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Understanding the mechanism of progressive debonding of bolts is of great significance for underground safety. In this paper, both laboratory experiment and numerical simulation of the pull-out tests were performed. The experimental pull-out test specimens were prepared using cement mortar material, and a relationship between the pull-out strength of the bolt and the uniaxial compressive strength (UCS) of cement mortar material specimen was established. The locations of crack developed in the pull-out process were identified using the acoustic emission (AE) technique. The pull-out test was reproduced using 2D Particle Flow Code (PFC2D) with calibrated parameters. The experimental results show that the axial displacement of the cement mortar material at the peak load during the test was approximately 5 mm for cement-based grout of all strength. In contrast, the peak load of the bolt increased with the UCS of the confining medium. Under peak load, cracks propagated to less than one half of the anchorage length, indicating a lag between crack propagation and axial bolt load transmission. The simulation results show that the dilatation between the bolt and the rock induced cracks and extended the force field along the anchorage direction; and, it was identified as the major contributing factor for the pull-out failure of rock bolt.

Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In the laboratory, sandy soil mixed with cement grout with water-cement ratio varies from (0.7:1 to 1.4:1). To evaluate the characteristics of soilcrete, 96 specimens were prepared in the laboratory and tested at different curing times. The results indicate that the Uniaxial Compressive Strength (UCS) of soilcrete decreases with increasing the (W/C) ratio of the grout, where the soilcrete strength of W/C ratio of 0.7 is higher about 237% of W/C ratio of 1.4 at 28-day; the evolution of the (UCS) is proportional to the logarithm of the curing time; the ratio between the modulus of elasticity (Etg50) to the maximum UCS varies from 113 to 175; when the water-cement ratio increases, the dry density of soilcrete decreases, as a result, the (USC) of soilcrete decreases.

An acceptable viscosity and an easy penetrability of cement - limestone filler grout in the granular matrix of self compacting concrete are an important factors that affecting both its rheological and its hardened properties. This experimental and theoretical work consists to study the effect of limestone filler fineness on the rheological behavior of cement - limestone filler grout. In the first part, five different grouts were prepared by varying the Blaine Specific Surface (BSS) of the limestone filler, 3060, 4750, 6320, 7680 and 9440 cm2/g, respectively. A large number of properties relating to the rheology and the stability are carried out on the five grouts such as grain dispersion, density, volume concentration of solid, dynamic viscosity and Marsh funnel flow. The second part consists to develop a theoretical model to predict the different rheological properties of the grout as function of limestone filler BSS. The results show that the rheological properties of cement-limestone filler grout such as the dispersion percentage, the intergranular distance and the flow time are strongly affected by the limestone fillers fineness. In addition, the experimental and the predicted results present a good agreement.

One solution to the high cost and scarcity of building materials is to use alternative and sustainable materials. The study presented herein developed an eco-friendly masonry grout using high volumes of palm oil clinker powder to replace cement and palm oil clinker to replace coarse aggregate. Several batches of grouts with different amounts of these materials were made to determine the technical viability of the grout. Scanning Electronic Microscope (SEM), X-Rays Diffraction (XRD), Energy Dispersive X-Ray (EDX) and Thermogravimetric Analyzer (TGA) analyses were conducted to investigate the microstructure characteristics of the grout, and water absorption, initial rate of absorption, sulphate attack and electrical resistivity tests were conducted to determine its durability. Compressive strength tests were conducted at different curing ages and the drying shrinkage of the grout was monitored for 180 days. The results indicate that the new grout is as good as a conventional grout but with added sustainable and economic benefits. The new grout can be used in masonry construction and can be used to alleviate the inadequate supply of affordable housing.

The grouting is used to reinforce soft ground and to prevent the leakage of water in the soil. The objective of the study is to enhance the compressive strength of grout materials by using reinforcing fibers and to increase the strength of soil using blast furnace slag powder. For this purpose, cement was replaced with the blast furnace slag powder by 30 to 60%. Furthermore, for comparison of carbon fibers with aramid fibers, each fiber was added by 0, 0.5, and 1.0% of the weight of material. As the contents of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased. This is due to the interlocking of fibers in the grout material that increased the uniaxial compressive strength. Moreover, the grout material reinforced with aramid fibers showed an increase of uniaxial compressive strength by at least 20% compared to the carbon fibers. An environmental assessment was done through a heavy metal leaching test and a pH test. The test result reveals that about 50% of chromium (VI) leaching decreased as 30% more blast furnace slag powder was used but the pH test shows about 0.5 pH increased as 30% more blast furnace slag powder was used. Further study is necessary for the pH test.

