Cement Sand Research Articles

Engineering Properties of Television Plastic Shell Waste (TPSW) to Replace Part of Sand–Cement Mortar

Adding domestic waste into cement mortar or replacing fine aggregate can effectively reduce the use of natural sand and gravel and reduce carbon emissions, thereby preventing waste from polluting the Earth’s environment. This study explored a sustainable method for recycling television plastic shell waste (TPSW) by using it as a partial replacement for sand in cement mortar production. By evaluating water–cement ratios (0.4, 0.5, 0.6), ages (3, 7, 28, 56, 91 days), and TPSW levels (0%, 5%, 10%, 15%), this research assessed key properties, such as the slump, compressive strength, and durability. The results show that the TPSW absorbed less water than natural sand, increased the number of pores and slightly reduced the strength. However, a 5% substitution led to a minimal performance loss after 91 days, while it improved the sulfate resistance and resistivity. Overall, incorporating 5% TPSW reduces the environmental impact and carbon emissions, offering a sustainable solution for cement production.

Effect of bottom ash powder replacement rate, water cement ratio and sand cement ratio on alkali activated slag mortar

The main objective of this study is to clarify the effect of bottom ash (BA) powder replacement rate, water-cement ratio, and sand-cement ratio on alkali-activated slag mortar (AASM) by comprehensively investigating the following parameters: fluidity, consistency, setting time, pH, compressive strength, and flexural strength, as well as observing the microstructure by XRD and SEM. Finally, the relationship between the parameters was explored by means of correlation coefficient heatmaps in concert with scatter plots (including quadratic polynomial linear fitting). The results show that it is feasible to use up to 60% of BA powder to replace slag for AASM. Meanwhile, it is suggested that the AASM with a water-cement ratio of 0.44 and a sand-cement ratio of 2.6 can obtain better workability, mechanical properties, and a denser microstructure. The incorporation of BA powder produces the unique hydration product Magadiite. In addition, the mechanical models of compressive strength and flexural strength of AASM were proposed . This study provides a reference for the application of BA powder in the alkali-activated system, which is beneficial for resource recycling.

Analysis of Porosity-Water/Binder Index for Prediction of Strength and Stiffness of Cemented Sands: A Comparative Study.

Artificial sand cementation improves stability, stiffness, and mechanical strength, making it a critical process in geotechnical applications. This study analyzes the capability of the porosity-water/binding agent index (ηCw/Biv) to predict cemented sands' unconfined compressive strength (qu) and stiffness (Go). Four Colombian sands, i.e., Luruaco, Medellín, Lorica, and Bogotá (stabilized with Portland cement), and were compared with three Brazilian sands: i.e., Osorio, Porto Alegre, and Rio Pardo were evaluated, stabilized with combinations of carbide lime and glass powder, using varying binder contents and a curing period of seven days subjected to ultrasonic pulse velocity (UPV) tests and unconfined compressive strength (UCS) tests. The results indicate that incorporating water content into the index significantly enhances predictive accuracy, achieving R2 values above 0.94 for Colombian sands and considerably better fits for Brazilian sands than the traditional porosity/binder index. This new alternative provides an appropriate parameter for representing the small-strain stiffness and unconfined compressive strength of artificially cemented sands stabilized with various types of binders. Furthermore, the new index proved to be more effective in predicting the behavior of uniform and loose-graded sands, such as those from Bogotá and Lorica, which rely more heavily on binder volume and water content to achieve greater strength and stiffness. Lastly, the predictive model, validated against experimental results, achieved reliability indices (R2) of 0.9791 for stiffness and 0.9799 for strength prediction.

Enhancement of Air-Entrained Grout-Enriched Vibrated Cemented Sand, Gravel and Rock (GECSGR) for Improving Frost and Thawing Resistance in CSGR Dams.

