Rheological Properties Of Grout Research Articles

Numerical investigation into effects of rheological properties on grout flow in rock fracture using Herschel-Bulkley model

Grouting is an essential technique for reducing the hydraulic conductivity and enhancing the strength of rock mass used in the Dongzhuang hydro-junction project. The rheological properties of grout are not to be disregarded during grouting. In this study, a numerical grouting model is established by combining a modified Herschel–Bulkley (HB) rheology model with the level set method. The effects of rheological parameters (power-law index n, consistency coefficient k, and yield stress τ0) on distribution pattern and flow characteristics of the grout are investigated. The HB model is more effective and precise than the Bingham model for predicting rheological characteristics. Numerical results indicated that distribution pattern and grout volume are primarily determined by n. A low shear rate inhibits the horizontal distribution and reduces the filling capacity of the grout, thus resulting in minimal deposition in the fracture. Grouts with a higher n and k require higher pressure to distribute around the fracture. The reduction in water volume in the fracture is calculated to provide comprehensive understanding into the sealing efficiency of the grout by varying the rheological parameters. This study provides valuable guidance regarding the different rheological parameter of grout in fractures, in addition to a novel concept for the optimal design of grouting distribution.

Theoretical and experimental study on the rheological properties of WIS grout and the dispersion and sealing mechanism

Recently a new grout material called water inflow sealing (WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter grouting (ICG) was proposed to investigate the influence of water dispersion on the rheological properties of the grout during the grouting process, and to testify the sealing performance of the grout, such as instant gelling ability (IGA) and anti-dispersion ability (ADA). In the experiment, dispersion was restricted in the downstream of the channel with a high turbulence intensity. The influences of ADA and IGA were therefore decoupled and evaluated separately. Experimental results revealed two distinctive sealing mechanisms of WIS. For a low initial velocity of water, WIS turned the shear flow of water into an overall movement of a plug by absorbing water into the particles. For a high initial velocity and the situation that the particles reached the outlet before sufficiently expanding, WIS modified the rheology of the water in the channel and reduced its velocity till the static state. The distinctive feature of WIS brings a reformation on the sealing mechanism and provides an effective way to control water inflow with high pressure and velocity.

Rheology-based determination of injectable grout fluidity for preplaced aggregate concrete using ultrasonic tomography

With the increasing use of preplaced aggregate concrete in construction, the grout filling in preplaced aggregate concrete is important for ensuring proper consolidation and high mechanical performance. This paper proposes a framework for determining the injectable grout fluidity for preplaced aggregate concrete according to the rheological properties of the grout mixture, which are associated with the filling performance for the given aggregates. To assess the grout filling, cost-effective, nondestructive ultrasonic pulse velocity (UPV) testing was performed, and ultrasonic tomography images were constructed for visually identifying internal air voids, which were verified by high-resolution micro-computed tomography. Rheometer tests evaluated the rheological properties of the grout mixtures. The UPV-based void-detection results and grout rheological properties were employed to determine the injectable grout fluidity range.

Study on a novel chemical slurry and the mechanical behavior of cemented sand

To enhance the strength and stability of the fine sandy soil in underground engineering construction, a novel chemical slurry was studied. Series of laboratory tests were performed to determine the effect of each component on the rheological properties of grout (e.g. viscosity, gel time and plastic strength). The relationship of the penetrability of grout in sand with different densities was explored by the falling-head permeability test. To assess the performance of cementation, the cemented sand specimens were prepared in the laboratory by hand mixing of grout and loose sand. A range of unconfined uniaxial compression tests, split tensile tests and direct shear tests were performed to determine the effect of several vital factors (e.g. the curing time, grout mix ratio and water content) on the mechanical properties of the cemented sand. As revealed from the results of the experiment, the slurry pertains to Newton fluid in the initial stage, which exhibits lower initial viscosity (2 mPa·s), controllable gel time (5–20 min) and higher plastic strength (35 kPa). In terms of the cemented sand, the maximal cohesion and friction angle is 403.8 kPa and 65°; the biggest compressive strength and tensile strength is 3.68 and 0.37 MPa. The slurry can enhance the strength and stiffness of the loose sand significantly, whereas the degree of improvement is dependent of the grout mix ratio and water content of cemented sand.

