects of diatomaceous earth mixing amount on the performance of curing materials for waste leachate treatment

With cement as a cementitious material, fly ash, diatomaceous earth, sugar filter mud, and river sand as materials, and waste leachate instead of water, orthogonal experiments were designed to derive the preliminary formulation of curing materials and to explore the effect of different diatomaceous earth mixing amount on the performance of curing material test blocks. The experimental results showed that as the amount of diatomaceous earth increased from 12.5% to 13.58%, the 28d compressive strength of the cured material test block decreased from 9.85 MPa to 7.35 MPa, the dry density decreased from 1012 kg/m3 to 912 kg/m3, the porosity of the test block increased from 18.94% to 23.34% and the water absorption increased from 43.91% to 66.36%. Comparison of the best formulation of curing materials selected for cement, fly ash, diatomaceous earth and sugar filter mud mass ratio of 31.09 wt.%, 51.82 wt.%, 12.94 wt.%, 4.15 wt.%, external mixing river sand 15 wt.%, with a water–solid ratio of 0.8 was added to the waste leachate to prepare the curing material test blocks.

Influence of Different Parameters on the Performance of Alkali-Activated Slag/Fly Ash Composite System.

In order to study the influence law of each parameter on the performance of the alkali-activated composite gelling system, the influence degree was sorted, and the most important parameter affecting each performance was found. The solution of liquid water glass and solid sodium hydroxide was used as the alkaline activator, and the mixing ratio was designed by the orthogonal test method. The effects of four parameters of fly ash content, water glass modulus, water glass solid content, and water–solid ratio on the working performance and mechanical properties of alkali-activated slag–fly ash composite cementation system were discussed. The gelling system was studied by microscopic experiments such as SEM and FTIR. The results show that the solid content of water glass has the greatest influence on the fluidity of the composite cementitious system, and the content of fly ash is the primary factor affecting the setting time of the material. The flexural and compressive strengths at the age of 7 d and 28 d were most affected by the content of fly ash, and the solid content of water glass had the greatest influence on the flexural and compressive strengths at the age of 2 d. From the perspective of microscopic morphology, in the high-strength samples, the fly ash particles and the remaining outer shell are embedded in the gel to form a dense whole. When the amount of silica in the composite gelling system is too high, it will cause the phenomenon of low macroscopic mechanical properties.

ELEMENTS OF TECHNOLOGY FOR THE SURFACE GIPSUM COMPOSITE AND ITS PROPERTIES, AS A FACING MATERIAL

The paper considers the issues of obtaining a composite material based on gypsum, fly ash and sulfur with improved performance. Regularities of impregnation of a gypsum sol matrix with a sulfur melt are established, taking into account the capillary-porous structure of the gypsum sol stone and the physical and technical properties of sulfur. The conducted studies make it possible to determine the sulfur mass transfer coefficient ams and the maximum sulfur-containing Us in impregnated products, depending on the initial values of the sulfur melt temperature, water-solid ratio and fly ash content. This allows to determine quickly and effectively the duration of impregnation to a given sulfur content for a specific composition and size of gypsum products. Technological factors influencing the hardening coefficient, water resistance and chemical resistance of gypsum ash products impregnated in sulfur melt have been studied. An analysis of the results shows that the strength of samples impregnated with sulfur increases while the degree of filling of the pore space with it is increasing. So, with increase in the relative sulfur content (v = Us / Usmax) from 0.30 to 0.90, the compressive strength increases from 10.1 to 42 MPa. It has been established that water resistance of the impregnated samples significantly depends on the degree of impregnation and the amount of fly ash. The experiments carried out give reason to believe that the material based on gypsum, ash and sulfur refers to waterproof materials, since the softening coefficient is higher than 0.7. It has been established that gypsum and gypsum samples impregnated with sulfur melt have a chemical resistance coefficient of at least 0.7, which allows them to be classified as chemically resistant. The resulting sulfur-gypsum composite is distinguished by high strength, water and corrosion resistance to aggressive environments of livestock complexes, food and chemical industries, where it should be used in the form of special facing products.

