Strength Of Slurry Research Articles

Experimental Study on Influencing Factors of Mixing Solidification Strength of Marine Soft Soil

It is a common problem that the soft soil solidified strength by mixing is low. In order to search for the sensitive factors that affect the solidified strength, a certain marine soft soil is taken as an object, four influencing factors, such as solidified material and its dosage, mixing uniformity, water-cement ratio and curing environment, were selected for experimental study, the results show that: (1) the effect of the curing material and its content on the curing strength is obvious: the curing agent of HR soft clay is 183-212% of the cement curing strength, and the curing strength of the same kind of curing material with 20% is 25-44% higher than that of 15%. 2 mixing uniformity has a significant effect on the curing strength: the curing strength of slurry and soft soil after mixing for 1 minute is very different, and the average strength is only 10% of the full mixing strength. The average strength of the three-minute-agitation was 49-50% of the full-agitation strength, while the average strength of the six-minute-agitation strength was 92-93% of the full-agitation strength. 3 the effect of water-cement ratio on the curing strength is obvious: the curing strength decreases by 24-47% when the water-cement ratio is 1.0 vs 0.6, and by 75-80% when the water-cement ratio is 3.0 vs 0.6. 4 curing environment has obvious influence on curing strength: compared with standard curing condition, curing strength of low temperature curing condition is reduced by 52-57%. This study has important guiding significance for soft soil foundation treatment and solidified soil based on soft soil.

Mixture optimization for mechanical, environmental, and economic objectives in grouting slurry for repairing earthen sites

Anchor and fissure grouting are used to repair earthen sites. However, the common method to obtain the compressive strength of grouting slurry would cause material, labor, and time losses. In addition the material properties, environmental and economic benefits have gained increasing attention. This study proposes a design framework for multi-objective proportioning optimization based on machine learning and metaheuristics. The results indicated that the eXtreme Gradient Boosting (XGBoost) model, whose hyper-parameters were optimized by a genetic algorithm, can accurately predicted the compressive strength of the slurries. The impact of the variables on development of compressive strength can explain the internal reaction mechanisms. The analytical framework based on meta-heuristic and technique for order of preference by similarity to an ideal solution (TOPSIS) provided Pareto-optimal solutions in design scenario of each sub-dataset. The framework proposed in this study can efficiently achieve mechanical, environmental, and economic design objectives of anchor grouting and fissure grouting slurries for repairing earthen sites.

Experimental study on the influence of content and fineness of fly ash on the mechanical properties of grouting slurries

AbstractExcavation gaps around the front shield can be generated during shield construction, resulting in significant ground settlement. Traditional synchronous grouting slurries are unsuitable for filling these gaps during tunneling under existing subway lines. To address this issue, experiments are conducted on mix characteristics and hardening properties of slurries with variations in fineness and contents of fly ash. The experimental and computed tomography scan results yield the following findings: (1) fly ash with high fineness can effectively reduce the early strength of slurries and enhance their injectability. This improves the filling effect on micropores in the slurry and ultimately enhances the final hardening strength. (2) Fineness of fly ash controls the process of slurry hydration. The higher the fineness of fly ash, the more visible the exothermic hydration of slurry and the earlier the highest temperature peak appears. (3) Fly ash with high fineness can effectively increase the density and consolidation rate of slurries, resulting in greater improvement in slurry strength, particularly when the ratio of fly ash to cement (mf/mc) is 0.75. (4) Fly ash with high fineness can effectively decrease the likelihood of appearance of pores in the slurry, optimize the pore structure, and enhance the strength of slurries after consolidation.

Research on the strength prediction for pervious concrete based on design porosity and water-to-cement ratio

Abstract The strength prediction of pervious concrete is hard to implement for the mix design due to the porous structure. This work studied the influence of the water-to-cement ratio on the fluidity, viscosity, and mechanical properties of cement paste. Then, the porosity, permeability, and compressive strength of the pervious concrete with various porosities were investigated, and the test results were fitted and analyzed. The result indicates that as the water-to-cement ratio increases, the viscosity of the cement paste reduces and the fluidity increases. The water-to-cement ratio has a negative linear relationship with net slurry strength. The porosity and permeability of pervious concrete fluctuate in accordance with the same rule as the water-to-cement ratio changes. The compressive strength of pervious concrete with varying design porosities increases initially, then declines as the water-to-cement ratio rises. According to the linear fitting analysis, when the water-to-cement ratio is constant, the permeability and compressive strength of pervious concrete have a positive and negative linear relationship with the design porosity, respectively. By analyzing the fitting results and combining the volume method of pervious concrete, a calculation method for mix proportion design is proposed to predict the strength of pervious concrete.