High-volume fly ash (HVFA) cementitious composites (paste, grout, mortar, and concrete) have been widely investigated as a class of sustainable materials due to their lower carbon footprint and often better life cycle performance than conventional Portland cement mixtures. Recent years have seen increased research in HVFA-based materials, and the potential of this type of mixtures in engineering applications has significantly improved. In this context, this work reviews the renewed knowledge of HVFA mixtures, focusing on the relevant papers published over the last decade. The effects of replacing cement with a HVFA binder on the fresh properties, mechanical properties, durability performance, and environmental impact of HVFA cementitious composites are explored. Measures that can compensate for the main drawbacks that limit the wider application of HVFA mixtures are discussed in detail. At last, we summarize the research needs and remaining challenges of HVFA cementitious composites.

Grouting is an important and convenient technique to improve rock properties. The grouting effectiveness depends on quantities of complex influencing factors. The investigation on the effects is essential for engineering applications. This study focuses on the evaluation of shear strength with experimental and numerical approaches. Firstly, the shear test of rock sample with cement grouting was carried out. Based on the tests, the numerical modelling of grouting was conducted. The effect of normal stress, grouting thickness and strength parameters of grout on the shear strength was studied, respectively. Then, the critical condition of effective grouting was proposed. Lastly, the mechanism in the influencing factors was discussed. Results show that the strength of grouted rock could be improved by increasing the normal stress and the grout parameters and decreasing the grouting thickness. The critical condition of effective grouting involves the grouting thickness and the strength parameters of grouting material. When the condition of effective grouting is satisfied, the grouting effect would be remarkable with additional supports, such as bolts. According to the opening of the dominant structural plane, the grouting parameters should be reasonably designed to meet the critical condition. The results could provide experimental and theoretical methodologies for the grouting design.

This paper presents three comparative in situ grouting tests for long-term settlement treatment of a cut-and-cover tunnel of Nanjing Metro Line 10. The characteristics of the tunnel settlement and induced structural damage are described in detail. Comparative grouting tests were conducted to identify the effects of the grouting sequence and grouting material on the tunnel settlement treatment. The test results show that the total amount of uplift of the tunnel associated with the bottom-up grouting sequence is greater than that associated with the top-down grouting sequence. When a mixture of cement and water glass was used as grout, the average cumulative deformation and average deformation rate of the tunnel 6 months after the completion of grouting were −11.2 mm (uplift) and 0.018 mm/day (settlement), respectively. These values satisfy the control requirements and are better than those obtained using a cement and bentonite mixture as grout. Hence, a bottom-up grouting sequence and a cement and water glass grout mixture are advised. The findings presented in this paper provide useful guidance for similar projects.

Formulating solution to obtain the required engineering properties by means of stabilizing the soil for placing infrastructural unit without undergoing large settlement, grouting is widely used restoration method for improving the relative density of the soil strata. This paper has analyzed two case scenarios about soil stabilization to accommodate reinforced cement concrete (RCC) structure to facilitate production units. Considering the soil characteristics and to avoid further collapse of the nearby establishment, injecting lime–cement composition to strengthen the loosen earth bearing capacity at certain depth has been followed. Accordingly, researchers have shown to mend on the discrepancy happened in both cases regarding strengthening of disturbed soil strata up to 2 to 2.5 times with respect to Standard Penetration Test-Number of Blows (SPT-N) values after carrying out pre- and post-dynamic cone penetration tests (DCPT) up to an average depth of 6 to 6.5 m from finished ground level (FGL), by using of grout injection procedure. Following methodology has been emanated and after conducting several trials resulted in appreciable improvement in soil consistency. Researchers believe that the study will be comparatively more suitable for improving problematic soils in South-Asian continent. In both cases, desired soil bearing capacity has been attained in most economical way and within stipulated time frame.

