Properties Of Grouting Materials Research Articles

Investigation on the pore size characteristics and mechanical properties of grouting materials scoured by flow water

Investigating the pore size characteristics and mechanical properties of the stone bodies formed by residual grout is crucial for understanding the authentic permeability and load-bearing capacity of grouting materials after being scoured by water flow. In this study, the pore size distribution, porosity, uniaxial compressive strength (UCS), and elastic modulus (E) of stone bodies formed by residual grout from polyacrylate latex-modified cement grouting material (PLMC) were systematically investigated, and pure cement grout (PC) as a control group. First, scouring tests were conducted on grouting materials with various water-to-cement ratios (w/c, 0.6–0.8) and polymer-cement ratios (p/c, 0–0.2) under different flow velocities (0–1 m/s). Subsequently, the pore size characteristics of stone bodies formed by residual grout under various conditions were studied via nuclear magnetic resonance test. Finally, the uniaxial compression tests were conducted to investigate the impact of water scouring on the mechanical properties of grouting materials, and the relationship between pore size characteristics and macro mechanical responses was analyzed. Results show that the stone bodies formed by residual grout compared to the non-scoured state develop mesopores and macropores, and the number of micropores also increased significantly. This porosity escalation results in a reduction in UCS and E. When the flow velocity reaches 1 m/s, the porosity of PLMC with w/c = 0.8 increases by 2.95 %, while UCS decreases by 14.6 % and E decreases by 37.4 %. PC demonstrates more pronounced changes, with a porosity increase of 7.01 %, UCS decreases by 32.9 %, and E decreases by 41.5 %. With the rise in w/c, the deterioration of pore structure and mechanical properties of the stone bodies formed by residual grout is more significant compared to the non-scoured state. Increasing p/c can mitigate the deterioration of the pore structure and mechanical properties. The findings provide meaningful guidance for the grouting reinforcement under dynamic water conditions.

Effect of Various Treatment and Drying Methods of Blood Meal Additive on Fresh State Properties of Grouting Materials

Effect of Various Treatment and Drying Methods of Blood Meal Additive on Fresh State Properties of Grouting Materials

Molecular simulation for the relationship between the functional groups of chemical admixtures and cement hydration product Ca (OH)2 in the grouting process

Complex geological problems caused by natural environment have emerged constantly, causing serious damage to the land use and groundwater ecological environment in the western region. How to deal with the relationship between the above factors and ecological environment protection is a new research topic at present. Broken rock mass, cracks and water inrush during construction can be blocked and reinforced by grouting to achieve environmental protection. Therefore, to develop accurate quantitative models for the hydration of cement and predict the properties of grouting materials plays a crucial role during the protection process. In this study, the hydration product Ca(OH)2 is taken as an example, and the adsorption processes of different functional groups on the surface of Ca(OH)2 were investigated using DFT. The adsorption energy of the (101) surface was −0.38 Ha in sulfonic group, the lowest on different crystal planes of Ca(OH)2, while the adsorption energy of different functional groups is sulfonic group > carboxyl group > amide group > benzene ring. The adsorption energy was the lowest when the hydroxyl and carboxyl ratio was 1:1, suggesting that the adsorption energy and hydration performance in different ratios of hydroxyl and carboxyl groups will also be discrepant. After the adsorption of functional groups with Ca(OH)2, the electron clouds and orbitals rearranged, new characteristic peaks of the s orbital were present in the vicinity of −15 eV, −13 eV, and −10 eV, respectively. Since the relationship between functional groups and cement hydration process of chemical admixtures was explored, the mechanism of the cement hydration reaction and the influence of cement-based admixtures was revealed from an electronic view, also to extract the key influencing factors for the grouting and develop accurate quantitative models to predict and tackle various geo-environmental hazards.

Carbon nanotubes assisted fly ash for cement reduction on the premise of ensuring the stability of the grouting materials

Cement-based grouting is the most used method to strengthen the fractured rock mass and reinforce the mechanical properties and impermeability of the surrounding rock. The balance among the strength, durability, workability and cost of the grout has always been the key to grouting engineering. In this study, we use carbon nanotubes (CNTs) as the nano-additive to assist fly ash in preparing high-performance cement-based grouting materials. The results show that CNTs can generate nucleation effects and pore-filling effects in cementitious composites to promote the hydration reaction of the grouting materials and optimize the pore structure of the hardened slurry. Two reinforcing roles, bridging and pulled-out role of CNTs, act in the hardened cement matrix, where the former can improve the mechanical properties of grouting materials through micro-friction toughening, and the latter can form a net-like distribution in cement matrix together to enhance the impermeability. More importantly, we found that 0.08 wt% CNTs combined with 20 wt% fly ash can be a good substitute for cement with a moderate proportion of grouting materials. Compared with plain cement slurry, the mechanical properties are basically unchanged, while the workability can be increased by about 5%, and the impermeability can be reinforced by 6%. The discovery of this research provides an excellent chance for utilizing the superior properties of CNTs to fabricate high-performance, cost-effective and environment-friendly grouting materials.

