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Development of a partial safety factor for high strength grouts in offshore applications During the design of grouted connections in offshore applications (wind turbines and platforms), the fundamental material interrelationships are derived primarily on the basis of DIN EN 1992 which is applicable to the design and construction of building of concrete, reinforced concrete and pre‐stressed concrete. In the paper at hand the application of the design value for the compressive strength of concrete fcd to modern, high performance grouts is discussed. Firstly, the components of the design value for the compressive strength of concrete fcd are presented in detail and it is then discussed how in the safety concept within the standards variances are considered in the underlying assumptions and uncertainties are taken into account during their determination. Coefficients of variation were determined based on values of compressive strength from realistic and offshore‐typical grouting experiments, which were applied during the determination of the partial safety factor for grout γG. The applicability of the design value of the compressive strength of concrete fcd under consideration of the derived partial safety factor for grout γG was subsequently tested and compared to the design value of DIN EN 1992. [ABSTRACT FROM AUTHOR]

Bio-concrete, which is a concrete with self-repair capability provided by microorganisms, is attracting much attention. In recent years, crack repair grouts based on microbial metabolism have been studied. Because such grouts are flowable aqueous solutions, they differ greatly from grouts based on inorganic or organic compounds and are expected to penetrate into cracks in concrete by capillary action. Therefore, press fitting of bio-grouts is unnecessary. As an additional advantage, these grouts do not impose a load on the environment. In this study, we performed benchtop experiments using conical tubes with a large amount of calcium source. The experimental results show that the addition of a large amount of calcium shows no substantial change in the amount of precipitate. In addition, the amount of precipitated crystals did not substantially differ even when the type of calcium salt was varied. Prolonging the standing time was led to crystal growth, and the amount of precipitates obtained increased. As a result of scanning electron microscopy observations of the crystals obtained under each growth condition, we confirmed that many yeast cells were mixed in the crystals. However, difference was observed in the crystal structure when calcium salt was varied. Moreover, Calcium carbonate formation was observed on concrete as a preliminary experiment for the crack repair of concrete. Crystals were generated even at room temperature, and better results were obtained when the temperature was set to 40 °C. [ABSTRACT FROM AUTHOR]

Despite the increasing number of studies on geopolymer-based materials, a lack of information still prevails concerning the use of geopolymer materials for the consolidation and conservation of the built heritage. Since the introduction of the term “geopolymer” by Davidovits, several studies have pointed out geopolymers as a potential replacement for traditional binders, mainly due to their advantages associated with mechanical properties and low carbon dioxide emissions. The geopolymers (also known as alkali-activated materials or inorganic polymers) are obtained by a chemical process through which precursors rich in silica and alumina interact with an alkaline medium to result in a material with binding properties. The aim of this study is to exploit the potential of geopolymer-based grouts in the consolidation of stone masonry buildings. Grouting or grout injection is a technique used for the consolidation of heritage masonry buildings; it consists of the introduction of a binding agent to fill the internal voids and cracks. An experimental program was carried out to improve knowledge of geopolymer grouts suitable for consolidation purposes. The experimental findings revealed that the silica-fume-based geopolymer grout has a worse performance from a rheological point of view, whereas it showed promising results in terms of mechanical strength when compared to traditional hydraulic-lime-based grout.

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

The structural behavior of prestressed high strength steel (HSS) tubular members is investigated through the execution of advanced finite element modeling. Numerical models are developed and validated against published experimental data on HSS tubular members subjected to different levels of initial prestress and loaded either in tension or compression. The effect of the presence or absence of grouting on the strength and ductility of the members is also considered. To numerically replicate the structural response recorded in the tests, some key modeling features including the employed numerical solver, the adopted material models and the element types warrant careful consideration. Upon developing of the finite element models, the numerically generated ultimate loads, the corresponding failure modes and the full load-deformation curves are compared to the experimental ones, indicating a successful validation. As anticipated, prestressing enhances the load-bearing capacity for the tensile members, whereas it is detrimental for the compressive ones. A series of parametric studies is performed to assess the influence of key factors on the structural response of prestressed HSS members and the obtained results are discussed. Design guidance for tensile and compressive prestressed tubular members is also provided. [ABSTRACT FROM AUTHOR]

