Water Binder Research Articles

Optimization of the Grout Mix Ratio and Simulation Test of Shield Tail Grouting Similarities in a Water-Rich Fine Sand Layer

When shield tunneling is performed in water-rich silt and fine sand strata, the grout becomes runny when diluted by groundwater. After dilution, the filling effect of the grout is not significant, and the level of surface settlement is very high. In this study, based on bidding section 04 of Tianjin Metro Line 11, traditional grouting materials were selected to conduct response surface method (RSM) tests. The purposes of the RSM analysis were to analyze the interactions between materials and their influences on grout performance and to optimize the grout mix ratio. Various admixtures were compared to assess the effects of different admixtures and compositions on the dispersion resistance and flow performance of the grout. Finally, a shield synchronous grouting test system was developed, and a similar indoor grouting simulation test was performed to analyze the influences of the different admixtures on the filling effects and to determine a reasonable grout mix ratio. The following three results were obtained. (1) The RSM was suitable for grout performance prediction and grout mix ratio optimization, and hydroxyethyl cellulose could improve the grout performance and increase the bond performance between the cementing material and aggregate. (2) Admixture incorporation enhancement could improve the grout utilization rate and increase the diffusion distance at the top of the tunnel, which would be conducive to filling the gap at the tail end of the shield. (3) The optimal preparation scheme of grout in water-rich fine sand formations included a water–binder ratio of 0.72, cement–sand ratio of 0.80, fly ash content of 5%, bentonite content of 14.94%, and admixture content of 0.8%–0.9%

Sonocatalytic induced dye degradation and antibacterial performance of SrTiO3 nanoparticles embedded cotton fabric

In the present work, a pigment paste was prepared by adding strontium titanate (SrTiO3) nanoparticles (NPs) particles to a water and adhesive binder paste. Screen printing was utilized to embed the cotton fabric with the prepared pigment paste. Sonocatalytic induced antibacterial and dye mineralization abilities were evaluated for the printed fabric. The produced samples were examined for efficacy against the pathogens E. coli and S. aureus. The prepared SrTiO3 embedded cotton fabric inhibited (after 2 h) E. coli and S. aureus by 99.3% and 96.09%, respectively. The coated fabric was able to reduce pathogens by more than 92% even after 15 washing cycles. The Rhodamine B (RhB) dye was mineralized by 53% in 210 min by STO printed fabric as opposed to about 8% by pristine cotton. The results revealed that the intrinsic properties of cotton including tensile, abrasion, and air permeability remained unaffected by the printing of STO-NPs onto fabric.

Experimental Development of an Innovative Approach to Enhance the Strength of Early Age Cemented Paste Backfill: A Preliminary Investigation of Microwave-Assisted Curing

In underground mining, the application of mine backfill has evolved into a standard practice. Mine backfill typically consists of tailings, water, and hydraulic binders. However, the high cost of binders has prompted scholars to research alternatives to reduce this cost while maintaining or even improving the properties of the backfill. One potential alternative is leveraging microwave irradiation. In this study, an innovative approach was developed to increase the unconfined compressive strength (UCS) of early age cemented paste backfill (CPB). Microwave treatment was applied to CPB samples at various curing ages for varying durations. The UCS and ultrasonic pulse velocities were measured and analyzed in an experiment with a full factorial design. Moreover, the microstructural properties of the CPB were investigated using mercury intrusion porosimetry. The results indicate a significant potential to increase the UCS of CPB by up to 25% when microwave-treating samples for 8 min after 7 days of curing. This approach could shorten mining cycle times and improve productivity, presenting a promising method to enhance CPB strength.

