Properties of Sugarcane Bagasse Ash Concrete Modified with Bacterial Treatment

Meddah M.S., Praveenkumar T.R., Vijayalakshmi M.M., Manigandan S., Arunachalam R.

Waste and by-product materials both in their macro and micro-sizes are nowadays gaining more importance and consideration for their use as a partial substitute of the virgin concrete s constituents. Nanoparticles have now also gained widespread recognition and used in various construction applications, especially cement-based materials. The present paper examines the impacts of a combination of Al2O3 nanoparticles along with Rice Husk Ash (RHA) on both mechanical properties (Flexure, Splitting tensile and Compressive) strengths and durability properties, including resistance to hydrochloric acid attack and chloride permeation. RHA substituted Portland cement (PC) at a fixed amount of 10%, and Al2O3 nanoparticles have been utilized as a partial substitution of PC at 1%, 2%, 3%, and 4%. Surface morphology and microstructure of modified cement concretes were assessed by means of the Scanning Electron Microscope (SEM). The results revealed that Al2O3 nanoparticles have double effects as a filling material. As a reactive one, increasing contribution in the volume of calcium silicate hydrates (C-S-H) formed thereby increases the strengths and durability properties of concrete material. It has also been found that 3% content of Al2O3 nanoparticles is the optimum content to substitute part of the cement leading to the greatest mechanical and durability properties enhancement. The combination of up to 3% Al2O3 nanoparticles along with 10%RHA to design modified cement concretes with enhanced strength and durability performances have revealed to be efficient and productive for eco-friendly concrete material.

Praveenkumar T.R., Vijayalakshmi M.M., Meddah M.S.

Sustainable development, climate change and the extensive extraction and consumption of non-renewable mineral resources are the greatest contemporary challenges facing humankind, especially construction industry. Reducing the mining and consumption of raw materials, and CO2 emission generated by the production of Portland cement clinker as well as improving concrete performance are now achievable targets even with the use of various recycled and by-product materials in a partial replacement of virgin materials. In the present study, concrete designed with Titanium dioxide (TiO2) Nanoparticles and rice husk ash (RHA) as pozzolanic materials used in a partial replacement of Portland cement (PC) has been investigated. RHA was used in a single amount of 10% while TiO2 nanoparticles was incorporated at different replacement levels varying from 0 to 5% as a partial replacement of PC. The morphological and mineralogical characteristics of TiO2 Nanoparticles were analysed using Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD), respectively. The blended cement concrete mixes have been assessed in terms of mechanical and durability performances including compressive, Flexural and Splitting Tensile strengths, resistance to Acid attack and Chloride Penetration. The results revealed that concrete mixes with a combination of 10%RHA and 3% TiO2 Nanoparticles as a partial replacement of PC showed the highest strengths and durability performances. Increasing the TiO2 Nanoparticles beyond 3% has resulted in a drop in strengths and durability properties. Thus, this replacement of 3% nano-TiO2 might be considered as the optimum replacement level.

Li Q., Hurt A.P., Coleman N.J.

Biodentine is one of the most successful and widely studied among the second generation of calcium silicate-based endodontic cements. Despite its popularity, the setting reactions of this cement system are not currently well understood. In particular, very little is known about the formation and structure of the major calcium silicate hydrate (C-S-H) gel phase, as it is difficult to obtain information on this poorly crystalline material by the traditional techniques of powder X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR). In this study, the hydration reactions of Biodentine are monitored by XRD, FTIR, isothermal conduction calorimetry and, for the first time, 29Si magic angle spinning nuclear magnetic resonance spectroscopy (29Si MAS NMR) is used to investigate the structures of the anhydrous calcium silicate phases and the early C-S-H gel product. XRD analysis indicated that the anhydrous powder comprises 73.8 wt% triclinic tricalcium silicate, 4.45 wt% monoclinic β-dicalcium silicate, 16.6 wt% calcite and 5.15 wt% zirconium oxide. Calorimetry confirmed that the induction period for hydration is short, and that the setting reactions are rapid with a maximum heat evolution of 28.4 mW g−1 at 42 min. A progressive shift in the FTIR peak maximum from 905 to 995 cm−1 for the O-Si-O stretching vibrations accompanies the formation of the C-S-H gel during 1 week. The extent of hydration was determined by 29Si MAS NMR to be 87.0%, 88.8% and 93.7% at 6 h, 1 day and 1 week, respectively, which is significantly higher than that of MTA. The mean silicate chain length (MCL) of the C-S-H gel was also estimated by this technique to be 3.7 at 6 h and 1 day, and to have increased to 4.1 after 1 week. The rapid hydration kinetics of Biodentine, arising from the predominance of the tricalcium silicate phase, small particle size, and ‘filler effect’ of calcite and zirconium oxide, is a favorable characteristic of an endodontic cement, and the high values of MCL are thought to promote the durability of the cement matrix.

