Content Of Mineral Admixtures Research Articles

Effect of number of neurons and layers in an artificial neural network for generalized concrete mix design

Selection of the number of neurons in different layers of an artificial neural network (ANN) is a key decision-making step involved in its successful training. Although the number of neurons in the input layer is decided by the number of input parameters, and similarly, in the output layer the number of neurons is fixed by the output parameters, however, the number of neurons in the hidden layer is not fixed, whereby the overall efficiency of the ANN depends upon the correct modeling of the realistic scenario in the form of a neural network. Concrete can be mixed in a huge variety of methods and compositions to achieve a specific or a combination of specific results. These results have been observed to repeat and follow patterns. Furthermore, for several types of concrete mixes, only actual physical trial data are available with no mix design method; this makes achieving different required results very complex and expensive task. Having an ANN to be able to predict a concrete mix to handle such variations will save a lot of time and money and will prove to be a universal mix design tool. A thorough analysis for deciding the number of neurons for mix design of concrete has been carried out in this research. The results of neural networks for a varying number of neurons and layers have been correlated. The data for a number of concrete mixes were sorted and normalized. Properties of concrete constituents like specific gravity of cement, coarse and fine aggregates, dry density of coarse and fine aggregates, cement type, type of mineral admixture, water-to-cement ratio, type and temperature of curing and hardened properties like compressive strength, modulus of elasticity and tensile strength were taken as input parameters. The contents of constituents of concrete such as water content, cement content, coarse aggregates content, fine aggregates content and content of mineral admixtures are regarded as output parameters. For 17 inputs and 5 outputs, it has been discovered that simple neural network with single or double hidden layers performed better that 3 or more such layers.

Experimental Study on the Flexural Strength of Marble Industrial Powder Concrete

The flexural strength and cube compressive strength of marble industrial powder concrete were studied by orthogonal test method. 25 orthogonal test groups and 1 contrast test group with the mineral admixture content 0% were designed to carry out the flexural and compressive tests. The strength of concrete with different substitution rate and fineness is obtained, and the mechanism of influence on each strength is analyzed. The experimental results show that the concrete flexural strength is reduced by the addition of marble powder, but it can meet the requirement of engineering application when the substitution rate is less than 10%. According to the orthogonal test, the main factor affecting the flexural strength of marble industrial powder concrete is the substitution rate of marble powder, and the secondary factor is the fineness of marble powder. The effect of marble powder on the flexural strength and compressive strength of concrete is basically the same. The ratio of flexural strength to cubic compressive strength of marble powder concrete with different substitution rate and fineness is 0.16.

Experimental Study On Properties Of High-Early-Strength Cementitious Grout

This paper studied the influences of mineral admixture content on the fluidity, compressive strength and vertical expansion rate of the cementitious grout, which based on a ternary composite cementitious material system of sulfoalminate cement, protland cement and gypsum. The influences of fly ash, slag powder and silica fume were investigated respectively. It was shown that: (1) The initial fluidity grew as the addition of fly ash content in the cementitious grout, 1 d compressive strength and 3 d compressive strength were reduced. (2) The slag powder had great impact on the fluidity, when the content of slag powder more than 18%, initial and 30 min fluidities declined. With the slag powder increased, 1 d, 3 d and 28 d compressive strengths decreased slightly, while 3 h vertical expansion rate increased. (3) The increased of silica fume content made the compressive strengths rised first and then fell. 1 d, 3 d and 28 d compressive strengths could reach their maximum values, when the amount of silica fume was 3.0%.

Metakaolin Influence on Concrete Durability Properties

Mineral admixtures are being used today almost in all concretes partially, to improve workability, engineering properties and also to enhance durability of the concrete. These admixtures are industrial by-products. In the present study, mineral admixture such as metakaolin (MK) is replaced partially in cement to investigate permanence properties of concrete in terms of initial water absorption, final water absorption and confrontation to acid attack. Inorder to identify the durability properties, concrete of M30 grade was prepared. The mineral admixture content was varied from 0% to 30% by volume of cement with 10% gradient. In acid attack, 3% H2SO4 solution is used for curing of specimens and the corresponding weight losses (%) were evaluated for curing periods of 7 days, 14 days and 28 days. Both initial and final water absorptions of the metakaolin-modified concrete have been improved when metakaolin content was increased up to 10% advantageously. And, also weight loss was decreased when metakaolin content varied from 0% to 30%.