Mechanical Properties and Optimal Mix Design of Phosphogypsum Cement Mineral Admixture Foam Light Soil

With the rapid growth of road transportation, the increase in road subgrade and pavement diseases has become a pressing issue, requiring the development of cost-effective filling materials that meet both strength and economic requirements. Foam lightweight soil, as a novel construction material, offers excellent characteristics such as adjustability in density and strength, high fluidity, and self-supporting capabilities. It has been widely utilized in various engineering applications, including road subgrade backfilling and retaining wall fillings. However, the conventional application of foam lightweight soil, predominantly cement-based, has raised concerns about pollution and high energy consumption due to large cement dosages. To address this issue, this study proposes the integration of phosphogypsum, a byproduct of wet-process phosphoric acid production, into foam lightweight soil. Phosphogypsum has a significant annual discharge and accumulation, but its comprehensive utilization rate remains relatively low. The research investigates the combination of phosphogypsum and foam lightweight soil by introducing mineral admixtures such as microsilica and slag powder to improve early strength development and reduce the influence of fluoride impurities on early strength. The optimal mix proportions for two types of foam lightweight soil, namely phosphogypsum cement microsilica foam (PGCF) and phosphogypsum cement slag powder foam (PGCS), were determined based on single-factor tests. The key parameters considered for optimization were water–binder ratio, foam content, and phosphogypsum dosage. The findings indicate that both PGCF and PGCS foam lightweight soil possess superior mechanical properties and thermal conductivity. By incorporating phosphogypsum into the mix, the early strength development of foam lightweight soil is effectively improved. Moreover, with suitable mix proportions, the maximum phosphogypsum dosage can be achieved, demonstrating potential economic and environmental benefits. In conclusion, this research provides valuable insights into the effective utilization of phosphogypsum in foam lightweight soil, offering a promising solution for the challenges associated with phosphogypsum disposal and the demand for sustainable construction materials in highway engineering.

Investigating hydration characteristics of Portland cement-calcium sulfoaluminate cement-gypsum ternary cementitious system with low water binder ratio:a magnetism-heat theory approach

This study is to elucidate the hydration characteristics in ternary cementitious materials of portland cement-sulfoaluminate cement-gypsum (TCM) under restricted water content based on magnetism-heat theory. The analysis of the micro/macro properties and reaction process of TCM is conducted through various techniques, including low-field nuclear magnetic resonance, isothermal calorimeter, and scanning electron microscope, etc. The results demonstrates that TCM prepared in this study exhibits a compressive strength exceeding 35 MPa within 4 h, thus satisfying the demands for rapid structural repair. Furthermore, the time duration of various hydration stages of TCM is effectively quantified using the magnetism-heat theory. This approach facilitated a quantitative division and understanding of the distinct stages of hydration. Lastly, the isothermal kinetic model accurately depicts the control stage of chemical reaction in TCM. With addition of 15% CSA, the chemical reaction control stage shifted to encompass Nucleation and Crystal Growth (NG) to Diffusion (D).

PH and Sugar Content of Honey Pineapple Jam (Ananas comosus L Merr) with Addition of Carrageenan

This study aims to evaluate the effect of adding carrageenan to the pH value and sugar content of honey pineapple jam. Honey pineapple (Ananas comosus L. Merr) was used as the main ingredient with the addition of carrageenan at concentrations of 0%, 0.2%, 0.6%, and 1%. The method used is a completely randomized design (CRD) with one factor and three replications. The results showed that the addition of carrageenan significantly (P<0.05) affected the sugar content in pineapple jam. The higher the carrageenan concentration, the lower the sugar content in pineapple jam. However, the addition of carrageenan had no significant effect (P>0.05) on the pH of pineapple jam. Carrageenan acts as a thickener and water binder in jam but does not substantially change the level of acidity (pH). Keywords: carrageenan, sugar content, honey pineapple jam, and pH

Properties of Cement-Based Materials with Low Water–Binder Ratios and Evaluation Mechanism under Further Hydration Effect

Unhydrated cementitious materials in high-performance concrete (HPC) and ultra-high-performance concrete (UHPC) undergo further hydration when they are further supplied with water. A further hydration experiment on cement pastes was conducted to study the effects of temperature and humidity on their macroscopic properties. A rapid evaluation mechanism for further hydration was eventually presented. The results obtained under the four analysed humidity conditions indicated that the compressive strength and flexural strength increased by 22.6% and 75.2%, respectively, after further hydration for 180 d at a relative humidity (RH) of 95%. Considering water soaking under three analysed temperature conditions, water soaking at 60 °C had the largest impact on macroscopic properties, such as compressive strength and flexural strength, which showed an increase of 31.4% and a decrease of 13.8%, respectively, after further hydration for 180 d. Moreover, the expansion strain at 60 °C was 1.1 times higher than the strain determined under water soaking at 40 °C. Considering the stability of the evaluation indices, the combined water content for further hydration, expansion strain, and compressive strength were used to evaluate further hydration effect. Considering the acceleration and damaging effects, water soaking at 60 °C was an effective method to accelerate further hydration.