Cemented Sand, Gravel, and Rock (CSGR) dams have traditionally used either Conventional Vibrated Concrete (CVC) or Grout-Enriched Roller Compacted Concrete (GERCC) for protective and seepage control layers in low- to medium-height dams. However, these methods are complex, prone to interference, and uneconomical due to significant differences in the expansion coefficient, elastic modulus, and hydration heat parameters among CSGR, CVC, and GERCC. This complexity complicates quality control during construction, leading to the development of Grout-Enriched Vibrated Cemented Sand, Gravel, and Rock (GECSGR) as an alternative. Despite its potential, GECSGR has limited use due to concerns about freeze-thaw resistance. This project addresses these concerns by developing an air-entrained GECSGR grout formulation and construction technique. The study follows a five-phase approach: mix proportioning of C1806 CSGR; optimization of the grout formulation; determination of grout addition rate; evaluation of small-scale lab samples of GECSGR; and field application. The results indicate that combining 8-12% of 223 kg/m3 cement grout with 2-2.23 kg/m3 of admixtures, mud content of 15%, a marsh time of 26-31 s. and a water/cement ratio of 0.5-0.6 with the C1806 parent CSGR mixture achieved a post-vibration in situ air content of 4-6%, excellent freeze-thaw resistance (F300: mass loss <5% or initial dynamic modulus ≥60%), and permeability resistance (W12: permeability coefficient of 0.13 × 10-10 m/s). The development of a 2-in-1 slurry addition and vibration equipment eliminated performance risks and enhanced efficiency in field applications, such as the conversion of the C1804 CSGR mixture into air-entrained GECSGR grade C9015W6F50 for the 2.76 km Qianwei protection dam. Economic analysis revealed that the unit cost of GECSGR production is 18.3% and 6.33% less than CVC and GERCC, respectively, marking a significant advancement in sustainable cement-based composite materials in the dam industry.

Experimental study on creep characteristics of cemented coal gangue backfill under uniaxial compression

ABSTRACT The uniaxial compression creep test is used to study the cemented coal gangue backfill body specimens with different cement-sand ratios (1:4,1:6,1:8, respectively). Through the processing and analysis of the creep curve, we discussed the influence of different cement-sand ratios, stress load and loading time on the strain, creep rate and long-term strength of the backfill body. These studies have revealed the creep law of the backfill body and obtained accurate conclusions. The results show that: (1) Different proportions of cemented coal gangue backfill body under the action of the set step by step axial loading stress, the strain is positively correlated with the change of loading stress. (2) With the increase of axial stress, the instantaneous deformation of cemented coal gangue backfill with three kinds of cement–sand ratio increases with the decrease of cement–sand ratio under the same axial stress. (3) With the increase of the axial stress of the three kinds of cement–sand ratio cemented coal gangue backfill body, the strain rate of the deceleration creep speed and the constant creep stage increases, and the duration of the deceleration creep stage increases. The average creep strain rate of the three kinds of cement–sand ratio cemented coal gangue backfill materials before entering the accelerated creep stage is determined. (4) Using an improved steady-state creep rate inflection point method, the long-term strength of three kinds of cement–sand ratio of cemented coal gangue backfill is determined, and it is concluded that the long-term strength decreases with the decrease of cement–sand ratio, which is positively correlated.

Sustainability assessment of granite cutting waste incorporated cement sand rendering mortar: Technical, environmental, cost, and social parameters

