scholarly journals Effect of Bacillus cohnii on Some Physicomechanical and Microstructural Properties of Ordinary Portland Cement

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Ngari Reginah Wangui ◽  
Joseph Karanja Thiong’o ◽  
Jackson Muthengia Wachira
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Microstructural Analysis ◽  
Strength Development ◽  
Microstructural Properties ◽  
Calcite Precipitation ◽  
Strength Tests ◽  
Compressive Strength Development ◽  
Sustainability Challenges ◽  
Cement Setting

Cement-made materials face durability and sustainability challenges. This is majorly caused by the presence of cracks. Cracking affects the mechanical strength of cement-based materials. Microbiologically induced calcite precipitation (MICP) has been found to enhance compressive strength, thus enhancing on the mechanical and durability properties of these materials. This paper presents the findings of a study conducted to investigate the effect of Bacillus cohnii on compressive strength development of OPC mortar prisms and the effect of Bacillus cohnii on cement setting time and soundness. Microbial concentration of 1.0 × 107 cells·ml−1 was used. Compressive strength tests analyses were carried out for each category of mortar prisms. Compressive strength tests were carried out on the 2nd, 7th, 14th, 28th, 56th, and 90th day of curing in distilled water and microbial solutions. All microbial mortars exhibited a greater compressive strength compared to the control with the highest observed at 90 days. Highest percentage gain in compressive strength was observed at 90 days which is 28.3%. Microstructural analysis was carried out using a scanning electron microscope (SEM) after 28 days of curing. The results indicated the presence of calcium carbonate and more calcium silicate hydrate (CSH) deposits on the bacterial mortars. The bacteria did not have an effect on cement soundness. Setting time was significantly accelerated.

scholarly journals Influence of Mechanical and Mineralogical Activation of Biomass Fly Ash on the Compressive Strength Development of Cement Mortars

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6654
Author(s):  
Jakub Popławski ◽  
Małgorzata Lelusz
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cement Mortar ◽  
Setting Time ◽  
Green Energy ◽  
Biomass Combustion ◽  
Strength Development ◽  
Compressive Strength Development ◽  
Biomass Fly Ash

Biomass combustion is a significant new source of green energy in the European Union. The adequate utilization of byproducts created during that process is a growing challenge for the energy industry. Biomass fly ash could be used in cement composite production after appropriate activation of that material. This study had been conducted to assess the usefulness of mechanical and physical activation methods (grinding and sieving), as well as activation through the addition of active silica in the form of silica fume, as potential methods with which to activate biomass fly ash. Setting time, compressive strength, water absorption and bulk density tests were performed on fresh and hardened mortar. While all activation methods influenced the compressive strength development of cement mortar with fly ash, sieving of the biomass fly ash enhanced the early compressive strength of cement mortar. The use of active silica in the form of silica fume ensured higher compressive strength results than those of control specimens throughout the entire measurement period.

scholarly journals Influence of component fineness on hydration and strength development in ternary slag-limestone cements

2019 ◽  
Vol 4 ◽  
pp. 81-88 ◽  
Author(s):  
Samuel Adu-Amankwah ◽  
Susan A Bernal Lopez ◽  
Leon Black
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Cementitious Materials ◽  
Particle Packing ◽  
Simultaneous Optimization ◽  
Strength Development ◽  
Heat Of Reaction ◽  
Hydration Kinetics ◽  
Compressive Strength Development ◽  
Furnace Slag

The quest for sustainable alternatives to Portland cement has led to the exploration of a range of materials or their combinations, often with the aim of exploiting synergies in reactions or particle packing to maximize performance. Simultaneous optimization of both presents a viable option to increase the efficiency of cementitious materials. The objective of this study was to evaluate the effect of varying the fineness of the constituents in ternary blends of CEM I – granulated ground blast furnace slag (GGBS) - limestone on hydration kinetics and strength development. Eight (8) ternary cement mixes were tested at 0.5 water/binder (w/b) ratio. Hydration was followed by isothermal conduction calorimetry and setting time. In addition, X-ray powder diffraction, thermogravimetric analysis and compressive strength development up to 180 days of curing were assessed. The efficiency associated with changing the fineness of each component was evaluated in terms of the net heat of reaction and compressive strength. The results show that fine CEM I is critical for hydration at early age, and this is reflected in the compressive strength accordingly. The benefits associated with finer GGBS and similarly limestone depend on the fineness of the other constituents in the blend. Optimization of these should consider the inter-dependencies in terms of kinetics and microstructure development.

Effects of Different Lithium Admixtures on Ordinary Portland Cement Paste Properties

2014 ◽  
Vol 919-921 ◽  
pp. 1780-1789 ◽  
Author(s):  
Yu Hai Deng ◽  
Chang Qing Zhang ◽  
Hai Qiang Shao ◽  
Han Wu ◽  
Nie Qiang Xie
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Lithium Carbonate ◽  
Lithium Hydroxide ◽  
Strength Development ◽  
Lithium Nitrate ◽  
Cement Pastes ◽  
Compressive Strength Development ◽  
Paste Properties

Lithium-based chemicals are known to their signal effect on restraining alkali-silica reaction but uncertain influence on workability and mechanical property in the concrete. The aim of this research is to analyze the effects of three lithium additiveslithium nitrate (LiNO3), lithium hydroxide (LiOH) and lithium carbonate (Li2CO3) at various dosages, with an extensive comparison on fluidities, setting times and compressive strength of cement pastes. The experimental study shows that test results vary with the type of admixture. In general, three conclusions can be made: 1) lithium nitrate and lithium hydroxide can enhance the fluidity of cement paste, but lithium carbonate has opposite effects; 2) all three lithium salts shorten setting time as well as decrease the strength at suitable dosages; 3) the variations in lithium additives dosages have different influence on the cement pastes setting time and compressive strength development.

scholarly journals The potential use of pumice in mine backfill

2020 ◽  
Vol 1 ◽  
Author(s):  
Mohammed A. Hefni
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Mining Industry ◽  
Strength Development ◽  
Natural Pozzolan ◽  
Mine Backfill ◽  
Natural Pozzolans ◽  
Cemented Backfill ◽  
Compressive Strength Development ◽  
Potential Use

Abstract The use of natural pozzolans in concrete applications is gaining more attention because of the associated environmental, economic, and technical benefits. In this study, reference cemented mine backfill samples were prepared using Portland cement, and experimental samples were prepared by partially replacing Portland cement with 10 or 20 wt.% fly ash as a byproduct (artificial) pozzolan or pumice as a natural pozzolan. Samples were cured for 7, 14, and 28 days to investigate uniaxial compressive strength development. Backfill samples containing 10 wt.% pumice had almost a similar compressive strength as reference samples. There is strong potential for pumice to be used in cemented backfill to minimize costs, improve backfill properties, and promote the sustainability of the mining industry.

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