scholarly journals Unsaturated Response of Clayey Soils Stabilised with Alkaline Cements

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2533
Author(s):  
Nuno Araújo ◽  
Manuela Corrêa-Silva ◽  
Tiago Miranda ◽  
António Topa Gomes ◽  
Fernando Castro ◽  
...  
Keyword(s):  
Triaxial Tests ◽  
Strength Increase ◽  
Soil Water Retention ◽  
Experimental Procedure ◽  
Retention Curve ◽  
Curing Conditions ◽  
Strength Tests ◽  
Before And After ◽  
Alkali Activated

The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each binder, as the OPC presented a higher air-entry value and a narrower suction range compared to the AAC solution. The significant differences between the curves obtained from each binder suggest the future development of a methodology to assess the quality of the AAC stabilisation.

scholarly journals Recycling and Application of Mine Tailings in Alkali-Activated Cements and Mortars—Strength Development and Environmental Assessment

2020 ◽  
Vol 10 (6) ◽  
pp. 2084 ◽  
Author(s):  
Nuno Cristelo ◽  
João Coelho ◽  
Mafalda Oliveira ◽  
Nilo Cesar Consoli ◽  
Ángel Palomo ◽  
...  
Keyword(s):  
Mine Tailings ◽  
Sodium Intake ◽  
Sodium Sulphate ◽  
Strength Development ◽  
Strength Increase ◽  
Fine Aggregate ◽  
Reaction Products ◽  
X Ray ◽  
Alkali Activated

Mine tailings (MT) could represent a step forward in terms of the quality of the aggregates usually used in civil engineering applications, mostly due to its high density. The Portuguese Neves Corvo copper mine, owned by the Lundin Mining Corporation, produces approximately 3 million tonnes per year. Nevertheless, it cannot be used in its original state, due to its high levels of sulphur and other metals (As, Cr, Cu, Pb, Zn). This paper focuses on the stabilisation/solidification of high-sulphur MT, without any previous thermal treatment, using alkali-activated fly ash (FA). The variables considered were the MT/FA ratio and the activator type and concentration. A fine aggregate was then added to the pastes to assess the quality of the resulting mortar. Maximum compressive strengths of 14 MPa and 24 MPa were obtained for the pastes and mortars, respectively, after curing for 24 h at 85 °C. Thermogravimetric analysis, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray diffraction, and infrared spectroscopy were used to characterize the reaction products, and two types of leaching tests were performed to assess the environmental performance. The results showed that the strength increase is related with the formation of a N-A-S-H gel, although sodium sulphate carbonate was also developed, suggesting that the total sodium intake could be optimized without strength loss. The solubility of the analysed metals in the paste with 78% MT and 22% FA was below the threshold for non-hazardous waste.

scholarly journals Alkali-Activated Fly Ashes: Influence of Curing Conditions on Mechanical Strength

2018 ◽  
Vol 3 (2) ◽  
pp. 57-67
Author(s):  
Filipe Almeida ◽  
Nuno Cristelo ◽  
Tiago Miranda ◽  
Castorina S. Vieira ◽  
Maria De Lurdes Lopes ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Relative Humidity ◽  
Mechanical Strength ◽  
Research Groups ◽  
Fly Ashes ◽  
Curing Conditions ◽  
Alkaline Activation ◽  
Strength Tests ◽  
Higher Temperature ◽  
Alkali Activated

Alkaline activation of fly ashes is a procedure that enables an alternative binder which has been receiving much interest by several research groups particularly on the manufacturing of mortars and concretes. The properties of the materials that are developed during the alkaline activation are influenced by the curing conditions (temperature and relative humidity). Another relevant facet related to the curing procedures is the possibility of carbonation occur, which may have an impact on the mechanical strength of the alkaline cements. In this research, several sets of curing conditions were tested to understand which one results in a higher strength and reveals carbonation. Uniaxial compressive strength tests were conducted to assess mechanical behavior. The outcome suggests that higher temperature and low relative humidity yields higher mechanical strength.

scholarly journals Hybrid Geopolymeric Foams for the Removal of Metallic Ions from Aqueous Waste Solutions

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4091 ◽  
Author(s):  
Giuseppina Roviello ◽  
Elena Chianese ◽  
Claudio Ferone ◽  
Laura Ricciotti ◽  
Valentina Roviello ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metallic Ions ◽  
Ultrapure Water ◽  
Experimental Procedure ◽  
Strength Tests ◽  
Before And After ◽  
Long Time ◽  
Alkaline Conditions ◽  
First Time

For the first time, hybrid organic–inorganic geopolymeric foams were successfully used as monolithic adsorbents for the removal of metallic ions pollutants from wastewaters. The foams were realized by the in situ foaming of a hybrid geopolymer obtained by a reaction of metakaolin and polysiloxane oligomers under strong alkaline conditions and then cured at room temperature. In this way, porous materials with densities ranging from 0.4 to 0.7 g/cm3 and showing good mechanical properties were produced. With the aim of producing self-standing monolithic adsorbents for the removal of metallic ions pollutants from wastewaters, these porous hybrid geopolymers were subjected to a washing pretreatment with ultrapure water, dried, and then used for absorption tests by dipping them into an aqueous solution with an initial concentration of 20 ppm of Pb2+, Cd2+, Cu2+, and Zn2+ ions. Preliminary results indicated that all the tested materials are effective in the adsorption of the tested metal ions and do not release the removed metal ions upon sinking in ultrapure water, even for a very long time. Interestingly, compressive strength tests performed before and after the washing treatments show that the foamed samples remain intact and maintain their physical–mechanical characteristics, suggesting that these kinds of materials are promising candidates for the production of self-standing, monolithic adsorbent substrates that can be easily collected when exhausted, which is a major advantage in comparison with the use of powdered adsorbents. Moreover, since these materials can be obtained by a simple and versatile experimental procedure, they could be easily shaped or directly foamed into precast molds to be used in packed beds as membranes.

