Showing papers in "Innovative Infrastructure Solutions in 2021"

State-of-the-art review on efficacy of xanthan gum and guar gum inclusion on the engineering behavior of soils

Abstract: Soil amelioration is a challenging task in bulk civil engineering applications such as embankment slopes, landfill liner, pavement subgrade, retaining wall back fill. The conventional chemical stabilization techniques (i.e., cement, calcium hydroxide, sodium chloride, calcium chloride, etc.) inherently suffer from associated carbon emissions during their production stages. With the advent of biopolymers derived from natural sources having low embodied energy levels, they can replace conventional stabilizers. The current review article highlights the significant properties of two such biopolymers, i.e., xanthan gum (XG) and guar gum (GG), and their innate potential in stabilizing different soil types including mine tailings. The issues arising with wet and dry mixing of these biopolymers and suggested measures have been critically addressed. The degradation characteristics of biopolymers, which limit their use for bulk civil engineering applications, have been critically discussed, and the potential solutions to overcome durability issues are suggested. Future applications of these biopolymers in geoenvironmental engineering relying on the metal encapsulation properties are discussed in detail. It is believed that the selected biopolymers in this review are renewable, sustainable and remarkable materials with low embodied energy levels and low carbon footprint values compared to existing conventional stabilizers.

A comparative review on foam-based versus lightweight aggregate-based alkali-activated materials and geopolymer

Abstract: Alkali-activated materials and geopolymer are major sustainable alternative binding materials to ordinary Portland cement products with higher thermal resistance and often better durability properties. In lightweight form, they have an unmatched lowered thermal conductivity and insulating properties making them a perfect fit for optimized structural components with highest strength to density ratio and major energy savings in green buildings. For them to produce lightweight materials, generally either certain foaming agent or some types of lightweight aggregates in virgin, expanded, or recycled form are utilized that reduce the overall density through higher overall porosity. In accordance, this review provides an updated information on recent advances while stressing the sustainability of lightweight geopolymer materials over ordinary Portland cement products that are vastly in use. In the end, recent mechanical and durability properties developed and documented are reviewed and provided for future applications. Based on the result of this review, the most common lightweight aggregates used in literature are perlite, pumice, shale, ceramsite, and slate sand, in expanded and porous form, along with recycled thermosetting (e.g., rubber), or thermoplastic (e.g., polyethylene) materials. In foam form, chemical and mechanical foaming are the most commonly used foaming techniques to increase porosity of final materials. The pore mechanism of foam-based geopolymer is found to be different from that of lightweight aggregate-based geopolymer. This variation results in different physico-mechanical and durability properties such as better insulation properties (and lower thermal conductivity) for foam-based versus better mechanical properties for lightweight aggregate-based geopolymer.

Waste tires steel fiber in concrete: a review

Abstract: The emergence of waste tire steel fiber (WTSF) which is an undervalued resource was borne out of the need to extract the useful materials in waste tires considering the sheer volume of this resource that is disposed of in landfills globally. These fibers find applications in tunnel linings, hydraulic structures, bridge decks, pavements and slope stabilization. The fiber length has positive influence on compressive strength (increased by more than 10%), flexural strength (increased by more than 50%) and split-tensile strength(increased by more than 30%) while slump and flow (increased by more than 80%) were reduced but can be avoided through careful mixing, reduction of coarse aggregates and utilization of short fibers. Utilization of WTSF contributes to the sustainability of the construction industry. This paper focuses on reviewing the contemporary management of waste tires, fresh and hardened properties of steel fibers extracted from the waste tires, usage of the steel fibers and the durability of concrete containing these fibers.

Use of natural vegetable fibers in cementitious composites: concepts and applications

Abstract: The application of vegetable fibers has gained great notoriety as a building material, due to its availability, mechanical properties and low cost. In this sense, the objective of this work is to carry out a bibliographic review on the application of this fibers in cementitious matrices, including concrete and mortar. This work analyzes the main characteristics of natural vegetable fibers that affect the properties of composites, such as geometric, physical, mechanical and chemical properties. The characteristics of the alkaline treatments carried out on the fibers are highlighted to improve the adhesion properties, durability, water absorption and tensile strength. Some case studies were analyzed in detail: coconut, bamboo and bananas fibers, all in combination with cementitious matrices. Finally, some suggestions for future work are highlighted, showing the need for further studies on the application of natural fibers in cementitious composites.