Protsak I.S., Morozov Y.M., Dong W., Le Z., Zhang D., Henderson I.M.

Three poly(organosiloxanes) (hydromethyl-, dimethyl-, and epoxymethylsiloxane) of different chain lengths and pendant groups and their mixtures of dimethyl (DMC) or diethyl carbonates (DEC) were applied in the modification of fumed silica nanoparticles (FSNs). The resulting modified silicas were studied in depth using 29Si, 1H, and 13C solid-state NMR spectroscopy, elemental analysis, and nitrogen adsorption-desorption (BET) analysis. The obtained results reveal that the type of grafting, grafting density, and structure of the grafted species at the silica surface depend strongly on the length of organosiloxane polymer and on the nature of the “green” additive, DMC or DEC. The spectral changes observed by solid-state NMR spectroscopy suggest that the major products of the reaction of various organosiloxanes and their DMC or DEC mixtures with the surface are D (RR’Si(O0.5)2) and T (RSi(O0.5)3) organosiloxane units. It was found that shorter methylhydro (PMHS) and dimethylsiloxane (PDMS) and their mixtures with DMC or DEC form a denser coverage at the silica surface since SBET diminution is larger and grafting density is higher than the longest epoxymethylsiloxane (CPDMS) used for FSNs modification. Additionally, for FSNs modified with short organosiloxane PMHS/DEC and also medium organosiloxane PDMS/DMC, the dense coverage formation is accompanied by a greater reduction of isolated silanols, as shown by solid-state 29Si NMR spectroscopy, in contrast to reactions with neat organosiloxanes. The surface coverage at FSNs with the longest siloxane (CPDMS) greatly improves with the addition of DMC or DEC. The data on grafting density suggest that molecules in the attached layers of FSNs modified with short PMHS and its mixture of DMC or DEC and medium PDMS and its mixture of DMC form a “vertical” orientation of the grafted methylhydrosiloxane and dimethylsiloxane chains, in contrast to the reaction with PDMS/DEC and epoxide methylsiloxane in the presence of DMC or DEC, which indicates a “horizontal” chain orientation of the grafted methyl and epoxysiloxane molecules. This study highlights the major role of solid-state NMR spectroscopy for comprehensive characterization of solid surfaces.Graphical abstract

Salvador R.P., Cavalaro S.H., Cincotto M.A., Figueiredo A.D.

The objective of this work is to parametrize the early age hydration behavior of accelerated cement pastes based on the chemical properties of cement and accelerators. Eight cements, three alkali-free and one alkaline accelerators were evaluated. Isothermal calorimetry, in situ XRD and SEM imaging were performed to characterize kinetics and mechanisms of hydration and the microstructure development. The reactivity of all accelerators is directly proportional to their aluminum and sulfate concentrations and to the amount and solubility of the setting regulator contained in cement. Alite hydration is enhanced if a proper C3A/SO3 ratio (between 0.67 and 0.90) remains after accelerator addition and if limestone filler is employed, because undersulfated C3A reactions are avoided. Combinations of compatible materials are recommended to enhance the performance of the matrix and to prevent an undesirable hydration behavior and its consequences in mechanical strength development.

Siddique R., Singh K., Kunal, Singh M., Corinaldesi V., Rajor A.

Influence of bacteria on the properties of concrete made with rice husk ash (RHA) is presented in this paper. For this purpose, control concrete was designed to have 28-d strength of 32.8 MPa. In the control concrete, cement was partially replaced with (0%, 5%, 10%, 15% and 20% by weight) RHA. Then, bacterium Bacillus aerius (105 cells/mL) was mixed in water during making of concrete. Tests were performed for compressive strength, water absorption, porosity, chloride permeability and abrasion resistance up the age of 56 d for all concrete mixtures with and without bacteria. Results indicated that inclusion of bacteria in RHA-concrete enhanced its compressive strength at all ages. However, best performance was achieved with 10% RHA wherein 28-d compressive strength was 36.1 MPa, and with bacteria, it was 40.0 MPa. Inclusion of bacterium in RHA concrete reduced its water absorption, porosity, and permeability at all ages, due to calcite precipitation, which in turn improves these properties. SEM and XRD analysis exhibited the formation of ettringite in pores, calcium silicate hydrate (CSH) and calcite which made the concrete denser. Findings of this investigation indicated the use of RHA and bacterium enhances the durability properties of concrete.

