Active Mineral Admixture Research Articles

Effects of Corn Cob Ash as Mineral Admixture on Mechanical and Durability Properties of Concrete – A Review

Concrete is the second most consumed product next to water on earth. Cement is the key ingredient for making concrete. India is the second largest cement producer in the world. The production of cement is emitting an equal amount of CO2 in to the atmosphere and is accounted as about 8% of the world’s total emissions. The addition of mineral additives as supplementary cementitious materials in concrete is one of the solution to avoid such environmental pollution. The natural mineral admixture obtained from the novel agricultural by-product, namely corn cob ash (CCA), is being utilized in cement manufacturing and concrete construction. The similarities in both physical and chemical properties of CCA were established when compared to the decade old agro-based mineral admixtures like rice husk ash (RHA) and sugar cane bagasse ash (BA) through research findings. The results are mentioned that the CCA can be used as chemically active mineral admixture and micro-filler in concrete. With this background, the paper presents a review on the effect of substituting CCA in fresh, mechanical and durability properties of concrete.

Application of Glass Fiber Reinforced Composite Materials in Construction Engineering

Glass fiber reinforced cement (GRC) is a new type of composite material formed by using alkali-resistant glass fiber as a reinforcing material and cement paste or cement mortar as a matrix. GRC is widely used in construction engineering. However, the durability of GRC is still a major problem in engineering applications, especially GRC materials have been in the hot and humid building engineering environment for a long time. The alkaline environment of the cement matrix will cause serious erosion of the glass fiber, and Will significantly reduce the mechanical properties such as flexural strength and toughness of GRC. In this paper, ordinary Portland cement is mixed with active mineral admixtures such as fly ash and silica fume to reduce the alkaline environment of GRC matrix, and to delay the erosion rate of glass fiber and increase the flexural strength and compressive strength of GRC; At the same time, the effects of different hot and humid building engineering environments on the mechanical properties of GRC were studied.

Improving the resistance of concrete for sleepers to the formation of delayed and secondary ettringite, the alkali-silica reaction, and electric corrosion

The paper reports results of examining the influence of modifier admixtures on the corrosion resistance of concrete for reinforced concrete sleepers based on the criteria of electric resistance, resistance to alkaline corrosion and corrosion due to the crystallization of delayed and secondary ettringite. This study was conducted within the framework of resolving the issue on premature destruction of reinforced-concrete sleepers caused by the progressing crack formation at the stage of heat treatment and subsequent operation. It has been established that the introduction of pozzolanic admixtures containing active Al 2 O 3 in their formulation to the composition of concrete for sleepers makes it possible to minimize the risk of corrosion predetermined by the reaction between aggregates’ silica and alkali and corrosion as a result of crystallization of delayed and secondary ettringite. The high efficiency of pozzolanic admixtures containing active Al 2 O 3 regarding the specified types of corrosion is due to binding alkali into the insoluble alkaline hydroalumosilicates, contributing to the compaction of the system with a decrease in the content of Na + /K + ions in the solution. A decrease in the content of alkali in the porous solution predetermines blocking the «alkali-silica reaction» and increasing the temperature of ettringite stability to higher values. This reduces the potential number of secondary ettringite forming cycles and the probability of delayed ettringite formation. The alternative mechanism of action of active Al 2 O 3 on pozzolan implies binding the SO 4 2– and Ca 2+ ions from a porous solution into low-sulfate forms of calcium hydro-sulfoaluminates, which excludes the crystallization of delayed and secondary ettringite. Reducing the consumption of cement and water through the use of admixtures-plasticizers makes it possible to increase the electrical resistivity of the modified concrete for sleepers above the level of a control composition without admixtures. The obtained results provide an opportunity to ensure the design durability of concrete in reinforced-concrete sleepers through their comprehensive modification by plasticizers and active mineral admixtures that contain active Al 2 O 3

Study on the properties of composite mineral admixture material for rapid repair

In this paper, the active mineral admixture was used to prepare the quick repair material that meets the requirements of 24h service. The development of the late strength, the shrinkage performance and wear resistance of the 60days were studied. The experimental results show that the composite mineral admixture is used to prepare the material for rapid repair, not only the early strength is high, but also the later strength is steadily increasing, and the dry age of 60 days is reduced, and the wear resistance is good. The use of industrial waste has certain economic and social benefits.