Undrained stability of unsupported conical slopes in two-layered clays

Abstract: A conical slope is widely used in many constructions of in situ piles, piers, footings, mat foundations, raft foundations, energy storages, or water tanks since this unsupported excavation is much cheaper than an excavation with supports. This paper presents new plasticity solutions for undrained stability of unsupported conical slopes in two-layered clays by using axisymmetric finite element limit analysis. Four parametric studies were performed on the slope height ratio, the slope inclination angle, the thickness ratio of two-layered clay, and the strength ratio of two-layered clay, where the stability factor of this problem is investigated. In all the cases, the exact stability factors are accurately bracketed by lower and upper bound solutions within 1%. The design charts for estimating the stability of conical slopes in two-layered clays are proposed. Three failure mechanisms, i.e., toe, based, and face failures are observed and discussed in the paper. The predicted failure mechanisms of the unsupported conical slopes in two-layered clays are presented in order to portray the impact of all considered dimensionless parameters.

Blast analysis of tunnels in Manhattan-Schist and Quartz-Schist using coupled-Eulerian–Lagrangian method

Abstract: The tunnels are the lifeline of urban centers and play a significant role in the mass transportation of goods and services. They are the locales of accident and target for subversive activities, including terror attacks. Society needs to be well aware of such accidents and mitigation methods. We have carried out the analysis of internal blast loading using finite element analysis for two different rock tunnels constructed in Manhattan-Schist and Quartz-Schist rock employing Abaqus. The coupled-Eulerian–Lagrangian method has been considered for advanced modeling of the air inside the tunnel and 100 kg of Trinitrotoluene (TNT) explosive. TNT has been considered as material for better results by using Jones–Wilkins–Lee model and Eulerian volume fraction tool in the Abaqus have been used. This study concludes that rocks having a higher angle of friction are more resistant to blast loading. Further, rocks having lower cohesion are more blast resistant. However, if the design of tunnel support remains constant in rocks, then, damage in the tunnel lining remains the same, but deformations vary.

Opportunities and challenges for the building monitoring systems in the age-pandemic of COVID-19: Review and prospects

Abstract: The latest COVID-19 pandemic outbreak posed a significant risk to millions of people worldwide who are safe and well-being. As the environment continues to be open from lockdowns and becomes unprecedentedly tenuous or what many called a “new norm,” it makes sense to focus on what the society has experienced, re-examine our fundamental beliefs, and map the path of designing and creating a sustainable world. This article has summarized the latest technologies that have been recently implemented to control the spreading of COVID-19 through embedded smart monitoring systems and communicate effectively with the building management infrastructure. This article also discussed the statistical research analysis, which motivates the achievement of the targeted sustainable development goals (SDGs). Last but not least, the implemented technologies and their related variables to be controlled, challenges, and new perspectives were also addressed.

Experimental study of ground improvement by using encased stone columns

Abstract: The application of stone columns increases the stiffness of soft soils which contributes to its load carrying capacity and accelerates the process of consolidation leading to reduction in settlement. However, under external loading, squeezing of adjacent soil into the columns not only compromises the integrity of the columns but also reduces its stiffness, strength and drainage properties. The present study investigates the use of vertically and horizontally reinforced stone columns, as a remedial measure for ordinary unreinforced stone columns. The vertical reinforcement is done by encasing the stone columns in geotextile and horizontally by placing geotextile circular discs within the columns at regular interval. Model tests on group of 3 and 4 unreinforced and reinforced stone columns have been conducted in weak sandy soil. The load–settlement response and failure modes for both reinforced and unreinforced groups have been studied. It is observed that reinforced group of stone columns depict better load bearing capacity as compared to unreinforced group. Moreover, bearing capacity for vertically encased and horizontally reinforced is almost similar, with horizontally reinforced group of 4 stone columns depicting slightly higher (1–2%) bearing capacity for a settlement of 30 mm. The experimental results are also validated with theoretical results and are found to be in good agreement.

Municipal solid waste incineration bottom ash: a competent raw material with new possibilities

Abstract: According to the economic feasibilities, municipal solid wastes (MSW) are being dumped or treated in different possible manners. Municipal solid waste incinerated ash (MSWIA) is one of the final products of MSW treatment plants after incineration. Due to less sustainable waste management options, MSWIA is produced in tons and dumped into landfills. Researchers in various developmental project suggest using MSWIA as an economical and eco-friendly mode of final disposal. The use of MSW incinerated bottom ash (MIBA) has an exceptional potential of supporting sustainability by conserving natural resources. The paper targets the possible benefits of MIBA in various construction and soil improvement projects by compensating the primary aggregates. The partial replacement of primary aggregates is a durable and cost-effective option for equal or improved strength. The addition of MSWIA is not new, but the studies available are limited in number. The presence of certain chemical compounds in MIBA is leading to advanced industrial-based applications. The residue can be a primary raw material for synthesizing new compounds, in land recovery and Hydrogen gas production. Some studies have favored its utilization in the most natural form, whereas some suggest avoiding the usage due to its various environmental and strength-based limitations. The article investigates significant studies and confirms the possible opportunities from waste residues for more competent raw material.