Degradation Mechanism of Ultra High-Performance Concrete under Coupling Erosion of Salt and Frost

Abstract With the use of ultra high-performance concrete (UHPC) in frozen areas, UHPC structures suffer from severe erosion under the interaction of salt ions and frost, resulting in significant performance degradation of UHPC structures. However, the performance degradation mechanism of different compositions and structures of UHPC under the coupling erosion of salt and frost is still unclear at present. In order to study the degraded behavior and mechanism of UHPC under the coupling erosion of salt and frost, various UHPCs were prepared and exposed to freeze–thaw (F-T) cycles and salt–freeze–thaw (S-F-T) cycles. The mass and compressive strength of the UHPCs before and after the F-T and S-F-T tests were compared to evaluate the performance degradation of UHPCs. The SPSS software correlation method, scanning electron microscope, and mercury intrusion porosimetry tests were used to analyze the mechanism of the coupling erosion of salt and frost on the UHPCs. Results indicate that UHPC with a lower water–binder ratio (WBR) and higher superplasticizer content exhibits better resistance to the coupling erosion of salt and frost. The resistance of UHPC to the coupling erosion of salt and frost will decline with the rise of WBR, and the WBR is the most significant factor affecting the coupling erosion of salt and frost for UHPC. The coupling of salt and frost decreases the compressive strength and leads to cracking of UHPC, which can be ascribed to the larger average pore size and higher cumulative pore volume caused by the salt ions. The hygroscopicity of salt ions increases the moisture in pores, and salt crystallization generates pressure in the pores, further aggravating the damage of UHPC.

Study on macro performance and micro-analysis of high strength grouting material

Wind turbine duct put forward higher requirements for the performance of grouting materials. In order to obtain more economical high strength grouting materials (HSG), three kinds of low price main components, cement, quartz sand (QS) and fly ash microspheres (MS) were utilized and developed. Macro performance and micro-analysis of the HSG were conducted. The macro performance tests revealed that the mix proportion of HSG is determined as, cement: QS: MS: superplasticizer: swelling agent = 80:10:10:0.3:0.12, water binder ratio is determined as 0.26. Compressive and flexural strength of the HSG exceeding 120 MPa and 20 MPa respectively. The HSG also showed good fluidity and homogeneity. The micro-analysis showed that a complete and continuous micro-structure was formed and interface transition zone could not be observed. XRD and TG-DSC results meant that the amount of AFt increased. On the contrary, the amount of Ca(OH)2 decreased. pore diameter of the HSG was mostly 10 nm. The addition of swelling agent and MS did not changed the types of hydration products of HSG, but the pore structure was optimized. Due to the cheap components, HSG contributed higher profits with the lower price, and which perform good economic benefits and market competitiveness.

Effect of elevated temperature on rice husk ash based self-compacting alkali activated slag concrete mixes under different cooling regimes

Here an attempt has been made to develop self-compacting alkali activated slag concrete mix using Rice Husk Ash as Binder. Investigation on the mechanical properties and residual strength when subjected to temperature of 200,400,600,800°C retention period1hour. The Rice husk ash Self Compacting Alkali Activated Slag Concrete mixes was made with GGBS, Rice husk ash and Lime as the binder, with its content varying from 550 to 650 kg/m3of fresh concrete. The W/B ratio of mixes varied in 0.7-0.88 range. The alkaline solutions had Na2O percentages in the range 5-7 with constant activator modulus maintained at 1. Final mix considered had lower water content, higher percentage of RHA and higher compressive strength. Trails showed Processed Rice Husk Ash30%, lime20% and GGBS50% for binder content 600kg/m3 and 6% Na2O dosage showed greater compressive strength and lower water binder ratio compared to other trail mixes. Results showed the slump flow, L–Box, U-box and V-Funnel as greater than 650mm, 0.85, 20mm and 10s resp. Fire damage of RSAASC was measured by subjecting to elevated temperature between 200-800°C for a retention period of 1hour. Cooled to room using furnace cooling, air cooling and sudden cooling. Results indicated reduced compressive strength with increased temperature.