The literature statistics unmistakably highlight the critical need to enhance the construction industry's sustainability to lower environmental damage and conserve natural resources. This study aims to evaluate the life cycle performance of mortar by assessing its ecological impacts, economic performance, and social feasibility, alongside a thorough technical performance evaluation. The technical performance evaluation performed through physio-mechanical performance revealed that 20% natural sand replaced by granite cutting waste (GCW) is best suitable for rendering application. The compatibility of GCW as natural sand is advocated by SEM and FTIR analysis. The three pillars of sustainability are evaluated as life cycle environmental impacts assessment (LCIA), life cycle cost analysis (LCCA) and social feasibility assessment (SLCA). For LCIA purposes, nine environmental impact (EI) categories have been studied. For LCCA, raw material procurement, transportation, repair, and maintenance have been utilized to obtain the life cycle costing. Social LCA (SLCA) was performed qualitatively through a five-point Likert scale-based questionnaire survey, and responses from 125 stakeholders were analysed using mean item score (MIS). The finding revealed that for GP20 mortar, all the nine EI categories had shown 10–13% lower environmental impacts and 7.2% lower cost than the GP0 mortar mix. The SLCA, comprising five subcategories, i.e., access to material resources, social acceptance, employment creations, safe and healthy living conditions, and community engagement, has positively impacted society when 20% GCW is utilized in rendering mortar as sand. The consolidated index calculation with higher ECM values for the GP20 mortar mix strongly endorsed a sustainable and viable alternative.

Study on Crushed-Stone Cementation Properties and Bottom Stope Stability of Goaf by Open Stope Mining in Inclined Ore Bodies

The mining of the part of the inclined ore body below a goaf is crucial for improving resource extraction and safe production. In this study, the cementation properties of crushed stone during the mining of the inclined ore body were investigated by means of laboratory experiments, theoretical analysis, and numerical simulation. Additionally, orthogonal experiments were performed to assess how factors like water–cement ratio, crushed-stone particle size, and cement–sand ratio affect the strength of the grouting concretion body (GCB). Furthermore, the fluidity of the slurry under different ratios was also measured. Considering both the fluidity of the slurry and the strength of the GCB, the optimal ratios of the slurry were determined to be a water–cement ratio of 2.5:1 and a cement–sand ratio of 1:4. This ratio was then used for crushed-stone cementing under the poorest crushed-stone particle size conditions, based on which mechanical parameters were obtained from experiments. Theoretical analysis equated the problem of the grouting range to the width of the plastic zone of surrounding rock, and a conclusion was reached that the width of the GCB should be at least 29 m. The numerical simulation results reveal that among 30 mining rooms formed below the GCB, 24 mining rooms are in a stable state and 6 mining rooms are partially damaged on a small scale. As a whole, the GCB formed by grout filling into the goaf manages to effectively support the stope below, and it is verified that the theoretical calculation method of the width of the GCB is feasible.

Microstructural Analysis of the Effect of Using Nano-silica on the Mechanical Properties of Cement–Sand Mortar Under the Effect of Heat

The performance of cement-based materials depends on the characteristics of solid particles at the nano-scale or nanometer porosities in the interfacial transition zone between cement particles and aggregate. Heat significantly affects the properties of these particles and the connection between them. Accordingly, the present study seeks to investigate the effect of nano-silica on the strength parameters of sand–cement mortar at high temperatures. In this regard, the sand–cement mortar was prepared by replacing 5, 10, and 15 percent of cement with nano-silica. The specimens were subjected to temperatures of 25, 100, 200, 400, 600, and 800 °C after curing at the ages of 3, 28, and 90 days. The effect of high temperatures on the physical and mechanical properties of sand–cement mortar was analyzed using macro-structural tests of compressive strength, loss in weight, and water absorption, and microstructural tests of X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that the macro-structural behavior of sand–cement mortar highly depends on the microstructure and changes in cement nanostructures during heat treatment. Primary portlandite and C–S–H nanostructure were destroyed at 600 °C, and alite, belite, and β-wollastonite were formed at 800 °C. Adding nano-silica improved the strength properties of sand–cement mortar against heat, so the compressive strength of 28-day specimens containing 15% nano-silica increased from 13.9 to 19.2 MPa at a temperature of 800 °C.

