scholarly journals Resilient performance of expansive subgrades stabilized with nanosized and activated fly ash

2021 ◽  
Author(s):  
Frank Ikechukwu Aneke ◽  
Mohamed Mostafa Hassan
Keyword(s):  
Fly Ash ◽  
Resilient Modulus ◽  
Morphological Changes ◽  
Expansive Soils ◽  
Pozzolanic Reaction ◽  
Exchange Capacity ◽  
Degree Of Saturation ◽  
Strength Development ◽  
High Plasticity ◽  
Test Result

Subgrades across arid and semi-arid region are known for its random swelling, with high plasticity due to moisture infiltration of the pavement structures. Subgrades materials are significantly influenced by the cahnges in degree of saturation, which is unavoidable. Studies in the past, have reported several positive results on the stabilization of expansive soils with additives like lime, cement, fly ash, etc. In this study, resilient performance of expansive subgrades treated with 0.5%, 1.0%, 1.5% and 2.0% of nanosized and activated fly ash (NFA and AFA) is presented. Series of cation exchange capacity tests, zero swelling tests (ZST) and resilient modulus (M_R ) tests were performed to study the effects of NFA and AFA on resilient modulus (M_R) and swelling index of the subgrades material respectively. Scanning electron microscopy (SEM) tests was conducted to evaluate the morphological changes in the subgrades, and compounds responsible for resilient strength development. The result showed that, NFA and AFA inclusions in the treatment of expansive subgrades caused an increase in resilient strength and decrease in swelling stress to a limiting stabilizer content of 0.5% and 1.0% beyond which, the resilient modulus values increased triggering a significant decrease in swelling stress. The test result revealed that the reduction was caused by the pozzolanic reaction between the stabilizers and available moisture required for full completion of pozzolanic process. Based on the test result, nano-fly ash exhibite high potential in improving resilient strength and reducing swelling stress to 58.7% and 63% respectively on the average compared to activated fly ash. This study suggest a feasible solution to improve the quality and performance of expansive subgrades.

Compressibility and hydraulic conductivity of a chemically treated expansive clay

2001 ◽  
Vol 38 (1) ◽  
pp. 154-160 ◽  
Author(s):  
Zalihe Nalbantoglu ◽  
Erdil Riza Tuncer
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Expansive Soil ◽  
Dry Weight ◽  
Pozzolanic Reaction ◽  
Exchange Capacity ◽  
Expansive Clay ◽  
Preconsolidation Pressure ◽  
Few Data ◽  
Published Research

The paper presents a series of laboratory tests and evaluates the effect of lime and fly ash on the compressibility and hydraulic characteristics of an expansive soil in Cyprus. The tests were performed at different percentages of lime (0–7%) and fly ash (15 and 25%) by dry weight of soil, and additional tests were also performed on soils treated with 15% fly ash plus 3% lime. Previously published research reveals that few data are available concerning the compressibility and hydraulic conductivity of lime-treated soils. The results of this study indicate an increase in the vertical effective yield stress (apparent preconsolidation pressure) and a decrease in the compressibility characteristics of the treated soils. Moreover, unlike some of the findings in the literature, higher hydraulic conductivity values were obtained with time. This finding has been substantiated by the reduced cation exchange capacity (CEC) values, which indicate that the pozzolanic reaction causes the soils to become more granular in nature, resulting in higher hydraulic conductivity.Key words: cementation, compressibility, fly ash, hydraulic conductivity, lime.

Fly-Ash Concretes of 50% of the Replacement Ratio to Reduce the Cracking in Concrete Structures

2013 ◽  
Vol 405-408 ◽  
pp. 2665-2670 ◽  
Author(s):  
Ming Jie Mao ◽  
Qiu Ning Yang ◽  
Wen Bo Zhang ◽  
Isamu Yoshitake
Keyword(s):  
Fly Ash ◽  
Concrete Structures ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Early Age ◽  
Replacement Ratio ◽  
Fly Ash Concrete ◽  
Massive Concrete ◽  
Normal Strength

Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

Beneficiation of Waste Fly Ash and Phosphogypsum— The Development of a New Material

2021 ◽  
Vol 47 (1) ◽  
pp. 70-81
Author(s):  
Tebogo Mashifana ◽  
Felix Okonta ◽  
Freeman Ntuli
Keyword(s):  
Fly Ash ◽  
Citric Acid ◽  
Chemical Composition ◽  
Detrimental Effect ◽  
Pozzolanic Reaction ◽  
Building Construction ◽  
Strength Development ◽  
Material Strength ◽  
Minimum Requirements ◽  
New Material