High-temperature performance of ambient-cured alkali-activated binder concrete

Abstract: Owing to their lower carbon footprint and efficient performance compared to portland cement (PC), alkali-activated binders (AAB) show promising potential as an alternative to PC. The present paper investigates the high-temperature performance of AAB concrete through compressive and bond strength tests. Four different AAB concrete mixes with varying proportions of fly ash: slag (100:0, 70:30, 60:40, and 50:50) cured under ambient conditions are exposed to elevated temperatures. The mechanical performance of AAB concrete is corroborated with microstructural changes. The results show that AAB concrete with fly ash: slag ratio of 70:30 exhibits the best mechanical performance after exposure to elevated temperatures. This behaviour is attributed to the growth of new crystalline phases of akermanite and gehlenite as observed from the X-ray diffraction patterns. This study shows that there is an optimum proportion of slag content beyond which the mechanical performance of AAB concrete significantly deteriorates when exposed to elevated temperatures. The failure pattern of AAB concrete during the bond strength test varies with the precursor proportion and the exposure condition.

Role of red mud as a cementing material in concrete: a comprehensive study on durability behavior

Abstract: Red mud (RM), a semi-solid residual of the alumina refinery process, has higher alkalinity, and its disposal leads to environmental imbalance. To overcome this issue, RM is partially replaced with cement in the range of 0% to 20% at an interval of 5%. The present research work majorly focused on durability and micro-level concrete studies containing pre-calcined (600 °C in 2 h) RM. The tests on red mud concrete, viz. compressive strength, sorptivity test, open porosity test, rapid chloride penetration test, accelerated corrosion test, water absorption test, X-ray diffraction, scanning electron microscope (SEM), and energy-dispersive spectroscope (EDS) analysis, have been conducted to investigate the comprehensive characterization of concrete with RM. From the compressive strength test results, maximum strength was observed at 10% replacement. Open porosity, chloride ions permeability, water absorption, and sorptivity values showed reduction at an increment of RM replacement level. RM concrete offered more corrosion resistance due to high alkalinity, which possessed a pH of more than 12.5. From the micro-level investigations such as SEM and EDS, higher C–S–H gel formation was observed in RM 10% replacement concrete. In the meantime, less number of pores was observed in all RM replaced concrete mixes.

Optimization of sustainable high-strength–high-volume fly ash concrete with and without steel fiber using Taguchi method and multi-regression analysis

Abstract: The progression of high-strength–high-volume fly ash concrete addresses fly ash as a resource productive material with the sustainability of the construction industry. This paper presents the evaluation and optimization of the sustainable mechanical properties of concrete with and without crimped steel fibers. In the first phase, the experimental tests are conducted to know the compressive strength, split tensile strength, and flexural strength obtained from the optimal mixes of concrete. Taguchi L16 orthogonal array experimental design is applied to optimize the performance of mechanical properties of concrete by using the design of experiments. The level of influence of fly ash percentage on mechanical properties of a concrete mixture is determined by multiple regression analysis. However, after multiple regression analysis, it is found that the error related to the correlation between experimental and analytical value strength is about 5%. Hence, it can be strongly recommended that the developed regression model is sufficient and has a competent approach to optimize the experimental as well as analytical value simultaneously. However, it is concluded that the Taguchi technique is an effective methodical model to reduce the overall investigational work. It is also an efficient approach to optimize designs for performance and quality. The present research confirms that with the mechanical properties of the high-strength–high-volume fly ash steel fiber concrete, it is a more suitable alternative sustainable solution to the concrete industry.

Effect of limestone powder on mechanical strength, durability and drying shrinkage of alkali-activated slag pastes

Abstract: The use of limestone powder (LSP) as a cement replacement is used in abundant applications due to its low cost and wide availability. Adversely, the use of LSP as a part of the precursors of alkali-activated materials (AAMs) is still in the developing stage. This scarcity of studies opened the door and encouraged the researchers for more investigations. Thus, this paper studied the effect of various amounts of LSP on some properties of alkali-activated slag (AAS) pastes activated with NaOH and Na2SiO3 solution. Slag was partially replaced with LSP at ratios of 15–60 wt%. The effects of LSP on mechanical strength, water absorption, chloride penetration permeability, drying shrinkage were studied. Advanced apparatuses were applied to detect the changes in crystalline phases, hydration products and microstructure of the pastes with and without the inclusion of LSP. The results confirmed that 15% LSP was the optimum amount, which is responsible for the highest mechanical strength, lowest water absorption and lowest charge passed. The drying shrinkage was mitigated with the inclusion of LSP. The inclusion of 15% LSP enhanced the 28-day compressive strength and flexural strength by 11.41% and 13.7%, respectively, while the water absorption, charge passed and drying shrinkage were decreased.