Experimental Research on the Workability and Mechanical Properties of Grouting Materials with Nano-Oxides

This work studied the effect of the nano-oxides, such as Nano-Fe2O3 (NF), Nano-Al2O3 (NA), Nano-MgO (NM), and Nano-SiO2 (NS), on the workability and mechanical properties of quick-setting grouting materials serviced in the underground environment. The results show that 2.0% NS could remarkably shorten the setting time of the grouting materials by 29.16%, compared to the control one (without nano-oxides), and the final setting time was shortened by 46.51%. The results also show that 2.0% NS could decrease the initial fluidity of the grouting material by 41.09%, compared to the control one, and the 30 min fluidity was decreased by 48.93%. The XRD results show that NF, NM, and NS contribute to a higher quantity of AFt than that NA. Moreover, grouting material doped with NF, NM, and NS produces more needle-like ettringite, leading to a more compact structure.

Study on Physical and Mechanical Properties of Micro-Cement Grouting Materials with Different Water-Cement Ratio

The water-cement ratio is one of the key parameters of grouting materials, which greatly affects the working performance and mechanical properties of grouting materials. This paper studies the physical properties, such as density, fluidity, consistency, bleeding rate, and stone rate, and the mechanical properties of flexural and compressive strength of micro-cement grouting materials with a water-cement ratio of 0.8:1, 1:1, 1.5:1 and 2.0:1 are investigated through a variety of indoor experiments. The results show that with the gradual increase of water-cement ratio, the density, consistency value, stone rate, flexural strength, and compressive strength of micro-cement grouting material gradually decrease, while the fluidity and bleeding rate of micro-cement slurry gradually increases. Although the slurry with a water-cement ratio of 1.5:1 and 2:1 has good fluidity, the high bleeding rate and the low stone body strength result in more water injected into the reinforced formation and low reinforcement strength. On the contrary, the slurry with a water-cement ratio of 0.8:1 has a low bleeding rate and high stone body strength, but low fluidity. The grouting performance and mechanical properties of the slurry with a water-cement ratio of 1:1 are relatively balanced. This study provides a basis for the subsequent on-site ultra-fine cement grouting project. A reasonable water-cement ratio can be selected according to the specific needs to ensure the reinforcement quality and safety of the grouting operation.

Optimization of the Physical and Mechanical Properties of Grouting Material for Non-Soil-Squeezing PHC Pipe Pile

The physical and mechanical properties of grouting materials greatly affect the friction resistance and the bearing performance of a non-soil-squeezing PHC pipe pile. Orthogonal tests for four factors at five levels were carried out to optimize the proportion of the water–cement mixture by using Portland cement as a raw material and a water-reducing agent, expansion agent and early-strength agent as additives. The following conclusions were obtained: (1) Both the water–cement ratio and the dosage of water-reducing agent are positively correlated with the fluidity of the water–cement mixture and have the greatest influence on the fluidity, followed by the expansion agent and early-strength agent. The saturation point of the water-reducing agent is 1.5%. (2) The strength of the grouting body decreases linearly with the increase of the water–cement ratio, and the dosage of the water-reducing agent has no obvious effect on the strength. As the dosage of expansion agent increases, the strength of the grouting body decreases rapidly. The expansion agent mainly plays a key role in the middle and late stages of the hardening process of the slurry. Early-strength agents have a greater impact on the early strength, but less on the later strength. When the slurry is solidified for 3 h, the early-strength agent has the greatest impact on the strength with an optimal dosage of 5%. (3) The volume of the grouting body has an inverse relationship with the water–cement ratio, and the optimal amount of expansion agent is 12%. The incorporation of an expansion agent makes the volume increase of the grouting body exceed the volume shrinkage ratio caused by the hardening of the grouting body with a curing time of more than 3 days, ensuring a slight increase in the volume of the grouting body. After 3 days, even though the effect of the expansion agent is gradually weakened, it can still ensure that the volume of the grouting body does not shrink. With the increase of the amount of water-reducing agent, the volume of the grouting body gradually decreases. When the amount of water-reducing agent exceeds 1.5%, the volume of the grouting body no longer decreases. (4) The early-strength agent has almost no effect on the volume of the grouting body. When the curing time is 3 h, the water–cement ratio has the greatest influence on the volume of the grouting body, followed by the water-reducing agent, and, finally, the expansion agent. After 3 h, the water–cement ratio still has the greatest influence, and the influence of the expansion agent gradually exceeds that of the water-reducing agent. The water-reducing agent mainly affects the volume of the grouting body in the water separation stage, and the expansion agent mainly plays a role in the middle and late stages of the slurry solidification. After optimized ratio analysis, the fluidity of the water–cement mixture can be improved, the volume shrinkage ratio rate can be lowered and the early strength can be increased.

