Coal gasification and composite ashes as partial replacements for Portland cement in concrete – strength and selected durability performance

MRS Advances ◽  
2020 ◽  
Vol 5 (54-55) ◽  
pp. 2807-2816
Author(s):  
Mike Otieno ◽  
Dikeledi Maboea
Keyword(s):  
Portland Cement ◽  
Coal Gasification ◽  
Gas Permeability ◽  
Concrete Strength ◽  
Replacement Level ◽  
Chloride Resistance ◽  
Weathered Coal ◽  
Negative Environmental Impact ◽  
Strength And Durability ◽  
Durability Performance

AbstractThis study investigated the use of mixed weathered coal fine ash (MWA) and coal gasification ash (CGA), sourced from Sasol® Ltd, South Africa, as partial replacements (10%, 15% and 30% by mass) of Portland Cement (PC) in concrete. The objective was to assess the feasibility of using the ashes, which are generally of lower quality than FA, in concrete in order to avert their negative environmental impact i.e. disposal in heaps and landfills. Companion reference concretes were made using conventional fly ash (FA). Two water-to-binder (w/b) ratios (0.50 and 0.60) were used. The concretes were tested for compressive strength (7, 28 and 56 days) and durability (gas permeability and chloride resistance at 28 and 56 days). In general, the results strongly suggest that the ashes can be used in conventional structural concrete – both from strength and durability viewpoints. Aspects that require attention when they are used include decrease in both workability and rate of strength gain. The gas permeability of the CGA and MWA concretes were similar to those for FA at all replacement levels but a 15% replacement level gave higher chloride resistance.

Curing of slag concretes at low temperatures: effect on selected durability properties

MRS Advances ◽  
2020 ◽  
Vol 5 (25) ◽  
pp. 1267-1275
Author(s):  
Mike Otieno ◽  
Riccardo Opeka
Keyword(s):  
Oxygen Permeability ◽  
Gas Permeability ◽  
Curing Temperature ◽  
Durability Properties ◽  
Chloride Resistance ◽  
Blastfurnace Slag ◽  
Water Sorptivity ◽  
Chloride Conductivity ◽  
Strength And Durability ◽  
Durability Performance

AbstractThe influence of low curing temperatures (5, 10 and 15 ± 2 °C) on the strength and durability properties of ground granulated blastfurnace slag (GGBS) and ground granulated Corex slag (GGCS) concretes was studied. A standard curing temperature of 23 ± 2 °C) was also used for comparative purposes. Test specimens were cast using 100% CEM I 52.5N (PC), and three PC/Slag (GGBS or GGCS) replacement ratios of 50/50, 65/35 and 80/20, and a w/b ratio of 0.40. The specimens were cured for 28 days by submersion in water at the respective curing temperatures and then tested for durability. Durability was assessed using oxygen permeability, water sorptivity and chloride conductivity tests. The results showed that durability of the concretes decreased as the curing temperature decreased – gas permeability and water sorptivity increased while chloride resistance decreased. It was also observed that at a given curing temperature, the slag blended concretes showed superior durability performance than the plain PC concretes.

scholarly journals Improving Marine Concrete Performance Based on Multiple Criteria Using Early Portland Cement and Chemical Superplasticizer Admixture

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4903
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee ◽  
Jaewook Jeong ◽  
Jaemin Jeong
Keyword(s):  
Portland Cement ◽  
Concrete Strength ◽  
Strength Development ◽  
Construction Productivity ◽  
Concrete Mix Design ◽  
Granulated Blast Furnace Slag ◽  
Chloride Resistance ◽  
Combined Use ◽  
Concrete Mix ◽  
Early Strength

This study sought to examine the performance design of concrete mix proportions to ensure chloride resistance and early strength with respect to C35 (35 MPa), which is the minimum compressive strength class of concrete used in a marine environment. For the proposed concrete mixture, C24 (24 MPa) was selected and binders for concrete were manufactured using a blend of OPC (ordinary Portland cement), EPC (early Portland cement), and GGBS (ground granulated blast-furnace slag). The results of the experiment confirmed that the combined use of EPC and GGBS greatly improve the early-strength development and chloride resistance of concrete. An analysis revealed that the time for removal of forms can be reduced by 5–9 h from the aspect of early concrete strength. Moreover, in terms of construction productivity, EPC and GGBS were reduced by up to 16.39 h/cycle compared to other concretes. Regarding economic and environmental impacts, EPC and GGBS were more effective than C35 concrete. This study is significant as its findings help make it possible to examine the most economical concrete mix design in relation to strength development according to the application of EPC, GGBS, and PC-based admixtures.

scholarly journals Strength and Durability Performance of Slag Blended Cements in High Temperature Environments

