scholarly journals Bacteria incorporated with calcium lactate pentahydrate to improve the mortar properties and self-healing occurrence

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Siti Khodijah Chaerun ◽  
Ridwan Syarif ◽  
Ridho Kresna Wattimena
Keyword(s):  
Organic Carbon ◽  
Physical Properties ◽  
Mineralogical Composition ◽  
High Energy ◽  
Calcium Lactate ◽  
Self Healing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Micro Cracks ◽  
Bacterial Inoculum

Abstract Concrete can be harmful to the environment due to its high energy consumption and CO2 emission and also has a potential crack formation, which can promote a drop in its strength. Therefore, concrete is considered as a non-sustainable material. The mechanisms by which bacterial oxidation of organic carbon can precipitate calcite that may fill the voids and cracks on cement-based materials have been extensively investigated to prevent and heal the micro-cracks formation. Hence, this study focused on utilizing a new alkaliphilic bacterial strain indigenous to an Indonesian site, Lysinibacillus sphaericus strain SKC/VA-1, incorporated with calcium lactate pentahydrate, as a low-cost calcium source, with various bacterial inoculum concentrations. The bacterium was employed in this study due to its ability to adapt to basic pH, thus improving the physical properties and rejuvenating the micro-cracks. Experimentally, the addition of calcium lactate pentahydrate slightly affected the mortar properties. Likewise, bacteria-incorporated mortar exhibited an enhancement in the physical properties of mortar. The highest improvement of mechanical properties (an increase of 45% and 36% for compressive and indirect tensile strength, respectively) was achieved by the addition of calcium lactate pentahydrate incorporated with 10% v/v bacterial inoculum [about 7 × 107 CFU/ml (colony-forming unit/ml)]. The self-healing took place more rapidly on bacterial mortar supplemented with calcium lactate pentahydrate than on the control specimen. XRD analysis demonstrated that the mineralogical composition of self-healing precipitates was primarily dominated by calcite (CaCO3), indicating the capacity of L. sphaericus strain SKC/VA-1 to precipitate calcite through organic carbon oxidation for self-healing the artificial crack on the mortar. To our knowledge, this is the first report on the potential utilization of the bacterium L. sphaericus incorporated with calcium lactate pentahydrate to increase the mortar properties, including its self-healing ability. However, further study with the water-cement ratio variation is required to investigate the possibility of using L. sphaericus and calcium lactate pentahydrate as an alternative method rather than reducing the water-cement ratio to enhance the mortar properties.

scholarly journals Influence of Water-Cement Ratio and Type of Mixing Water on the Early Hydration Performance of Calcium Sulphoaluminate (CSA) Cement

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chuanlin Wang ◽  
Meimei Song
Keyword(s):  
Compressive Strength ◽  
Physical Properties ◽  
Setting Time ◽  
Hydration Process ◽  
Chemical Shrinkage ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Calcium Sulphoaluminate ◽  
Mixing Water

The present work studies the influence of water-cement ratio and types of mixing water on the hydration process and microstructure of calcium sulphoaluminate (CSA) cement. Experimental tests on the setting time, physical properties, compressive strength, chemical shrinkage, X-ray diffraction (XRD), and scanning electron microscopy (SEM) of CSA cement paste were carried out. The XRD analysis confirmed that the main hydration product is ettringite in both freshwater and seawater mixed CSA cement with different w/c ratios. The SEM analysis and physical properties test show that both low w/c ratio and seawater can improve the microstructure of CSA cement. The test results also find out that the high w/c ratio can accelerate the hydration process, extend the setting time, lower the compressive strength, and increase the chemical shrinkage of CSA cement, and the seawater presents a similar influence except for the mechanical property. The seawater increases the compressive strength of CSA cement in the early stage of hydration but will increase the microcracks at the later hydration stage of CSA cement and reduce its mechanical properties.

scholarly journals Hardening Characteristics of Self-healing Cement Mortars

2021 ◽  
Vol 283 ◽  
pp. 01006
Author(s):  
Tong Ye ◽  
Zhuangzhaug Liu ◽  
Lin Li
Keyword(s):  
Cement Mortar ◽  
Self Healing ◽  
Transportation Engineering ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cement Mortars ◽  
Basic Performance ◽  
Curing Methods ◽  
Healing Agent ◽  
Water Conservancy

In water conservancy and transportation engineering, self-healing cement has been widely used. This paper researches the optimal water-cement ratio of self-healing cement mortar to obtain the best basic performance, and on this basis, researches the occasional effect of self-healing agent and fibers on the mechanical properties of cement mortar. In addition, the research on the shrinkage characteristics and impermeability of cement mortar by self-healing agent was carried out to provide the basis for the curing methods of bacterial cement in the project. Finally, the microstructure of self-healing cement provides a theoretical basis for the macroscopic performance. The results show that the best water-cement ratio of the self-healing cement mortar is 0.42, and the fiber can effectively improve the toughness of the material. In addition, bacterial can increase the auto-shrinkage and impermeability of cement. These results will offer valuable experience for experimenters to assist the experiment work.