Effects of waste glass addition on the physical and mechanical properties of brick

Abstract: The use of industrial and municipal wastes to develop sustainable construction and building materials plays a significant role to improve the environment and economy by preserving natural resources and reducing waste management costs. Recycling also helps to reduce land, water, and air pollution as well as waste landfilling issues. The present work has been done to explore the prospect of partial replacement of natural soil for brick manufacturing with municipal waste, which is soda-lime glass. In this study, the effect of waste glass additives on the physical and mechanical properties of brick has been investigated. Bricks were manufactured using 2%, 4%, 10%, 16%, 30%, and 40% of waste glass replacing natural clay. Compressive strength, water absorption, and other tests were carried out to determine the mechanical performance and durability of the prepared brick specimens. An increase in compressive strength and decrease in water absorption of the samples were observed with the addition of waste glass. It was found that the developed bricks have been satisfying the parameters of the Grade-A and Grade-S brick in accordance with the Bangladeshi standard for conventional building clay brick (BDS 208). Results obtained from this study indicated that partial replacement of natural clay in brick with waste soda-lime glass makes the brick production sustainable and eco-friendly.

An evaluation of the advantages of friction TMD over conventional TMD

Abstract: The seismic performance of conventional tuned mass damper (TMD) has been often improved when more TMD mass ratio is utilized. One limitation in using higher TMD mass ratios for tall buildings is the challenges of designers from the practical point of view. So far, conventional TMD has been more uneconomical. The research on the seismic performance of friction tuned mass dampers (FTMD) is still going on. This paper aimed at evaluating the advantages of the optimal design of friction TMD over conventional TMD for tall structures. For this aim, an optimal design was developed based on a multi-objective cuckoo search optimization algorithm to find the optimal TMD and FTMD parameters, including mass, damping, frequency ratios, and the friction coefficient. Here, the seismic performances of a 40-storey tall building were evaluated and compared from structural responses and energy. Results showed that both dampers could significantly reduce the maximum floor displacement, drift, and acceleration. Furthermore, the FTMD system exhibited a better performance in reducing the roof displacement against the TMD system when the mass ratio was less than 0.03. These advantages are considered to be very important from a practical point of view.

Experimental and computational response of strip footing resting on prestressed geotextile-reinforced industrial waste

Abstract: Geotechnical engineering practices involves the use of geosynthetic as one of the major construction materials for stabilizing terrains and these materials have been also proven to be technically efficient. In view of the above, a series of model load tests with variation in the depth of geotextile and prestressing force were carried out to study the strength and deformation characteristics of ferrochrome slag reinforced with single prestressed geotextile layer. The present study provides a sustainable replacements solution for industrial waste such as ferrochrome slag. It is also found that pretensioning of reinforcements is effective in comparison with simple reinforcement. The load settlement curves demonstrate that reinforcements and prestressing significantly reduce the settlement of a strip footing resting on geotextile-reinforced ferrochrome slag. Also, a pretensioning force of 9 kN/m is found to have the least settlement. Further, this study proposes the use of artificial neural network and extreme learning machine (ELM) to predict settlement using basic input parameters. Application of computational models provides an innovative solution for predicting the settlement of footing with ease and in a cost-efficient manner. The computational model concludes that the developed ELM models are efficient and effective in predicting the settlement of a footing and can be used as a robust tool for preliminary assessments.

Estimation of modified expansive soil CBR with multivariate adaptive regression splines, random forest and gradient boosting machine

Abstract: Construction of flexible pavement on expansive soil subgrade relies on the safe determination of California bearing ratio (CBR) value, a critical component in flexible pavement design. However, its determination, particularly in the laboratory, often consumes sufficient man-hours. This necessitated the urgency to explore alternative procedures, such as the development of reliable models to estimate the CBR of subgrade especially modified expansive soil subgrade. In the present study, three machines learning models, which are multivariate adaptive regression splines (MARS), random forest and gradient boosting machine models, were developed to predict the CBR of expansive soil subgrade blended with sawdust ash, ordinary Portland cement and quarry dust. The performance of the models was evaluated using several error indices, and the results obtained from the evaluation showed that the random forest model has superior predictive ability when compared with the MARS and gradient boosting machine models. Specifically, the R2 values for the training and testing data for the random forest model, which were, respectively, 0.84829 and 0.75282, clearly indicated that the random forest model has good predictive ability and possesses greater generalization ability than the other developed models in this study.

