Concrete Curing Research Articles

Fresh and Mechanical Characteristics of Alkali Activated Fly Ash Slag Concrete Activated with Neutral Grade Liquid Glass

Abstract: The development and use of geopolymer concrete continues to evolve as researchers and engineers refine mix designs, develop standardized guidelines, and explore new applications. One of the key benefits of geopolymer concrete is its lower carbon footprint compared to traditional Portland cement concrete. This reduction in carbon emissions is due to the elimination of clinker production, which is energy intensive and emits significant amounts of carbon dioxide. This sustainable alternative to Portland cement concrete plays an important role in reducing the environmental impact of the construction industry. Many prior studies on fly ash-slag based geopolymers have primarily focused on the characteristics of concrete that has undergone heat curing. This approach is seen as a constraint when it comes to in-situ casting applications in ambient conditions. Ambient curing of geopolymer concrete is a more energy-efficient and environmentally friendly option compared to heat curing, as it doesn't require the use of specialized curing chambers or high temperatures. However, it may require longer curing times to achieve the desired strength and making it important to plan the construction schedule accordingly. An experimental study was carried out using neutral grade liquid glass with a silica modulus (SiO2/Na2O) of 2.92 coupled with combinations of fly ash and Ground Granulated Blast Furnace Slag (GGBS) in proportions of 30:70, 50:50. The primary aim is to explore how altering the ratios of fly ash and GGBS impacts the mechanical characteristics of the resultant concrete for different solution/ binder ratios (0.6, 0.65 and 0.7) with a fixed binder quantity of 400 and 500 Kg/m3 under ambient curing conditions. The experimental program employed the fractional factorial method of experimentation to minimize the number of mix variations. In general, the findings indicated that higher levels of neutral-grade sodium silicate led to improvements in all mechanical properties. Conversely, an increase in the alkaline solution-to- binder ratio and curing temperature had a detrimental impact on the alkaliactivated slag concrete. Optimal results for hardening of concrete for demolding were obtained after two days of casting. The implications of this research could lead to the development of more sustainable and environmentally friendly alternatives in the field of construction materials.

A Study of the Effects of Saltwater on the Formation, Curing and Strength of Concrete

Concrete is extensively used in all construction works such as buildings, bridges, roads and dams worldwide. It is made by simply combining cement, aggregate, sand and water in the appropriate proportion. This paper explores the investigational study on the outcome of using saltwater in coastal regions for blending and curing concrete since palatable water is a deficient asset on the earth. As most of the ions in seawater comprise Na, Mg, Cl- and SO42-, this research aimed to observe how concrete behaves after the addition of NaCl and MgSO4 salt separately for mixing concrete and curing at different concentrations. Concrete cylinders were cured using fresh water as well as saltwater separately. A total specimen of 42 cylinders was cast with 100%, 75% and 50% ion concentrations of NaCl, MgSO4 and freshwater specimens prepared for the reference concrete, which were exhibited for 7 days and 28 days of curing. A comparatively higher compressive strength was found for a 50% salt concentration of MgSO4 and for 75% salt concentration of NaCl. The comparison of compressive strength using NaCl and MgSO4 samples between this research and previous researches was derived for 7 days and 28 days. A correlation between the compressive strength and ion concentrations of NaCl and MgSO4 for 28 days was derived by performing linear regression analysis. The relations obtained by this analysis can be utilized for further prediction of compressive strength at any other ion concentrations of these salts. IUBAT Review, 6(2): 25-40

Effect of surface curing condition on the humidity field and moisture transfer in concrete