Grouting is one of the most commonly adopted technique for soil improvement and strengthening. Adding super plasticizers, accelerators, antifreezes, air entraining agent improves the performance of the cement grout. The performance of the grout while injecting in the sand column mainly depends on its fluidity property. Keeping it in mind about the water cement ratio, the strength of the sand column is studied in two sets of experiments one by sand column with cement grout only and another set by sand column with cement grout added with super plasticizers by varying the water cement ratios. Strength parameters like angle of internal friction and cohesion were obtained be direct shear test and unconfined compressive strength test on the specimens by varying the water content. An increase of 15.2kPa to 60.33 kPa was observed in the cohesion value for specimens with 10% water content and 13.8 kpa to 47.2kPa cohesion value observed in the specimens with 20% water content. The angle of internal friction was decreased from 360 to 160 for 10% water content whereas 300 to 100 for 20% water content. A series of experiments were conducted on the sand column grouted with cement and for different water cement ratios as 1.5, 2.0 and 2.5. Another set of experiments were repeated by adding 2%super plasticizer Sulphonated Melamine Formaldehyde (SMF). The experiment results revealed that at lower water cement ratio higher value of compressive strength was observed. It was also observed that the strength increases with curing period.

Cement grouted bituminous mix (CGBM) is a composite mixture where cementitious grout slurry is penetrated within the air voids of an Open-graded bituminous mix (OGBM). The CGBM surface has both flexible and rigid pavement merits and is considered a semi-flexible pavement type. Further, the choice of cold mix layer of CGBM also minimises the challenges associated with conventional hot mix types. In the present study, cementitious grout slurry is prepared using cement, fly ash, silica fume, and polycarboxylic ether-based superplasticiser to make the CGBM samples. To study the effect of grouting, the prepared CGBM samples were tested in the laboratory at 1, 3, 7 and 28 days after the curing period. Compressive strength, Marshall stability, indirect tensile strength, and resistance against the CGBM mix's moisture damage, improve with the increase in the curing period. CGBM mixes are less temperature susceptible and exhibit better resistance against moisture damage and abrasion loss. A trial section is constructed as per the design developed in the laboratory. The paved CGBM surface's field performance reveals that grout material is significantly improving the CGBM mix's behaviour. The evaluation of CGBM is considerably beyond the defined criterion in the Indian standards code, i.e. MoRTH (Ministry of Road Transport and Highways) fifth revision. Results and analysis presented in this manuscript may help the engineers to analyse the CGBM layer further.

Fiber-reinforced cementitious matrix (FRCM) and steel-reinforced grout (SRG) have been increasingly applied as externally bonded reinforcement to masonry members in the last few years. Unlike fiber-reinforced polymer (FRP), FRCM and SRG have good performance when exposed to (relatively) high temperature and good compatibility with inorganic substrates, and they can be applied to wet surfaces and at (reasonably) low temperatures. Although numerous studies investigated the mechanical properties and bond performance of various FRCM and SRG, new composites have been developed recently, and their performance still needs to be assessed. In this study, the bond behavior of three FRCM composites and one SRG composite applied to a masonry substrate is investigated. Sixteen single-lap direct shear tests (four tests for each composite) are performed. The FRCM studied comprised one layer of carbon, PBO (polyparaphenylene benzobisoxazole), or alkali-resistant (AR)-glass bidirectional textile embedded within two cement-based matrices. The SRG composite comprised one layer of a unidirectional stainless-steel cord textile embedded within a lime-based matrix. The results show a peculiar bond behavior and failure mode for each composite. Based on these results, the behavior of the carbon and PBO FRCM is modeled solving the bond differential equation with a trilinear cohesive material law (CML).

Cement grout is commonly used in construction practices for connecting sections and embedding rebar in masonry walls. The present study explains the laboratory investigations undertaken to develop cement-based grouts incorporating silica fume, fly ash and fine sand. In mixes which showed stiff nature at lower water cement ratios (W/C), superplasticizer is added and the optimum dosage is fixed. Silica fume is used as mineral admixture to replace cement by a mass percentage of 10. The filler used is fine sand and fly ash (class F) and cement to filler ratio is maintained as 1. Preliminary study which included trials for compressive strength and mini slump flow spread of various grouts with varying water cement ratios and superplasticizer dosage was done. After eliminating the unstable mixes, rheological studies were conducted for the stable mixes. All mixes showed poor workability at low W/C but increased superplasticizer dosage improved workability. Fineness of constituent materials governed the viscosity of grout samples to a great extent. The mixes incorporated with fillers were more viscous compared to those without fillers. By increasing W/C, viscosity of grouts can be lowered but it paves way for other problems such as excessive bleeding or grout instability.