Liquefaction study of fine-grained soil using computational model

Abstract: Liquefaction is one of the most disastrous phenomena that arises due to earthquakes and has always been a major concern for engineers due to the damages and devastation it causes to the environment, structures and the human life. Liquefaction evaluation has been studied vigorously by many researchers for past few decades and based on their observations various researchers gave different limits of PI and other geotechnical parameters which classified soil in liquefiable, potentially liquefiable and non-liquefiable zones, but the question of reliability still needs to be addressed. The present study provides a new set of range for plasticity index and wc/LL ratio for liquefaction classification of fine-grained soil. The present study develops a computational model based on in situ soil properties to evaluate liquefaction potential. Artificial neural network (ANN) model has been developed for predicting liquefaction susceptibility. The significance of plasticity index on liquefaction has been primarily considered while developing the ANN model. The results confirm that the use of artificial intelligence shows the best success rate amongst all the considered approaches for prediction of liquefaction. Due to its efficient cost and quick predictions, it can be used as a sustainable method for evaluating and predicting risk against seismic hazard and infrastructural development.

Application of integrated fuzzy FCM-BIM-IoT for sustainable material selection and energy management of metro rail station box project in western India

Abstract: Fuzzy Factor Comparison Method is a paired comparison-based Multi-Criteria Decision-Making method which can be effectively applied for selection of the best feasible alternative among a set of available alternatives. This paper aims at developing a methodology by application of fuzzy Factor Comparison Method for selection of most feasible, sustainable material for the design of floor, ceiling, walls, cladding, openings and fenestrations for an infrastructure transportation facility like metro rail station box of Ahmedabad, India. Results of fuzzy Factor Comparison Method reveal that polished Kota stone tiles, toughened fibreglass ceiling, Kota stone wall tiles and insulated fibreglass door appear to be the most feasible sustainable materials. Evaluation of the alternative building materials and design strategies was carried out through Building Information Modelling, and the observed results show 73% of average embodied energy savings achieved by the suggested alternative materials instead of the existing ones. Furthermore, this study also proposes a framework for real-time automated Building Information Modelling-enabled energy management system for the elevated metro rail station by the Internet of Things sensors. It has been observed that more than 25% of the operational cooling load can be reduced by the proposed integrated Building Information Modelling-Internet of Things framework. This novel approach plays a key role in the sustainable future of infrastructure projects.

Effect of graphene oxide on high-strength concrete induced with rice husk ash: mechanical and durability performance

Abstract: The global shift to usage of eco-friendly materials has driven a movement for the utilization of many additives in construction practices. Moreover, the application of nanomaterials has also been increased for enhancing the performance of concrete. This paper primarily focuses on the reinforcing effects of graphene oxide (GO) on high-strength concrete (HSC) made with and without rice husk ash (RHA). Cement was replaced with 10% RHA by weight. GO was added in different proportions of 0.025, 0.050, 0.075 and 0.1% by weight of cement. Performance of engineered mixes was evaluated as mechanical (compressive, flexural and splitting tensile strength), durability (water absorption, sorptivity, rapid chloride penetration and acid resistance) and microstructural (SEM and EDAX). The results depicted that mechanical and durability properties of HSC increased significantly on the incorporation of GO and further increased with partial replacement of cement with 10% RHA. The optimum performance in terms of mechanical and durability properties was achieved by a combination of 10% RHA and 0.075% GO. Increasing the percentage of GO beyond 0.075% results in drop-in strength and durability properties. Furthermore, the microstructural studies indicated that the mixes containing both RHA and GO exhibited a denser microstructure, by consuming calcium hydroxide and producing additional C–S–H gel in the matrix, concluding the practicability for use of GO and RHA in HSC.

Experimental investigation of Bambara nut shell ash in the production of concrete and mortar

