The characteristics of structural concrete using bacteria improvement

Concrete is a porous material and its porosity is accompanied by ingress of aggressive agents to decrease its strength and durability. Natural ingredient with filling capacity can be added to concrete to improve its characteristics. There are some natural waste materials which are known as good materials for partial replacement of ordinary Portland cement in the production of concrete. Construction problems and mix design complexity using these waste materials are the reasonable evidences for a need for another type of concrete. In recent times, the application of microorganism in cementations materials has received a lot of interest. One significant area of interest is bacterial concrete. The concept is to introduce bacteria in concrete, which will aid in mineral precipitation of pores and tiny cavity areas. Bacillus is a type of bacteria that can produce as a binding filler material to enhance concrete characteristics. This study provided an insight of a new biotechnological method based on calcite precipitation to improve the strength of structural concrete. It is clear that mineral precipitation has the potential to enhance construction material resistance towards degradation processes. Different cell concentrations of bacteria from 103 to 107cfu/ml were introduced in concrete and significant increase in the compressive strength was obtained in the case of 105cfu/ml at different ages. Subsequently, to the structural concrete, five different cell concentrations of bacteria (10×105 to 50×105cfu/ml) were introduced and significant increase in the compressive and flexural strength were obtained when 30×105cfu/ml of bacteria was added to concrete at different ages (7, 14, 28 and 60 days). This appropriate cell concentration (30×105cfu/ml) was applied again to the various grades of structural concrete (30, 35, 40, 45, and 50MPa) by mixing water (per ml) in the current experimental approach. It was found that the compressive strength of the higher grade of structural bacterial concrete has improved as compared to lower grade due to more precipitation of calcite. In order to study the durability of structural concrete against aggressive agents, specimens with appropriate cell concentration were immersed in different types of acids solution (sulphuric and hydrochloric acids) to compare their effects on 60th, 90th and 120th day. The experiment demonstrated that bacterial concrete had decreased in weight and strength losses when compared to the ordinary Portland cement concrete without bacteria as control, especially in the highest grade of structural bacterial concrete (50MPa).It was also found that maximum compressive strength and weight loss occurred during sulphuric acid immersion. Microbial calcite precipitation was also quantified by X-ray diffraction (XRD) analysis, visualized by scanning electron microscopy (SEM) and analysed by energy dispersive spectrometer (EDS). An increase in density and uniformity of bacterial concrete was observed compared to the ordinary Portland cement concrete because of calcite deposition. Eventually, it was discovered that addition of Bacillus species bacteria had a positive effect on the strength and durability of structural concrete

A novel taxanomy on self-healing concrete research development

Self-healing concrete has beenwidely recognized as remedial technique to improve the durability of concrete.Some review papers have been published on self-healing concrete. Yet thehierarchical structure foritsclassificationneeds to be reviewed. This study presents a novel taxonomy making use of advances inknowledgefor self-healing concrete. The study addresses the general taxonomy of self-healing concrete to beclassified into three categories i.e., natural, chemical and biological processes. The focus is on the study ofthe biological processes.The review and taxonomy presents a new insight into the research on treatment ofunexpected cracking of concrete. The information presented in this paper is significant for biotechnologistsand bioprocess engineers to have comprehensive updates on the current status-quo ofself-healing concrete

Decrease of Tregs cells and increase of exhausted Treg cells as the predictors of COVID19 severity

Background: T cells and regulatory T cells (Tregs) play a critical role in viral infectious immunity. Exhaustion of T cells during infection and decreased Tregs both contribute to the exacerbation of the disease. In the present study, we assessed T cells and regulatory T cells of COVID-19 patients and a control group according to the expression of the PD-1 molecule. Methods: Forty-two COVID-19 patients and 40 controls were enrolled in the study. In COVID-19 patients, blood samples were collected on the first day of their hospitalization. Regulatory T cells (CD4+, CD25+, FOXP3+), CD4+PD-1+, and PD-1+ regulatory T cells were assessed by flow cytometry. Results: The percentage of CD4+PD-1 + T cells in COVID-19 patients was significantly higher compared to the control group (P < 0.0001). The percentage of PD-1+ regulatory T cells was significantly increased in the patient group compared to the control group (P < 0.0001). However, the Treg percentage was significantly decreased in the patient group compared to the control group (P < 0.0001). The frequency of CD4+PD-1 + T cells, Tregs, and PD-1+ Tregs had acceptable sensitivity and specificity for assisting in the diagnosis of severe/critical COVID-19. The declined Tregs and enhanced CD4+CD25+, CD4+PD-1+, and PD-1 + T cells were associated with disease severity. Conclusion: The decrease in Tregs and the increase in exhaustion of these cells and T cells play an important role in COVID-19 pathogenesis. These immune parameters could be used as meaningful indicators for assisting in the diagnosis of severe/critical COVID-19