Hydration and degradation mechanism of sodium hexametaphosphate chemically bonded material under CO2 sequestration

CCUS (Carbon Capture Utilization and Storage) technology is considered the most economical and feasible technology to significantly reduce CO2 emissions. The sealing integrity, especially degradation resistance, of cementing cement sheaths in CO2 sequestration wells plays an essential role in the efficient and long-term safe storage of CO2. This work applied various analytical methods to study the phosphate chemically bonded materials prepared by incorporating different dosages of phosphate into high alumina cement at 50 °C. Results show that the maximum slurry strength was achieved at the sodium hexametaphosphate dosage of 3%. The higher dosage of sodium hexametaphosphate generated more C-A-P-H gel phases in the cement matrix. The increase of capillary force caused by C-A-P-H gel during degradation will cause the cement stone to change from passive intrusion of CO2 to spontaneous imbibition, which deepens the intrusion of CO2. However, the C-A-P-H gel does not participate in the degradation reaction and prevents the degradation of the hydration products by CO2, thus not causing a reduction in the mechanical strength of the cement stone.

Experimental Study on the Strength and Hydration Products of Cement Mortar with Hybrid Recycled Powders Based Industrial-Construction Residue Cement Stabilization of Crushed Aggregate.

The strength-formation mechanism for industrial-construction residue cement stabilization of crushed aggregate (IRCSCA) is not clear. To expand the application range for recycled micro-powders in road engineering, the dosages of eco-friendly hybrid recycled powders (HRPs) with different proportions of RBP and RCP affecting the strengths of cement-fly ash mortar at different ages, and the strength-formation mechanism, were studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the early strength of the mortar was 2.62 times higher than that of the reference specimen when a 3/2 mass ratio of brick powder and concrete powder was mixed to form the HRP and replace some of the cement. With increasing HRP content substituted for fly ash, the strength of the cement mortar first increased and then decreased. When the HRP content was 35%, the compressive strength of the mortar was 1.56 times higher than that of the reference specimen, and the flexural strength was 1.51 times higher; XRD and SEM studies of the hydrated cement mixed with HRP showed that the amount of CH in the cement paste was reduced by the pozzolanic reaction of HRP at later hydration ages, and it was very useful in improving the compactness of the mortar. The XRD spectrum of the cement paste made with HRP indicated that the CH crystal plane orientation index R, with a diffraction angle peak of approximately 34.0, was consistent with the cement slurry strength evolution law, and this research provides a reference for the application of HRP to produce IRCSCA.

Evaluation of Concrete Abrasion Using Traditional and High-Speed Underwater Methods

With the increasing height of new dams, the number of high-water-head and high-flow spillway buildings is gradually increasing, and concretes are required to have better abrasion resistance. Current standards offer a method for evaluating the abrasion resistance of concrete, but when evaluating the abrasion resistance of high-performance concretes, it is necessary to extend the test time to more than 120 h. In this study, an improved way of the current code-specified underwater method was proposed to shorten the testing time, called the high-speed underwater method (HSUM), and the test results of the two methods were evaluated using three-dimensional (3D) laser-scanning technology. It was found that the abrasion efficiency of the HSUM was about twice as much as that of the code-specified method. HSUM resulted in a significant acceleration of the concrete coarse aggregate abrasion process. The average abrasion depth of concrete was between 0 and 6.5 mm (HSUM after 15 h and code method after 30 h), and the abrasion mainly occurred on the surface of slurry, when the abrasion resistance of concrete was obviously affected by the strength and volume of slurry. When the average abrasion depth of concrete exceeded 6.5 mm, it entered the aggregate abrasion stage, and its abrasion resistance was influenced by the aggregate hardness and aggregate content, and the correlation with the slurry strength decreases. The surface roughness parameters Sq and Sa of HSUM concrete increase significantly compared with the code method. HSUM allows for a reduction in experimental time and high performance in evaluating the abrasion resistance of high-performance concretes or concretes with special aggregates (high-strength granite aggregates and cast stone aggregates).