Calcareous sands are typical of warmer seas and are encountered in several high growth locations around the world. Despite having high frictional resistance with friction angles exceeding those of siliceous sands, the in situ behaviour is characterised by particle damage and extreme contraction at high confining stresses. This behaviour results in very low values of skin friction for driven piles in calcareous deposits, where the contraction dominates the pile response. The MIxed Drilled Offshore Steel (MIDOS) pile is a novel mixed-in-place technology which has many advantages over driven steel piles and conventional drilled-and-grouted (D&G) piles. The MIDOS is based on the deep-mixing technology normally used as an onshore ground improvement technique. The mechanical technology and in situ pile performance were successfully demonstrated during an in situ test in silica sand. A laboratory based study was undertaken to assess the MIDOS performance in calcareous sand. Geotechnical tests, grout tests and steel–grout pull out tests were performed to assess the sands and to model the behaviour at the interface of the steel reinforcement and the grout body. These preliminary results demonstrate that the frictional shaft resistance at the pile–soil interface is comparable for both silica and calcareous sands, and as there is no stress relief or contraction during the installation process, the geotechnical performance of the MIDOS pile is deemed comparable for both soil types tested. [ABSTRACT FROM AUTHOR]

CSA cement was used as cementitious material to study grout, the setting time and flowability of grout were regulated by retarder and superplasticizer, and the effect of curing conditions on the performance of grout was studied under low temperature. The results showed that, retarder regulated both of the setting time and flowability of grout, the optimum mix amount of retarder was 0.65%; the mechanical properties of grout under negative temperature were improved by pre-curing, when the time of pre-curing at 5 °C was 4h,the compressive strength of grout curing at -5 °C after 3days was 46.9MPa, and 87.2MPa after 28 days; the grout can be used for the area where the minimum temperature is above -5 °C in winter. [ABSTRACT FROM AUTHOR]

This study investigated the change created in physical properties by irradiating ultrasonic waves in Portland cement grout. In previous research, the grout equipment was scaled-up and a grout circulation system was used for the experiment. The physical properties of ordinary grout materials were compared with those irradiated by ultrasonic waves to observe its effects. This was done by analyzing and comparing the viscosity, strength and granularity. The results indicate that grout irradiated by ultrasonic waves outperformed the non-irradiated grout in all categories of physical properties. [ABSTRACT FROM AUTHOR]

This article investigates the use of photon attenuating inclusions (PAI) for enhancing radiographic imaging of cementitious materials in composite structures. By targeting characteristic high attenuation regions in the photon energy spectrum, PAI can improve void detection in the parent material by increasing contrast in radiographic images. Radiographic imaging of cementitious grout specimens with 5% and 15% weight fractions of candidate PAI materials (Fe, BaCO3, BaSO4) was performed to characterize X-ray attenuation. Virtual radiography simulations were then conducted to evaluate the application of PAI to grout void detection in post-tensioned concrete construction. The simulations demonstrate that grout void detection is most effective when the high energy region of the emission spectrum is near the K-edge of the PAI material. [ABSTRACT FROM AUTHOR]

Earth was used in the past to produce mortars either on its own or in combination with other materials (such as lime and sand). Earth mortars were used both in adobe and in stone masonry structures. This article aims to study stone masonries made with earth mortar and their strengthening by grouting. Six wallettes were constructed, in order to study the mechanical properties of the two- and three-leaf stone masonry before and after grouting. In parallel, several compositions of grouts, having different ratios of hydraulic lime (NHL5), earth and water, were designed and evaluated regarding their injectability properties (fluidity-penetrability, stability tests). Moreover, flexural and compressive strength tests were performed. Thus, this project led to the development of a number of suitable mixes that satisfy the performance criteria set for their design. The suitability of those mixes from the mechanical point of view was checked by injecting them to wallettes, subsequently tested in compression. [ABSTRACT FROM AUTHOR]