Abstract: The goal of producing concrete that provides long-term durability with regard to characteristics like strength and reduced susceptibility to alkali–silica has led to the development of several high-performance materials. While the use of Bambara nut shell ash in concrete is gaining acceptance in various applications, the mineralogical composition of such by-product materials cannot be easily controlled as a manufactured pozzolan. In this research work, the characterization and use of Bambara nut shell ash in concrete production were investigated. A mix proportion of 1:3:6 with water cement ratio of 0.55 were used. The percentage replacement of cement with Bambara nut shell ash (BNSA) is 0%, 5%, 10%, 20%, 30% and 40%. Concrete cubes of 150 mm × 150 mm × 150 mm of OPC/BNSA were cast and cured at 3, 7, 28, 60 and 90 days , respectively. At the end of each period of hydration, three replicate concrete samples for each period of hydration were crushed and their average comprehensive strength was recorded. The result for the compressive strength test indicated rise in percentage difference as the BNSA replacement ratio increases from 5 to 40% with a value of 20.69–46.53%, respectively. The concrete density response showed slight increment in percent difference with a value of 0.85–3.47% for BNSA replacement ratio of 5–40%, respectively. The Poisson ratio test results obtained indicate percentage difference increase as the BNSA ratio increases from 5 to 40% with a value of 5.17–11.14%, respectively. Furthermore, the Young’s modulus of elasticity results obtained showed percentage difference rise from 9.4 to 14.17% as BNSA ratio increases from 10.81 to 29.412% and as BNSA replacement ratio increases from 5 to 40%, respectively. The results indicate satisfactory performance at 5% replacement.

Development of expansive soil geopolymer binders for use in waste containment facility

Abstract: Waste containment facilities require liners and covers for safe waste disposal, which can be efficiently achieved using robust green technologies. In the present study, a systematic approach was adopted towards the development of reliable expansive soil geopolymers suitable for waste containment application. Various factors that influence geopolymerisation were considered including the precursor type (PT), precursor content, liquid alkali hydroxide type (LT), activator-to-precursor ratio (A/P) and method of preparation. Multiresponse optimisation for permeability, volumetric shrinkage and unconfined compressive strength was executed to achieve soil geopolymers that satisfy the regulatory requirement as hydraulic barrier materials. This was done using a robust experimental design and the utility concept to prescribe a framework for achieving reliable soil geopolymers. The results obtained show that significant interactions between the factors (PT × LT) and (PT × A/P) affected the response characteristics and consequently the soil geopolymer performance. The aptness of the multiresponse optimisation was confirmed at 95% confidence interval, which revealed that the developed soil geopolymers can be used in waste containment facility under certain conditions. Evidence of the geopolymerisation process was clarified using microstructural analyses. Scanning electron microscopy and energy-dispersive spectroscopy supported the formation of N–A–S–H and K–A–S–H gels. Moreover, diffraction patterns for new minerals such as muscovite and crystobalite were formed, with the disappearance of clay minerals. The presence of aluminosilicate gel binding systems was revealed by Fourier transform infrared spectroscopy. The participation of clay minerals in the geopolymerisation distinguishes the developed expansive soil geopolymer from the conventional geopolymers developed for concrete applications.

A simple approach for estimating contribution of vetiver roots in shear strength of a soil–root system

Abstract: Bio-engineering technology, using vegetation, is an innovative and low-cost measure to address slope failure-related problems. To quantify the contribution of vegetation roots for increasing the strength of soil, several laboratory and field investigations have been conducted in this study. At first, the morphological characteristics of vetiver (Chrysopogon zizanioides) were studied. It was found that vetiver root can grow up to 1 m in three months in sandy soil. The average tensile strength of full-grown vetiver root was 27 MPa, and with the increase in root diameter, root tensile strength decreases. A correlation was developed between the tensile strength and diameter of the root, which was compared with previous studies. Laboratory tests were conducted on root mixed soil and found that the shear strength of rooted soil increases with the increase in root length and decrease in soil water content. Also, an attempt has been made to estimate the improved shear strength of rooted soil by developing a correlation between the additional shear strength of rooted soil and the tensile strength of roots per unit area of soils. To evaluate the shear strength of vetiver-rooted soil, in situ tests were conducted in naturally grown vetiver land for both rooted soil and bare soil. An approximately linear relationship was observed between the additional shear strength of rooted soil and the mobilized tensile strength of roots. Finally, a mathematical model was developed based on the experimental outcomes. This simple model can be used to estimate the shear strength parameters of rooted soil.

Compressive strength prediction model of high-strength concrete with silica fume by destructive and non-destructive technique

Abstract: The study proposes a new model for estimating the compressive strength of high-strength concrete using destructive and non-destructive testing. The effect of silica fume replacement level and its cementing efficiency factor on compressive strength and ultrasonic pulse velocity (UPV) were experimentally examined. In the present work, the cementing efficiency factor (k) for silica fume at different percentage replacement level has been assumed, and at the constant water-to-binder ratio, the compressive strength has been obtained. An exponential relationship is proposed between UPV and compressive strength with a high correlation coefficient. A statistically noteworthy model with a high correlation coefficient R2 > 0.90 is established to study the influence of the variables (%SF and k) on UPV results. Finally, the two proposed models were amalgamated to develop a new model to predict the 28-day compressive strength of high-strength concrete. The validity of the model has been verified with the results obtained by different researchers on different types of specimens. The proposed new model is for the strength range of the 40–75 MPa.