Simulation of Grouting Process in Rock Masses Under a Dam Foundation Characterized by a 3D Fracture Network

Grouting plays a crucial role in dam safety. Due to the concealment of grouting activities, complexity of fracture distribution in rock masses and rheological properties of cement grout, it is difficult to analyze the effects of grouting. In this paper, a computational fluid dynamics (CFD) simulation approach of dam foundation grouting based on a 3D fracture network model is proposed. In this approach, the 3D fracture network model, which is based on an improved bootstrap sampling method and established by VisualGeo software, can provide a reliable and accurate geometric model for CFD simulation of dam foundation grouting. Based on the model, a CFD simulation is performed, in which the Papanastasiou regularized model is used to express the grout rheological properties, and the volume of fluid technique is utilized to capture the grout fronts. Two sets of tests are performed to verify the effectiveness of the Papanastasiou regularized model. When applying the CFD simulation approach for dam foundation grouting, three technical issues can be solved: (1) collapsing potential of the fracture samples, (2) inconsistencies in the geometric model in actual fractures under complex geological conditions, and (3) inappropriate method of characterizing the rheological properties of cement grout. The applicability of the proposed approach is demonstrated by an illustrative case study—a hydropower station dam foundation in southwestern China.

Rheological Characteristics of Cement Grout and its Effect on Mechanical Properties of a Rock Fracture

Grouting reinforcement, which has an obvious strengthening effect on fractured rock mass, has been widely used in various fields in geotechnical engineering. The rheological properties of grout will greatly affect its diffusion radius in rock fractures, and the water–cement ratio is an important factor in determining the grouting flow patterns. The relationship between shear stress and shear rate which could reflect the grout rheological properties, the effects of water–cement ratio, and temperature on the rheological properties of grouting was studied in the laboratory. Besides, a new method for producing fractured rock specimens was proposed and solved the problem of producing natural fractured rock specimens. To investigate the influences of grouting on mechanical properties of a rock fracture, the fractured rock specimens made using the new method were reinforced by grouting on the independent designed grouting platform, and then normal and tangential mechanical tests were carried out on fractured rock specimens. The results showed that the mechanical properties of fractured rock mass are significantly improved by grouting, the peak shear strength and residual strength of rock fractures are greatly improved, and the resistance to deformation is enhanced after grouting. Normal forces affect the tangential behavior of the rock fracture, and the tangential stress strength increases with normal forces. The strength and stability of fractured rock mass are increased by grouting reinforcement.

Mechanisms of Degradation in Rheological Properties Due to Pumping and Mixing

Abstract Excessive mixing and/or pumping can result in a degradation of rheological properties specifically for self-compacting concrete (SCC) or grouts. Consequently, adverse effects on the concrete performance and structural defects are experienced. In order to identify the dominant factors that influence the rheological properties in the process chain, our study focused on rheological behavior of cement-based grouts after mixing and pumping by examining the results from field and laboratory trials that measured the effects of several pumping parameters on grout characteristics, by describing the effects of compressive stress, shear stress, and sedimentation on grout properties at a laboratory scale, and by analyzing the results using rheographs. The underlying physico-chemical mechanisms were studied using amount of plasticizer adsorbed and specific surface area development during initial hydration. Our observations revealed that mixing and shear stress during pumping, respectively, do exhibit the most pronounced influence on the rheological properties of grouts. Pressurization and sedimentation (while grouts settle) induce only little changes. The degradation of rheological properties is explained by an increase of the specific surface area available for adsorption of plasticizer. This increase seems to be due not only to dispersion of the particles but also to an accelerated creation of pre-hydrates.

Grout rheological properties for preplaced aggregate concrete production

This paper investigates the effect of cement based grout rheology on the injection process through coarse aggregate for producing preplaced aggregate concrete. Four different sands were used in the grout production at different water-cement ratios and cement-sand ratios. Superplasticiers and pulverised fuel ash were also employed in the grout production. Coarse aggregate of known weight was compacted into 150 mm cubic forms, and then the grout was injected through a plastic pipe under self weight into the stone ‘skeleton’. It has been found that there are threshold values of the rheological parameters beyond which full injection is not possible. In particular, all grout mixes with and without additives and admixtures exhibited the same yield stress threshold value for full injection, whereas the threshold values for other rheological properties including the grout plastic viscosity, flow time and speed were different according to the materials added to the mix.