Experimental research on the performance of a Novel Geo-filament anchor for an Earthen architectural site

At present, most studies of anchorage techniques for earthen architecture ruins are conducted so as to improve the anchor force, however, the damage caused to the ruins by anchor reinforcement has not been fully considered in practice and no special anchor technique has been applied to reinforce the small sliding mass. This paper summarizes the application and R&D of anchor rod techniques as applied to the protection of the Gaochang Ruins, Turpan, in China. Based on the reinforcement of the small sliding mass of the earthen historical ramparts, a new type of Geotechnical Filament Anchor (GFA) is designed. By changing six parameters, including anchorage length (L), GF thickness (H), bore diameter (D), slurry strength (S), GFA surface state (R) and inclination Angle (A), the tensile strength, failure mode, load displacement (P-S) relationship and strain (ζ-L) distribution characteristics are studied, and corresponding analysis is performed on the test data and phenomena. (1) A formula for the design value of the anchorage force N is presented. (2) Combining the data on the strain distribution at the GF-slurry interface under the action of N, the shear stress distribution model of the anchorage system is obtained. (3) Taking into account the soil mechanical properties of the above-mentioned ruins, the shear stress diffusion coefficient (α) is conceptualized, the formula for the shear strength of the grouting material is obtained, and the allowable ranges of L, D, H, R, and S determined. A new design is proposed for the application of anchorage techniques to earthen ruins in the context of protection of cultural relics, which promotes the design and calculation method described in this paper.

Study of the Effect of Grouting Material Strength on Semiflexible Pavement Material

In this study, cement mortars with different strengths are poured into the large void matrix asphalt macadam material as a semiflexible pavement (SFP) material and the experimental research is carried out. The current research on SFP is mainly focused on the performance of grouting materials and the influence of grouting matrix materials on the overall mechanical properties of SFP and road performance. However, there are some flaws in the study of the influence of grouting material strength on the performance of SFP materials: the difference between the strengths of the selected grouting materials is relatively small, and in some studies, the chosen grouting material strength is low, which leads to insignificant improvements of SFP material performance; besides, the research indicators are also not very comprehensive. In this study, cement grouting asphalt macadam materials are selected as the research object to examine the effect of grouting material strength on the mechanical properties and road performance of SFP materials. Grouting materials with strengths of 19.8 MPa, 30.7 MPa, and 40.2 MPa were poured into the matrix asphalt macadam with a target void ratio of 24% and asphalt content of 2.9% to prepare the corresponding SFP test specimens. The SFP specimens were then subjected to the compressive test, flexural and tensile test, high-temperature stability test, and low-temperature crack resistance test, and the compressive resilient modulus was measured, thereby analyzing the effect of the cement slurry strength on the cement grouting asphalt macadam materials. The results show that when the strength of the cement mortar is 19.8 MPa, 30.7 MPa, and 40.2 MPa, the corresponding SFP material has better mechanical properties. When the strength of the grouting material is 40.2 MPa, the compressive strength of the SFP material is about the same as that of the grouting material. The strength is more than double that of 19.8 MPa and 30.7 MPa, and the flexural tensile strength and elastic modulus also have the above growth laws. The low-temperature crack resistance and high-temperature stability of the SFP material are enhanced with the increase in the strength of the grouting material. When the strength of the grouting material is 40.2 MPa, the mechanical properties and road performance of the SFP material are relatively better. This study provides a reference for strengthening the mechanical properties of SFP materials and boosting the crack resistance of SFP.