Stress-Strain Relationships of Fiber Reinforced Phosphogypsum under Uniaxial Compression

To investigate the stress-strain relationship of fiber reinforced phosphogypsum (PG) under uniaxial compression, a total of twenty-seven PG prism specimens were fabricated and tested. The influences of the content of admixture, content of fiber, and water-solid ratio on the stress-strain curve of the specimens were investigated. Three kinds of failure modes were summarized by observing the experimental phenomena; they were called “compaction failure,” “tension failure,” and “mixed stress failure,” respectively. Through in-depth analysis of the test data, it was found that decreasing the water-solid ratio can lead to increasing the peak stress and secant modulus of specimens; increasing the fiber content can lead to improving the mechanical property of PG mixture specimens. However, adjusting the contents of the cement and quicklime has no significant effect on the mechanical property of specimens. In addition, according to the test data and the characteristics of stress-strain curves, the stress-strain curve of PG specimens was divided into four parts, and a mathematical model was developed to predict the stress-strain curve of PG specimens. The validations of the model showed that the curves calculated by the proposed model were well in agreement with the test data of this study and previous studies.

Effects of Replacing Dietary Fish Meal by Soybean Meal Co-Fermented Using Bacillus subtilis and Enterococcus faecium on Serum Antioxidant Indices and Gut Microbiota of Crucian Carp Carassius auratus

Fermented soybean meal (FSM) is an important feed material that can replace fish meal to solve the shortage of animal protein. To improve the utilization of FSM, we optimized the co-fermentation conditions of soybean meal using Bacillus subtilis and Enterococcus faecium and studied the effects of replacing fish meal with different proportions of FSM on serum antioxidant indices and gut microbiota (GM) composition of crucian carp (Carassius auratus). Our results showed that the co-fermentation of soybean meal was the most effective when the ratio of B. subtilis X-2 and E. faecium X-4 was 2:3, glucose addition was 4.5%, KH2PO4 addition was 0.15%, MgSO4·7H2O addition was 0.1%, anhydrous sodium acetate addition was 0.4%, fermentation time was 120 h, and the solid–water ratio was 1:1. Replacing 40% fish meal with FSM in the feed significantly improved the serum T-AOC, POD, and IgM levels in C. auratus. Although there were significant differences in the midgut and hindgut microbiota structures of C. auratus, the addition of FSM to the feed did not cause significant differences in the GM structure, whether in the midgut or hindgut. Therefore, 40% FSM is the most suitable substitute for fish meal in the feed of C. auratus.

Workability and Mechanical Properties of Superplasticized Microfine Cement Grouts

Superplasticizer (SP) is essential to enhance the groutability of microfine cement (MC) in civil engineering, however, combined effects of cement type, SP type, amount of SP and water-solid ratio (W/S) on engineering performance of MC are not clear currently. In this research, workability and mechanical properties of superplasticized microfine cement grouts (SMCG) with various SPs are evaluated systematically. Three different MCs (CEM I, CEM II/B-M and CEM III/B based on EN 197-1) and four SPs (one naphthalene-based (N), one melamine-based (M) and two polycarboxylate-based (PCE)) were used to study the effect of grout formulation. The properties investigated included rheological behavior (mini-slump, flowability, time-dependent viscosity and initial viscosity), fresh-state property (bleeding, effective W/S and final setting time), mechanical performance (shrinkage, flexural strength (FS), unconfined compressive strength (UCS), and FS/UCS) and microstructure. The new method of static viscosity was adopted and viscoelasticity was evaluated. The ranges of W/S and SP content were 1.0–2.0 and 0–2.5%, respectively. The results show that the dispersion effects of SP on rheological behavior were followed by PCE, M and N in order of the influence degree. The instability, long-setting and oversaturation were easily caused by excessive SP. SP could be helpful for improving FS or bending toughness. Considering workability and mechanical performance of SMCG, the W/S is suggested to be within 1.5, the optimal amounts of N, M and PCE are recommended as 1.5–2.0%, 1.2–1.5% and 0.9–1.2%, respectively.