In order to study the influence mechanism of different curing methods on the humidity field and scientifically design the surface curing methods, the humidity field of C30, C50 and C80 concrete cured with plastic film (PF), controlled permeability formwork liner (CPFL) and moisture retention curing film (MRCF) was measured by the designed testing device. And the pore structure of cement paste in the surface area of concrete with different curing methods was analyzed by mercury intrusion pore test (MIP). The theoretical calculation model for concrete humidity field considering the influence of surface curing method was also established. The results show that: CPFL curing improves the compactness of the concrete surface area by eliminating excess water and gas, reducing the rate of water loss and humidity decrease during the later drying process. It is more effective for the low strength concrete; MRCF curing extends the humidity saturation period and improving the final humidity level. It is more effective for the high strength concrete; PF curing creates an almost absolute humidity environment to prevent the moisture transfer during the curing period; The established model can accurately describe the impact of three different curing methods on the humidity changes for different strength concretes. It can be used to quantitatively analyze the humidity changes of concrete under different curing and environmental conditions. This study systematically clarifies the effect mechanism of different types of surface curing methods on the humidity field of concrete for the first time. And it will provide theoretical support for the scientific selection of concrete curing methods and accurate prediction of humidity field.

Study on accelerating activation of recycled hardened concrete powder based on microbial induced calcium precipitation

The CO2 atmosphere in the flue gas of cement kiln was simulated in this paper, and different methods were used to activate the RHCP with particle size < 75 µm under normal temperature and pressure. The effects of different activation methods were studied, and the mechanism of CO2 storage was clarified. On the basis of concrete carbonization curing, a new technology based on MICP was proposed. During the activation of RHCP, a Bacillus strain capable of secreting carbonic anhydrase was introduced into the CO2 carbonization system of RHCP. Carbonic anhydrase could accelerate the capture and conversion of CO2 into bicarbonate ions and carbonate ions. Calcite-type CaCO3 and amorphous silica gel were formed by the reaction of CO2 with active components in RHCP. Finally, the generated product filled the pores to make the microstructure of the slurry denser, and CO2 was also permanently sealed. The results showed that the MM-RHCP not only improved the activity index of the mortar, but also improved the potential for storing CO2 in RHCP. Through FT-IR, XRD, SEM-EDS, TGA and nitrogen adsorption pore size analysis, it was further proved that the use of microbial mineralized RHCP could accelerate the formation of CaCO3, ettringite and SiO2·n H2O. In addition, the CO2 storage capacity of MM-RHCP was greater than that of DC-RHCP and LP-RHCP. The RHCP after mineralization treatment could replace cement as mineral admixture, and this technology realized the resource utilization of solid waste. At the same time, CO2 was permanently fixed in RHCP. Therefore, it provided a new way for deep carbon sequestration in the cement industry.

Effect of load on bonding properties and salt freeze-thaw resistance of bridge expansion joint concrete

In the seasonal frozen regions, the bridge expansion joint concrete (BEJC) is susceptible to damage during its service life, not only from vehicular loads but also from chloride salt erosion and the effects of freeze-thaw cycles. This study investigates the basic physical and mechanical properties of BEJC under different curing conditions. A rapid chloride permeability test was conducted to comparatively analyze the concrete's chloride ion penetration resistance. The microscopic crack width on the concrete bond surface is evaluated to assess the concrete bond performance under different loading durations. Additionally, the study explores the coupled effect of wheel loads and single-sided salt freeze-thaw cycles (WL-SFT) on the freeze-thaw resistance of BEJC, delving into factors such as spalling mass, water absorption rate, and pore structure characteristics (including air content, specific surface area, spacing coefficient) and connectivity. The results indicate that for specimens subjected to loading at 1–14 days and 3–14 days, the average crack widths on the bond surface are 14.36 µm and 10.09 µm, respectively, representing 5.27 times and 3.70 times those of unloaded specimens. The bond strength also decreases by 34.8% and 14.2%, respectively, compared to unloaded specimens. The increase in crack width leads to a reduction in bond strength, highlighting the importance of bond strength as a consideration for the actual opening time of roads in engineering projects. Furthermore, due to its smaller and more stable pore structure, the study suggests that WL-SFT almost does not damage standard curing (SC) concrete; however, it slightly disrupts the pore structure of natural curing (NC) concrete. In comparison, WL-SFT leads to the generation of more microcracks in both the surface and deeper layers of low-temperature curing (LC) concrete, resulting in the destruction of its pore structure and connectivity.

Climate performance of liquefied biomethane with carbon dioxide utilization or storage

In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture.