Effect of silica fume and PCE-HPMC on LC3 mortar: Microstructure, statistical optimization and life cycle Assessment

With immense carbon emissions, the cement and concrete industries account for nearly eight percent of the world’s total. As the demand for urbanisation increases, the carbon footprint of the industry will also increase rapidly. A sustainable and greener low carbon cement called limestone calcined clay cement (LC3) is being developed as a promising alternative to ordinary Portland cement (OPC). The present study investigates the effects of silica fume (SF) on LC3 with variable dosages of polycarboxylate ether-based superplasticizer (SP) and hydroxypropyl methylcellulose (HPMC) admixtures. Using three level-three factorial (33) Box Behnken Design and response surface methodology (RSM), SF content, SP content, HPMC content, and flow value were set as input parameters to optimise and evaluate the eight output response parameters, namely, water binder (w/b) ratio, compressive strength (7 and 28 days), modulus of rupture, porosity, water absorption, ultrasonic pulse velocity, and water sorptivity. With a combined desirability of 90.8% for an optimised mix, the model showed that with 0% SF, 0.811% SP, 0.923% HPMC, and 124.12 mm of FV, a LC3-50-based cement system with higher physico-mechanical properties can be developed. The microstructural analysis was also conducted through a scanning electron microscope (SEM), Thermogravimetric Analyzer (TGA), and X-ray diffraction (XRD). The results showed Calcium silicate hydrate (C-S-H) development along with consumption of portlandite (CH) for LC3-50-based cement systems. Sustainability analysis of LC3-based mortar in terms of carbon emissions showed a 33.82% reduction in CO2 emissions as compared to OPC.

Influence of Corn Cob Ash-Silica Fume Blend on the Mechanical and Durability Properties of Concrete

— This research explored the feasibility of corn cob ash-silica fume blend in the production of pozzolanic cement to produce High-Performance Concrete. The cement in concrete was partially replaced by corn cob ash-silica fume blend in 5,10,15 and 20% by weight of cement and was compared to a control mix of 0% replacement. An intelligent mix design, Densified Mix Design Algorithm (DMDA), was used to effectively reduce both water and cement content. In order to create high strength and workability, a polycarboxylate-based super plasticizing admixture was utilized in conjunction with a low water binder ratio of 0.35. Compressive strength was appraised to determine the mechanical properties at days 3,7,14,28 and 56 to determine the optimum percentage replacement and compared to the control at the specific ages. With the optimum percentage replacement, the flexural test was investigated at 28 days. Water absorption and electrical resistivity tests were also investigated as potential indicators of durability. All of the blends that included corn cob ash and silica fume produced a higher strength than the control except 15 and 20%, with 10% replacement yielding a cube strength of 61 MPa at day 56.

Effects of Water—Binder Ratio on Strength and Seismic Behavior of Stabilized Soil from Kongshavn, Port of Oslo

In many civil engineering problems, soil is stabilized by a combination of binders and water. The success of stabilization is evaluated using seismic tests with measured P-wave velocities. Optimization of process, laboratory testing and data modelling are essential to reduce the costs of the industrial projects. This paper reports the optimized workflow of soil stabilization through evaluated effects from the two factors controlling the development of strength: (1) the ratio between water and binder; (2) the proportions of different binders (cement/slag) were changed experimentally in a mixture of samples to evaluate the strength of soil. The experimental results show an optimal combination of 30% cement and 70% slag with a binder content of 120 kg/m3 and a maximum water binder ratio (w/b) of 5. Such proportions of mixture demonstrated effective soil stabilization both on a pilot test scale and on full scale for industrial works. The correlation between the compressive strength and relative deformation of specimens revealed that strength has the highest values for w/b = 5 and the lowest for w/b = 7. In case of high water content in soil and wet samples, the condition of a w/b ≤ 5 will require a higher amount of binder.