Experimental study of the relationship between bond strength of aggregates interface and microhardness of ITZ in concrete

• A research on the acquisition of macro-mechanical data of the ITZ in the meso-mechanical calculation of concrete. • The mechanical properties of the ITZ with different mix ratios were measured, the relationship between the bond strength and the microhardness of the ITZ in concrete is established. • A two-parameter linear relationship between the splitting tensile strength of the interface bond and the age and the W/B ratio was established. • The priority order of the calculated value of the interface strength in the numerical analysis of concrete meso-mechanics is proposed. The problem of taking macro-mechanical data of the interface between aggregates and slurry in the calculation of meso-mechanics of concrete was studied in this paper. Through a systematic standard interface test study where the interfacial bond splitting tensile strength method and the interfacial transition zone (ITZ) microhardness method were used, mechanical properties were investigated at macro-scale (bond strength), and followed by ITZ microhardness at meso-scale, moreover the relationships between macro- and meso-mechanical properties were established. The results show that interfacial bond splitting strength of aggregates-slurry gradually increases with increasing hydration age and decreases with increasing water-binder ratio; the ITZ thickness decreases and the ITZ microhardness valley value increases with the extension of curing age. There is a certain correlation between macro-scale mechanical strength of interface and meso-scale mechanics of ITZ. There is a significant linear relationship between the splitting tensile strength of the interface bond and the splitting tensile strength of the cement slurry, so the interface strength can be calculated according to the splitting tensile strength of the slurry substrate. The interfacial bond splitting tensile strength and ITZ microhardness valley have different degrees of correlation. The interfacial bond splitting tensile strength has a particularly significant linear relationship with the microhardness value of the cement paste substrate. Therefore, the calculation value of the interface strength in the numerical analysis of concrete micromechanics should preferably adopt the linear relationship formula with the microhardness of the cement paste substrate.

Influence of Paste Strength on the Strength of Expanded Polystyrene (EPS) Concrete with Different Densities.

Concrete in which EPS (expanded polystyrene) particles partially or completely replace concrete aggregates is called EPS concrete. Compared to traditional concrete, EPS concrete has a controllable low density and good thermal-insulation performance, which make it promising for prospective applications. At present, research on EPS concrete mostly focuses on increasing its strength and EPS surface modifications. Few researchers have studied the influence of cementitious material strength and EPS-concrete density on the strength of EPS concrete. In this research, cement was used as the main material, and fly ash, silica fumes, and blast furnace slag were selected as admixtures. By changing the mixing proportions of the admixtures, the basic properties, such as the paste strength, change. Based on the mix proportions of the above different raw materials, EPS concrete with different density levels was prepared to explore the influence of the density of EPS concrete and the strength of cementitious materials on the strength of EPS concrete. The influence of the slurry strength on EPS-concrete strength was weaker than that of the density of EPS concrete. When the strength range of the cementitious materials is 35.7~70.5 MPa, the compressive strength range of 1000 kg/m3, 1200 kg/m3, and 1400 kg/m3 EPS concrete is 8.8~17.6 MPa, 11.4~18.0 MPa, and 15.7~26.6 MPa, respectively. Based on the experiments, the fitting equation to determine the EPS-concrete strength–EPS-concrete density–cementitious material strength is z = 69.00087 + 0.0244x − 0.1746y − 0.00189x2 + 0.0000504706y2 + 0.00028401xy. Additionally, a strength-increasing design method for EPS concrete with different densities prepared by conventional Portland cement is clarified. This study can guide the preparation of EPS concrete.

Study on Application of Recycled Red Brick Aggregate to Concrete Block

Construction waste in Our country has a good recycling system, can carry out the production of various recycled building materials. In order to understand the availability of red brick in construction waste, the effect of the content of red brick in recycled aggregate on the physical properties and strength of recycled concrete is discussed to explore whether recycled concrete containing red brick is suitable for application in masonry blocks. The results show that there is no significant correlation between the content of red brick and the compressive strength of recycled concrete, while the slurry strength is positively correlated with the compressive strength of recycled concrete. The strength of recycled concrete can be improved by reducing the water-cement ratio. However, reducing the water-cement ratio will reduce the workability of concrete, which needs to be compensated by adding water-reducing agent. According to the experimental results of unit weight, water absorption, ultrasonic wave velocity and resistance properties of recycled concrete, the content of red brick can improve the porosity of recycled concrete and have a negative effect on durability. The overall experimental results are verified by the relevant specifications, and the recycled concrete containing red brick is suitable for class N block and meets the relevant requirements of the specifications.