Cold weather concreting: provisions of codes and research advances

In cold regions, concrete practitioners face challenges in achieving the target performance criteria of concrete produced at low temperatures. When concrete temperature drops to −2.8°C, the hydration development of cementitious binders nominally ceases due to the freezing of mixing water, which results in hydraulic and osmotic pressures that exceed the tensile capacity of concrete, especially at early age (immature stage). Subsequently, the hardening and strength gain rates of concrete are adversely affected, resulting in insufficient microstructural development and irreversible deterioration, which makes concrete applications challenging under cold weather. Therefore, multiple investigations have been conducted to develop efficient approaches to overcome the challenges of placing concrete at low temperatures. The current paper synthesises code provisions in North America and Europe and state-of-the-art knowledge on cold weather concreting, in terms of mixture components as well as new inventions and methods of concrete curing and protection at low temperatures. Hence, it should provide informative guidance for the construction industry in cold regions to improve cold weather concreting practices.

Combined effect of internal curing and hydration promotion on concrete performances: Contributions of roof-tile waste aggregate and chloride-based accelerator

Internal curing (IC) of concrete has recently been the subject of research due to its advantages, particularly in long-term performance. However, IC often decreases early-age strength and requires sufficient external curing time to be most effective. On the contrary, a chloride-based accelerator (CA) is well-known for accelerating early-age cement hydration and strength development. Therefore, this study aimed to investigate the combined effect of IC using roof-tile waste aggregate and CA using sea salt on concrete performance. Several concrete mixtures were cast with single or combined effects under poor and standard curing conditions. Roof-tile waste was used to partially replace normal coarse or fine aggregate to provide IC for concrete. Subsequently, the compressive strength and carbonation rate, as mechanical and durability indices, respectively, were measured until approximately 8 years of age. The combined effect resulted in significant strength improvement compared with the single effects under the same curing conditions. At approximately 8 years, under standard curing conditions, the IC effect increased the compressive strength by 40%, while the combined effect increased it by 60% compared to normal concrete. Concrete with combined effects also performed better in terms of durability tests but with a smaller magnitude than the strength index.

Effect of steel fibres and expansive agents on compressive behaviour of circular CFST columns

Concrete filled steel tube columns (CFSTCs) are commonly used in large-span bridges and high-rise buildings. As the shrinkage of concrete may lead to significant degradation in the mechanical performance of CFSTCs, expansive concrete or fibre reinforced concrete is usually employed to improve the mechanical performance of CFSTCs. This study presents an experimental study on the combined effects of expansive agents and steel fibres on the axial compressive behaviour of circular CFSTCs. 13 CFSTCs were designed and manufactured using concrete mixes with varying expansive agent rates and steel fibre contents. The time-dependent expansive behaviours of the specimens were monitored during the concrete curing period. Then, the 13 specimens were tested under axial compression load. The failure modes, compression load-axial strain relationship, hoop strain and axial strain relationship, and ductility were investigated. The results demonstrated that the combined addition of expansive agents and steel fibres would substantially improve the compressive strength and ductile behaviour of CFSTCs.

Investigation of Using Waste Glass Powder (WGP) as a Partial Natural Sand Replacement in Concrete for a Potential Use in Iraqi Construction Field

Abstract Glass waste contributes about 5% of the total solid waste generated worldwide that ends up in landfills without recycling resulting in considerable environmental harm. In this research, Waste Glass Powder (WGP) was studied to be used as a supplementary material substituted with sand in the concrete mix. The concrete mixes were prepared by replacing the natural sand with WGP in weight proportions of 10% to 50%, with a 10% increment to examine the mechanical effect of WGP addition on concrete performance in the fresh and hardened status. The concrete mixes were tested to evaluate the compressive strength for curing ages 7, 14, 21, 28, 56, and 90 days. Splitting tensile strength was also tested for curing at ages of 7, 14, 21, and 28 days. The obtained results showed a notable decrease in workability value for all concrete mixes with WGP addition. Also, the addition of WGP decreases the compressive strengths of all concrete mixes. However, the WGP enhanced the splitting tensile strength by about 12%. It has been concluded that the WGP can be used as a substituted material replaced with sand up to 30%, which was the optimum replacement ratio based on the Iraqi required specifications. By using this ratio, the compressive strength was decreased by 18% at 28 days of concrete curing age.