Study of rheological properties of carbon nanotube-reinforced ultrafine cement grouting materials

In this study, three different diameters of multi-walled carbon nanotubes (MWCNTs) dispersed by polyvinyl pyrrolidone (PVP) were used to reinforce superfine cement grouting materials. The effect of MWCNTs and PVP on the rheological properties of grouting material were accordingly studied. It was found that the yield stress (τ0) and plastic viscosity (η) decreased slightly when PVP content was low and increased when PVP content increased. The effect of MWCNT diameter on τ0was not found to be clear but was more significant on η. The smaller the MWCNT diameter, the quicker η increased. It was also found that the thixotropic ring area increased as the MWCNT content increased. The addition of PVP and MWCNTs caused an increase in the number of entanglement points in different scales, which was the main reason for the viscosity and thixotropy increase. Therefore, the rheological properties of superfine cement grouting material should be adjusted when MWCNTs are added as a reinforcing component. Owing to the wrapping of PVP on cement particles, which isolates the contacting part between water and cement particles, it slows down the hydration rate of cement and thus slows down the fluidity loss of the slurry.

Experimental study on the mechanical properties of grouted sleeve joint with the fiber-reinforced grouting material

In recent years, more and more attention has been paid to the grouting material and technology of sleeve connection due to the wide application of prefabricated construction. The performance of sleeve connection, normally determined by the grouting material and technology of sleeves, has a significant influence on the seismic performance of prefabricated concrete structures. This paper presented an experimental study on the mechanical properties of the fiber-reinforced grouting materials and grouted sleeve joints, and the experimental parameters included the fiber type, fiber volume fraction, and fiber length. The main properties of the grouting materials were investigated, including fluidity, compressive strength, and flexural strength. The test results showed that the incorporation of fibers with different types, volume fractions, and lengths had different effects on the mechanical properties of the grouting material. Based on the grouting material tests, the sleeve splice test was conducted to investigate the influence of different anchorage lengths on the sleeve splice under the uniaxial loading, which indicated that substantial improvement could be observed for the mechanical properties and residual bond strength of the splices with fiber-reinforced grouting materials.

Preparation and engineering properties of low-viscosity epoxy grouting materials modified with silicone for microcrack repair

Microcracks are common in the cast-in-situ concrete pavement of the bridge deck, DDMS was selected as modifier, AD- I, AD- II and AD- III active diluents were used as viscosity reducers to effectively repair the cracks. And the preparation process of low-viscosity epoxy grouting materials modified by silicone was optimized. Then the working properties (viscosity, gelation time and groutability) and mechanical properties of silicone modified low-viscosity epoxy grouting materials were clarified. Finally, the evolution law of mechanical properties of low-viscosity epoxy grouting material modified by silicone under high temperature impact, temperature change cycle and freeze–thaw cycle was revealed. The results show that the physical and mechanical properties of grouting material prepared under the conditions of reaction temperature 100 °C, reaction time 3 h and DDMS content 11% were the best. The repair depth of low-viscosity epoxy grouting material modified with silicone in 0.5 mm wide crack exceeded 10 cm within 5 min at 25 °C. But its gel time was longer, up to 24 ~ 28 h. After curing for 3 days, the shear strength and bond strength of the silicone modified low-viscosity epoxy grouting material under room temperature reached more than 90%, and its high-temperature shear strength and bond strength reached 70%~90%. Compared with EP grouting material, the low-temperature and normal-temperature impact toughness of the grouting material after adding diluent and DDMS increased by 57%~71% and 31%~48%, respectively. After high-temperature impact, temperature change cycle and freeze–thaw cycle, the mechanical properties of silicone modified low-viscosity epoxy grouting material decreased slightly, but it was still stronger than EP grouting material. Its tensile strength was still higher than 30 MPa, elongation at break was higher than 5.0%, and bond strength was higher than 3.0 MPa.