The aim of the paper is to show one of the soil strengthening technologies - mass mixing. Two variations are to be distinguish – dry and wet type. In the first case the binding process take place with the use of ground water and the binder (cement, fly ash). In wet mass mixing the soil; is mixed with cement or cement-fly ash grout. The application of each type is dependent of the type of soil and its moisture content. The paper describes case studies of dry type: S5 road in the section Korzensko – Widawa, open pool complex in Olawa, Szczecinek bypass. Wet type case study is described as well – part of the “Wiślanka” gallery in Żory and site in Warsaw. The analysis of mentioned case studies has shown that the technology can be used in all type of civil engineering objects. While it is one of the technologies which is based on mixing of the existing soil, it is especially important to do comprehensive soil investigation and trial mixes before the start of the jobsite. One of the advantages is that the quality control in case of wet mass mixing is made similarly to DSM (deep soil mixing).

Drilling activities in the hydrocarbon supply chain are complicated and costly processes. In recent decades, due to the enormous potential to improve various fundamental properties in hydrocarbon well cementing, nanotechnology has earned broad attention for use in petroleum energy sector. The usage of nanotechnology in the field of hydrocarbon cementing grout also offers assistance to most of the complex challenges associated with oil well cementation. By using nano-silica in oil well cementing process, cement properties such as durability and strength are improved. The nano-silica particles are emerging as a better replacement for traditional additives such as silica and calcium chloride, since much less is needed. Increment in cement properties occur considering the width and size of these very-fine particles and nano-silica’s large specific surface area. As a multifunctional additive, nano-silica acts. Fresh and hardened cement properties are enhanced by the existence of these nano-silica particles. As nano-silica particles are incorporated in the slurry paste of cement, it is observed that there is a decrease in the time of thickening process, increase in physical properties such as compressive strength, a decrease in porosity as well as permeability in hardened cement, and substancial decrease in fluid loss. The addition of particles of nano-silica enables effective cementation. It also enhances integrity of the wellbore. By forming C–H-S gel to eliminate excessive CH in cement slurry, nano-silica forms refined pore, denser and compact microstructure cement for efficient ring sealing.

When grouting in a sand layer, the filtration of the layer on cement particles is an important aspect affecting the grout dispersion. However, few laboratory studies have been conducted to investigate the distribution of cement particles along the direction of dispersion. In this study, a group of laboratory tests were conducted by grouting in a sand layer under different levels of pressure. The distributions of cement particles in sand after curing were then measured using the EDTA titration test. The results show that, due to the filtration effect, the cement content along the radial direction of dispersion decreases nonlinearly in a reversed S shape. The filtration effect becomes more obvious when grouting with a higher grout concentration. With the decrease in grout concentration, the filtration effect becomes weak and cement particles could disperse farther in the sand layer, but the cement content in a farther location becomes lower and the improvement of the soil strength is limited. In the end, the measured results were compared with the calculated results according to an existing theoretical study and the trend reasonably matches with each other.

In Korea, earthquakes have continued to occur even after the occurrence of Gyeongju and Pohang earthquakes of 2016 and 2017, respectively, raising awareness of earthquakes. Because earthquakes cause damage to not only structures but also humans, it is essential to improve the seismic performance and design earthquake-resistant structures to minimize earthquake damages. If the seismic performance of a structure is improved through ground improvement and reinforcement, ground response analysis should be performed considering the dynamic properties of the site of the structure. In addition, cement has been widely used as a material for ground improvement, but recently, ground improvement methods in which biopolymers are utilized for ecofriendly construction have been investigated extensively. However, studies on the changes in the dynamic properties of ground improved using biopolymers, and the ground-response analysis has not been investigated in detail. In this study, resonant column tests were performed using samples mixed with cement and sodium alginate to evaluate the effects o f ground improvement using a biopolymer. In addition, the dynamic properties of the improved samples were adopted in performing the ground response analysis, which demonstrated confirmed the ground stability after ground improvement. From the results, the ground dynamic properties, shear modulus, and damping ratio were influenced when the biopolymer and cement were mixed with the soil. Furthermore, the ground response analysis confirmed that the maximum ground acceleration on the surface decreased.