Experimental Investigations on Alkali-Activated Slag Cementitious Material

2014 ◽  
Vol 672-674 ◽  
pp. 1823-1827
Author(s):  
Xiao Wei Sun ◽  
Wan Yang Niu ◽  
Ling Ling Wang
Keyword(s):  
Water Glass ◽  
Setting Time ◽  
Cementitious Material ◽  
Curing Temperature ◽  
Experimental Investigations ◽  
Strength Increase ◽  
Curing Conditions ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

These are many factors that can influence the properties of alkali-activated slag cementitious material, such as the modulus and content of water glass, water-cement ratio, curing conditions, and so forth. The rules that how these factors affect setting time and strength of the material are systematically discussed in the paper. It is found that the setting time of the material depends on the concentration of alkaline ions in solution; The material will have the best strength when the modulus and content of water glass are 1.4 and 8%, respectively. The curing temperature increase will be helpful to compressive strength increase.

Kepuasan Masyarakat Terhadap Pelayanan Kelurahan Setelah Pemekaran Di Tangerang Selatan

Liquidity ◽  
2018 ◽  
Vol 2 (2) ◽  
pp. 151-159
Author(s):  
Pitri Yandri
Keyword(s):  
Public Perception ◽  
Service Personnel ◽  
Urban Services ◽  
Hospitality Workers ◽  
Care Workers ◽  
Before And After ◽  
Cartesian Diagram ◽  
Better Than

The purpose of this study is (1) to analyze public perception on urban services before and after the expansion of the region, (2) analyze the level of people's satisfaction with urban services, and (3) analyze the determinants of the variables that determine what level of people's satisfaction urban services. This study concluded that first, after the expansion, the quality of urban services in South Tangerang City is better than before. Secondly, however, public satisfaction with the services only reached 48.53% (poor scale). Third, by using a Cartesian Diagram, the second priority that must be addressed are: (1) clarity of service personnel, (2) the discipline of service personnel, (3) responsibility for care workers; (4) the speed of service, (5) the ability of officers services, (6) obtain justice services, and (7) the courtesy and hospitality workers.

Strategic Role of Zakat in Multidimensional Quality of Life in Sijunjung, Indonesia

2018 ◽  
Vol 15 (1) ◽  
pp. 55-72
Author(s):  
Herlin Hamimi ◽  
Abdul Ghafar Ismail ◽  
Muhammad Hasbi Zaenal
Keyword(s):  
Quality Of Life ◽  
Positive Impact ◽  
Wealth Distribution ◽  
Absolute Poverty ◽  
Before And After ◽  
The Status ◽  
Being There ◽  
The Impact

Zakat is one of the five pillars of Islam which has a function of faith, social and economic functions. Muslims who can pay zakat are required to give at least 2.5 per cent of their wealth. The problem of poverty prevalent in disadvantaged regions because of the difficulty of access to information and communication led to a gap that is so high in wealth and resources. The instrument of zakat provides a paradigm in the achievement of equitable wealth distribution and healthy circulation. Zakat potentially offers a better life and improves the quality of human being. There is a human quality improvement not only in economic terms but also in spiritual terms such as improving religiousity. This study aims to examine the role of zakat to alleviate humanitarian issues in disadvantaged regions such as Sijunjung, one of zakat beneficiaries and impoverished areas in Indonesia. The researcher attempted a Cibest method to capture the impact of zakat beneficiaries before and after becoming a member of Zakat Community Development (ZCD) Program in material and spiritual value. The overall analysis shows that zakat has a positive impact on disadvantaged regions development and enhance the quality of life of the community. There is an improvement in the average of mustahik household incomes after becoming a member of ZCD Program. Cibest model demonstrates that material, spiritual, and absolute poverty index decreased by 10, 5, and 6 per cent. Meanwhile, the welfare index is increased by 21 per cent. These findings have significant implications for developing the quality of life in disadvantaged regions in Sijunjung. Therefore, zakat is one of the instruments to change the status of disadvantaged areas to be equivalent to other areas.

Effect of new dietary supplement on sperm quality

2012 ◽  
Vol 153 (45) ◽  
pp. 1787-1792 ◽  
Author(s):  
Mária Horváth ◽  
Endre Czeizel
Keyword(s):  
Adverse Effect ◽  
Clinical Trial ◽  
Dietary Supplement ◽  
Male Fertility ◽  
Sperm Quality ◽  
Sperm Count ◽  
Before And After ◽  
The Usa ◽  
New Treatments

Introduction: There is a decline in male fertility thus new treatments are needed. Aims: To test the efficacy of a new dietary supplement developed in the USA and registered as a curing drug in Hungary (OGYI). Methods: In a clinical trial 100 men with low sperm quality (spermium count 5–20 M/ml, good motility 10–40%, and adverse shape 30–50%) were examined. Results: Sperm parameters were measured before and after a 3-month treatment and after another 3-month without treatment. This dietary supplement statistically and clinically significantly improved sperm count and motility. In 74 cases this dietary supplement demonstrated a beneficial effect on sperm quality (more than 10% increase in sperm count, or quality of motility, or shape); in 16 cases the improvement exceeded 30%. No adverse effect could be accounted for this treatment. Conclusions: This new dietary supplement may contribute to the treatment of male infertility. Orv. Hetil., 2012, 153, 1787–1792.

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