Effect of mineral admixtures on the properties of grouting materials made from a ternary complex system

Novel research on the preparation of grouting materials with a high volume of mineral admixtures is presented. The grouting materials were made from a ternary complex system containing sulfoaluminate cement, aluminate cement and gypsum. The maximum contents of fly ash (FA) and ultrafine slag (UFS) in the grouting materials only containing FA or UFS were 17 wt% and 23 wt%, respectively. It was found that the incorporation of both FA and UFS greatly improved the properties of the grouts, mainly due to their composite compensation effect. The grouts containing UFS and FA in the weight ratio of 1:5, replacing 40% of the cementitious materials, showed high fluidity and the initial and 30 min fluidity values were the same (320 mm). The compressive strength at 3 d and 28 d reached 56·5 MPa and 76·4 MPa, respectively.

Study on Properties of Grouting Materials and Reinforcement Effect in Coal Roadways Influenced by Dynamic Pressure

In order to study the occurrence mechanism of rock burst in coal roadways under the influence of mining activities, the study took five main coal roadways in Yuwu Colliery as an engineering background. The occurrence mechanism of rock burst was analyzed by theory of dynamic and static combined load. Furthermore, based on the prevention mechanism of weak-strong structure, this paper puts forward to use a hierarchical coupled grouting method to reinforce the cataclastic surrounding rock of main coal roadways, and the laboratory test results show that slurry properties of superfine cement is better than that of regular cement. The numerical simulation law of slurry diffusion shows that the water-cement ratio and fracture aperture have obvious influence on the final diffusion distance, but the grouting pressure almost has no effect on it. A bolt-mesh-cable and grouting combined reinforcement method was applied in the five main coal roadways, and the borehole observation and deformation monitoring results show that the control effect of surrounding rock is satisfactory and the rock burst accidents caused by mining disturbance are effectively prevented. The study conclusions provide theoretical foundation and a new guidance for preventing rock burst in coal roadways.

Effect of Nanosilica on the Fresh Properties of Cement-Based Grouting Material in the Portland-Sulphoaluminate Composite System

The effect of NS particle size and content on the fresh properties of the grouting material based on the portland-sulphoaluminate composite system was analyzed. The experimental results indicated that air content increased and apparent density decreased, with increased NS content, but the NS particle sizes have minimal effect on the air content and apparent density. The setting time of mortar was significantly shortened, with increased NS content; however, NS particle sizes had little influence on the setting time. The effect of fluidity on the mortars adding NS with particle size of 30 nm is larger than NS with particle sizes of 15 and 50 nm and the fluidity decreased with increased NS content, but the fluidity of mortars with the particle sizes of 15 and 50 nm is almost not affected by the NS content. XRD analysis shows that the formation of ettringite was promoted and the process of hydration reaction of cement was accelerated with the addition of NS. At the microscopic level, the interfacial transition zone (ITZ) of the grouting material became denser and the formation of C-S-H gel was promoted after adding NS.

Development and materials characteristics of fly ash- slag-based grout for use in sulfate-rich environments

This study improves cement–water glass two-shot grouting materials by adding fly ash and slag, making a new kind of anti-seepage grouting material for the prevention of soil contamination. The chemical corrosion mechanism and chemical resistance properties of the new grouting material were studied, and the contamination prevention performance of the anti-seepage system in complex geological environments, such as tailings ponds and heavy metal-contaminated sites, was also evaluated. The basic properties of the grouting materials, including stability and mobility, were tested. Sodium sulfate was used to corrode the grout gels after demolding, and the effects of chemical corrosion on mechanical properties were tested by unconfined compressive strength tests. The strength of the solution gels increased rather than decreased when fly ash and slag were added. The effect of chemical corrosion on grouting material composition was analyzed by X-ray diffraction. The results show that CaSO4·2H2O crystals have a higher diffraction peak under sodium sulfate corrosion than in standard curing conditions. This difference explains the reason for the increasing strength of the material. The effect of chemical corrosion on the gels’ microstructure was analyzed by SEM. Numbers of clubbed tri-sulfur calcium sulphoaluminate and diamond-shaped gypsum crystals were found.