Tziviloglou E., Wiktor V., Jonkers H.M., Schlangen E.

The innovative technology of self-healing concrete allows the material to repair the open micro-cracks that can endanger the durability of the structure, due to ingress of aggressive gasses and liquids. Various concepts of self-healing concrete have been developed, with target on the recovery of water tightness after cracking. Among those, bacteria-based self-healing concrete has shown promising results regarding the improvement of crack sealing performance. In this study, the bacteria-based healing agent is incorporated into lightweight aggregates and mixed with fresh mortar. By this means, autogenous healing of concrete is enhanced and upon cracking the material is capable to recover water tightness. The study focuses on the investigation of the effect of healing agent when incorporated into the mortar matrix and the evaluation of the recovery of liquid tightness after cracking and exposure to two different healing regimes (water immersion and wet-dry cycles) through water permeability tests. It was found that the compressive strength of the mortar containing lightweight aggregates is not affected by the presence of the healing agent. The study also reveals that the recovery of water tightness does not differ substantially either for specimens with or without healing agent when immersed continuously in water. Conversely, the recovery of water tightness increases significantly for specimens containing the healing agent compared to specimens without it, when subjected to wet-dry cycles. Oxygen concentration measurements and bacterial traces on calcite formations confirmed the bacterial activity on specimens containing the healing agent.

Luo M., Qian C., Li R.

Bacteria-based self-healing concrete is a relatively new technique, therefore it is important to gather more results in simulate real conditions before applied on a bigger scale. In the present study, bacteria-based self-healing concrete was developed by adding the microbial self-healing agent which has the potential to improve self-healing capacity mainly by bacteria induced mineral precipitations. The precipitations formed at the cracks surface of the cement paste specimens were analyzed with Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Spectrometer (EDS), and then examined by X-ray Diffraction (XRD). Moreover, the influence of crack width, curing ways and cracking age on the crack self-healing of cement paste with microbial self-healing agent was researched by the characterization methods of area repair rate and anti-seepage repair rate. The results showed that the microbial self-healing agent could be used to achieve the goal of concrete crack self-healing. The precipitations formed at the cracks surface were calcite, which appeared lamellar close packing morphology. However, the capacity of concrete crack self-healing depended on many factors. The crack was more and more difficult to be repaired with the increase of average crack width and the repair ability of microbial repair agent was limited for specimens with crack width up to 0.8 mm. Water curing was shown to be the best way for bacteria-based self-healing concrete. In addition, the crack healing ratio of specimens dropped significantly along with the extension of cracking age. When the cracking age was more than 60 days, the crack healing ratio was very small. The results above suggested that the optimal conditions were needed for the practical application of microbial self-healing agent.

Nosouhian F., Mostofinejad D., Hasheminejad H.

Bacterial carbonate precipitation, which is based on urea hydrolysis, has been used as a surface treatment technique to decrease the permeation properties of concrete. Since permeability acts as the main reason of concrete degradation in harsh environments, this study evaluates microbial surface treatment in order to prevent sulphate ions penetration. Five groups of concrete specimens were cast and cured and were then surface treated applying three different microbial suspensions employing Sporosarcina pasteurii, Bacillus subtilis and Bacillus sphaericus bacteria. Durability was assessed through the mass losses, volume changes (expansion), water absorption and compressive strength. In order to consider further permeation properties, chloride penetration of biologically treated concrete was examined by a rapid chloride permeability test (RCPT). Experimental results and a durability loss index (DLI) indicated that biological surface treatment reduces concrete degradation in sulphate environments and improves durability characteristics. Also, the RCPT results confirmed that this technique limits chloride penetration into the concrete.

Krishnapriya S., Venkatesh Babu D.L., G. P.A.