Shotcreting with Cement–Sand Mixtures Under the Influence of an Electrostatic Field

One of the primary and still unresolved problems of shotcreting is the high rebound rate of the material, which reaches over 20% in “dry” shotcreting. There is a practical need to improve the very principle of shotcreting and methods for optimizing the movement of torch particles. Materials and Methods: The purpose of this study was to justify the use of the electrostatic treatment of cement–sand mortar in the process of performing shotcreting works using the dry method. It was proposed that the binder and then the finished mixture be ionized step-by-step (by passing it through a non-uniform electrostatic field formed by corona electrodes). As a result, the shotcrete will be held on the fence. Results: Analysis of the modeling results shows that the presence of an electrostatic field slows down the particle and reduces the kinetic energy of the rebound. After theoretical calculations, experiments were conducted, during which, the torch size and the plant productivity were changed, and the rebound mass was weighed. After application to the surface, prototypes were formed and subjected to strength tests. It was determined that gunning in a sharply non-uniform electric field demonstrates its practical and economic efficiency due to the uniform deposition of charged particles on the treated surface and low power consumption. Conclusions: It was established that the electrostatic treatment of a cement–sand mixture during application allows concrete particles to be retained on the shotcrete surface, the rebound of the material to be reduced and the strength of concrete to be increased.

Effects of seawater on properties of bentonite cut-off walls with/without cement addition

Bentonite-based cut-off walls have been widely used to protect coastal areas against seawater intrusion. However, salts contained in coastal soils affect the properties of bentonite cut-off walls, and the interactions between seawater and bentonite minerals with or without cement remain unclear. The aim of this study was therefore to evaluate the effects of seawater on the workability, strength and permeability of bentonite-based mixtures, prepared using three types of bentonite (sodium, calcium and seawater bentonite). The underlying mechanisms were further investigated through Atterberg limits, mineralogical and microstructural analyses. The results showed that cation exchange between seawater and bentonite leads to alterations in montmorillonite type and particle arrangement. This leads to a significantly reduced liquid limit and a slightly decreased plastic limit of bentonite, therefore narrowing the range of workable water content for bentonite–sand mixtures. Compared with sodium/calcium bentonite, seawater bentonite was less impacted by seawater, but showed a larger increment in workability after cement addition due to palygorskite dissolution. Under similar workability, the bentonite–sand–cement mixture with calcium bentonite yielded the highest strength and the lowest permeability. These findings illustrate correlations between bentonite mineral alterations and the properties of bentonite–sand mixtures with or without cement, and offer guidance for the construction of cut-off walls in coastal regions.

Mechanical properties of aeolian sand cemented via microbially induced calcite precipitation (MICP)

The cementation of desert aeolian sand is a key method to control land desertification and dust storms, so an economical, green and durable process to reach the binding between sand grains needs to be searched. The method based on the microbially induced calcite precipitation (MICP) appeared in recent years as a promising process that proved its efficiency. The feasibility of the MICP technique to treat aeolian sand composed by low clay content, fine particles, low water content and characterized by weak permeability was demonstrated in the present paper. The effects of initial dry density, cementation number and curing time on the permeability and strength of MICP-treated aeolian sand were investigated using permeability tests and unconfined compressive strength (UCS) tests. The microstructure of aeolian sand was observed by scanning electron microscopy (SEM) tests and X-ray diffraction (XRD), aiming to reveal the solidification principle of MICP. The tests result indicated that when the initial dry density and the cementation number rose, the hydraulic conductivity of aeolian sand decreased while the mechanical strength given by UCS values improved. When the initial dry density was 1.65 g/cm3, the curing time was 3 h and the cementation number reached 20, the hydraulic conductivity and UCS reached 0.00151 cm/s and 1050.30 kPa, respectively. With increasing curing time, the hydraulic conductivity first decreased, followed by an increase, while the UCS exhibited an up and then a downtrend. Furthermore, the correlation between UCS values and the CaCO3 content reached a high R2 value equal to 0.912, which confirmed that the cementation occurred in sandy material and governed the soil strengthening. Indeed, the calcium carbonate crystals observed by SEM and XRD enhanced the friction between particles when they wrapped around the sand grains surface, while carbonates reduced the soil permeability when filling the pores and sticking the sand particles together. Finally, the theoretical and scientific knowledge brought by the present study should help in managing sand in desert areas.