Risk Assessment System Based on Fuzzy Composite Evaluation and a Backpropagation Neural Network for a Shield Tunnel Crossing under a River

Constructing a shield tunnel that crosses under a river poses considerable safety risks, and risk assessment is essential for guaranteeing the safety of tunnel construction. This paper studies a risk assessment system for a shield tunnel crossing under a river. Risk identification is performed for the shield tunnel, and the risk factors and indicators are determined. The relationship between the two is determined preliminarily by numerical simulation, the numerical simulation results are verified by field measurements, and a sample set is established based on the numerical simulation results. Fuzzy comprehensive evaluation and a backpropagation neural network are then used to evaluate and analyze the risk level. Finally, the risk assessment system is used to evaluate the risk for Line 5 of the Hangzhou Metro in China. Based on the evaluation results, adjustments to the slurry strength, grouting pressure, and soil chamber pressure are proposed, and the risk is mitigated effectively.

Application of cellulose-based polymers in oil well cementing

Cellulose-based polymers have been successfully used in many areas of petroleum engineering especially in enhanced oil recovery drilling fluid, fracturing and cementing. This paper presents the application of cellulose-based polymer in oil well cementing. These polymers work as multifunctional additive in cement slurry that reduce the quantity of additives and lessen the operational cost of cementing operation. The viscosity of cellulose polymers such as hydroxyethyl cellulose (HEC), carboxymethylcellulose (CMC) and hydroxypropyl methylcellulose (HPMC) has been determined at various temperatures to evaluate the thermal degradation. Moreover, polymers are incorporated in cement slurry to evaluate the properties and affect in cement slurry at 90 °C. The API properties like rheology, free water separation, fluid loss and compressive strength of slurries with and without polymer have been determined at 90 °C. The experimental results showed that the viscosity of HPMC polymer was enhanced at 90 °C than other cellulose-based polymers. The comparative and experimental analyses showed that the implementation of cellulose-based polymers improves the API properties of cement slurry at 90 °C. The increased viscosity of these polymers showed high rheology that was adjusted by adding dispersant which optimizes the rheology of slurry. Further, improved API properties, i.e., zero free water separation, none sedimentation, less than 50 ml/30 min fluid loss and high compressive strength, were obtained through HEC, CMC and HPMC polymer. It is concluded that cellulose-based polymers are efficient and effective in cement slurry that work as multifunctional additive and improve API properties and cement durability. The cellulose-based polymers work as multifunctional additive that reduces the quantity of other additives in cement slurry and ultimately reduces the operational cost of cementing operation. The comparative analysis of this study opens the window for petroleum industry for proper selection of cellulose-based polymer in designing of cement slurry.

Experimental study on mechanical properties of anti-seepage slurry in landfill

Municipal solid waste has increased with the development of urbanization which sets a high request to the stability of landfill. The strength of anti-seepage slurry plays a crucial role in the stabilization of landfill. The ratio of each component was changed to test the slurry strength of different ages. Results show that the slurry strength increased with the raise of cement paste because the strength was mainly determined by the skeleton structure. In contrast, the excessive bentonite reduced the strength of slurry, for the excessive bentonite may package the skeleton structure of cement-fly ash instead of filling in. The dosage of Na2CO3 and PVA increasing to 3.0 g also reduced the strength of the slurry, because the water absorbability and expansibility of bentonite were inhibited and the effect of reinforcement on cement-fly ash structure was weaken.

Developing a Polypropylene Fabric, Silica Fume, and Redispersible Emulsion Powder Cementitious Composite for Dynamic Water Environment.