Orthogonal Test Design for the Optimization of Preparation of Steel Slag-Based Carbonated Building Materials with Ultramafic Tailings as Fine Aggregates

The high carbonation potential makes ultramafic tailings ideal aggregates for carbonated building materials. This paper investigates the preparation condition of ultramafic tailings and steel slag through orthogonal experiments. The results show that compressive strength has a positive exponential correlation with the CO2 uptake of the carbonated compacts. The optimized conditions include a slag-tailings ratio of 5:5, a carbonation time of 12 h, a grinding time of 0 min, and a water-solid ratio of 2.5:10, when the compressive strength of the carbonated compacts reaches 29 MPa and the CO2 uptake reaches 66.5 mg CO2/g. The effects on the compressive strength ordered from high to low impact are the slag/tailings ratio, carbonation time, grinding time of steel slag, and water–solid ratio. The effects on the CO2 uptake ordered from high to low impact are the slag–tailings ratio, water–solid ratio, carbonation time, and grinding time of steel slag. A high water–solid ratio hinders the early carbonation reactions, but promotes the long-term carbonation reaction. Steel slag is the main material being carbonated and contributes to the hardening of the compacts through carbonation curing at room temperature. Ultramafic tailings assist steel slag in hardening through minor carbonation and provide fibrous contents. The obtained results lay a solid foundation for the development of tailings-steel slag carbonated materials.

Mechanical activation of medium basicity steel slag under dry condition for carbonation curing

This paper attempts to turn medium basicity basic oxygen furnace (BOF) slags into construction materials by carbonation curing and enhance the reaction rate by utilizing mechanical activation. It was found that BOF slag becomes an aggregated after 30 min of grinding, providing the specific surface area was reduced with prolonged milling. The silicates, hydroxides, sulfates, aluminates and ferrates comprising BOF slag became amorphous after mechanical activation, however, the RO phase was nearly unchanged, and CaO crystalized. Mechanical activation cannot enhance the carbonation conversion of BOF slag after carbonation up to 24 h in duration alone. However, mechanical activation improved the compressive strength of carbonated BOF slag compacts when the water-solid ratio was high. The accelerated hydration reaction forms C-S-H and C-A-S-H, acted as catalysis for the carbonation process. To effectively activate the steel slag for carbonation curing at ambient temperature, this method that could enhance the rate of carbonate precipitation and is preferred to simply grinding.

PRELIMINARY ACTIVATION OF CEMENT-SAND MIXTURE IN ORDER TO INCREASE THE STRENGTH OF CONCRETE

The article discusses an effective technology for producing concrete with increased strength. For this purpose, it is proposed to perform preliminary mechanical activation of cement with sand with natural humidity (5-8%) in an energized apparatus, which is a rotary-type centrif-ugal mixer-disintegrator. During mixing, cement hydration occurs with the formation of nanodis-persed hydration products on the surface of cement grains, which are stripped off withsand and enter the mixture. Thus, in the micro-volumes of the cement-sand mixture, there is a uniform dis-tribution of the fraction of nanodispersed particles –highly dispersed products, preliminary hydra-tion of cement. The activity of the resulting activated mixture during subsequent hydration was determined using a differential microcalorimeter with a water-solid ratio (V/T) equal to 0.2. Calo-rimetric studies have shown that the temperature change inthe cement-sand mixture proceeds sim-ilarly to pure cement in contact with water, but after the first induction period. The mechanism of interaction of cement with water in the sand mixture changes significantly, which is accompanied by an increase in the temperature difference of the material in the cells to 0.87-0.88 °C and this difference is maintained for a long period of time. This is explained by the fact that the formation of cement hydration products occurs not only due to the processes of cement hydration, but also additionally during the chemical reactions of the formation of calcium hydrosilicates during the interaction of activated nanodisperse products and quartz sand.The preparation of concrete using an activated cement-sand mixture with a large aggregate and an estimated amount of water can significantly increase the strength of concrete and its other performance characteristics.