Experimental evaluation of strength and durability characteristics of geopolymer stabilised soft soil for deep mixing applications

Abstract: Vast deposits of high water content soft clays pose severe problems and are not suitable for construction of engineering projects due to their inadequate bearing capacity and inherent large swelling and shrinkage ability. Deep soil mixing (DSM) is one of the widely accepted methods for improving soft soil properties like increase in bearing capacity and reduction in settlement that are of utmost importance for the construction of any structure. In this study, ground granulated blast furnace slag (GGBS)-based geopolymer was used to investigate its efficiency as a sustainable replacement to cement for DSM applications, thereby reducing the carbon footprint. A total of 27 GGBS-geopolymer mixes and 9 cement-treated reference mixes were cast and tested for strength and durability characteristics. The variables of the study include binder content (10, 20, and 30%), activator/binder ratio (0.5, 0.75, and 1.0), and initial soil moisture content (0.75wL, wL, 1.25wL). Different tests were conducted to explore the properties of stabilised clays, such as unconfined compressive strength, flexural strength, and durability against wetting drying cycles. To meet the requirements of DSM application, binder dosage greater than 10% and A/B ratio greater than 0.5 were recommended. With an increase in initial soil moisture content, the strength of the treated specimens under unconfined compression and flexure reduced and thus increased binder dosage helps to meet the DSM requirements for high water content soils. From the present study, it can be concluded that using slag-geopolymer binder for stabilising soft soil is an effective and sustainable alternative to cement in DSM applications.

CFRP for strengthening and repairing reinforced concrete: a review

Abstract: Carbon fibre-reinforced polymer (CFRP) is an emerging reinforcement in concrete materials and possesses many attractive mechanical and physical characteristics. Amongst other mechanical properties, CFRP has good compressive, flexural and shear strengths, and its usage improved ductility and suitability for preventing cracks. Thus, the application of CFRP is increasing in the construction industry. This review work highlights the effect of CFRP reinforcement on mechanical properties of reinforced concrete (RC) and self-compacting concrete (SCC) members. The scope of this review work is to highlight the effect on strengthening and repairing of RC members and SCC reinforced with CFRP material. A variety of research work has been reviewed on the use of CFRP in RC members, but the data remain limited yet. Thus, the critical review has been conducted from last 2-decades research on CFRP reinforcement in RC and SCC, and almost 60 researches and review articles have been involved in this discussion. The reviewed articles indicated that CFRP reinforcement can be suitable for the strength enhancement of RC members considering the strength-to-weight ratio despite its failure to produce more strength than steel reinforcement. Furthermore, CFRP is a good choice for repairing RC members due to its easy installation and other characteristic values. Therefore, CFRP reinforcement, which offers resistance to cracking, corrosion and temperature, is the best choice for concrete production.

Influence of red mud on performance enhancement of fly ash-based geopolymer concrete

Abstract: This paper presents the strength, durability and microstructural characteristics of fly ash based geopolymer concrete in addition to red mud. The study explores the influence of other parameters on the compressive strength of GC such as Na2SiO3 to NaOH ratio (liquid-to-liquid), and alkaline solution to binder ratio. The presence of high alkalinity in the red mud was enough to dissolve FA, thus ensuing the formation of aluminosilicate gels. The X-ray diffraction analysis showed the geopolymerization process and confirmed the composition of end products. Based on the experimental results, it could be recognized that GC with 10% replacement of FA with RM has shown better strength and durability properties. The results depicted that the GC mix M8 attained enhanced compressive strength i.e., 47.6 MPa indicating that the GC can be used as materials for load-bearing members in structures. The SEM images showed that a huge quantity of geopolymeric products was generated in a geopolymer by the reaction of OH− with the aluminosilicate components in FA and RM in a strong alkaline nature. Due to minor porosity, good pore structure and lower chloride ion permeability, GC can be significantly better than conventional cement concrete.