Effect on properties of geopolymer concrete by inclusion of recycled aggregate and methods to enhance the packing density of aggregate

Purpose This study aims to practically determine the optimum proportion of aggregates to attain the desired strength of geopolymer concrete (GPC) and then compare the results using established analytical particle packing methods. The investigation further aims to assess the influence of various amounts of recycled aggregate (RA) on properties of low-calcium fly ash-based GPC of grade M25. Design/methodology/approach Fine and coarse aggregates were blended in various proportions and the proportion yielding maximum packing density was selected as the optimum proportion and they were compared with analytical models, such as Modified Toufar Model (MTM) and J. D. Dewar Model. RAs for this study were produced in laboratory and they were used in various amounts, namely, 0%, 50% and 100%. 12M NaOH solution was mixed with Na2SiO3 in the ratio of 1:2. The curing of concrete was done at the temperatures of 60° and 90 °C for 24, 48 and 72h. Findings The experimentally obtained optimum proportion of coarse to fine aggregate was 60:40 for all amounts of RA. Meanwhile, MTM and Dewar Model resulted in coarse aggregate to fine aggregates as 40:60, 45:55, 55:45 and 55:45, 35:65, 60:40, respectively, for 0% 100% and 50% RAs. The compressive strength of GPC elevated with the increase in curing regime. In addition, the ultrasonic pulse velocity also displayed a similar trend as that of strength. Originality/value The GPC with 50% RAs may be considered for use, as it exhibited superior properties compared to GPC with 100% RAs and was comparable to GPC with natural aggregates. Furthermore, compressive strength is correlated with split tensile strength and ultrasonic pulse velocity.

Multivariate Regression and Variance in Concrete Curing Methods: Strength Prediction with Experiments

Because concrete strengths and quality are affected by various factors, multivariate regression models are often used to analyze the differences between predicted and target outputs. However, the variableness of a predicted output and how individual input parameters affect prediction reliabilities are still uncertain in practical applications, especially for the prediction of compressive strengths of concrete. This study aims to develop multivariate models for predicting concrete strengths and providing the variance analysis of prediction results by comparisons with experiment outcomes. First, this paper provides an in-depth examination of established variance analysis methods in the context of commonly used multivariate regression models. Then, based on Gaussian process regression, this study melds principal component analysis (PCA), linear discriminant analysis (LDA), and multivariate analysis of variance (MANOVA) to assess the variability in concrete strength prediction using different curing methods. This innovative approach proves effective in evaluating the precision of the correlation and regression models (R-squared values ≥ 0.9049). The comparison between prediction results and experiment outcomes shows that retaining heat in cylinders can make them become too hot and overestimate in-place concrete strength. This study improves the methodologies of regression modeling for variance analysis and improves the reliability of concrete strength prediction. Additionally, the outcomes of this research can help save a substantial amount of financial resources and time that are required to obtain experimental data on the strengths of concrete components.

Real-time monitoring of concrete curing using fiber Bragg grating sensors: Strain and temperature measurement

Real-time monitoring of concrete curing using fiber Bragg grating sensors: Strain and temperature measurement

Enhancement of tensile performance of concrete by using synthetic polypropylene fibers

The research attempted to investigate the effect of polypropylene fibers (PP fibers) on the mechanical characteristics of concrete. According to ASTM C39/C39M and ASTM C 1609/C1609M, standard testing methods were used to examine the concrete compressive and flexural strength, post-cracking behavior, and toughness. The mechanical properties were evaluated at different ages of concrete curing, namely 1 day, 7 days, and 28 days, and for different quantities of fiber volume portions, specifically 0.0%, 0.5%, and 1.0%. The results demonstrate that a fiber volume of 0.5% is the most effective in obtaining the highest compressive strength. The recorded values at the related testing ages were 31.07 MPa, 41.51 MPa, and 46.68 MPa. Additionally, the utilization of 0.5% and 1.0% volume of PP fiber in concrete resulted in improved flexural strength and post-cracking performance. The toughness values for these mixes were 2.0 and 2.6 times higher than those for the plain concrete. Upon analyzing the fracture surface, there was a homogeneous distribution of fibers, which played a significant role in enhancing the overall functionality of the concrete. The research validated that the inclusion of polypropylene fibers substantially enhanced the mechanical characteristics of concrete, emphasizing the potential of fiber reinforcement in concrete-based implementations.