On the Initial Fabric of Naturally Occurring and Reconstituted Weakly Cemented Geomaterials

The understanding of naturally occurring materials such as clay, sand, hard and soft rocks under a common theoretical framework has been a topic of persistent research interest. Over the past few decades, various sample reconstitution techniques have been developed in the literature to mimic in situ conditions, and to parse carefully the influence of various components in a cohesive-frictional geomaterial such that their behavior can be folded into the broad ambit of a continuum mechanics framework. The initial fabric of natural rock specimens is compared with reconstituted cemented sand samples using X-ray computed tomography (XRCT) scans. The efficacy of laboratory reconstitution techniques in replicating the initial microstructural features of natural rocks is evaluated here. Additionally, discrete element method (DEM) protocols which are often employed in generating cohesive granular ensembles are employed here and compared against the naturally occurring and artificially reconstituted fabric. A significant difference is observed in the grain boundaries of reconstituted and naturally occurring rocks. Additionally, the arrangement of particles, the orientation of grain contacts, and their coordination number are examined to assess the efficacy of laboratory-reconstituted specimens at micro-length scale.

Compressive Strength Characteristics of Compressed Stabilized Earth Block (CSEB) Units and Walls

This paper is mainly focused on compressive strength behavior of Compressed Stabilized Earth Block (CSEB) units and CSEB walls. Compressed Stabilized Earth Block (CSEB) is a rectangular block used in wall construction. The ingredients of CSEB are soil, cement, fine aggregate, crusher dust, and a small amount of water. These blocks have less energy consumption and carbon emission, and they provide improved thermal insulation. In addition, they use local resources and disseminate appealing aesthetics with elegant profile and uniform size. Due to these advantages CSEB can be used as a green construction material. This research aims to study the strength characteristics of CSEB wall in compression and evaluate the suitability of CSEB walls as load bearing walls in structures. This research studies physical and mechanical characteristics of CSEB units made from red residual soil of Lele (Lalitpur) with 8% cement for stabilization. This paper discusses the compressive strength behavior of walls constructed of size 0.660m x 1.100m x 0.220m using CSEB units in cement sand mortar and stabilized mud mortar separately which were tested after 28 days. The experimental values after laboratory testing of CSEB masonry wall with height to thickness ratio 5:1 for cement sand mortar (1:6) and stabilized mud mortar (stabilized with 8% cement and 16% extra sand) separately are compared with relevant values from different codes. Results obtained from compressive strength tests of masonry walls constructed in the laboratory and those values from different codes concerning the strength of masonry unit and mortar are compared and found to be in agreement. The comparison of laboratory results with codal provisions of design of masonry walls illustrate that CSEB masonry walls can be designed in the similar way as brick masonry walls.

Study on Freeze–Thaw Resistance of Cement Concrete with Manufactured Sand Based on BP Neural Network

In this study, experiments were conducted on the freeze–thaw performance of manufactured sand cement concrete with different sand ratios and fly ash contents. The research found that during 200 freeze–thaw cycles, as the fly ash content increased, the concrete exhibited a higher mass loss rate and a decline in the relative dynamic modulus of elasticity. This was due to the lower activity of SiO2 and Al2O3 in the fly ash, which reduced the hydration products. Incorporating an optimal amount of manufactured sand can increase the density of concrete, thereby improving its resistance to freeze–thaw cycles. However, when the content of manufactured sand was high, its large surface area could interfere with the hydration process and reduce strength, thereby diminishing the freeze–thaw resistance of the concrete. Given that studying the freeze–thaw resistance of manufactured sand concrete is time-consuming and influenced by many factors, a prediction model based on a BP (back propagation) neural network was developed to estimate the mass loss rate and the relative dynamic modulus of elasticity following freeze–thaw cycles. After validation, the model was found to be highly reliable and could serve as a foundation for mix design decisions and freeze–thaw performance prediction of manufactured sand cement concrete.