In this paper, a high-performance micro-expansion cementitious grout was prepared by using a combination of sulphoaluminate cement, Portland cement and gypsum. And influence of compounding ratio of sulphoaluminate cement and Portland cement, water-binder ratio, silica fume content and aggregate type on the fluidity and mechanical properties of the grout was studied. The results show that, the combination of sulphoaluminate cement and Portland cement can improve the early compressive strength of grouting. When the compounding ratio is 2-8, the 1 d and 3 d compressive strength is 35.7 MPa and 61.7 MPa respectively. The fluidity of grouting increases with increasing water-binder ratio, and the compressive strength decreases. When the water-binder ratio is 0.26, the initial fluidity of grout is 335 mm, the 1 d, 3 d, and 28 d compressive strengths are 36.0 MPa, 61.7 MPa, and 90.6 MPa respectively. Silica fume can enhance the grouting strength. When the silica fume content is 3.0%, the compressive strength of grouting reaches the maximum, and the 1 d, 3 d and 28 d compressive strengths are 36.9 MPa, 63.6 MPa and 92.1 MPa respectively. [ABSTRACT FROM AUTHOR]

This study proposes a mathematical approach to obtain the optimal proportion of the grout constituents for a semi-flexible pavement. Grout mixes were prepared using three different water-cement ratio, three sand sizes, one sand-cement ratio, four/five different percentages of super plasticizer, and two different types of super plasticizer. The grout mixes were tested for flowability and strength using Marsh cone test and cube compressive strength test, respectively. The laboratory results were utilized to validate the proposed mathematical programming approach while obtaining the optimal proportion of grout constituents. Experimental results indicated that a minimum of 2% naphthalene super plasticizer and 1% polycarboxylate super plasticizer are required, irrespective of any combination, to achieve the desired flow time of the grout. The flow time and compressive strength were found to be associated with type of super plasticizer used. The proposed approach was found to be statistically satisfactory, with 95% confidence level, for determining the optimum grout constituents. The validation of the grout penetrability, using the proposed approach, has also been provided. Researchers and field engineers may consider to employ this analytical approach for grout constituent proportioning by partial or total replacement of cement with silica fume or fly ash. [ABSTRACT FROM AUTHOR]

The design of alkali-activated soil reinforcement grouts faces several challenges regarding the required rheological, mechanical and microstructural properties. In this type of applications, the wide variety of source materials and the necessary addition of water affect the structuration processes and extend to the hardened state properties. A comprehensive characterisation of the specificities of these materials and the relations between the multiple factors is essential. This study aims at linking the physicochemical aspects of alkali-activated materials and their early age as well as long term behaviour. This analysis was carried using conventional evaluation methods as well as innovative approaches to examine the influential parameters for a rational design process. Coupling micromechanics and multiscale homogenisation can offer valuable data and help relate the microstructure to the macroscopic mechanical properties. Finally, the better resistance of alkali-activated materials in acid conditions provides a solution for projects involving chemically aggressive environments. [ABSTRACT FROM AUTHOR]

Although many examples of water leakages are observed between the high column of the bridge and the deck, the gaps in between them are not recognized as degradation. However, if water leaks from the gap, deterioration of the reinforced concrete becomes faster than expected, so even though this is not an urgent matter, some inexpensive repairs would be necessary. In this study, the applicability of bio-grout using microbial metabolism for crack repairs was investigated. Bio-grout is a repair material using microbial metabolism, mainly based on water. Therefore, bio-grout is expected to penetrate cracks more easily due to a capillary tension that is quite different from conventional inorganic or organic grout. Therefore, it is unnecessary to press fit the grout into cracks, and this grout is environmentally friendly. This study examined the mixture proportion of the bio-grout used to produce a significant amount of calcium carbonate. Further, the precipitation amount of calcium carbonate was investigated via sedimentation analysis using a geochemical code. The simulation model based on the geochemical code successfully reproduced, the precipitation amount of calcium carbonate with reasonable precision. [ABSTRACT FROM AUTHOR]

Research and experience has shown that given specific loading scenarios and reinforcement configurations, reinforced concrete members may experience nonductile shear failures that can occur in sudden and brittle modes, often leading to structural collapse. It is desirable, therefore, to avoid shear failures and strengthen reinforced concrete elements with potential deficiencies. Candidates for strengthening include concrete elements that ACI 318 permits to be constructed without shear reinforcement (for example, shallow beams, joists, slabs, footings, and others) and concrete in rehabilitated or repurposed structures. This research investigated the effectiveness of two post-installed reinforcement types (undercut anchors and grout-in-place threaded rods) for strengthening reinforced concrete beams in shear. The results from six full-scale shear tests, compared to design provisions in ACI 318-14 and AASHTO LRFD 2014, indicate that highstrength post-installed reinforcement may be used to strengthen beams in shear and achieve deformation and load capacities similar to traditionally reinforced elements. [ABSTRACT FROM AUTHOR]