Waste phosphogypsum (PG) was treated with citric acid, oxalic acid, sodium carbonate and sodium bicarbonate to reduce the contaminants in the material and render the material applicable for other applications. The chemical composition revealed that the material was laden with contaminants such as fluorides and phosphorous which have a detrimental effect on the development of material strength. Citric acid was the best leaching reagent to reduce the radionuclides in PG and it was selected as the leaching reagent to treat PG. The chemical composition of both the raw PG and treated PG showed that there was insufficient pozzolans in the materials to trigger the pozzolanic reaction for strength development. Therefore the PG had to be stabilized with fly ash and lime. The optimum mix ratio of the raw PG composite that yielded the highest UCS was made up of 50% raw PG and 30% FA, while 30% treated PG and 50% FA yielded the highest strength. The variation in strengths between the raw and treated PG was due to differences in the microstructure of the materials and the particle size distribution. The strength obtained met the minimum requirements for the material to be used in bulk as building construction elements.

Evidence for Minimal Pozzolanic Reaction in a Fly Ash Cement During the Period of Major Strength Development

1988 ◽  
Vol 136 ◽  
Author(s):  
Sidney Diamond ◽  
Qizhong Sheng ◽  
Jan Olek
Keyword(s):  
Fly Ash ◽  
Plain Concrete ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Inert Material ◽  
Microscope Examination ◽  
Intimate Contact ◽  
Cement Pastes ◽  
Minimal Evidence ◽  
Water Contents

ABSTRACTStrengths developed in fly ash concretes usually equal or exceed that of similar plain concrete after a few months, with much of the response usually attributed to “pozzolanic” reaction between ash and secondary calcium hydroxide (CH). The CH contents of pastes made with five different fly ashes were determined by DTA for periods up to six months. The CH contents found did not decrease notably over the period, and were substantially identical to that expected for plain cement pastes diluted with the same amount of inert material as the amount of fly ash used. Scanning electron microscope examination of the pastes showed only minimal evidence of reaction even up to 1 year of age, although many fly ash grains were in intimate contact with CH. Non-evaporable water contents of the fly ash pastes were substantially higher than expected at each age, suggesting that the fly ash promoted more complete cement hydration or that the hydration products formed bound substantially greater amounts of water than plain cement paste ordinarily does.

Evidence for Minimal Pozzolanic Reaction in a Fly Ash Cement during the Period of Major Strength Development

1988 ◽  
Vol 137 ◽  
Author(s):  
Sidney Diamond ◽  
Qizhong Sheng ◽  
Jan Olek
Keyword(s):  
Fly Ash ◽  
Plain Concrete ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Inert Material ◽  
Microscope Examination ◽  
Intimate Contact ◽  
Cement Pastes ◽  
Minimal Evidence ◽  
Water Contents

AbstractStrengths developed in fly ash concretes usually equal or exceed that of similar plain concrete after a few months, with much of the response usually attributed to “pozzolanic” reaction between ash and secondary calcium hydroxide (CH). The CH contents of pastes made with five different fly ashes were determined by DTA for periods up to six months. The CH contents found did not decrease notably over the period, and were substantially identical to that expected for plain cement pastes diluted with the same amount of inert material as the amount of fly ash used. Scanning electron microscope examination of the pastes showed only minimal evidence of reaction even up to 1 year of age, although many fly ash grains were in intimate contact with CH. Non-evaporable water contents of the fly ash pastes were substantially higher than expected at each age, suggesting that the fly ash promoted more complete cement hydration or that the hydration products formed bound substantially greater amounts of water than plain cement paste ordinarily does.

scholarly journals Strength, Hydraulic, and Microstructural Characteristics of Expansive Soils Incorporating Marble Dust and Rice Husk Ash

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Fazal E. Jalal ◽  
Sultani Mulk ◽  
Shazim Ali Memon ◽  
Babak Jamhiri ◽  
Ahsan Naseem
Keyword(s):  
Rice Husk ◽  
Rice Husk Ash ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Sensitivity Analyses ◽  
Waste Materials ◽  
Strength Development ◽  
High Plasticity ◽  
Preconsolidation Pressure ◽  
Marble Dust