Pengaruh Binder Akrilik terhadap Sifat Fisik dan Mekanik Mortar Polimer

Initial damage to the structure occurs in the outer layers of the affected surface exposure to the peat environment and the static and dynamic movement of the structure. To prevent structural damage, the latest technological innovations are needed in the use of mortar constituent materials to increase the strength of the mortar. Polymer mortar is a composite material formed from a mixture of fine aggregates, cement, water and polymer binders or binders with a certain level. The purpose of this study is to determine the effect of the use of acrylic binders on the physical and mechanical properties of polymer mortars and the influence of peat water on the future of the mortar. The substitution of acrylic binders with water consists of 3 substitutions, namely 20%, 30% and 40% and 0% as controls. The results of the search for acrylic binders on the mortar mixture obtained a minimum physical property value at 30% acrylic use in the 28-day test, namely. The porosity value of the mortar is 9.80%, the waterabsorption value of the mortar is 4.67% and 4.72%, and the sorptivity value of the mortar is 0.70. From the value of physical properties obtained the degree of tightness of the polymer mortar well with the use of acrylic binders in the mixture. For the mechanical properties of polymer mortar, compressive strength testing is carried out with optimum compressive strength at the use of 30% acrylic. The value of the compressive strength of the mortar is 33 Mpa.

Preparation a High-Performance of Gangue-Based Geopolymer Backfill Material: Recipes Optimization Using the Taguchi Method.

The strip filling method in underground reservoir needs high strength to achieve the requirements of water storage. In order to address the challenges associated with costly and weak filling materials, this study aimed to develop an economically efficient and high-strength gangue-based geopolymer backfill material (GBGBM). To achieve this, the Taguchi method was employed to design a series of 25 experiments, each consisting of four factors and five levels. This study focused on investigating the effects of different gangue gradation levels, sand ratios, water binder ratios (w/b), and aggregate binder ratios (a/b) on the working characteristics and unconfined compressive strength (UCS) of the GBGBM. The optimal combination of the GBGBM was determined by employing a signal-to-noise ratio (S/N)-based extreme difference and variance analysis. The results revealed that the w/b ratio exerted the most substantial influence on both the slump and UCS. Specifically, when employing a gradation of 50%, a sand ratio of 55%, an a/b ratio of 2.5, and a w/b ratio of 0.64, the slump measured 251.2 mm, the UCS at 3d reached 5.27 MPa, and the UCS at 28d amounted to 17.65 MPa. These findings indicated a remarkable improvement in early UCS by 131.14% and the late UCS by 49.45% compared to gangue-based cement backfill material (GBCBM). Additionally, this study examined the hydration products and microstructures of both GBGBM and GBCBM using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) analyses. Significantly, the GBGBM exhibited notable advantages over the GBCBM, including a 78.16% reduction in CO2 emissions, a 73.45% decrease in energy consumption, and a 24.82% reduction in cost. These findings underscore the potential of GBGBM as a sustainable and cost-effective alternative to GBCBM.

Compressive Strength Prediction of BFRC Based on a Novel Hybrid Machine Learning Model

Basalt fiber-reinforced concrete (BFRC) represents a form of high-performance concrete. In structural design, a 28-day resting period is required to achieve compressive strength. This study extended an extreme gradient boosting tree (XGBoost) hybrid model by incorporating genetic algorithm (GA) optimization, named GA-XGBoost, for the projection of compressive strength (CS) on BFRC. GA optimization may reduce many debugging efforts and provide optimal parameter combinations for machine learning (ML) algorithms. The XGBoost is a powerful integrated learning algorithm with efficient, accurate, and scalable features. First, we created and provided a common dataset using test data on BFRC strength from the literature. We segmented and scaled this dataset to enhance the robustness of the ML model. Second, to better predict and evaluate the CS of BFRC, we simultaneously used five other regression models: XGBoost, random forest (RF), gradient-boosted decision tree (GBDT) regressor, AdaBoost, and support vector regression (SVR). The analysis results of test sets indicated that the correlation coefficient and mean absolute error were 0.9483 and 2.0564, respectively, when using the GA-XGBoost model. The GA-XGBoost model demonstrated superior performance, while the AdaBoost model exhibited the poorest performance. In addition, we verified the accuracy and feasibility of the GA-XGBoost model through SHAP analysis. The findings indicated that the water–binder ratio (W/B), fine aggregate (FA), and water–cement ratio (W/C) in BFRC were the variables that had the greatest effect on CS, while silica fume (SF) had the least effect on CS. The results demonstrated that GA-XGBoost exhibits exceptional accuracy in predicting the CS of BFRC, which offers a valuable reference for the engineering domain.