2017 ◽  
Vol 1 (2) ◽  
pp. 265-272 ◽  
Author(s):  
O. R. Ogirigbo ◽  
I. Inerhunwa
Keyword(s):  
High Temperature ◽  
Portland Cement ◽  
Chloride Ion ◽  
Chemical Compositions ◽  
Ion Permeability ◽  
Replacement Ratio ◽  
Blended Cements ◽  
Strength And Durability ◽  
Durability Performance ◽  
Better Than

In this study, two slags of different chemical compositions were blended with a CEM I 52.5R-type Portland cement at 30% wt. replacement ratio. Various tests such as strength, water and chloride ion permeability test were carried out at a high temperature of 38°C. The performances of the slag blends were measured against that of a CEM I 42.5R-type Portland cement. The results obtained showed that the performances of the slag blends were better than that of the CEM I 42.5R cement. In comparing the performances of the slags, the blend prepared from slag 1 had higher strengths and better transport properties than that prepared from slag 2, and this was attributed to the higher basicity and alumina content of slag 1. The findings of the study suggest that in tropical/ high temperature environments, the chemical composition of the slags play an important role in determining their performance.

Strength and durability of concretes containing 50% Portland cement replacement by fly ash and other materials

1990 ◽  
Vol 17 (1) ◽  
pp. 19-27 ◽  
Author(s):  
B. W. Langan ◽  
R. C. Joshi ◽  
M. A. Ward
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Abrasion Resistance ◽  
Air Entrainment ◽  
Replacement Level ◽  
Freeze Thaw ◽  
Void System ◽  
Strength And Durability ◽  
Air Void

Results are presented from an investigation on the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement. Seven fly ashes (sub-bituminous, bituminous, and lignitic), together with limestone and an inert material (silica flour), were used as replacement materials. Durability studies included freeze–thaw testing (ASTM C666A), scaling resistance (ASTM C672), and abrasion resistance (ASTM C944). The air void system was assessed using the modified point count method of ASTM C457. The results indicate that although concretes with a 50% replacement level of cementitious material did not perform as well as the control concretes with no replacement, such concretes were able to meet minimum durability requirements. As anticipated, air-entrainment is the overriding factor that allows concrete to meet freeze–thaw durability requirements. In the context of this study, compressive strength does not appear to be a significant factor in freeze–thaw durability. Results indicated that concretes with compressive strengths of less than 10 MPa will still pass the freeze–thaw test, provided an adequate air void system is in place. Abrasion resistance tends to increase with compressive strength but not in all the cases. Key words: concrete, fly ash, compressive strength, durability, mineral admixtures.

Mechanical strength and durability performance of autoclaved lime-saline soil brick

2017 ◽  
Vol 146 ◽  
pp. 403-409 ◽  
Author(s):  
Tung-Chai Ling ◽  
Kim Hung Mo ◽  
Lie Qu ◽  
Jiujun Yang ◽  
Lei Guo
Keyword(s):  
Mechanical Strength ◽  
Saline Soil ◽  
Strength And Durability ◽  
Durability Performance

scholarly journals Effect of High-Dispersible Graphene on the Strength and Durability of Cement Mortars

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 915
Author(s):  
Xiaoqiang Qi ◽  
Sulei Zhang ◽  
Tengteng Wang ◽  
Siyao Guo ◽  
Rui Ren
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Cement Mortar ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Chloride Ion Penetration ◽  
Cement Mortars ◽  
Strength And Durability ◽  
Durability Performance

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO2-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO2-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO2-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO2-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO2-RGO cement mortars were conducted, and it was found that with the same amount of TiO2-RGO and GO, the TiO2-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO2-RGO prepared by titanium dioxide (TiO2) intercalation can better improve the strength and durability performance of cement mortars compared to GO.

scholarly journals Environmental Assessment of Frost-resistant Concrete with Superabsorbent Polymers

2020 ◽  
Vol 63 (2) ◽  
pp. 43-62
Author(s):  
Gui Li ◽  
Marianne Tange Hasholt ◽  
Ole Mejlhede Jensen
Keyword(s):  
Environmental Impact ◽  
Concrete Strength ◽  
Significant Loss ◽  
Strength Increase ◽  
Life Cycle Assessment Methodology ◽  
Void System ◽  
Strength And Durability ◽  
Air Entraining Agents ◽  
Air Void ◽  
The Impact

AbstractAir-entraining agents (AEA) are normally used to improve the frost resistance of concrete. However, it is not possible to accurately control the air void system in concrete with AEA. Thus, a significant loss of concrete strength is caused by over-dosing voids, and this increases the environmental impact from concrete structures. Superabsorbent polymer (SAP) can also be used to produce frost-resistant concrete. Compared to AEA, it can be used to precisely engineer the air void structure of concrete, promote cement hydration, and mitigate self-desiccation cracks. In this study, life cycle assessment methodology is applied to evaluate the overall environmental impact of frost-resistant concrete based on AEA and SAP, respectively. The results illustrate that frost-resistant concrete with SAP has a lower environmental impact than frost-resistant concrete with AEA if the strength and durability of concrete are considered in the defined functional unit. In addition, frost-resistant concrete with SAP reduces the environmental burdens of the vertical elements such as columns, but it increases the environmental load of the horizontal elements such as slabs, where the strength increase cannot be utilized. Moreover, the inventory data for AEA and SAP can affect the impact assessment results.