The objective of this research work is to isolate and identify calcite precipitating bacteria and to check the suitability of these bacteria for use in concrete to improve its strength. Bacteria to be incorporated in concrete should be alkali resistant to endure the high pH of concrete and endospore forming to withstand the mechanical stresses induced in concrete during mixing. They must exhibit high urease activity to precipitate calcium carbonate in the form of calcite. Bacterial strains were isolated from alkaline soil samples of a cement factory and were tested for urease activity, potential to form endospores and precipitation of calcium carbonate. Based on these results, three isolates were selected and identified by 16S rRNA gene sequencing. They were identified as Bacillus megaterium BSKAU, Bacillus licheniformis BSKNAU and Bacillus flexus BSKNAU. The results were compared with B. megaterium MTCC 1684 obtained from Microbial Type Culture Collection and Gene Bank, Chandigarh, India. Experimental work was carried out to assess the influence of bacteria on the compressive strength and tests revealed that bacterial concrete specimens showed enhancement in compressive strength. The efficiency of bacteria toward crack healing was also tested. Substantial increase in strength and complete healing of cracks was observed in concrete specimens cast with B. megaterium BSKAU, B. licheniformis BSKNAU and B. megaterium MTCC 1684. This indicates the suitability of these bacterial strains for use in concrete. The enhancement of strength and healing of cracks can be attributed to the filling of cracks in concrete by calcite which was visualized by scanning electron microscope.

Seddik Meddah M.

Designing a sustainable concrete has become a vital requirement for today’s concrete. Introducing various cementing and pozzolanic materials in concrete in replacement of Portland cement seems to be the appropriate way to lower the environmental impact of concrete industry. This paper reports results on concrete performance produced with two types of pozzolanas including natural pozzolana (NP) obtained from volcanic ash and shale ash (SA) used, in various proportions ranged from 10–45%, as a partial substitute of Portland cement (PC). Concrete mixtures were designed with a wide range of water-to-cementitious ratios (w/c) ranged from 0.79 to 0.45. The key mechanical properties and durability performance of binary blended cement concretes were investigated. Using both NP and SA has resulted in a strength loss; while SA seems to perform better than NP in terms of strength development and durability performance. The blended cement concretes with 10–15% pozzolanas was found to have a good resistance to carbonation and chloride ions ingress and are freeze–thaw durable. However, with replacement level higher than 20%, the durability factor, chloride ions and carbonation resistance drop down. Overall, the results indicate that the mechanical and durability performances of binary blended cements with NP and SA are strongly linked to their intrinsic characteristics including chemical composition, fineness, particle size distribution and potential reactivity.

Wang J.Y., Soens H., Verstraete W., De Belie N.

Microcapsules were applied to encapsulate bacterial spores for self-healing concrete. The viability of encapsulated spores and the influence of microcapsules on mortar specimens were investigated first. Breakage of the microcapsules upon cracking was verified by Scanning Electron Microscopy. Self-healing capacity was evaluated by crack healing ratio and the water permeability. The results indicated that the healing ratio in the specimens with bio-microcapsules was higher (48%–80%) than in those without bacteria (18%–50%). The maximum crack width healed in the specimens of the bacteria series was 970 μm, about 4 times that of the non-bacteria series (max 250 μm). The overall water permeability in the bacteria series was about 10 times lower than that in non-bacteria series. Wet–dry cycles were found to stimulate self-healing in mortar specimens with encapsulated bacteria. No self-healing was observed in all specimens stored at 95%RH, indicating that the presence of liquid water is an essential component for self-healing.

Dhami N.K., Reddy M.S., Mukherjee A.

The investigation on the synergistic role of urease (UA) and carbonic anhydrase (CA) in biomineralization of calcium carbonate in Bacillus megaterium suggested that the precipitation of CaCO3 is significantly faster in bacterial culture than in crude enzyme solutions. Calcite precipitation is significantly reduced when both the enzymes are inhibited in comparison with those of the individual enzyme inhibitions indicating that both UA and CA are crucial for efficient mineralization. Carbonic anhydrase plays a role in hydrating carbon dioxide to bicarbonate, while UA aids in maintaining the alkaline pH that promotes calcification process.

Chahal N., Siddique R.