Amelioration of freeze thaw damage of concrete with multi-walled carbon nano tubes

2020 ◽  
Vol 18 (1) ◽  
pp. 58-65
Author(s):  
Mudasir Peerzada ◽  
Javed Ahmed Naqash
Keyword(s):  
Frost Damage ◽  
Split Tensile Strength ◽  
Content Type ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Freeze Thaw ◽  
Micro Cracks ◽  
Carbon Nano Tubes ◽  
Carbon Nano Tube ◽  
Main Factor

Purpose In cold areas, frost damage is the main factor for diminution of durability and serviceability of structures. Due to incessant freeze thaw regimes, micro cracks spread and deteriorate concrete to point of failure. Design/methodology/approach The study aims to evaluate the fresh and hardened properties of concrete after thirty freeze-thaw cycles tailored with carbon nano tubes. For this purpose, samples with 0.4, 0.45, 0.48, 0.5 and 0.55 water cement ratio while 0.5 and 1% carbon nano tube (CNT) content by weight of cement were prepared. Findings At 0.48 water cement ratio and 0.5% CNT by weight of cement workability reduced by 37% and water absorption reduced by 0.04%. But compressive strength, split tensile strength and flexural strength increased by 15.38, 33.02 and 15.75%, respectively, after 30 freeze thaw cycles. Also, weight loss reduced with addition of 0.5% CNT by weight of cement after freeze thaw cycles. Originality/value Novelty of this research is to tailor traditional concrete with new materials.

Strength Indicators Of Cement Systems With Additives Of Surface - Active Substances

2021 ◽  
Vol 03 (05) ◽  
pp. 203-209
Author(s):  
Teshaboeva Nodira Djuraevna ◽  
Keyword(s):  
Mineralogical Composition ◽  
Strength Characteristics ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Surface Active ◽  
Active Substances ◽  
Control Samples

In the article, the study was to establish the effect of surfactant additives on the strength characteristics of cement systems. The determinations were carried out on cements of various mineralogical composition, freshly ground and stale, on cement-sand mortars and concretes. For control samples and with additives, the same plasticity was chosen, and the water-cement ratio than for various additives fluctuated within certain limits.

Effects of Water Cement Ratio on Strengths Characteristics of Concrete Produced with Recycled Iron and Steel Slag (RISS) Aggregate

2021 ◽  
Vol 107 ◽  
pp. 97-112
Author(s):  
Akeem Ayinde Raheem ◽  
Oluwaleke A. Olowu ◽  
Anthony Ajibola Hungbo ◽  
Emmanuel Olatunde Ibiwoye
Keyword(s):  
Structural Integrity ◽  
Silicon Oxide ◽  
Steel Slag ◽  
Mineralogical Composition ◽  
Iron And Steel ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
The Common ◽  
Compressive And Flexural Strengths

Effects of Water cement ratios on strengths characteristics of concrete produced with Recycled Iron and Steel Slag (RISS) aggregates was studied to understand the structural integrity of RISS aggregate in concrete and to determine the veracity of RISS aggregate as alternative aggregate to granite in concrete works. Mineralogical composition of the aggregate showed Silicon oxide (quartz) as the common mineral; both aggregates are well graded, strong and durable. Lower water cement ratios improved both the compressive and flexural strengths of RISS and granite concrete.

scholarly journals Use of Nondestructive Testing of Ultrasound and Artificial Neural Networks to Estimate Compressive Strength of Concrete

Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 44
Author(s):  
Fernando A. N. Silva ◽  
João M. P. Q. Delgado ◽  
Rosely S. Cavalcanti ◽  
António C. Azevedo ◽  
Ana S. Guimarães ◽  
...  
Keyword(s):  
Neural Networks ◽  
Compressive Strength ◽  
Artificial Neural Networks ◽  
Cross Sections ◽  
Influential Factors ◽  
Average Error ◽  
Ann Model ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Artificial Neural

The work presents the results of an experimental campaign carried out on concrete elements in order to investigate the potential of using artificial neural networks (ANNs) to estimate the compressive strength based on relevant parameters, such as the water–cement ratio, aggregate–cement ratio, age of testing, and percentage cement/metakaolin ratios (5% and 10%). We prepared 162 cylindrical concrete specimens with dimensions of 10 cm in diameter and 20 cm in height and 27 prismatic specimens with cross sections measuring 25 and 50 cm in length, with 9 different concrete mixture proportions. A longitudinal transducer with a frequency of 54 kHz was used to measure the ultrasonic velocities. An ANN model was developed, different ANN configurations were tested and compared to identify the best ANN model. Using this model, it was possible to assess the contribution of each input variable to the compressive strength of the tested concretes. The results indicate an excellent performance of the ANN model developed to predict compressive strength from the input parameters studied, with an average error less than 5%. Together, the water–cement ratio and the percentage of metakaolin were shown to be the most influential factors for the compressive strength value predicted by the developed ANN model.

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