Effects of the secondary minerals of the natural pozzolans on their pozzolanic activity (original) (raw)
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Pozzolanic Characteristics of a Natural Raw Material for Use in Blended Cements
2009
In this study, the potential use of a natural raw material in the manufacture of blended cements was investigated. Mineralogical, petrographic and chemical analyses of the samples showed that the natural raw material was a porphyritic volcanic rock close to trachyandesite composition with a SiO 2 +Al 2 O 3 +Fe 2 O 3 content of 79.86%. Further experiments were also designed to determine the physical properties and pozzolanic activity of the raw material. The mortar samples, made with a binder of ground trachyandesite and lime, developed compressive and flexural strengths of 2.5 and 3.3 times respectively higher than those required for a natural pozzolan. Further tests revealed that when the ground trachyandesite replaced 30% w/w of Portland cement, the blended cements produced had the desired physical and chemical characteristics with compressive strengths higher than 32.9 N/mm 2 . These findings suggest that this material can be used in the production of blended cements.
A CRITICAL EVALUATION ON POZZOLONIC PROPERTIES OF SELECTED MATERIALS AND THEIR REPLACEMENT IN CEMENT
Increase in population in the country is demanding more and more infrastructure projects and housing which intern is demanding more and more cement manufacturing. This is resulting in releasing of huge amount of CO2 into the atmosphere which is causing environmental problems. There is a need to look for alternative materials which lessen emanation of green house gasses. As a piece of this various alternative materials to cement have been explored by various researchers. In the present study it is focused on basalt, fly ash, metakaolin, tank sediments, sludge of vitrified ceramic tile plant, clayey soil and clay deposits. Published articles related to the pozzolonic materials are collected and complied. Most relevant papers are sorted out and studied in depth to understand the problems, methodology, results obtained and conclusions drawn. Metakaolin was tried by several researchers and it is found to be promising At Present metakaolin available in the market is costly and this cost factor is one of the constraint in utilization, hence we need to explore alternative low cost materials that can be used in the place of existing metakaolin after treatment.
Study of Effects of Natural Pozzolan on Properties of Cement Mortars
Journal of Materials in Civil Engineering, 2006
Natural pozzolans, also known as trass, can be used in cement manufacturing due to their cementitious properties after reaction with calcium hydroxide. At different mixture proportions, the strength, setting time, workability, and soundness of the cement mortar made will differ. In this paper, cement mortars with six different natural pozzolan additions ͑ranging from 0 to 35%͒ were employed while using one type of natural pozzolan. As the experimental results show, increase in a natural pozzolan addition decreases the early age strength of cement significantly as expected and decreases the soundness of mortar by two-thirds. In addition, the workability conditions relatively improve and the settings delay for awhile.
The fabrication of cement containing active mineral additives such as the natural Pozzolan presents a definite interest because of reduction of production costs and CO 2 emissions into the atmosphere. The present work focuses on the development of a new hydraulic cement binder by partially substituting the clinker for natural Pozzolan from the volcanic deposit of Difan-Amran in Yemen. The amount added varies with a step of 5 % within the range from 0 % to 40 %. The physical, chemical and mechanical analysis of the different formulations developed shows that the substitution of clinker for natural Pozzolan results in a new hydraulic binder of improved physical, chemical and mechanical properties. The increase of the additive content results in: (i) increase of the Blaine specific surface area facilitating the concrete hydration during the mixing; (ii) increase of the setting time of the paste augments; (iii) decrease of the density providing to prepare a relatively lightweight concrete; (iv) decrease of the mixing water quantity resulting in compressive strength increase. The production of the cementitious materials based on this new hydraulic binder minimizes the emission of CO 2 into the atmosphere on one hand, while on the other it decreases the energy consumption leading thus to production of less expensive construction materials.