Comparative analysis of quaternary blended self-compacting concrete (QBSCC) mixes incorporating induction furnace slag (IFS) and crushed stone aggregate: A performance study

This study explores using Induction Furnace Slag (IFS) as aggregate in Quaternary Blended Self-Compacting Concrete (QBSCC) mixes. The experimental work consists of two stages. Stage I focuses on determining the optimal QBSCC mixes, aiming to develop environmentally friendly Self-Compacting Concrete (SCC) by utilizing different types and ratios of cementitious materials. A total of 27 QBSCC mixes were prepared with a reference SCC mix consisting of 100% ordinary Portland cement (OPC), are prepared considering water binder (w/b) ratio of 0.4. The quaternary blended mixes are created by combining OPC, class F Fly Ash (FA), Silica Fume (SF) and Ground Granulated Blast Furnace Slag (GGBFS). The replacement ranges for SF are set between 2.5% and 7.5% in increments of 2.5%, for FA between 10% and 20% in increments of 5%, and GGBFS between 30% and 50% in increments of 10%. In stage II, the optimized QBSCC mixes are further enhanced by incorporating IFS, the properties in the fresh state such as slump flow, V-funnel, L-box, and J-ring tests are conducted for all SCC mixes, all of which comply with the EFNARC guidelines. The mechanical characteristics studied, includes compressive strength (cube and cylinder), split tensile strength (at 3, 7, 28, and 56 days), flexural strength (at 28 and 56 days), elastic modulus, shear strength and pull-out bond strength (at 56 days) are evaluated. It is noted that the hardened properties of SCC mixes containing IFS exhibit slightly higher values compared to crushed stone aggregate SCC mixes. Furthermore, an increase in Supplementary Cementitious Material (SCM) content in QBSCC mixes leads to a decrease in the hardened properties, irrespective of the kind of aggregate used. The QBSCC mixes identified as SCC57.5/42.5, SCC52.5/47.5, and SCC47.5/52.5 are determined to be the preferred blends for producing Self-Compacting Concrete (SCC). Remarkably, Induction Furnace Slag (IFS) can be utilized as both fine and coarse aggregate, completely replacing conventional aggregates, regardless of the content of supplementary cementitious materials (SCM). This finding highlights the notable effectiveness of IFS as a replacement material in SCC production.

Effects of Superplasticizer and Water–Binder Ratio on Mechanical Properties of One-Part Alkali-Activated Geopolymer Concrete

This study presents an investigation of the mix proportion and mechanical properties of one-part alkali-activated geopolymer concrete (GPC). The procedure for determining the mix proportion of one-part alkali-activated GPC, which uses a solid alkali activator in crystal form, is proposed. The proposed procedure was applied to a series of mixed proportions of GPC with different amounts of solid crystalline alkali activator (AA), water (W), and superplasticizer (SP), using the ratio between them to the total amount of binder (B, fly ash, and granulated blast furnace slag) by weight in order to evaluate their effect on the workability and compressive strength of the GPC. The slump, compressive and tensile strength, and elastic modulus of the one-part alkali-activated GPC were tested in various ways. The test results showed that solid crystalline alkali activators, water, and superplasticizers have significant effects on both the workability and compressive strength of GPC. The amount of one-part alkali activator should not exceed 12.0% of the total binder amount by weight (AA/B = 0.12) in order not to lose the workability of GPC. The minimum W–B ratio should be at least 0.43 to ensure the workability of the sample when no superplasticizer is added. An amount of 2.5% can be considered as the upper bound when using superplasticizer-based polysilicate for GPC. In addition, the elastic modulus and various types of tensile strength values of the one-part alkali-activated GPC were evaluated and compared with that predicted from compressive strength using equations given by two common ACI and Eurocode2 codes for ordinary Portland cement (OPC) concrete. Modifications of the equations showing the relationships between splitting tensile strength and compressive strength, as well as between elastic modulus and compressive strength and the development of compressive strength under the time provided by ACI and Eurocode2 for OPC concrete, were also made for one-part alkali-activated GPC.

