Effect of natural pozzolan on concrete durability (original) (raw)
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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.
Effect of pozzolans with different physical and chemical characteristics on concrete properties
Materiales de Construcción, 2016
The durability of concrete structures is an important issue nowadays. Specifically in the case of reinforced concrete bridges or other infrastructures one of the main form of environmental attack is the penetration of chloride ions, which leads to corrosion of concrete steel reinforcement. This study aims to evaluate the effect of the introduction of metakaolin and diatomite, two chemically and physically different pozzolans, on the resistance of concrete to the penetration of chlorides but also the effect on other properties of concrete, namely, its compressive strength and its porosity distribution. The results of this study show that the pozzolans physical and chemical characteristics have a strong influence on the pozzolans behavior and, consequently, on the concrete properties.
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.
2010
Sulfate attacks and chloride corrosion are the most important problems concerning the durability of concrete structures in hot regions of the Persian Gulf and Oman Sea. Natural pozzolans are natural mineral admixtures which can improve concrete durability against sulfate attacks and chloride corrosion. This paper presents the results of experimental study on the effect of natural pozzolans: Jajrood Truss, Eskandan Pumice, Abyek Tuff, and Khash Pumice, on the ordinary structural concrete durability. Concrete specimens were made of three pozzolan replacement levels, and Rapid Chloride Penetration test, Electrical Resistance test, and Half Cell Potential test were conducted at different ages. In addition, strength reductions and mass changes of concrete specimens immersed in sodium sulfate solution and expansion of concrete prisms immersed in sodium sulfate solution and magnesium sulfate solution were studied. Generally, the results indicate that natural pozzolans have positive effects on concrete specimen resistance to the chloride ions penetration and bars corrosion in comparison with concretes containing ordinary cement.
Experimental Research on Natural Pozzolan as Cement Replacement
ABUAD International Journal of Natural and Applied Sciences
This paper presents the properties of mortar and concrete with NBRRI pozzolan as partial replacement of cement. In this research, NBRRI pozzolan from NBRRI and local cement (Dangote) are used. Firstly, chemical composition of NBRRI pozzolan and Dangote cement are analyzed. And then the physical properties of local materials used in this research are determined according to ASTM procedure. Partial replacement percentages of pozzolan are considered 10%, 20%, 30% and 40%. The strength of mortar and concrete with NBRRI pozzolan (0%, 10%, 20%, 30%, and 40%) is tested at 7 days, 14 days and 28 days. From the trial mix design, the water-cement ratio (0.555) is obtained by using the least square method. To get target strength (4000 psi), by using water-cement ratio (0.555) and 68% of maximum aggregate size (20 mm), the concrete mix proportion (1:1.9:3) is obtained. The compressive strength of concrete with various percentages of NBRRI pozzolan at 21 days and 28 days are more than 7 days and...
Performance of Pozzolanic Concrete Using Different Mineral Admixtures
Pakistan Journal of Engineering and Applied Sciences, 2016
Concrete is probably the most extensively used construction material in the world. However, environmental concerns regarding rapid consumption of natural resources and CO2 emission during cement manufacturing process have brought pressure to reduce cement consumption by the use of cement replacement materials (CRMs). The utilization of calcined clay (metakaolin) and silica fume in concrete has received considerable attention in recent years. Brick powder has not got much popularity with respect to strength enhancement but it is effective to reduce drying shrinkage. The following study has been focused to determine the performance of locally available metakaolin, silica fume and brick powder as CRMs in concrete. This study focuses on compressive strength, drying shrinkage and sulfate attack properties of the concrete. Concrete cubes were used for compressive strength determination and mortar prisms for determination of drying-shrinkage and sulfate attack. 5%, 10% and 15% replacement ...
Natural Pozzolan as a Partial Substitute for Cement in Concrete
The Open Construction and Building Technology Journal, 2013
In this paper, the use of natural pozzolan as a partial cement substitute in concrete materials is investigated. By means of a test series, four mixes using three types of natural pozzolan, as well as a Class F fly ash, are evaluated. The effectiveness of each pozzolan in controlling alkali-silica reactions has been studied. Correlations have been revealed between the mechanical properties of the proposed mixes and a Portland cement control mix. The results are also compared with industry standards for mortars made with fly ash and silica fume. The paper's findings indicate that one type of pozzolan may be used as a substitute for fly ash, but not for silica fume.
Engineering Properties of Alkali-Activated Natural Pozzolan Concrete
ACI Materials Journal, 2011
The development of alkali-activated binders with superior engineering properties and longer durability has emerged as an alternative to ordinary portland cement (OPC). It is possible to use alkali-activated natural pozzolans to prepare environmentally friendly geopolymer cement leading to the concept of sustainable development. This paper presents a summary of an experimental work that was conducted to determine mechanical strength, modulus of elasticity, ultrasonic pulse velocity, and shrinkage of different concrete mixtures prepared with alkali-activated Iranian natural pozzolans-namely Taftan andesite and Shahindej dacite, both with and without calcining. Test data were used for Taftan pozzolan to identify the effects of water-binder ratios (w/b) and curing conditions on the properties of the geopolymer concrete, whereas the influence of material composition was studied by activating Shahindej pozzolan both in the natural and calcined states. The results show that alkali-activated natural pozzolan (AANP) concretes develop moderate-to-high mechanical strength with a high modulus of elasticity and a shrinkage much lower than with OPC.
Investigation on Expansion of Mortars Containing Tuff Natural Pozzolan Due to Sulfate Attack
Sulfate attack and its effects are important from both scientific and industrial viewpoints. It is perceived that cements containing pozzolan have better performance in sulfate solutions, since the pozzolanic reactions reduce the quantity of Calcium hydroxide and increase Calcium silicate hydrate. This paper investigates the physical/mechanical properties of concretes made by blended cement containing Tuff natural pozzolan, and Portland cement. The microstructure of mortars under sulfate attack is studied using SEM analysis and reaction products are characterized using EDS analysis. The results suggest that, contrary to previous opinions, mortars containing pozzolan show more expansion and unsatisfactory performance in sulfate solution.
Effect of large amounts of natural pozzolan addition on properties of blended cements
Cement and Concrete Research, 2005
In this study, the effects of 35, 45, and 55 wt.% natural pozzolan addition on the properties of blended cement pastes and mortars were investigated. Blended cements with 450 m 2 /kg Blaine fineness were produced from a Turkish volcanic tuff in a laboratory mill by intergrinding portland cement clinker, natural pozzolan, and gypsum. The cements were tested for particle size distribution, setting time, heat of hydration, compressive strength, alkali-silica activity, and sulfate resistance. Cement pastes were tested by TGA for Ca(OH) 2 content and by XRD for the crystalline hydration products. The compressive strength of the mortars made with blended cements containing large amounts of natural pozzolan was lower than that of the portland cement at all tested ages up to 91 days. Blended cements containing large amounts of pozzolan exhibited much less expansion with respect to portland cement in accelerated alkali-silica test and in a 36-week sulfate immersion test. D