This paper aims to research the potential use of cold-bonded geopolymer stabilizer made from limestone dust and bottom ash for grouting and deep soil (clay) mixing. For this purpose, the rheology and strength performances of the cement (PC)-based grouts with the stabilizers of limestone dust (LD), bottom ash (BA), geopolymerized cold-bonded limestone dust (GLD), and geopolymerized cold-bonded bottom ash (GBA) were investigated. The rheometer tests were conducted for the rheological performances at a wide range of stabilizer replacement (0–100%) and water/binder (w/b) ratio (0.75–1.5). Using proper replacements from the grout rheology, the unconfined compressive strength (UCS) tests (7 days, 28 days) were performed for the grouting (w/b = 1) and deep mixing (w/b = 1–1.25). The effect of stabilizer on the failure patterns was also examined from specimens of UCS tests. From the experimental work, the rheology of grout mixtures indicated (i) the adequacy of low amount of stabilizer replacements (

Based on the analyzing of industrial materials has been established that lot of gas wells characterized of inter-string flows and could not been effective be on stream. The article has been shown, that main base of this problem is poor quality well cementing, first off all the interval of reservoir horizon. After researched of information of well cementing has been ascertained that first eight hour of the curing of cement is attended by drop of the hydrostatic pressure. It becomes the main reason of oil and gas inflow. The drop of cement stone sealing properties during long time maintenance is result of poor cement stone resistance to thermocorrosion in the subsurface conditions. This is the reason that new cementing slurry recipe should be prepared. This recipes should be provides a differentiated rate of strength gain during the time of waiting the cement in conditions with high technological properties for long time maintenance. One of the most dangerous process during well construction is oil and gas inflow or inter-string flows in time of wait-on-cement time. This time is characterized special conditions of cement stone, because it represents as permeable matrix with hydration products, and with porous full by water. It is the best conditions for the flow of fluid throw pores. It can be the reason of suffusion channeling. In order to prevent for oil and gas inflow the article has been invited the achieve optimal distribution the pressure. For the realized this purpose can been used cementing process with two cement slurry batch with different setting up time. In practice of cementing of casing with length of section capital string, which shut off the gas more than 400 m, use differentiation the wait-on-cement time the portion of cementing slurry with length of cement column. In result start of time wait-on-cement in the bottom portion should be less for 2-3 hour than top portion. Keywords: water-mixture ratio, rheological properties, wellbore pressure, component of cement mortar column, cement mortars, cement mortar hardening, rate of strength gain, strength of cement ring References: Bandur R. V., Luzhanytsya O. V., Mykhaylenko S. H. [and other]. 2005. The problem of selection of the formulation of cementing solutions for a specified downhole conditions. Issues of development of the gas industry of Ukraine: Collection of scientific works UkrSGRI. Kharkiv. P. 135-137. (in Ukrainian) Bonett A., Delyus P., Shuger L 1998 Gas Migration - Looking Into the Problem. Oil and gas review. Spring. Р.18-23. (in Russian) Bulatov A.I. 1991. Grouting materials and well cementing technology. Moscow: Nedra. P. 336. (in Russian) Gorsky V.F. 2006. Cementing materials and solutions. Chernivtsi: 524 p. (in Ukrainian) Danyushevskiy V. S., Aliyev R. M., Tolstykh. I. F. 1987. Grouting Materials Reference Moscow: Nedra. P. 373. (in Russian) Luzhanitsya O. V., Mikhaylenko S. G., Kotskulich Y. S., Lazarenko O. G. 1997. To the problem of tightness of the annulus in the early stages of the grout. Exploration and development of oil and gas fields. Series: Drilling of oil and gas wells. - Ivano-Frankivsk: IFDTUNG. №34. Р. 88-91. (in Ukrainian) Instructions for determining the conditions of use of gas wells with the presence of intercolumn pressure drilled on the shelf of the Black and Azov Seas: Approved. Derzhnaftogazprom of Ukraine, OJSC «Ukrainian Oil and Gas Institute», NPC «Chornomornaftogaz» 1997; Validity is not set. Derzhnaftogazprom of Ukraine. 11 p. (in Ukrainian) Kuksov A.K. 1985. Improving the quality of well cementing. Oil industry. №9. P. 25-27. (in Russian) Orlovsky V.M. 2015. Grouting materials that expand during hardening. Monograph. Poltava. 129 p. (in Ukrainian) Levayn D. K., Tomas E. I., Bezner H.P., Tolpa D. K. 1980. Prevention of gas migration in the annulus of a cemented well. Oil, gas and petrochemicals abroad. N 10. P. 8-12. (in Russian) Technological regulations on cementing of casings in wells at the fields of JSC «Ukrnafta» for 1996- Derzhkomnaftogaz OJSC UkrNGI. 1995. Kyiv. 36 p. (in Ukrainian)