On the Utilization of Pozzolanic Wastes as an Alternative Resource of Cement
Materials, 2014
Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly
Investigation of mechanical activation effect on high-volume natural pozzolanic cements
Open Chemistry
Mechanical activation is one of the most preferred methods to increase the reactivity of mineral, mining, and industrial wastes or materials with low pozzolanic content in cement production. The mechanical activation process of such materials takes a long time and requires high grinding energy. Although it seems like an advantage to using the materials in cement production by gaining reactivity thanks to mechanical activation, mechanical activation is a long duration and expensive process, causing an increase in cement production costs. In this study, a hybrid method is proposed for the mechanical activation of materials in a shorter duration and with lower energy consumption. A roller press and a hammer grinder were integrated before the laboratory type ball mill to realize the mechanical activation processes. To perform the mechanical activation processes in this way, two different hybrid grinding methods were tested and compared. Both methods activated volcanic tuff samples with ...
An overview on the Influence of Pozzolanic Materials on Properties of Concrete
Concrete is the most normally used material for construction. The worldwide production of cement has significantly increased since 1990.Production of cement results in a lot of environmental toxic waste as it involves the emission of CO2 gas. Complementary cementitious materials are finely ground solid materials that are used to replace a portion of the cement in a concrete mixture. These complementary materials may be naturally occurring, manufactured or natural waste. Various types of pozzolanic materials that improve cement properties have been used in cement industry for a long time. This paper reviews the use of pozzolanic material in concrete. A detailed literature review is carried
Construction and Building Materials, 2018
h i g h l i g h t s System of physical and chemical techniques for assessment of technogenic pozzolans. Physical and chemical prerequisites, reactivity, performance in blended cements. Evaluation of synergistic calorific effects. Pozzolan effectiveness coefficient as a new criterion. Practical application demonstrated for fly ash from a coal power plant. g r a p h i c a l a b s t r a c t system of physical and chemical techniques for assessment of technogenic pozzolans physical and chemical prerequisites, pozzolan effecƟveness coefficient origin, granulometry, reacƟvity in blended cements chemical and mineralogical composiƟon, amorphous content synergic calorific
Nigerian Journal of Technological Development, 2019
Abundant aquatic animal by-products are available in Nigeria which include clam, oyster, rock Snail and periwinkle shells. These are usually dumped on open lands without any economic value after fleshy parts of these animals had been consumed by humans, hence, result into environmental problems. In the agricultural sector, Rice husk and Palm oil fuel ashes are by-products from rice and palm oil industries after the husks have been used as source of fuel. Disposal of these wastes are always a major issue as they constitute nuisance to the environment. This research has collected and characterized these wastes in the laboratory to ascertain their suitability as supplementary cementitious materials. With this study, physical properties such as particle size, specific gravity, specific surface area and morphology are conducted by Scanning Electron Morphology, SEM; chemical analysis are carried out with the aid of X-ray Fluorescence (XRF), for microstructure examination, X-ray Diffractio...
American Journal of Engineering and Applied Sciences
The effect of pozzolanic material on the mechanical properties and microstructure of clinker Portland cement mortar was studied. The main objective of this research is to formulate a Pozzolanic blended cement mortar with high mechanical properties to reduce CO2 emissions and energy conservation uses in the clinker industry. The present investigation aims to study the effect of fresh basalt on the properties of clinker and Portland cement pastes. The rate of hydration was studied from the determination of free lime and combined water up to 90 days of hydration. The physicalmechanical properties such as compressive strength, phase composition, and microstructure of mortar were investigated. The results revealed that the water consistency increased with the basalt substance while the setting time was somewhat elongated. On the other hand, the combined water increases with the basalt content and curing time. This can be primarily due to the influence of nucleating of basalt as a filler in pozzolanic cement generation. The fresh mortar pastes were first cured at 100% relative humidity for 24 h and then cured in water for 90 days. The results showed that the compressive strength of the cement mortars with basalt pozzolanic mixed cement was higher than plain clinker Portland cement mortar; the improvement in compressive quality was 10% to 15% basalt.