Rheology of Grouts for Masonry Injection

Grout injection technique applied in a multiple leaf masonry walls aims at increasing the compactness of the masonry and, therefore, improving their monolithic behaviour by bonding the separated segments together without compromising the architectural value of the masonry building. The success of the injection grouts depends mainly on their rheological properties. This means that the flow properties of fresh grouts are as important as their properties in the hardened state, since they govern the ability of the grout to flow and fill the voids within masonry. In practice, the variability of voids within masonry requires ability to fine tune the rheological properties of the grout, in order to optimal fill all voids with grout. So, models were developed with the main purpose of predict and control the rheological properties of grouts just performing simple flow tests traditionally used in the field. It is well known that flow tests commonly performed (such as Marsh cone and slump test), which try to describe the workability of cementitious materials, only give a qualitative result that can not be expressed in physical rheological units. However, the proposed models allow calculating a physical parameter (e.g. viscosity) instead of an empirical one (e.g. fluidity). This research shows the effect of grout design variables on the properties of natural hydraulic lime grouts based on the correlation between rheometry measurements and simple flow tests. Furthermore, the proposed models can be very useful to smooth the grout design methodology, since these models enable the prediction of rheological properties of the grout without the need for expensive and complex equipment, such as rheometers or viscometers.

Groutability of granular soils using sodium pyrophosphate modified bentonite suspensions

Groutability of granular soils using sodium pyrophosphate (SPP) modified bentonite suspensions was studied to investigate its applicability in permeation grouting. While the relative grain size of the soil and the grout has been widely used to evaluate the groutability of granular soils with particulate grouts, such criteria do not account for the effect of chemical modifications of grouts such as the changes in their rheological properties. The modification of grouts may improve the depth of its penetration, and thus changing the groutability of the granular soils. For such cases, the rheological properties of grouts become crucial to evaluate groutability of soils. In this study, the rheological properties of bentonite suspensions were measured at various bentonite fractions (5%, 7.5%, 10%, and 12% by total mass of suspension) modified with 0%, 1%, 2%, 3%, and 4% SPP (by mass of dry bentonite), respectively. The small amounts of SPP effectively improved the mobility of the concentrated bentonite suspensions allowing the evaluation of change in groutability at different rheological properties but same concentrations. The modified bentonite suspensions were injected into the saturated sand columns prepared at various experimental conditions (effective particle size, relative density, and fines content) under two different constant pressures (35 and 140kPa). The results showed that the injected pore volumes increased with an increase of the apparent viscosity at equilibrium (high shear rates). A new groutability criterion for granular soils is proposed based on the rheological properties of the suspensions, relative density of the sand, relative grain size of the sand and bentonite, and injection pressure. The proposed groutability criterion provides a more accurate prediction of groutability in granular soils when using modified bentonite suspensions.

Rheological performance and compressive strength of superplasticized cementitious mixtures with micro/nano-SiO2 additions

This study aims to assess the effects of micro and nano-SiO2 under various dosages of carboxylated-polyether-copolymer-type superplasticizer on the rheological properties of grouts in the fresh state. In the hardened state, compressive tests and scanning electron microscopy were used to characterize type I Portland cement mortars. During Stage-I, the rheology of superplasticized grouts (w/b=0.35 and 0.40) was obtained by the Marsh cone test. Mineral admixtures in superplasticized grouts decrease the flow times and the saturation dosages when compared to the superplasticized-control specimens. In Stage-II, experimental designs at w/b=0.35 produced flow area, unit weight and air content in mineral admixture-systems better than in superplasticized-control samples. During Stage-III, the maximum strength in the nano-SiO2-system was obtained at 1.0wt%, whereas in micro-SiO2-systems, this effect occurred at 15wt%. SEM examinations in the interfacial transition zone suggest that compressive strengths of nano-SiO2-systems were controlled by both densification and filler effects, whereas micro-SiO2-systems were controlled only by the latter.

The use of rheology in the study of the composition effects on the fresh behaviour of hydraulic lime grouts for injection of masonry walls

The injection of grouts inside multi-leaf stone masonries is a technique widely used for structural consolidation. To ensure an adequate flow of the grout inside the masonry, it is crucial to assure good fresh grout properties, such as good rheological behaviour. The scope of this paper is to provide preliminary indications and valuable data about the effects of specific hydraulic lime grout composition on their rheological behaviour with the purpose of a successful injection process. Through the use of rotational rheometer together with the Taguchi method, it was possible to study the influence of water/binder ratio, the type and dosage of superplasticizer and the partial replacement of hydraulic lime by silica fume, upon the grout rheological properties. The study leads to the conclusion that polycarboxylate-based superplasticizers present better performance from a rheological point of view than the naphthalene-based superplasticizer and that the water/binder ratio and superplasticizer dosage are the most determinant factors in the fresh grout rheological behaviour. On the other hand, silica fume dosage turned out to be the factor with the least contribution to improve the grout rheological behaviour compared to the other two factors reported in this study. The results summarised in this paper are part of a larger study and precede the analysis of the performance of those grouts when injected into different porous media that simulate old masonries.