Effect of middle stud on ultimate strength and behavior factor of brick masonry shear wall in cold formed steel frame

AbstractLightweight steel framing is one of the modern construction technology systems. This system is mostly used for low to mid-rise buildings. The lightweight steel framing system has many advantages, including lightness, ease of installation, high execution speed, and being more cost-efficient. Since the manufacturers of cold formed steel frames use bricks in an unprincipled way to cover these structures and because of less laboratory research in this regard, in the present research to principled use of this structure, the effect of the middle stud was evaluated on seismic behavior of brick shear wall in cold formed steel frame with brick face. For this purpose, four cold formed steel frames were made in two different configurations (without middle stud and with middle stud) using cement sand mortar, wire mesh, and brick shear walls. Based on the results, the middle stud would cause weakness in the permissible deformation of the brick walls, and in shear walls without middle stud, deformations occur along with the acquisition of resistance to larger deformations. Accordingly, the presence of the middle stud increases the average shear strength by 30%, and this increase in resistance causes a decrease in the behavior factor and ductility of the walls, which practically indicates the seismic behavior of the frames with the middle stud.

Mechanical performance study of PVA fiber-reinforced seawater and sea sand cement-based composite materials

Due to the swift progress in the construction sector, there is a global concern about the potential scarcity of river sand and freshwater resources. The development of new construction materials is considered an inevitable trend for industry growth. PVA fibers, known for their strong corrosion resistance, cost-effectiveness, and high toughness, have the potential to enhance the corrosion resistance and seismic performance of structures in marine environments. However, their mechanical properties and durability in the seawater and sea sand environment are not well understood. Therefore, the investigation of the impact of seawater and sea sand on the mechanical properties and durability of PVA fiber-reinforced cement composites is considered crucial. A mechanical performance analysis of PVA fiber-reinforced seawater and sea sand fiber cement composites was conducted in this study. PVA fiber volume fractions of 0%, 0.75%, and 1.5%, cement composite matrix strength grades of C30 and C50, and curing periods of 28 days, 90 days, and 180 days were examined, investigating their influence on the bending toughness of PVA fiber-reinforced seawater and sea sand cement composites. Specific conclusions include the addition of fibers increased the peak bending load, had a less corrosive effect in seawater, and improved the flexural toughness of the material. The most significant improvement was observed at 1.5% fiber content, where the load-deflection curve was fuller and the energy absorption capacity of the material increased by 33–109%, maintaining good bending toughness. Furthermore, higher fiber contents are required for high-strength cementitious composites to improve flexural toughness and durability. The formulation of calculation formulas for predicting bending strength and corresponding deflection, which fit well with the experimental results; and the development of a calculation model for the bending toughness index of PVA fiber-reinforced seawater and sea sand cement composites, providing an effective prediction of material bending toughness.

Tension Capacity of Crushed Limestone-Cement Grout.

The feasibility of using crushed limestone instead of sand in cement grout is examined in this work. This study entails performing several tests, including the Brazilian test, the compressive strength test, and the stress-strain correlation test. The curing times used were 7, 14, and 28 days for mixtures with various proportions of cement to limestone (1:1, 1:2, and 1:4). The conventional sand-cement grout laboratory tests were prepared using a similar methodology to examine the effectiveness of the suggested substitute. The findings show that the limestone-based grout has sufficient strength, but that it is less than that of the typical sand material. The values of the tensile strength and elastic modulus were determined. A focus was made on the tensile strength and stress-strain relationship. A special laboratory set-up was used to look at the progress of failure using strain gauges fitted to the cylindrical samples both vertically and horizontally. The angular shape of the particles' ability to interlock is responsible for the material's increase in strength. According to this study, crushed limestone can be used as a substitute for sand in circumstances where sand supply is constrained. The suggested grout can be used in the shotcrete of tunnels and rock surfaces.