Experimental Investigation of the Material Performance of the Ultrahigh Early Strength Concrete

Aiming at some special working condition, the high performance concrete (HPC) is investigated by combining the ordinary concrete with the chemical additive or the active mineral admixture. The ultrahigh early strength concrete is one of the most popular HPC which has been extensively used in the construction of roads and tunnels, owing to the advantage of setting in a shorter time. Therefore, there is a growing need to investigate the material performance of the ultrahigh early strength concrete. In this study, several sets of contrast tests are well designed and conducted in order to experimentally investigate the material performance difference between the capability of the ultrahigh early strength concrete with specific mix proportion and the ordinary concrete such as the setting time, the workability, the impermeability and the compressive strength. The experiment results show that the ultrahigh early strength concrete works better than the ordinary concrete in most of the above material characteristics. To be specific, the ultrahigh early strength concrete appears the extremely higher compressive strength in the same curing time, the better permeability resistance and the slightly lower workability. Obviously, this kind of concrete is more prone to the application in the rapid construction of roads and tunnels.

Effects of Pumice-Based Porous Material on Hydration Characteristics and Persistent Shrinkage of Ultra-High Performance Concrete (UHPC).

In this paper, two kinds of pumice particles with different diameters and water absorption rates are employed to substitute the corresponding size of river sands by volume fraction, and their effects on the hydration characteristics and persistent shrinkage of Ultra-High Performance Concrete (UHPC) are investigated. The obtained experimental results show that adopting a low dosage of 0.6–1.25 mm saturated pumice as the internal curing agent in UHPC can effectively retract the persistent shrinkage deformation of concrete without a decrease of strength. Heat flow calorimetry results demonstrate that the additional water has a retarding effect and promotes the hydration process. X-ray Diffraction (XRD) and Differential Thermal Gravimetry (DTG) are utilized to quantify the Ca(OH)2 content in the hardened paste, which can confirm that the external moisture could accelerate the early cement hydration and secondary hydration of active mineral admixtures. The Ca/Si ratio of C–S–H calculated by the Energy Dispersive Spectrometer (EDS) reveals that the incorporation of wet pumice can transform the composition and structure of hydration products in its effective area.

ОПТИМИЗАЦИЯ ПРОЦЕССА ВЫБОРА ТИПА ЦЕМЕНТА ДЛЯ ИЗДЕЛИЙ, ЭКСПЛУАТИРУЮЩИХСЯ В АГРЕССИВНЫХ СРЕДАХ

Currently, in industrialized countries in order to prevent corrosion of the hydration-hardened building products a tendency to use methods reducing the permeability of concrete to aggressive agents of the environment is applied. The authors believe that to protect concrete and reinforced concrete against corrosion, it is necessary to use all available means at the disposal of specialists, the most important of which is the correct choice of cement. Increasing corrosion resistance by reducing the water-cement ratio of the concrete mixture is a universal way, but not always it can ensure preserving the performance properties of concrete products and structures in aggressive environments for their entire service life. In this regard, recommendations for choosing the type of cement for the most frequently encountered aggressive environments are given. The analysis of literature sources shows that in many cases it is advisable to use cement with active mineral admixtures.

Hydration characteristics and structure formation of cement pastes containing metakaolin

Metakaolin (MK) is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin). An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM) data confirm, that hardened cement paste containing MK has crystalline structure with dominance of partially crystalized hydrosilicates and gel-like formations.

Hydration characteristics and structure formation of cement pastes containing metakaolin

Metakaolin (MK) is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin). An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM) data confirm, that hardened cement paste containing MK has crystalline structure with dominance of partially crystalized hydrosilicates and gel-like formations.

Study of the pozzolanic activity of a dredged sediment from Dunkirk harbour

Admixtures or supplementary cementitious materials are generally characterised by their ability to react in specified conditions. This can be assumed through the pozzolanicity. In this study, the pozzolanic activity of a certain category of materials was investigated. For this purpose, the Frattini test conforming to NF EN 196-5 French standard, the accelerated Chapelle test, the measurement of the electrical conductivity and the calculation of mechanical activity coefficient were performed. The raw sediment from Dunkirk harbour presented a relatively low pozzolanic activity regardless of the test considered. However, the study of direct or flash calcined materials evidenced that sediment acquired at the end of these processes an improvement of pozzolanic activity. The comparative study conducted on several common admixtures also inferred that the Chapelle and mechanical activity index methods are quite appropriate and reliable. Nevertheless, in the conductivity test, a correction must be applied due to the presence of dissolved salts. A mechanical activity coefficient of χA=0.88 and χA=0.73 was determined for STFC (flash) and STDC (direct lab kiln) respectively.As a result, sediment, following an optimized treatment can be used as active mineral admixture in cementitious matrixes.