Post-tensioned (PT) construction incorporating bonded tendons with cementitious grouts has been used for highway bridges. The tendon duct and the encapsulating grout materials provide barrier corrosion protection for the embedded high-strength steel strand. Although generally used in good engineering practice, cases of PT tendon corrosion have been documented relating to inadequate detailing for joints, development of grout bleed water, and, more recently in the past several years, segregation of thixotropic grouts. In the latter case, cases of thixotropic grouts (which have been developed to mitigate grout bleeding), developed physically and chemically deficient grout, have been characterized to have high moisture content and elevated sulfate ion concentrations. The early presence of elevated sulfate ion concentrations in the deficient grout was attributed to hindering stable steel passivation. Case studies of PT corrosion associated with grouts with elevated sulfate concentrations are presented followed by a review of electrochemical techniques and measurements used to identify the role of sulfates in steel corrosion in alkaline solutions such as polarization techniques, electrochemical impedance spectroscopy, and electrochemical noise.

This study investigated the influence of fluorogypsum and KH 2 PO 4 on the mechanical properties and hydration mechanisms of aluminate cement based grouting materials. Physical properties including setting time, pH value and the compressive strength of aluminate cement based grouting materials with different mix design were investigated. The influencing factors and hydration mechanisms were quantified and discussed through XRD, TG, SEM and NMR. The water-cement ratio was fixed at 0.40, and the fluorogypsum content accounted for 10 wt% of the cement mass. With increasing KH 2 PO 4 content, the setting time initially decreased and then prolonged, while the compressive strength at 3d and 28d first increased and then decreased. Among these variations, a content of 0.2 wt% KH 2 PO 4 exhibited the optimal performance with initial and final setting times of 264 min and 308 min, respectively. The compressive strengths at 3 days and 28 days were recorded as 26.4 MPa and 60.5 MPa, respectively, exhibiting an increase of 76% and a remarkable enhancement of 228.80% compared to that of pure aluminate cement. The addition of fluorogypsum facilitated the formation of AFt, while KH 2 PO 4 regulated the slurry's pH, concurrently enhancing AFt production, and the morphology of AFt transformed from acicular to a more slender fiber shape, which exhibited improved interlacing and overlapped properties, thereby promoting strength development. The hydration process was analyzed in conjunction with low-field nuclear magnetic resonator analysis. The findings revealed that the samples containing 10 wt% fluorogypsum and 0.2 wt% KH 2 PO 4 in aluminate cement exhibited the highest levels of chemically bound water at both 3d and 28d, followed by samples with 10 wt% fluorogypsum in aluminate cement, while those composed solely of aluminate cement displayed the lowest content. The T 2 spectra data were also fitted to a function, revealing a positive correlation between pore evolution and the hydration rate of the samples. • Fluorogypsum and KH 2 PO 4 can shorten the setting time and increase the compressive strength of calcium aluminate cement. • Fluorogypsum contributed to AFt formation; KH 2 PO 4 further increased AFt and modified its morphology. • KH 2 PO 4 changed the morphology of AFt to elongated fibers and optimized the pore structure. • Hydration of aluminate cement can be significantly enhanced by combined addition of fluoropgypsum and KH 2 PO 4. • Fluoropgypsum alone could still cause a substantial promotion effect on the hydration rate of aluminate cement. [ABSTRACT FROM AUTHOR]

Offshore oil and gas pipelines are susceptible to corrosion and need rehabilitation to keep them operating in-service conditions. Fibre composite filled with epoxy-based grout is emerging as an effective repair and rehabilitation system for offshore pipelines performing underwater. In such applications, the infill grout is often subjected to moisture and elevated temperature along with compressive, tensile and localised stresses at the defect. Current standards and practices for composite repairs suggest detailed investigation of the fibre reinforced sleeve, while the characterisation of the infill material is yet to be conducted for performance evaluation. The present work investigates the mechanical and thermal properties of three epoxy grouts as candidates for infill in a grouted sleeve repair for underwater pipeline. An understanding on the effect of hygrothermal ageing on the grout properties for defining the period of 1000 hours as “long-term” according to ISO/TS 24817, in comparison to their unconditioned state, is also presented. The compressive and tensile strength of the unconditioned grouts ranges from 100–120 MPa, and 19–32 MPa, respectively, which indicates that these grouts are suitable for structural rehabilitation of the pipelines. Moreover, the glass transition temperatures, Tg and Tt of the unconditioned grouts are found to be within the ranges of 50–60 °C, and 80–90 °C, respectively, which are reduced by about 20°C after conditioning.