Microbially induced calcium carbonate precipitation to combat desertification: A field application experiment

Combating desertification and recovering vegetation can help resolve global ecological problems. Microbially induced calcium carbonate precipitation is a natural and widespread phenomenon that has been a green and efficient approach for environmental issues. However, long-term field experiments are lacking and microbially induced calcium carbonate precipitation biological routes for desert restoration is unclear. Therefore, we investigated soil wind erosion resistance and soil characteristics via mixed methodology involving field and laboratory experiments and revealed the biological route. Our objective was to evaluate sand fixation efficiency and clarify the biological route. Results demonstrated that (1) microbially induced calcium carbonate precipitation produced sand cement, increased soil hardness, and changed soil characteristics. (2) Compared with CK, 25%, 50% and 75% treatments (MICP treatment from low to high concentration) reduced soil loss by 34.93%, 31.62% and 51.93%, respectively, and wind erosion decreased by 69.09%–77.27% at highest wind speed. (3) The 75% treatment had the greatest effect on wind erosion resistance. (4) Microbial activity changes the mechanism of wind erosion which meteorological effects change from direct to indirect after treatment. These results can address challenges and overcome the natural disadvantages of microbially induced calcium carbonate precipitation and contribute to technologies for combating desertification using soil microbial approaches.

Experimental study on the road performance of molybdenum tailings sand stabilized with cement and fly ash

The large accumulation of molybdenum tailings (MoT) has resulted in a series of hazards, including environmental pollution, damage to water resources, and increased risk of geological disasters. This study employs ordinary Portland cement (OPC) and fly ash (FA) stabilization of MoT sand and seeks the optimal mix ratio through experimentation. The strength properties of MoT sand stabilized with different proportions of OPC and FA are studied and analyzed through unconfined compressive strength tests, splitting tensile strength tests, and splitting rebound modulus tests. Additionally, the microstructure of MoT sand stabilized with OPC and FA is analyzed using scanning electron microscopy (SEM). The results indicate that with an increase in OPC content, the compressive strength, splitting tensile strength, and splitting rebound modulus all increase. With an increase in FA content, the compressive strength gradually increases, while the splitting tensile strength and splitting rebound modulus show a trend of initially increasing and then decreasing. The results show that the optimal mix proportion for OPC and FA-stabilized MoT sand is 7 % OPC content and 15 % FA content. This mixture is suitable for a heavy traffic base of expressways and class I highways, as well as for an extra heavy traffic base of class II and below highways. The research results can provide reference for using OPC and FA stabilized MoT sand as roadbed material.

Experimental Study for the Matching of Explosives and Rocks Based on Rock Hydrophysical Properties

The study of the hydrophysical properties of rocks is indispensable for the development of hydraulic engineering, especially for blasting operations in water. Reasonable matching between explosives and rocks increases the utilization of explosive energy and improves the blasting performances. Based on the energy law in the rock blasting process, the matching relationship between explosives and rock is studied by combining experimental and theoretical methods for the hydrophysical properties of the rock itself. Firstly, the theoretical solutions for crushing-zone energy, fragmentation energy and fragment-throwing energy are derived. Subsequently, concrete blocks are prepared with four types of cement–sand ratios, and four types of emulsion explosives are used to carry out single-hole blasting tests in which a high-speed camera is used to capture the trajectory of the blasting fragments that are later collected. Finally, the crushing energy, fracturing energy and fragment-throwing energy are calculated according to the test results and the basic parameters of the used explosives and concrete models. The results show that the size and distribution pattern of blasting blocks are significantly affected by the hydrophysical properties of concrete and explosive properties; the higher the energy consumption in the rupture zone, the smaller the size of the fragments and the more uniform the distribution. Moreover, the median utilization efficiency of explosive energy on rock breaking is 26.4%, the energy consumption in the crushing zone is approximately 8.4%, that in the rupture zone is approximately 10.9%, and that in the throwing energy of fragments accounts for approximately 7.1%. It is also found that the traditional wave impedance matching theory fails to obtain the best explosive energy utilization. On the contrary, the concrete specimen had the best fracturing effect and the highest energy utilization of 30.77% when the impedance ratio of concrete to explosives is 1.479.