Influence of active mineral additives on the basic properties of the gypsum cementpozzolan binder for the manufacture of building products

The diversity of active mineral admixtures of different origin, mineral composition, dispersion and activity, including by-products in many industrial processes necessitates investigating their properties and characteristics of interaction with gypsum cement compositions. Completed research allowed to define the hydraulic activity of the investigated mineral admixtures and their effect on the rheological and mechanical properties of the composite binder, as well as to determine their optimal content in the mixture. It was shown that the use of the tested active mineral admixtures in optimal amounts allows to obtain stable gypsum cement-pozzolanic system and improve the performance properties of products based on them, resulting in increase of the tensile strength in bending from 2 to 48%, at a compression - from 4 to 49% and can significantly extend the range of use them in the manufacture of a broad spectrum of building products.

To the question of peculiarities of thermal activation of natural siliceous raw material

The results of research of activity enhancement of natural siliceous raw material are given in the article. Fossil meal of Khotynetsky deposit, diatomite of Sharlovsky deposit, silica clay of Balasheika deposit were used as natural active mineral admixtures. The influence of heat-treating temperature and dispersion on activity of different types of siliceous raw material is studied. The increase of activity of fixation of Ca(OH) 2 in several times is traced after heat-treating at a certain temperature in the range from 100 to 800°C. The type of activity change is discovered. Explanation is given connected with the change of silica structure in the surface layer. Parameters of the highest activity are defined for every type of siliceous raw material.

Basic Properties of Structural LWAC Based on Waste and Recycled Materials

AbstractThis paper presents results of experimental research on the impact of different types of lightweight aggregates and supplementary cementitious material (fly ash and metakaolin), on basic physical and mechanical properties of structural lightweight aggregate concrete (LWAC). The used aggregates are: lightweight aggregate obtained by firing waste materials (mixture of stone sludge, paper sludge, and fly ash) and expanded recycled glass. The results showed that it is possible to obtain structural LWAC with both types of lightweight aggregates even with substitution of cement with fly ash up to 45% (by mass). LWAC with high amount of active mineral admixtures and low water-binder ratio achieved higher compressive strength and specific strength compared to LWAC made only with portland cement. Comparison of static (Ec) and dynamic (Ed) modulus of elasticity showed that, for everyday engineering practice, static modulus of elasticity of LWAC can be determined using proposed expression Ec=0.65·Ed with hig...

Biofuel Combustion Fly Ash Influence on the Properties of Concrete

Cement as the binding agent in the production of concrete can be replaced with active mineral admixtures. Biofuel combustion fly ash is one of such admixtures. Materials used for the study: Portland cement CEM I 42.5 R, sand of 0/4 fraction, gravel of 4/16 fraction, biofuel fly ash, superplasticizer, water. Six compositions of concrete were designed by replacing 0%, 5%, 10%, 15% 20%, and 25% of cement with biofuel fly ash. The article analyses the effect of biofuel fly ash content on the properties of concrete. The tests revealed that the increase of biofuel fly ash content up to 20% increases concrete density and compressive strength after 7 and 28 days of curing and decreases water absorption, with corrected water content by using plasticizing admixture. It was found that concrete where 20% of cement is replaced by biofuel ash has higher frost resistance.

Influence of Inertia and Low Active Mineral Admixture on Strength and Microstructure of Cement-Based Materials

Cement-based materials were investigated by comparing the strength and microstructure of pastes and mortar containing limestone powder or low quality fly ash. The compressive strength of the mortar at 28 and 90 d was examined whose microstructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis, and differential thermal analysis (TG-DTA). The results indicated that the strength of mortar decreased with increasing mineral admixtures. The limestone powder mainly acted as inert filler and hardly took part in the chemical reaction. Low quality fly ash may accelerate the formation of hydration products in samples with more chemically bonded water. This further resulted in a higher degree of cement hydration and denser microstructure, while the overall heat of hydration was reduced. At the early stage of hydration, low quality fly ash can be considered as an inert material whereas its reactivity at the later stage became high, especially for ground low quality fly ash.