Experimental and analytical investigation on the age-dependent tensile strength of low-calcium fly ash-based concrete

Abstract: In this study, the age-dependent splitting and flexural tensile strength have been investigated by incorporating the various percentages of fly ash in the plain concrete mixes. The partial replacement of cement by fly ash was varied from 0 to 60% on an equal weight basis. Standard concrete specimens were cast for measuring splitting and flexural tensile strength at different ages, i.e., 7, 28, 56, 90, 150, and 180 days, for all plain and fly ash concrete mixes. Experimental results show that the fly ash produced a significant effect on the tensile strength of concrete mixes. It has been observed that the fly ash concrete mixes gain considerable tensile strength with respect to age beyond 28 days. In the low-calcium fly ash concrete mixes, the rate of development of tensile strength from 28 to 180 was observed higher in comparison with the plain concrete mixes. The assessment of the existing models for the estimation of age-dependent tensile strength recommended by design codes and researchers with experiments has also been done on various mixes of plain and fly ash concrete. New models to predict the age-dependent splitting and flexural tensile strength of concrete having different percentages of fly ash are proposed. The present experimental and analytical study will be helpful for the designers and practicing engineers for fixing preliminary dimensions of reinforced and prestressed concrete members and mix proportioning of low-calcium fly ash concrete mixes.

A study on the uniaxial compressive behaviour of graded fiber reinforced concrete using glass fiber/steel fiber

Abstract: Hybrid fiber reinforced concrete (HyFRC) effectively utilises the combined benefits of different fiber types present in it for enhancing its properties. The mechanical behaviour of HyFRC with varying lengths of fibers was not completely understood to date, and hence, this study focuses on the uniaxial compressive behaviour of HyFRC with two different fiber lengths. In the first phase of the study, fresh properties and the uniaxial compressive behaviour of M30 grade mono glass fiber reinforced concrete (MGFRC) reinforced with glass fibers of 6 mm and 12 mm length and M30 grade mono steel fiber reinforced concrete (MSFRC) using crimped steel fibers of 25 mm and 50 mm length were evaluated and reported. In the second phase of investigation, fresh properties and uniaxial compressive behaviour of graded fiber reinforced concrete (GrFRC), obtained by blending two different lengths of fibers (Glass Fiber/Steel Fiber) were evaluated and reported. From the results, the uniaxial compressive response of the concrete was improved by the addition of glass fiber or steel fiber to the concrete. Graded FRC exhibited better synergy compared to Mono FRC in uniaxial compression for both glass and steel fiber reinforced concrete. Among all the MGFRC and GrGFRC mixes, GrGI combination (75% short length glass fiber + 25% long length glass fiber) grading of glass fibers exhibited better performance, similarly, of all MSFRC and GrSFRC mixes, GrSIII combination (25% short length steel fiber + 75% long length steel fiber) grading of steel fibers exhibited better performance. The addition of graded glass fibers to the concrete enhances the pre peak behaviour of the stress–strain curve considerably, and the addition of graded steel fibers to the concrete improves the post peak behaviour of the stress–strain curve remarkably. From this study, we can conclude that adding graded fibers (glass fiber/steel fiber) has proved to be advantageous in enhancing the uniaxial compressive behaviour of concrete.

Failure assessment of dysfunctional flexible pavement drainage facility using fuzzy analytical hierarchical process

Abstract: Drainage system is an important facility in the road which aids the road pavement to withstand and absorb storm water and environmental stresses. When it is inadequate, the roadway suffers premature failure due to increase in moisture content of the pavement materials. For technical emphasis of the hazardous effects of dysfunctional drainage facilities on road, a case study of a failed highway, connecting Anambra state and Imo state Nigeria, was investigated. Site observation, samples collections and experimental methods were carried out in this study with the aim of investigating the drainage challenges which resulted to the failure. Soil classification and determination of the general subgrade soil properties were carried out through experimental methods. The soil was classified as A-6 by AASHTO with 32% liquid limit, 17% plastic limit, 15% plasticity index, 18% of OMC, 1.97 g/m3 of MDD, SG of 2.6 and 20% CBR-value which indicated high swelling potentials unsuitable for road construction. The asphalt concrete properties results showed averaged stability, BCT, flow, voids in total mix and voids filled results of 4.5%, 3200 N, 1.88 mm, 12% and 55% respectively, which failed to meet the FMW specifications. The road drainage facility which was observed as the primary cause of the deterioration was systematically assessed using FAHP and AHP multi-criteria technique in decision making to ascertain the cause of inefficient pavement drainage facility leading to rapid road failure. Through experimental results obtained and relevant literatures, ranking values were properly assigned to generate the PwCM used for determination of the criteria weights. The computed priority vector showed a result of 4.52% for slope stability problems, 57.28% for inadequate drainage/culvert capacity, 11.68% for drainage discontinuity and 26.52% for material related problems. The generated results were validated using student’s t test statistical analysis at 95% confidence level to obtain P(T < = t) two-tail, Pearson correlation and t Critical value of 0.99992, 0.99983 and 3.182, respectively, which indicates that no significant difference exist between the two results. Topography study, rainfall intensity evaluation and re-designing of the highway drainage system were recommended with reconstruction of the failed road using standard materials.