In the dynamic water environment, grouting requires a material with higher strength and anti-washout performance to prevent groundwater inrush. This study aims to develop a dynamic water slurry by mixing polypropylene fiber (PP fiber), silica fume (SF) and the polymer material of redispersible emulsion powder (REP) to the Portland cement. Towards this aim, a series of tests, including strength, gel time, bleeding rate, fluidity, and anti-washout, were conducted to evaluate the effects of SF, PP fiber, and REP on the slurry properties. The test results show that: (1) SF displays significant effects on strength, gel time, fluidity, and bleeding rate of cement slurry. Differently, PP fiber mainly affects the stress–strain behavior of the slurry and can improve the ductility significantly. (2) By mixing SF and fiber simultaneously, the slurry strength can increase by about 30%, and its strain can extend by more than 70%. Meanwhile, the composite slurry possesses great anti-washout properties at a low flow velocity (v ≤ 0.4 m/s), and the grouting retention rate (GRR) can reach up to 98.7%. However, the GRR decreases to a maximum value of 31.3% when v = 0.6 m/s. (3) By mixing the REP into the fiber-SF composite slurry, the GRR can further increase, reaching more than 60% even when v = 0.6 m/s. As a result, the developed fiber-SF cementitious composite slurry, which when mixed with REP, presents a favorable performance in the dynamic water environment.

Improvement of Barrier CMP Performance with Alkaline Slurry: Role of Ionic Strength

With the development of ultra-large scale integrated circuits, chemical mechanical planarization (CMP) has been one of the most critical processes to achieve global planarization. The ionic strength of slurry is one of the key factors influencing the material removal rate and surface quality during CMP process. In this paper, potassium nitrate was used to enhance ionic strength in baseline slurry, and the removal mechanism of copper and TEOS (tetraethylorthosilicate) were investigated. The results showed that, when the potassium ionic strength was 100mM, TEOS and copper removal rate can reach 768Å/min and 395Å/min respectively, and the removal rate selectivity ratio was 1.98 which can match well with the industrial production requirement. On pattern wafer, after polishing 60s, the dishing and erosion were amended to be 570 ± 50Å and 195 ± 30Å respectively, and the number of total defects was about 9. Such results provide guiding significance for industrial production.

Effect of nanosilica on the mechanical properties of oil well cement at low temperature

Low temperatures affect the development of cement slurry strength in cementing operations, thereby increasing the risks of shallow water/gas channelling and operation costs. Accelerators such as calcium chloride are often used to rapidly improve the mechanical properties of cement. However, accelerators often have negative effects, including decreased cement stone volume, increased permeability and decreased protection against sulfate corrosion. The effects of nanosilica (NS) on the properties of cement slurries were studied at low temperatures. It was found that the early strength of cement slurries was significantly enhanced with the addition of NS. Furthermore, sedimentary stability and the ability to control fluid loss were improved at low temperatures. Mechanistic analysis showed that the early strength improvement was primarily due to the pozzolanic effect of the NS and the bridging and pull-out effects of the AFt (Al2O3-Fe2O3-tri) phase. The use of NS as an accelerator for low-temperature cementing may have broad applications.

Effects of slurry on stickiness of excavated clays and clogging of equipment in fluid supported excavations

Mechanized excavation of tunnels and fabrication of deep foundation elements in soft ground often requires a fluid support of the temporarily created openings. The supporting fluids are generally mixtures of bentonite with water, enhanced by chemical additives for difficult geological conditions. The properties of the slurries are chosen to guarantee the stability of the excavation, in particular providing sufficient support to the coarse grained soil layers. When these are interlaid with clayey layers, excavation can be hindered by clogging problems, requiring time consuming cleaning works and causing construction delays. Clogging is caused by the stickiness of the excavated clay, which can be affected both by the clay mineralogy and the composition of the supporting slurry. The paper investigates these effects by means of a laboratory experimental study using novel stickiness tests: the mixing test and a model TBM cutter-head test. For bentonite slurries, the stickiness of the excavated soil was found to correlate with the shear resistance of the slurry. Therefore, increased slurry strength, while beneficial for excavations in coarse soils, may lead to increased susceptibility to clogging under mixed face conditions. In contrast, some pure polymer slurries can help to combine high slurry resistance with low clogging potential by protecting clay aggregate surface from penetration of water.

Comparison of gas migration test and building structural strength of slurry in the aspect of limiting gas invasion

Comparison of gas migration test and building structural strength of slurry in the aspect of limiting gas invasion