To study the influence factors of low-temperature performance of semi-flexible pavement materials, a freezing test was conducted, and the cracking temperature was used as the evaluation index to study the influence of asphalt type (90 matrix asphalt, SBS-modified asphalt, TPS high-viscosity modified asphalt), cement-based grout material types (ordinary grout, rubber powder grout, emulsified asphalt grout), and skeleton void ratio (20%, 24%, 28%, 32%) on the low-temperature performance of semi-flexible pavement materials. Results indicate that the freezing test can effectively distinguish the low-temperature crack resistance improvement benefits of semi-flexible pavement materials with different asphalt, cement-based grouting materials, and skeleton void ratios. Cracking temperature can effectively evaluate the low-temperature performance of semi-flexible pavement materials. The substrate void ratio is in the range of 20%-32%, and the cracking temperature changes with the increase in the substrate void ratio, decreasing initially and then rising. When the void ratio is around 24%, the best low-temperature performance of semi-flexible materials is achieved. The improvement effect of the elasticity of grout on the low-temperature crack resistance of semi-flexible pavement materials is obvious; the improvement effect of emulsified asphalt grout on the low-temperature performance of semi-flexible pavement materials is better than that of rubber powder grout. After the modified asphalt is used in the substrate, the cracking temperature is reduced by 31.4%-38.3%, which is much greater than the effect of grouting. At the same time, the elasticity of the base asphalt is more effective than the viscosity increase in improving the low-temperature crack resistance of semi-flexible materials.

A new method for treatment of dredger fill was proposed to address its low bearing capacity, high consolidation cost, and long treatment duration. In this method, cotton straw is used as both the draining and reinforcement material. Specifically, cotton straw bundles are driven into the dredged soil and vacuum preloading is then performed. Subsequently, environmentally friendly grout is poured into the cotton straw bundles, and solidified vertical reinforcements are thus formed, allowing dredged soil to be treated. Design parameters for the cotton straw draining were obtained from previous laboratory test. Based on a real-world project, a field test was performed to study treatment of dredged soil through cotton straw drainage and reinforcement, and a comparison was drawn with the traditional cement mixing vertical reinforcement method. The vacuum degree, settlement, and water content of reinforced soil suggested a good ability of cotton straw drainage to solidify dredged soil. The static load test indicated that vertical reinforcement after grouting demonstrated better strength than cement reinforcements. This study provides new insights into the treatment of dredger fill and can broaden the application of cotton straw and also reduce environmental pollution caused by cotton straw burning.

Flowing water grouting is a big challenge in the tunneling and underground engineering. To enhance the early strength and grouting effectiveness of slurry for flowing water grouting, nano-CaCO3 and fly ash were mixed with cement based grout. A series of physical simulation tests were conducted to simulate the flowing water grouting process in rough rock fracture, and investigate the effect of nano-CaCO3 content on the fluid pressure and sealing efficiency of grouts. Results of viscosity tests show that the viscosity of grouts decreased with an increase of nano-CaCO3 content. Scanning electron microscope (SEM) tests indicate that nano-CaCO3 can promote the formation of fibrous hydrates and enhance the flowing water resistance of grouts. Increasing nano-CaCO3 content resulted in the first increase while later decrease of maximal fluid pressure (MFP) and sealing efficiency (SE) of grouts. Reducing water cement ratio of grouts and incorporating fly ash can effectively improve the SE of flowing water grouting.

Efficacy of added nano-CaCO3 (NC) on engineering performances, including fluidity, initial setting time, bleeding rate and yield stress of cement grouts was investigated in this study. Results showed that the fluidity and bleeding rate for NC-cement (NCC) composite grout first decreased with increased NC content (i.e., ratio of NC mass to cement mass) and then slightly recovered as the NC content exceeded 2%. The initial setting time was always reduced while the yield stress increased with increased NC content. The microstructure of NCC was analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the NC can promote the cement hydration, but an excess amount of NC will inhibit the cement hydration and affect the engineering performances of cement grouts. The optimum NC content for modification of cement grouts was thus 2%.