Due to their porous nature, lightweight aggregates have been shown to exhibit thermal properties that are advantageous when used in building materials such as lightweight concrete, grout, mortar, and concrete masonry units. Limited data exist on the thermal properties of materials that incorporate lightweight aggregate where the pore system has not been altered, and very few studies have been performed to quantify the building energy performance of structures constructed using lightweight building materials in commonly utilized structural and building envelope components. In this study, several lightweight concrete and masonry building materials were tested to determine the thermal properties of the bulk materials, providing more accurate inputs to building energy simulation than have previously been used. These properties were used in EnergyPlus building energy simulation models for several types of commercial structures for which materials containing lightweight aggregates are an alternative commonly considered for economic and aesthetic reasons. In a simple model, use of sand lightweight concrete resulted in prediction of 15–17% heating energy savings and 10% cooling energy savings, while use of all lightweight concrete resulted in prediction of approximately 35–40% heating energy savings and 30% cooling energy savings. In more complex EnergyPlus reference models, results indicated superior thermal performance of lightweight aggregate building materials in 48 of 50 building energy simulations. Predicted energy savings for the five models ranged from 0.2% to 6.4%.

The development of civilization, and subsequent increase in the number of new buildings, poses engineering problems which are progressively more difficult to solve, especially in the field of geotechnics and geoengineering. When designing new facilities, particular attention should be paid to environmental aspects, and thus any new facility should be a passive building, fully self-sufficient in energy. The use of load-bearing energy piles could be a solution. This article presents research on the cement slurry formulas with the addition of graphite and graphene, that can be used as a material for load-bearing piles. The proposed solution is to introduce U-tubes into the pile to exchange heat with the rock mass (the so-called energy piles). A comparison of four slurry formulas is presented: the first one consisting mainly of cement (CEM I), graphite, and water, and the remaining three with different percentages of graphene relative to the weight of dry cement. The results could contribute to the industrial application of those formulas in the future.

This research aimed to study the impact response of topology optimized hammerhead pier beam (HPB) based on the density approach. The HPB is prepared with the concept of preplaced aggregate fibrous concrete (PAFC) comprising two primary approaches; first, the coarse aggregate and fiber are prepacked into the designed formwork. Second, the gaps between the aggregate and fiber are filled with cement grout. In this work, an attempt has been made to study an impact response of HPB made with PAFC. Five HPBs were prepared and strengthened with steel fibers with two different schemes, Firstly, the HPB was reinforced with a full cross-section at 2 and 4% of steel fiber, while another set of beams were only reinforced in the tension zone with the same amount of fibers. The study parameters included compressive strength, impact strength, impact ductility index, number of main and secondary cracks, and failure pattern. It was observed that the PAFC had an increase in compressive strength up to 56.9%, compared with nonfibred concrete. A fully fibered concrete beam with 4% fiber addition was the best at taking impact, and the initial crack and failures were observed at 2725.1 J and 3009.8 J, respectively, compared with non-fibered and tension zone fibered concrete beams. Compressive local damage and transverse flexural cracks were observed, which had caused initial cracks and final failure. The HPB with a full reinforced scheme at 4% dosage exhibited higher impact strength than the normal concrete and beam reinforced only in the tension zone.

The injection of grouts is a consolidation technique suitable for overcoming the structural deterioration of old stone masonry walls. Grouting operations involve introducing a suspension (grout) into a masonry core with the aim of improving the load capacity of the wall, as well as reducing its brittle mechanisms. The yield stress of injection grouts will affect the injection pressure and their flow inside the masonry. However, the determination of some rheological properties such as yield stress in hydraulic grout is challenging, due to the combined effects of hydration reactions and interactions between the particles present in the suspension. In this study, the determination of the yield stress of natural hydraulic lime-based grouts with polypropylene fibers was carried out. The changes in yield stress with time, fibers content and hydration were evaluated by two measurement methods using a rotational rheometer. Additionally, the static and dynamic yield stress as well as the critical shear–strain rate were determined, which provided useful information on the grout design in order to achieve successful grouting operations.