Differentially expressed inflammatory cell death-related genes and the serum levels of IL-6 are determinants for severity of coronaviruses diseases-2019 (COVID-19)

Background: Inflammatory cell death, PANoptosis, has been suggested to orchestrate the lymphocyte decrement among coronavirus disease-2019 (COVID-19) patients. The main aim of this study was to examine the differences in the expression of key genes related to inflammatory cell death and their correlation with lymphopenia in the mild and severe types of COVID-19 patients. Materials and Methods: Eighty-eight patients (36 to 60 years old) with mild (n = 44) and severe (n = 44) types of COVID-19 were enrolled. The expression of key genes related to apoptosis (FAS-associated death domain protein, FADD), pyroptosis (ASC (apoptosis-associated speck-like protein containing caspase activation and recruitment domains (CARD)), the adapter protein ASC binds directly to caspase-1 and is critical for caspase-1 activation in response to a broad range of stimuli), and necroptosis (mixed lineage kinase domain-like, MLKL) genes were examined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay, and compared between the groups. The serum levels of interleukin (IL)-6 were measured by enzyme-linked immunosorbent assay (ELISA) assay. Results: A major increase in the expression of FADD, ASC, and MLKL-related genes in the severe type of patients was compared to the mild type of patients. The serum levels of IL-6 similarly indicated a significant increase in the severe type of the patients. A significant negative correlation was detected between the three genes' expression and the levels of IL-6 with the lymphocyte counts in both types of COVID-19 patients. Conclusion: Overall, the main regulated cell-death pathways are likely to be involved in lymphopenia in COVID-19 patients, and the expression levels of these genes could potentially predict the patients' outcome

Identification of gaps to conduct a study on biological self-healing concrete

Biological self-healing concrete is a new idea to have concrete structures with more durability. Although, several papers have been published on biological self-healing concrete, a suitable instruction to conduct this type of studies is not reported. Aim of this paper is collecting comprehensive information about conducting a study on self-healing concretes based on previous studies. This paper present many new ideas that have not been completely study. Some idea such as application of fungi, thermopiles bacteria, mix culture of microorganisms or using of aerobic or anaerobic bacteria to design biological selfhealing concrete are suggested in this paper. Ideas of this paper can help researchers to find a suitable and novel subject in biological self-healing area to conduct a strong research

Application of Proteus mirabilis and Proteus vulgaris mixture to design self-healing concrete

This study investigated two indigenous micro-organisms that can be isolated from soil. The isolated micro-organisms could precipitate calcium carbonate. These micro-organisms were applied to design self-healing concretes. Concrete is one of the most important materials which is used to build structures. Strength and durability of concrete is very important. Hence, a lot of research in this field is being conducted. Although a few reports can be found on the use of different micro-organism to design self-healing concretes, no research has been carried out to isolate suitable indigenous micro-organisms in Malaysia. In this study two strains of microorganisms were isolated from soil. Broken concrete was treated by a medium culture (MC) containing micro-organisms. Results of this study showed that, cracked concrete could be filled by calcium carbonate after treating by a MC containing micro-organisms. However, this treatment is not very effective on the strength of concrete. Results of this study can be used to have a better grasp of biological self-healing concrete, it is extremely important to have cheap and durable materials to build concrete structures in future

A review of self-healing concrete research development

Self-healing concretes are being widely recognized as a remedial technique to improve the durability of concrete. Although, few review papers on self-healing concrete were published, a strong review on all aspects of self-healing concrete cannot be found. In this paper, natural, chemical and biological processes of self-healing concrete technologies were completely reviewed. The main focus of the study is for the biological processes. The review presents a new insight into the research for the treatment of unexpected cracking of concrete. The information presented in this paper can be considered significant for biotechnologists and bioprocess engineers to have comprehensive updates on the current status-quo of self-healing concrete