Improving the waterproofing efficiency by using a plugging compound

Increasing the efficiency of water shut-off works is one of the important tasks for the sustainable well operation. The article discusses the use of various plugging compositions for water inflow into a well isolating, their advantages and disadvantages, conditions of use, and presents the results of a study of the proposed composition. The composition of an aqueous solution of polyaluminium chloride and a suspension of gypsum anhydrite is considered. The composition contains 45-55 mass percent of 15-25 percent aqueous solution of polyaluminium chloride and 45-55 mass percent suspension of gypsum anhydrite at a water-solid ratio of 0.9. The technical result is an increase in the efficiency of water inflow into the well isolating by obtaining a homogeneous, dense plugging mass formed by mixing the components of the composition and gaining maximum strength over time. Keywords: well; water cut; isolation; water inflow; plugging mass; bottomhole formation zone; oil production; polyaluminium chloride; anhydrite.

Corrosion-resistant facing material with of mineral binders and assets modified by sulfur melt

The paper considers the issues of obtaining a composite material based on gypsumbinder and sulfur with high performance. Technological factorsinfluencing the hardening coefficient, water resistance and chemical resistance of gypsum products impregnated in sulfur melt have beenstudied. The regularities of impregnation of gypsum matrix with sulfur melt are established takinginto account the capillary-porous structure of gypsum stone and physical and technical properties ofsulfur. The regularities of impregnation of gypsum matrix with sulfur melt are established taking intoaccount the capillary-porous structure of gypsum stone and physical and technical properties ofsulfur. Research and consideration of mass transfer indicators during impregnation of gypsumconcrete products with sulfur melt allowed to optimize the technology. Thus, by the method ofcapillary impregnation on the original laboratory installation, the mass transfer coefficients forsulfur were measured. As a result of these studies, the dependences of the mass transfer coefficienton the temperature of the sulfur melt, the rate of heating of the melt, the concentration of the fillerand the water-solid ratio were obtained. Products made of composite material based on gypsum andsulfur have the following construction and technical characteristics: compressive strength, not lessthan 30.0 MPa; flexural strength, not less than 6.0 MPa; water resistance coefficient, not less than0.7; coefficient of corrosion resistance, not less than 0.7; wear resistance, no more than 0.3 g / cm2 .Analysis of the main construction and technical characteristics of the composite material based ongypsum and sulfur shows that the resulting composite has high strength, water and corrosionresistance to various aggressive environments. Facing tiles made of this material have highperformance characteristics and should be used in the lining of buildings of railway infrastructure,drainage systems, fertilizer storage, floors and walls of the chemical and food industries.

ACCOUNTING FOR THE INFLUENCE
 OF HUMIDITY PROPERTIES OF AUTOCLAVE-
 CURED CELLULAR CONCRETE
 IN THE DESIGN AND CONSTRUCTION
 OF ENCLOSING STRUCTURES

The results of studies of porosity, water
 absorption, moisture shrinkage and frost
 resistance of cellular concrete, which are some
 of the main factors determining the durability
 of cellular concrete enclosing structures
 manufactured using autoclave hardening
 technology, are considered.
 Methods for determining water absorption,
 moisture shrinkage and frost resistance are
 presented. The relationship between the
 moisture shrinkage and the capillary forces
 (the sum of the surface tension forces on the
 micromeniscs of liquid in the capillaries of
 cellular concrete), as well as the dependence
 of the shrinkage on the size (radius) of the
 capillary and gas pores of cellular concreteand on the water-solid ratio (W/S-factor) of
 cellular concrete, is established.
 In the field of frost resistance of cellular
 concrete, the relationship between the
 structure of the pore space of concrete
 and its deformation characteristics under
 the action of negative temperatures is studied.
 The effect of the presence of gas pores in
 cellular concrete on the reduction of frost
 expansion deformations is described.