Rheology and setting time of saline cemented paste backfill

As many mines around the world are situated in freshwater-scarce regions and corporations are challenged to meet increasing sustainability and environmental responsibility standards, many mining operations are seeking to use locally available saline groundwater or ocean water as mixing water in cemented backfill. However, the implications of this decision on the rheological properties (which control the flow ability or transportability) and setting time of cemented backfill must be better comprehended to allow for a confident selection of this practical solution. Hence, the effects of mixing water salinity and binder type on the rheological properties and setting time of cement paste backfill (CPB) were investigated. Viscosity, yield stress, and setting time testing were conducted on CPB made with Portland cement type I (PC) and varying slag replacement quantities, silica tailings (ST), and mixing water with NaCl concentrations from 0 g/L to 300 g/L. Supplemental testing and analyses included pH determination, TG/DTG and XRD microstructure analyses, zeta potential measurements, and electrical conductivity monitoring. Results indicate that low NaCl concentrations (10 g/L − 35 g/L) in PC-CPB increased the yield stress above the control while higher concentrations (100 g/L − 300 g/L) decreased it. An increase in NaCl concentration led to slower increase in viscosity over the first two hours of curing. Low NaCl concentrations reduced the time to initial and final setting while high concentrations increased it. These behaviors were mainly due to the effects of the Na and Cl ions on the dissolution of the cement components, and on the changes in zeta potential due to chloride adsorption. Increases in slag replacement quantities on saline CPB had minimal effect on the yield stress during the first two hours after mixing but decreased the viscosity. All tested slag contents increased the time to initial setting, though a replacement content of 75% did not increase the initial setting time as much as lower quantities. A slag replacement content of 25% increased the final setting time, though higher contents decreased it. This behavior was due to the slower reaction rate of slag, combined with slag’s consumption of NaCl and CH and greater chloride binding capabilities. The results of this study will aid mines in designing more cost-effective and efficient backfill programs.

Study on the Sulfate Erosion Behavior of Cement-based Materials with Different Water-to-binder Ratios Containing Stone Powder in a Low-Temperature Saline Soil Area

To research the performance of low-temperature sulfate corrosion resistance of concrete mixed with stone-powder in saline soil area of Qinghai-Tibet Plateau. In this work, the influence of the water-to-binder ratio and stone powder types on the low-temperature sulfate erosion behavior of cement-based materials was studied, and in order to predict its erosion life, a Wiener stochastic process model was established. The results show the following: 1) The samples of limestone powder cement-based materials (LCBM) with different water-to-binder ratios showed the same law in sulfate erosion; the greater the water-to-binder ratio is, the more serious the sample is eroded, and the difference is the rate of erosion reaction. The greater the water-to-binder ratio is, the earlier the characteristic peak of thaumasite appears. The electric pulse accelerated erosion lifetimes of the cement-based limestone powder with water binder ratios of 0.3, 0.4 and 0.5 were 185 days, 136 days and 110 days, respectively. 2) Quartz stone powder cement-based materials (QCBM) showed different erosion laws compared with LCBM. When soaked in sulfate, the macroscopic and microscopic changes of QCBM were basically in a mineral additives state, However, when the electric pulse accelerated the erosion, the QCBM was more severely attacked than the LCBM. The final erosion products of the cement-based limestone powder with water binder ratios of 0.4 are not only gypsum and ettringite but also thaumasite, while the quartz powder cement-based materials with water-binder ratios of 0.4 are only gypsum and ettringite.