scholarly journals STRENGTH AND DURABILITY TEST (SULPHATE ATTACK) ON LIGHT WEIGHT CONCRETE BY PARTIAL REPLACEMENT OF VERMICULITE FOR FINE AGGREGATE AND SILICAFUME FOR CEMENT

2021 ◽  
Vol 5 (12) ◽  
Author(s):  
M. Preethi ◽  
Md. Hamraj ◽  
Ashveen Kumar
Keyword(s):  
Sulphuric Acid ◽  
Concrete Strength ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Sulphate Attack ◽  
Durability Test ◽  
Measuring Machine ◽  
Strength And Durability ◽  
The Impact ◽  
Current Report

The present study focuses on the preparation of M30 grade concrete by replacing fine aggregate with 0%,5%,10%,15%,20%,25% of vermiculite and cement with 0% and 10% of constant silica fume to improve the performance of concrete. Via experimentation, the impact of acid exposure on concrete strength and weight is investigated in the current report. Concrete cubes of different mixes(12no.’s) are casted and exposed to Sulphuric acid of (pH=3). Cubes with dimensions of 100mm x 100mm x 100mm are cast with M30 concrete and then immersed (cured) in water for 28 days. The cubes are then soaked in 4 percent concentrated Sulphuric acid for 7 days. The compressive strength of the cured cubes is then measured using a compressive measuring machine.

scholarly journals Influence of mineral additions on the microstructure of concrete in chloride environment

2018 ◽  
Vol 1 (1) ◽  
pp. 283-292
Author(s):  
Walid Fouad Edris ◽  
Safwat Abdelkader ◽  
Encarnacion Reyes Pozo ◽  
Amparo Moragues Terrades
Keyword(s):  
Portland Cement ◽  
Blast Furnace Slag ◽  
Mercury Intrusion Porosimetry ◽  
Gas Permeability ◽  
Chloride Diffusion ◽  
Mercury Intrusion ◽  
Experimental Campaign ◽  
Mineral Additions ◽  
Chloride Environment ◽  
Furnace Slag

In this work we have designed an experimental campaign with four different dosages of concrete to study the influence of the principal additions used in marine environments. The effect of material composition [Sulfate Resistant Portland Cement (SRPC), Blast Furnace Slag Portland Cement (BFSPC), Silica Fume (SF) and Fly Ash (FA) with four different mix designs] was performed by means of differential thermal analysis (DTA), mercury intrusion porosimetry (MIP), gas permeability, chloride diffusion and mechanical properties of concrete. In order to simulate the aggressiveness of the marine environment the concretes were immersed in a sodium chloride solution with a concentration of 1 molar during different times of 182, 365 and 546 days. According to the results obtained, the SRPC and SRPC+FA samples suffered the highest rise in permeability, porosity and chloride diffusion, and the greatest loss in compressive strength

scholarly journals Bloques de Tierra Comprimida (BTC) estabilizados con cal y cemento. Evaluación de su impacto ambiental y su resistencia a compresión

2020 ◽  
Vol 10 (2) ◽  
pp. 70-81
Author(s):  
Santiago Pedro Cabrera ◽  
Yolanda Guadalupe Aranda-Jiménez ◽  
Edgardo Jonathan Suárez-Domínguez ◽  
Rodolfo Rotondaro
Keyword(s):  
Compressive Strength ◽  
Environmental Impact ◽  
Portland Cement ◽  
Life Cycle Analysis ◽  
Negative Impact ◽  
Santa Fe ◽  
Compressed Earth Blocks ◽  
Earth Blocks ◽  
Negative Environmental Impact ◽  
The City

This work presents the evaluation of the environmental impact and compressive strength of Compressed Earth Blocks (CEB) stabilized with hydrated aerial lime and Portland cement. For this, 12 series of blocks stabilized with different proportions of lime and cement were manufactured and the Life Cycle Analysis (LCA) methodology was used. After conducting these assays and simulations, it could be concluded that, using earth and sand typical of the city of Santa Fe (Argentina), stabilized with certain percentages of Portland cement between 5 and 10% in weight, CEB can be produced with sufficient levels of strength for them to be used in load-bearing walls, in this way minimizing the negative environmental impact associated with their manufacturing. It is also concluded that the stabilization with aerial lime does not increase the CEB’s compressive strength and, on the contrary, significantly increases their negative impact on the environment.

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