Utilization of OPC and FA to enhance reclaimed lime-fly ash macadam based geopolymers cured at ambient temperature

One kind geopolymer composite cementitious material was synthesized under the activation of modified water glass, using reclaimed lime-fly ash macadam powder (RLFMP) as basic raw material, fly ash (FA) and ordinary Portland cement (OPC) as compound additive. The effects of OPC content, alkali content, water glass modulus and water–solid ratio on the setting time, compressive and flexural strength of the geopolymers cured at room temperature were investigated by orthogonal experiment. In addition, the mineralogical phases, micro-morphology and pore distribution characteristics of the final products were characterized through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and Mercury Intrusion Porosimetry (MIP). The results indicated that the OPC content had the most significant effect on the setting time and mechanical properties of geopolymers. With the increase of OPC content, the setting time of geopolymer mortars was greatly shortened, and the compressive strength and flexural strength were obviously improved. When OPC content was 10% of the total cementitious powder mass, alkali content was 11%, water glass modulus was 1.4, and water–solid ratio was 0.35, the 28 day compressive strength of geopolymer pastes cured at room temperature reached the highest of 43.2 MPa. Microstructure analysis showed that the incorporation of OPC promoted the full dissolution of silica-alumina raw materials in alkaline environment, improved the degree of geopolymerization and formed the C-(A)-S-H gel products in the reaction system. The C-(A)-S-H gel products were synergistic with the N-A-S-H gel products generated by pure geopolymerization to enhance the compactness and adhesion of the matrix, which was conducive to the improvement of the mechanical properties of geopolymer. This study demonstrates the feasibility of preparing geopolymer with RLFMP at room temperature, which widens the source of geopolymer raw materials and provides a new type of geopolymer composite.

Dried Figs Quality Improvement and Process Energy Savings by Combinatory Application of Osmotic Pretreatment and Conventional Air Drying.

This study concerns the implementation of osmotic dehydration (OD) as a pre-treatment of air-drying in fig halves, aiming at drying acceleration, energy savings and product quality improvement. The effect of solid/liquid mass ratio, process temperature (25–45 °C) and duration (up to 300 min) on water activity (aw) and transport phenomena during OD, was modelled. The effective diffusion coefficients, drying time and energy consumption, were also calculated during air-drying at 50–70 °C. At optimum OD conditions (90 min, 45 °C), the highest water loss and solid gain ratio were achieved, while the aw (equal to an initial value 0.986) was decreased to 0.929. Air-drying time of OD- and control samples was estimated at 12 and 21 h, at 60 °C, respectively, decreasing the required energy by up to 31.1%. Quality of dried figs was systematically monitored during storage. OD-assisted air-drying led to a product of improved quality and extended shelf-life.

Hydrothermal Treatment of Herb Residue for Solid Fuel Production

Hydrothermal processing is appraised as one of advanced technologies for wet solid waste handling. In this study, herb residue was subjected to hydrothermal treatment. Calorific value, yield, and also proximate analysis of obtained hydro-char were investigated. A cylindrical reactor with an internal volume of 2.5 Litres made of stainless steel and a low-tech component was used in the experiment. The reactor was equipped with a stirrer to ensure heat transfer took place through the entire parts of the solid-water mixture. Solid products were dried by a microwave oven before analysis. The results show that the final temperature, holding time, and solid-water ratio have various effects on the hydro-char yield, calorific value, and proximate analysis of the hydrothermal products. The hydro-char yield decreased with the increase in final temperature and holding time. Meanwhile, the highest hydro-char yield was obtained at the solid-water ratio of ¼. The hydro-char calorific value increased with the increase in final temperature, holding time, and solid-water ratio. The rise in final temperature, holding time, and solid-water ratio resulted in a lower moisture content and volatile matter but higher fixed carbon. Meanwhile, the ash content increased with the solid-to-water ratio.