Expansive/swell-shrink soils exhibit high plasticity and low strength, which lead to settlement and instability of lightly loaded structures. These problematic soils contain various swelling clay minerals that are unsuitable for engineering requirements. In an attempt to counter the treacherous damage of such soils in modern geotechnical engineering, efforts are underway to utilize environmentally friendly and sustainable waste materials as stabilizers. This study evaluates the strength and consolidation characteristics of expansive soils treated with marble dust (MD) and rice husk ash (RHA) through a multitude of laboratory tests, including consistency limits, compaction, uniaxial compression strength (UCS), and consolidation tests. By using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, the effect of curing on UCS after 3, 7, 14, 28, 56, and 112 days was studied from the standpoint of microstructural changes. Also, the long-term strength development of treated soils was analyzed in terms of the interactive response of impacting factors with the assistance of a series of ANN-based sensitivity analyses. It is found from the results that the addition of MD and RHA lowered down the water holding capacity, thereby causing a reduction in soil plasticity (by 21% for MD and 14.5% for RHA) and optimum water content (by 2% for MD and increased by 6% for RHA) along with an increase in the UCS (for 8% MD from 97 kPa to 471 kPa and for 10% RHA from 211 kPa to 665 kPa, after 3 days and 112 days of curing, respectively). Moreover, from the oedometer test results, m v initially increased up to 6% dosage and then dropped with further increase in the preconsolidation pressure. Furthermore, the compression index dropped with an increase in the preconsolidation pressure and addition of MD/RHA, while the coefficient of permeability (k) of RHA stabilized soil was higher than that of MD-treated samples for almost all dosage levels. The formation of the fibrous cementitious compounds (C-S-H; C-A-H) increased at optimum additive dosage after 7 days and at higher curing periods. Hence, the use of 10% RHA and 12% MD as replacement of the expansive soil is recommended for higher efficacy. This research would be helpful in reducing the impacts created by the disposal of both expansive soil and industrial and agricultural waste materials.

Strength Development and Microstructural Investigation of Calcium Carbide Residue and Fly Ash Prepared with Optimized Alternative Green Binders

2021 ◽  
Vol 904 ◽  
pp. 429-434
Author(s):  
Papantasorn Manprom ◽  
Phongthorn Julphunthong ◽  
Pithiwat Tiantong ◽  
Tawat Suriwong
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Raw Materials ◽  
Extended Period ◽  
Calcium Carbide ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Chemical Compositions ◽  
Microstructural Investigation ◽  
Calcium Carbide Residue

The development of new environmentally friendly binder from calcium carbide residue and fly ash wastes were investigated in this study. The key point of this work is difference to several previous investigations in that the optimized mixture proportion of the raw materials were calculated based on their chemical composition and their reaction. The compressive strength development over the curing age was also compared with reference mortar created with OPC binder. Mortar cubes were cast from the mix containing the calcium carbide residue and fly ash, at the optimized ratio. The compressive strength of the mortar was then monitored over an extended period: at 56 days it was 10.66 MPa, which is approximately 47% of the reference mortar. The morphologies and chemical compositions of the developed mortar showed the presence of spherically shaped of unreacted fly ash powder particles embedded in a cement C–S–H gel resulting from the pozzolanic reaction of raw materials.

Evaluation of the Curing Time Effect on the Swelling, Unconfined Strength and Resilient Modulus of an Expansive Soil Improved with Hydrated Lime

2021 ◽  
pp. 036119812110570
Author(s):  
İ. Süt Ünver ◽  
M. A. Lav ◽  
E. Çokça ◽  
G. Baykal
Keyword(s):  
Resilient Modulus ◽  
Expansive Soils ◽  
Dry Weight ◽  
Soil Samples ◽  
Natural Soil ◽  
High Plasticity ◽  
Expansive Clay ◽  
Curing Time ◽  
Clay Deposits ◽  
Swell Potential

Soils with high plasticity and high swell potential undergo great volume changes in the presence of unstable water content changes. The resulting expansion leads to damage to pavements and/or lightweight structures with such a subsoil. Expansive soils can be improved by adding chemical stabilizers such as lime, fly ash and micro cement. To construct a highway on an expansive subgrade soil, the subgrade should be stabilized to satisfy the minimum requirements of the highway standards. In this research, expansive clay samples were collected from clay deposits in the Akyurt district of Ankara (Turkey), near Esenboğa Airport. The swelling, strength and resilient modulus properties of the soil samples were determined via laboratory tests. First, reference tests were carried out on natural soil samples. Then, the clay samples were mixed with lime agent at different percentages (1%, 3%, 5%, 7% and 9%) according to the dry weight of the soil. The index, swelling, strength and resilient modulus (Mr) properties of these samples were determined. The soil samples were tested at 7, 28, 56 and 90-day curing times for each percentage of lime agent considered. The changes in the abovementioned properties, especially with regard to the effect of curing time on improvement, were interpreted in this research. Designing for a 7% lime content and a 28-day curing time can be a sound solution for addressing the expansive clay studied in this research, since the criteria of the Turkish Highway Standards are satisfied under these conditions.

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