Characterisation of the effects of hemp shives for internal curing of concrete

The effectiveness of hemp shives for the internal curing of concrete has been experimentally investigated in the current study. The effect of internal water embedded through pre-saturated hemp shives on concrete curing was assessed by comparing the strength and shrinkage response of a hemp-concrete composite to those of a traditional concrete mix. Three different hemp shive sizes and two different curing conditions (sealed and unsealed) were considered to replicate typical curing conditions at construction sites. Strength results were compared to a Control Mix subjected to standard laboratory curing conditions. It was observed that the compressive strength of the hemp-concrete composite increased with the reduction of particle size and dosage of hemp shives. The mix that included 1 % shives in the size range 1 to 2 mm was identified as the optimum mix achieving a strength up to 83 % to that of the Control Mix. Importantly, a reduction in unrestrained shrinkage was observed for this mix compared to the control samples. Microstructural analysis of the hemp-concrete composite confirmed that continued hydration took place due to the presence of internal water supplied by the hemp shives. As a result, with the inclusion of saturated hemp shives the process of cement hydration and strength gain continued for a longer period even in the absence of external curing water compared to that of traditional hydration.

Effect of precuring time on the strength, microstructure, and energy consumption of direct electric curing concrete

The study assesses the role of precuring duration in facilitating the rapid curing of concrete and its associated impacts on current, resistance, and temperature variations during direct electric curing (DEC) of concrete. Additionally, the research examines the effects of precuring duration on aspects such as concrete strength development, pore structure, hydration product morphology, and the interfacial transition zone. For a comprehensive analysis, it introduced the "unit-strength energy–time product" as a measure to compare the relative benefits and drawbacks of DEC and steam curing concerning concrete productivity and environmental implications. the findings reveal that the variations in current, resistance, and temperature during DEC are affected by the precuring time duration, with both current and temperature decreasing with an increase in precuring time. A precuring duration of 90 min under DEC yields an early high strength. At this point, the 1 d compressive strength of the concrete specimen is 51.5 MPa, representing 90.51 % of the 28 d strength, without any significant reduction in the late strength. DEC also mitigates the pore-coarsening effect induced by steam curing, thereby reducing the specimen's porosity and enhancing the performance of the interfacial transition zone. The precuring time and energy required for DEC are significantly lower compared to steam curing. The optimal DEC regime, consuming a mere 450 min, contrasts with the lengthy 780 min process required for steam curing. By considering time and energy consumption, the unit-strength energy–time product of DEC ranges between 22.01% and 27.86 % (at age 1 d) and 17.93%–23.45 % (at age 28 d) of that of steam curing. In summary, the research provides evidence that an appropriately devised DEC regime can augment production and energy efficiency, possibly instigating a technological transformation in contemporary construction practices.

Prediction of Concrete Constituents’ Behavior Using Internet of Things (IoT)

Due to the challenges of providing constant observation and control of the curing environment, the effectiveness of the conventional concrete process on site is poor. This causes a significant difference in the curing regimes encountered by various concrete pours. Yet, the potential of Internet of things (IoT) technologies has not yet been exploited in this context. To improve concrete practice, technologies have been harnessed that reduce human participation and enable more rigorous management of the ambient variables impacting curing. The interior temperature of concrete may be directly measured in real time and continuously monitored by a management system for in-place concrete using an all-in-one wireless sensor network (WSN) during the initial phases of curing. Without considering the wiring at the building site, the algorithm may also provide a well-informed choice about the removal of the formworks. To monitor and regulate the moisture content of hardening concrete to the levels necessary for high-quality hardened concrete, this research study looked at an IoT-based concrete curing control system based on sensor technologies. The effectiveness of this IoT-based technique was compared to the effectiveness of conventional curing procedures based on on-site trials. According to the findings, the system developed beats the conventional method in terms of both the effectiveness of concrete curing and the amount of time required for supervision.