Research on Optimal Proportion and Performance of Cement-Clay Slurry

For the cement-clay slurry commonly used in dynamic water grouting, consider adding coal ash to optimize the performance of cement-clay slag composite slurry and discuss the reaction mechanism of the slurry through microchemical element analysis; the orthogonal test was used to study the influence of various factors on material setting time, solidification ratio, water segregation rate, and the optimized ratio of the slurry that was obtained by integrating the unconfined compressive strength of grouting concretion body and slurry configuration cost. The results showed that the water-solid ratio had the greatest influence on the comprehensive performance, followed by the amount of coal ash admixture. The best performance of the composite slurry was obtained with a water-solid ratio of 0.8:1 and a cement:coal ash:clay:quicklime:sodium sulfate:water mass ratio of 1:0.45:0.20:0.05:0.07:1.32. Finally, by comparing the mechanical properties of the optimized slurry and the grouting concretion body, it is proved that the optimized slurry has superior performance to meet the general grouting project requirement.

Performance assessment of a newly developed and highly stable grouting material for a completely weathered granite dam foundation

Grouting is one of the most important techniques in anti-seepage and reinforcements of sandy soil dam foundations. However, there is a lack of stable grouting materials as the existing materials show many limitations. This paper proposed a new grouting material to improve the anti-seepage and mechanical performance of completely weathered granite. This grout of desirable groutability, stability, and strength was produced by wet grinding clay cement slurry. The effects of different clay contents and water–solid ratios on the engineering properties of the grouting material and the formation mechanism of the slurry were studied through a series of laboratory experiments. The optimal formulations of the grout were determined by comparing the engineering performance of the new grout with of the superfine cement slurry and the wet-ground fine cement slurry. The recommended parameters for the new grout included a specific gravity of 1.15 for the clay slurry and a water–solid ratio of 1.0 (the mass proportions of clay and cement to the total solids are 25% and 75%, respectively). Finally, a grouting simulation experiment and a field grouting test were conducted to verify the groutability and effectiveness of the proposed grouting material. The results indicate that the grout is an economical and environmentally friendly grouting material with good groutability.

Physical test of fracture development in the overburden strata above the goaf and diffusion process of permeable grout slurry

The massive mechanized and irrational coal mining has generated many goafs (i.e., mined-out areas) in China. To manage these goafs effectively, grouting technique has been commonly used to fill the fractures in the overburden strata. However, little is known about the development and distribution of fractures in the overburden strata above the goaf. The lab-scale simulation of fracture development, as well as the grouting process, can provide valuable information for managing a real goaf by the grouting technique. Based on the mechanical properties of rocks and soils in the goaf of Kangjiagou coal mine in Shanxi Province, an experimental system was designed to simulate the development of fractures in the overburden strata above the goaf and study the diffusion behaviors of the grout slurry under different conditions (such as grout volume, grouting pressure, porosity, and water-solid ratio). The physical model test showed that more fractures were found in the fractured and caved zones, with fracture porosity ranging from 15.05 to 40.79%. The grouting experiment showed that, when the water-solid ratio was smaller than 1.15 and the grouting pressure was lower than 0.3 MPa, the changes in diffusion radius were stable during the grouting process. To maintain the stable changes in diffusion radius and reach a high filling ratio, the grouting pressure should be controlled in the range of 0.2–0.4 MPa at the porosity of 24.8% and 0.5 MPa at the porosity of 35.1%. The findings derived from this study are widely applicable under real engineering contexts.

Features of monolithic house building

The article considers the problems of monolithic house building in Russia. The version of design of cellular concrete compositions based on assessment of water-solid ratio (W/S) and determination of optimal content of plasticizers of the new generation is proposed. It has been found that in order to obtain heat-insulating cellular concrete, the range of W/S is in the range from 0.35 to 0.5, and the percentage of plasticizer is up to 0.5 of the weight of binder.