Highlights • Review on application of polyurethane grout for improving the properties of weak soils. • The paper also covered the chemistry of polyurethane components and its applications. • The methods of grouting and grouting materials were also explored. • Improving polyurethane by incorporating fillers and other additives are also covered. Abstract The recent need to develop infrastructure, driven by global population growth is forcing societies to construct on any soil type available within their vicinity including weak soils. However, due to the poor physical and engineering properties of weak soils, they are not suitable for construction purposes. Given many ground improvement techniques that are presently employed to improve the properties of weak soils and to reduce the potential damages caused by them, this paper addresses this issue by conducting a literature review and collecting information on the application of polyurethane chemical grout for improving the properties of weak soils. While, many researchers have investigated the application of polyurethane, its application and the methods of improving the properties of weak soils, including detailed information on the application of polyurethane on weak soils for improving its properties is limited. Accordingly, this paper has examined the chemistry of each component of polyurethane and its application and explored the methods of grouting, grouting materials, the advantages and disadvantages as well as the applications of grout both in the field and in the laboratory. The review also discussed the possible means of improving polyurethane by incorporating reinforcing fillers, surfactant, catalyst and other additives. The review concluded that improved polyurethane has the potential to improve weak soil types for infrastructure development. [ABSTRACT FROM AUTHOR]

Gypsum and grout are finishing materials found in almost all constructions. Specifically, gypsum has been widely used because of its low cost in the composition of drywall. However, in humid environments, they are susceptible to microorganism infestation. In this work, silver nanoparticles (Ag-NPs) were incorporated to gypsum (643 and 321 ppm) and grout (227 ppm) and the antimicrobial activity tested. The MIC value for Ag-NPs solution was 26.8 µg ml−1 for Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli and 428 µg ml−1 for the A. Niger. Another MIC test with specimen component dilutions indicated that grout and gypsum do not exhibit antibacterial activity against S. aureus. However, when incorporated with Ag-NPs, both grout and gypsum demonstrate growth inhibition. In a biofilm test performed with S. aureus, SEM images revealed crenation of bacteria in contact with specimens containing Ag-NPs. The addition of Ag-NPs causes change in color that was measured through CIELAB (International Commission on Illumination) color coordinates. There is no difference in the L value parameter (lightness) for all materials tested. However, the comparison between the parameters a (green-red coordinate) and b (blue-yellow) for gypsum and grout results in a statistically significant difference (p < 0.05, Kruskal). The values of b increase as the Ag-NPs concentration increases because of the yellowish coloration of the solution. It can be concluded that Ag-NPs can be incorporated to gypsum and grout, maintaining its antimicrobial feature improving the material properties, which can benefit health and the environment. [ABSTRACT FROM AUTHOR]

Abstract Cement-based materials containing carbon nanotubes (CNT) has enhanced electrical and thermal characteristics. This study aimed to detect voids in prestressed concrete (PC) grout using CNT. CNT cement grout specimens were fabricated and tested inside ducts. Test parameters were type of CNTs, concentration of CNTs, and void ratio of grout. Thermal imaging analysis and electrical resistance analysis were performed to detect and identify the void configuration. The field emission scanning electron microscopy (FE-SEM) images were taken to obtain detailed information of microstructure of tested specimen. It was concluded that MWCNT grout was appropriate to detect the void in duct using thermal image analysis. SWCNT grout was more suitable to identify void in duct through electrical resistance analysis. [ABSTRACT FROM AUTHOR]

There is great interest among geotechnical engineers to develop environment-friendly grouting materials for ground improvement. Biomineralisation is the process where micro-organisms produce minerals; mainly carbonate products that provide a basis to develop ‘biogrout’. Biogrout could be an excellent material for the purpose of ground improvement with several advantages over current remedial measures, to improve the mechanical properties, to decrease the permeability of porous materials, and to modify the properties of soil. In this review article, the conventional soil improvement practices are discussed with their drawbacks. In order to overcome drawbacks of those conventional processes, state-of-art on biologically based grout material is proposed for soil improvement. Further, an attempt has been made to compile the current knowledge on biogrout and identify research gaps for future research. [ABSTRACT FROM AUTHOR]