Influence of water-repellent admixtures on the properties of cements

Influence of organic fatty acid and composition on its basis on the physical and mechanical properties of the cement is investigated. Fatty acids are used in the building industry as water-repellent admixtures. The effectiveness has those admixtures that form on the surface of the cement not solid, but "mesh" protective layer that easily destroyed using traditional method of cement production of concrete and mortar mixes, providing access of water to hydrophilic surface of cement grains.The effect of oleic acid on the physical and mechanical properties is investigated for a trade cement, clinker and Portland cement on its basis, slag and Portland slag cement on its basis. It is found that oleic acid gives hydrophobic properties for trade cement and Portland cement while slowing down the process of its thickening and gives small hydrophobic properties for blast furnace slag slowing down the thickening of Portland slag cement.It is researched an influence of hydrophobic compositions based on oleic acid and investigated admixture with food processing waste vegetable oil on physical and mechanical properties of Portland cement and Portland slag cement. It is found that hydrophobic composition effectively hydrophobize the clinker and slag surfaces under certain optimal concentrations without reducing strength of cements.Hydrophobic composition may be used as a water-repellent admixture for cement and active mineral admixtures to increase the longevity of materials and prevent clumping.

Investigation on masonry waste aggregate natural hydraulic lime mortars incorporating diatomite

In order to make the most of energy and resources and obtain mortars with beneficial properties, diatomite is employed in this paper as a partial replacement of natural hydraulic lime (NHL) and masonry waste as aggregate to prepare mortars with different water–binder ratios (w/b). Tests are conducted after 14, 28 and 90 d of curing, namely, compressive and flexural strength, microstructure, mass variation, apparent density, water absorption, sulfate resistance and, additionally, percentage strength and pozzolanic indexes are used to characterise the role of the pozzolanic effect in improving the mortars' strength. The results show that the introduction of diatomite improves the strength of mortars. The enhancement of strength is attributed to the pozzolanic reaction between diatomite and calcium hydroxide in NHL, which proceeds noticeably after 14 d of curing. The diatomite replacement percentage and w/b influenced apparent density, water absorption and strength of mortars; high density and low water absorption are propitious to strength enhancement. Sulfate resistance of mortars prepared with diatomite incorporation is improved greatly. The percentage strength and pozzolanic indexes of mortars indicate that diatomite has a significant pozzolanic effect and is a good active mineral admixture for NHL mortars.

The Mechanical Properties of Lightweight Concrete under Different Factors

By choosing domestic ceramsite as lightweight aggregate, mixing with active mineral admixture (fly ash) and the water reducing agent, and adopting the method of absolute volume to design the three ceramsite concretemixture ratio, 27 groups, 243 lightweight aggregate ceramsite concrete test cubes of 100mm×100mm×100mm are obtained for compressive strength test, and the physical and mechanical properties of the aggregate are studied. At the same time, through the systematic test, the influences of the aggregate strength, water-binder ratio, fly-ash content, etc on ceramsite concrete are studied. Finally the best mixture ratio scheme for ceramsite concrete is gained, providing theoretical basis for the application of lightweight aggregate concrete.

Effect of activators, admixtures and temperature on the early hydration performance of desulfurization ash

The methods of activators, active mineral admixtures and temperature were used to activate the pozzolanic and self-cementitious properties of desulfurization ash, as well as to compare and analyze the 7days and 28days compressive strengths of desulfurization ash mortar. Meanwhile, the early hydration process and hydrated products of desulfurization ash were analyzed with X-ray diffraction analysis (XRD), FT-IR spectra (FT-IR) and scanning electron microscopy (SEM). The research results show that different kinds of activators and active mineral admixtures can activate the early active of desulfurization ash, as follows, the first is quicklime, then sodium silicate, slag powder, triethanolamine, Na2SO4 and the last is silica. By the combination of organic chemical activators and inorganic mineral admixtures mentioned above, the 7days and 28days compressive strengths of desulfurization ash mortar can be up to 20MPa and 22.3MPa, respectively. The strength can still be raised by enhancing the proper curing temperature.

The Discussion about Concrete on the Relationship between Corrosion Resistance and Time under Bending Loads

Through the corrosion test method of different active mineral admixture concrete under bending loads,we studied the C50 concrete specimen under bending loads on corrosion resistance and with the relation to corrosion time about the condition of specimen in saline soil. The results showed that the maximum corrosion effect on concrete with the saline soil in the short-term (1 year) appeared from the sixth to the ninth month (under maximum corrosion loss coefficient), but in other time is smaller. Concrete with gas forming admixture exhibit best corrosion resistance, fly ash concrete come second and normal concrete show worst performance in corrosion resistance, we propose corrosion prevention measures for concrete structures under loads in saline soil region to improve the durability of concrete structures according to the result.