Cement-based grout has been used for ground improvement. Owing to environmental issues related to cement, its usage should be reduced. In this study, an inorganic binder is introduced to reduce the use of cement in grout. To evaluate the transient electrical and mechanical properties of the sand–cement admixture samples improved with the addition of inorganic binders, two non-destructive testing methods, the electrical resistivity and free–free resonant column tests, were adopted in addition to the unconfined compressive strength (UCS) test. Experimental tests were performed considering four different mixing ratios and three different cement contents, depending on the curing time. The results show that the mixing ratio and curing time have considerable effects on the electrical and mechanical properties of the mixture. The UCS decreases as the cement content decreases. However, sufficient UCS is expected to be obtained when the inorganic binder content is increased in the mixture. From the results, it is found that geotechnical properties of the mixture can be estimated in the field with proper non-destructive testing methods. It is expected that the data and trends proposed in this study can be used as a reference in predicting grouting quality in the field.

The cement manufacturing process causes environmental problems such as carbon dioxide emissions. Bentonite-cement-water glass grouting (BCG) is a grout with low environmental impact, designed to reduce the use of cement. The significance of this study is to explore the fundamental properties of BCGs with the bentonite contents of up to 50%, and the antiwash-out and permeability characteristics of BCG in comparison with cement-water glass grout (CG). The effects of water-to-solid ratios (W/S), bentonite content, water glass content and the volume ratio of bentonite-cement slurry to water glass slurry (Va: Vb) on the fundamental properties of BCGs were tested in the laboratory. The results show that the BCGs have excellent characteristics of high viscosity, low bleeding, short and controllable setting time, and high early strength. The BCGs have been applied to the pre-grouting of the water-rich sandy pebble stratum in the Wangfujing North Station section of Beijing Metro Line 8 and achieved better water sealing and reinforcement effects than CG.

To explore some solutions for construction or repair problems, it is necessary to determine the performance of a quick-setting grout such as a sulfoaluminate cement-based grout (SACG). In this study, two typical sulfoaluminate cement (SAC) and one ordinary Portland cement (OPC) were prepared, the water/solid (W/S) ratio was selected as 0.6:1-1.2:1. The properties investigated were: the rheological behaviours, i.e., mini-slump, flowability; the fresh-state properties, i.e., effective W/S or stability, flowability losing time and initial/final setting time; the mechanical performance, i.e., flexural strength (FS), unconfined compressive strength (UCS); the mineral characteristics; microstructure and erosion resistance coefficient. The mechanical strength of blended (SAC+OPC) suspension-sodium silicate double slurries (volume ratios of 1:1-5:1) were determined to provide optimisation suggestions for the double slurries. The results showed that the approximate combination of an anti-washout agent and a superplasticiser should be used, the mineral composition and volume ratio were the main influence factors for the flowability losing times. The strength developments of the SACG were relatively low at high W/S. The strengths of the SAC double slurries are low, and a 10%-30% SAC and volume ratio of 3:1 are recommended if the SACG double slurries are applied. The sulfate erosion resistance coefficients of the SACG were much higher than 1.0 and they have obvious advantages for sulfate erosion resistance.

Water seepage is the primary cause of stone carvings corrosion in karst caverns, which is typically treated with cement-based grout intervention. In this paper, long-term monitoring (more than 1 1/2 years) was carried out in Qinglin cave and Yanxia cave in Hangzhou, China, to quantitatively evaluate the advantages and disadvantages of ordinary Portland cement- and superfine cement-based grout intervention. Results showed that both materials were efficient in preventing water seepage, reducing it by half after the grout interventions. Grout intervention had obvious efficacy in blocking off the strong water seepage points, at the same time decreasing seepage differences among seepage points. Ion Chromatography results suggested that the concentrations of Ca2+, Cl− and SO42− in the seeped water in both caves increased after intervention, and the concentration of SO42− in the seeped water after superfine cement application in Qinglin cave was much more than that in the seeped water in Yanxia cave, where ordinary Portland cement was applied. Therefore, using superfine cement may bring more potential risks than ordinary Portland cement. However, X-ray diffraction (XRD) and conductivity analysis results presented that these ions seemly did not deposit on rock surfaces of the caves during the monitoring period.