• Sporosarcina pasteurii effects the permeation properties of fly ash and silica fume concrete. • Bacterial deposition of calcite increases the strength of concrete. • Deposition of calcite thereby reduces water porosity, absorption and chloride permeability. Durability of concrete can be enhanced by using a novel technique which involves bacterial-induced calcite precipitation. Bacteria are capable of precipitating calcium carbonate by providing heterogeneous crystal nucleation sites in super-saturated CaCO 3 solution. The initial objective of the research work involved the isolation of urease producing bacteria from alkaline soil. The bacteria were identified by the ability to sustain itself in alkaline environment of cement/concrete. The bacterial isolate was analyzed through DNA sequencing and the bacteria was identified as Sporosarcina pasteurii, which showed maximum urease production when it was grown on urease agar and broth. The significant objective of the research work further involved the use of ureolytic bacteria ( S. pasteurii) in concrete which would make it, self-healing. The bacteria present in the concrete rapidly sealed freshly formed cracks through calcite production. The bacterial concentrations were optimized to 10 3 , 10 5 and 10 7 cells/ml. In concrete mix, cement was replaced with fly ash, and silica fume. The percentage replacement of fly ash and silica fume was by weight of cement. The percentage use of fly ash was 0%, 10%, 20% and 30%, and that silica fume were 0%, 5% and 10%. The experiments were carried out to evaluate the effect of S. pasteurii on the compressive strength, water absorption, water porosity and rapid chloride permeability of concrete made with fly ash and silica fume up to the age 91 days. The test results indicated that inclusion of S. pasteurii enhanced the compressive strength, reduced the porosity and permeability of the concrete with fly ash and silica fume. The improvement in compressive strength was due to deposition on the bacteria cell surfaces within the pores which was scanned by electron microscopy and confirmed by XRD which revealed calcium carbonate precipitation. This precipitation reduced the chloride permeability in concrete with fly ash and silica fume. The bacteria improve the permeability of concrete by improving its pore structure and thereby enhancing the life of concrete structures.

Phillips A.J., Gerlach R., Lauchnor E., Mitchell A.C., Cunningham A.B., Spangler L.

Microbially-induced calcium carbonate (CaCO3) precipitation (MICP) is a widely explored and promising technology for use in various engineering applications. In this review, CaCO3 precipitation induced via urea hydrolysis (ureolysis) is examined for improving construction materials, cementing porous media, hydraulic control, and remediating environmental concerns. The control of MICP is explored through the manipulation of three factors: (1) the ureolytic activity (of microorganisms), (2) the reaction and transport rates of substrates, and (3) the saturation conditions of carbonate minerals. Many combinations of these factors have been researched to spatially and temporally control precipitation. This review discusses how optimization of MICP is attempted for different engineering applications in an effort to highlight the key research and development questions necessary to move MICP technologies toward commercial scale applications.

Anand P., Singh S.D., Bhowmik P.N., Boya V., Pandey S.

This study explores optimizing concrete mix designs by incorporating agricultural waste by-products to promote sustainability in the construction industry. Data were collected on parameters such as by-product content, compressive strength, tensile strength, sulfate resistance, chloride ion penetration, water-cement ratio, curing duration, and slump. Machine learning models, including Linear Regression, Random Forest, Gradient Boosting, Support Vector Regression, and Artificial Neural Networks, were applied to predict these properties. The models were evaluated using metrics such as Root Mean Squared Error (RMSE), Mean Absolute Percentage Error (MAPE), and the coefficient of determination (R²). Sequential Least Squares Quadratic Programming (SLSQP) was used to optimize the mix designs. The study aimed to identify the optimal by-product type and percentage that maximizes strength and performance. Results indicated that Corn Cob Ash (15–20%) is optimal for early strength development, while Palm Oil Fuel Ash, Rice Husk Ash, Sugarcane Bagasse Ash, and Wheat Straw Ash are suitable for mid- and later-stage strength. This research presents a machine learning-based approach to optimizing concrete mixes, reducing the need for extensive experimental testing while advancing sustainable construction practices.

Varshney H., Khan R.A.

This research paper delves into an innovative approach leveraging pozzolanic material, particularly Metakaolin (MK), as a sustainable substitute for cement in concrete production. The study explores the integration of MK at various ratios, examining its impact on the creation of eco-friendly bio-mineralized concrete. By assessing MK ratios up to 15% by weight of cement, this work identifies a threshold—10% MK—that significantly enhances concrete properties, notably reducing permeability by 23.63% at 28 days. Incorporating bacteria at a concentration of 10^5 cfu/ml further amplifies these benefits, showcasing a 19% increase in compressive strength and a remarkable 43.23% reduction in permeability through calcium carbonate deposition. This synergy between MK and bio-mineralization not only fortifies concrete but also curtails cement content while maintaining or even enhancing its durability and strength. The research underscores the potential of MK and bio-mineralization as game-changing, eco-conscious solutions for concrete manufacturing, advocating for their adoption in construction to mitigate cement's environmental impact and address waste disposal, ultimately fostering sustainable growth in the industry. The study's findings spotlight a paradigm shift toward integrating biological processes into construction engineering, paving the way for a greener, more resilient built environment.