Effect of Micro Lime on The Ambient Cured Sugarcane Bagasse Ash-Based Geopolymer Concrete

Geopolymer concrete has been the ideal replacement for Ordinary Portland cement concrete in producing green concrete. The binder in geopolymer concrete is a cementitious paste made from amorphous Aluminosilicate and activated by an Alkaline solution. The geopolymerization process is initiated at elevated temperatures. Thus, the curing requires elevated temperatures. This curing method limits the application of geopolymer concrete in the construction industry. In a geopolymer mix, the presence of Calcium ions allows the formation of Calcium Aluminate Silicate and Calcium Silicate Hydrate gels, allowing ambient temperature curing. Therefore, this study investigates the effect of micro lime on the Sugarcane Bagasse Ash-based geopolymer concrete. The micro lime was added to the geopolymer concrete in 1, 3, 5 and 7% by the Sugarcane Bagasse Ash weight. A mix design was based on a Densified Mix Design Algorithm. The tests carried out included compressive strength and water absorption. Ambient curing of the SCBA-based geopolymer concrete was achieved with 1% of the micro lime. The compressive strength increased with the increase of the micro lime, 10N/mm2 at 1%, to 18.25N/mm2 at 7% micro lime. The ambient temperature-cured geopolymer concrete at 3% micro lime had the lowest water absorption rate.

Bacterial Viability in Self-Healing Concrete: A Case Study of Non-Ureolytic Bacillus Species.

Cracking is an inevitable feature of concrete, typically leading to corrosion of the embedded steel reinforcement and massive deterioration because of the freezing-thawing cycles. Different means have been proposed to increase the serviceability performance of cracked concrete structures. This case study deals with bacteria encapsulated in cementitious materials to "heal" cracks. Such a biological self-healing system requires preserving the bacteria's viability in the cement matrix. Many embedded bacterial spores are damaged during concrete curing, drastically reducing efficiency. This study investigates the viability of commonly used non-ureolytic bacterial spores when immobilized in calcium alginate microcapsules within self-healing cementitious composites. Three Bacillus species were used in this study, i.e., B. pseudofirmus, B. cohnii, and B. halodurans. B. pseudofirmus demonstrated the best mineralization activity; a sufficient number of bacterial spores remained viable after the encapsulation. B. pseudofirmus and B. halodurans spores retained the highest viability after incorporating the microcapsules into the cement paste, while B. halodurans spores retained the highest viability in the mortar. Cracks with a width of about 0.13 mm were filled with bacterial calcium carbonate within 14 to 28 days, depending on the type of bacteria. Larger cracks were not healed entirely. B. pseudofirmus had the highest efficiency, with a healing coefficient of 0.497 after 56 days. This study also revealed the essential role of the cement hydration temperature on bacterial viability. Thus, further studies should optimize the content of bacteria and nutrients in the microcapsule structure.

EFFECT OF BACTERIAL CURING AND BACTERIAL ADDITIVE ON CONCRETE PROPERTIES

In this study, calcium carbonate was formed on the surfaces and inner structure of concrete using the microbially induced carbonate precipitation method. Bacillus megaterium bacteria were supplemented into the curing water and concrete mixtures. Three types of concrete were tested: control concrete, bacteria-containing concrete, and concrete cured in bacterial liquid. Compressive strength, water absorption, capillary water absorption, scanning electron microscopy (SEM), and mapping analyses were conducted to investigate the effects of bacterial additive or bacterial curing to concrete specimens. Bacteria spore added to the concrete mixture and curing in bacterial media increased the compressive strengths of concrete by up to 9,52 % at the end of 28 days of curing. Bacterial curing and the addition of bacteria spores caused a reduction in water absorption rates owing to changes in the concrete structures. Calcite only formed on the surfaces of the samples treated with bacterial curing liquid, thereby limiting its effect on capillary water absorption. In contrast, capillary water absorption in the bacterial concrete decreased by 50 % compared to the control concrete. The crystalline structures of calcium carbonate and bacterial concrete were analysed through SEM imaging. Mapping analysis revealed that the primary elements of calcite were considerably more concentrated on the surface of bacterial concrete than in the control concrete.