Experimental Research on Rheological Properties of Cemented Mortar in Tail Void Grouting of Shield Tunnel

Grout flow pattern and rheological parameters determine grouting pressure transfer process in annular tail void and filling rate for shield tail void. However, cemented mortar is a mixture of cement, fly ash, sand, bentonite and water, which lead to grout rheological properties and rheological parameters are difficultly determined. Based on orthogonal experimental design method, grout rheological properties were tested by rotational viscometer. Utilizing variance and poly-nonlinear regression analysis, the qualitative and quantitative relationships between mix ratios and rheological parameters were obtained respectively. It is shown that cemented mortar flow pattern commonly agree with Bingham fluid type, and plastic viscosity varies between 1 and 4Pa•s, and shear yield stress varies between 10 to 40Pa respectively. Water-binder ratio and bentonite-water ratio are key influencing factors for grout rheological parameters. With the water-binder ratio increasing and bentonite-water ratio decreasing, plastic viscosity and shear yield stress present reducing tendency.

Rheological properties of grouts with viscosity modifying agents as diutan gum and welan gum incorporating pulverised fly ash

This investigation was undertaken to evaluate the influence of the dosage of the second generation of viscosity modifying agent (diutan gum) on fluidity and rheological parameters of cement-based materials grout compared to welan gum. All grouts were made with 0.40 water-to-binder ratio (W/B). The fresh properties of control grouts made without any viscosity modifying agent (VMA) and with superplasticizer (SP) were compared to those of grouts made with 0.02, 0.04, 0.06 and 0.08% diutan gum by mass of binder. Similar mixes made with welan gum were compared to those containing diutan gums. The effect of admixtures on fluidity and rheological parameters are discussed in this paper. The effect of the replacement of cement by pulverised fly ash (PFA) was also investigated. Grouts with replacements of PFA of 5, 13 and 20% by mass were used with the same W/B. Similar control grouts and mixes incorporated different dosages of PFA made with welan gum were made in order to compare the fluidity and the rheological parameters to the previous grouts made with diutan gum. The results show that the increase of the dosage of diutan gum and welan gum for a given dosage of SP increases significantly the yield value, the apparent and plastic viscosity and reduces the fluidity. With an increase in dosage of SP, the apparent viscosity at low shear rate decreases dramatically than that at high rate of shear rate due to the pseudo-plastic rheology of the grouts containing VMA. Both VMAs exhibited high apparent viscosity values at low shear rates which were attributed to the entanglement and intertwining of VMA polymer chains at low shear rate and association of water between adjacent chains. For a given dosage of VMA, diutan gum showed a high apparent viscosity than welan which could be attributed to the molecular weight and to the long-side chain of diutan gum leading to greater entanglement and intertwining. For any given dosage of SP, the diutan gum exhibited higher yield value and plastic viscosity than welan gum. Diutan gum grouts demonstrate a greater yield value and apparent and plastic viscosity than welan gum for control and PFA grouts. The replacement of cement by PFA resulted in a reduction of yield value and an increase in plastic viscosity.

Influence of microstructure on short-fatigue-crack growth: Plumtree, A. and O'Connor, B.P.D. Fatigue Fract. Eng. Mater. Struct. 1991 14 (2–3), 171–184

This study aims to assess the effects of micro and nano-SiO2 under various dosages of carboxylated-polyether-copolymer-type superplasticizer on the rheological properties of grouts in the fresh state. In the hardened state, compressive tests and scanning electron microscopy were used to characterize type I Portland cement mortars. During Stage-I, the rheology of superplasticized grouts (w/b = 0.35 and 0.40) was obtained by the Marsh cone test. Mineral admixtures in superplasticized grouts decrease the flow times and the saturation dosages when compared to the superplasticized-control specimens. In Stage-II, experimental designs at w/b = 0.35 produced flow area, unit weight and air content in mineral admixture-systems better than in superplasticized-control samples. During Stage-III, the maximum strength in the nano-SiO2-system was obtained at 1.0 wt%, whereas in micro-SiO2-systems, this effect occurred at 15 wt%. SEM examinations in the interfacial transition zone suggest that compressive strengths of nano-SiO2-systems were controlled by both densification and filler effects, whereas micro-SiO2-systems were controlled only by the latter.