Effect of Recycled Concrete Waste Aggregate on the Fresh State Properties of Self Compacting Concrete

In this investigation an attempt is made to replace coarse aggregate partially or fully by recycled concrete waste aggregates and the fresh state properties of modified SCC (Self Compacting Concrete) was elaborated by conducting slump flow, V-funnel, L-Box and J-ring tests. The properties such as filling ability, passing ability, segregation, bleeding and stability of the modified SCC were determined by using the fresh state tests. The results of this experiment revealed that it is possible to modify SCC by partially or fully replacing the coarse aggregate by RCWA. The optimum mix also determined by varying RCWA and mineral admixture content in SCC.

Experimental study on the performance of lime-based low carbon cementitious materials

In this study, a novel type of lime-based low carbon cementitious material (LCM) was designed and prepared using low contents of hydrated lime and Portland cement and a high content of mineral admixtures. The mechanical properties, workability, heat of hydration, hydration degree, porosity, hydration products, and microstructure of LCM were systematically investigated. The test results indicated that LCM showed good mechanical properties and workability compared with conventional blended cement. The compressive strength of LCM can achieve 50–60 Mpa at curing 28 d and more than 70 Mpa at curing 180 d. The hydration products of LCM were mainly composed of ettringite, portlandite, and C–(A)–S–H gel according to X-ray powder diffraction results. Analysis suggests that a small amount of Portland cement in LCM accelerated the pozzolanic reaction of mineral admixtures due to the alkalinity, and the Ca2+ ion concentration in the pore solution increased. Meanwhile, the hydrated lime reacted with mineral admixtures in long-term hydration and increased the mechanical property of LCM. In addition, LCM exerted a notable reduction in carbon emission, energy consumption and environmental burden compared with Portland cement. The quantitative calculation suggested that the energy intensity and carbon emission of the LCM are only approximately 24–45% and 13–38% that of Portland cement, respectively.

A Multi-factor Model of Chloride Diffusion Coefficient of 180d Cured Concrete with High-volume Mineral Admixture

This paper describes a multi-factor model of chloride diffusion coefficient of long-age (180d) cured concrete with high-volume mineral admixture. The RCM (rapid chloride migration) tests were conducted on 15 specimens with different mixtures proportions to analyze the effect of the water/binder ratio, the total content of mineral admixture, the different combination of FA (fly ash) and GGBS (ground granulated blast-furnace slag) on the chloride diffusion coefficient. Based on the data of orthogonal experiments, a multi-factor coupling model of chloride diffusion coefficient of 180d cured concrete is developed through regression analysis, which can be verified by the data in full range design. The experimental results show that the water/binder ratio, the content of FA and GGBS have a certain impact on the chloride diffusion coefficient, and the predicted values from multi-factor coupling model of chloride diffusion coefficient is in good agreement with the experimental data.

Blended cement hydration assessment by thermogravimetric analysis and isothermal calorimetry

In the present study, the hydration of Portland cement pastes containing 5%, 10%, 15% and 20% tuff, limestone filler and granodiorite was investigated by thermogravimetric analysis coupled with differential scanning calorimetry and microcalorimetry isotherm. The monitoring of the hydration kinetics by thermogravimetric analysis made it possible to quantify the quantity of water combined with the cement (nonevaporable water) and the degree of hydration. By coupling this technique to the differential scanning calorimetry, it was also possible to measure the energy absorbed or released by the material during its decomposition. The results showed that the non-evaporable water content and the degree of hydration of the mixtures containing various mineral admixtures were relatively lower with respect to the reference mixture when as the content of mineral admixture increased. The effect of the evolution of the hydration process on the mechanical properties of mortars was also monitored. The relative variation of the compressive strength to that of the flexural strength was evaluated at 7, 28 and 90 days. Results showed that all the mixtures have a greater contribution in flexion than in compression.

Experimental Study on Influence of Fly Ash on Properties of Gold Tailings Reactive Powder Concrete

In this study, the tail ore was be used as a fine aggregate of RPC or gelled material, because it is rich of silicon and its particle size is peculiar. Through choosing the raw materials reasonably, optimizing the water/cement ratio, water reducing agent dosage and mineral admixture content, the economical RPC was be prepared with tail sand instead of the grinding fine quartz sand, mixing different properties of mineral admixtures.

Biphasic carbonation behaviour of structural lightweight aggregate concrete produced with different types of binder

This study aims to characterise the carbonation behaviour of structural lightweight aggregate concrete (SLWAC) produced with different types of aggregate, w/c ratios and types and content of mineral admixtures (silica fume, fly ash, lime filler) by means of accelerated carbonation tests. A new biphasic model to describe the carbonation behaviour of SLWAC is suggested. Based on this model, the carbonation coefficient of SLWAC is estimated as a function of the w/c ratio, for different density classes of lightweight aggregates. It is concluded that the carbonation resistance of SLWAC cannot be properly predicted by its compressive strength and that the carbonation rate is little affected by the type of binder, being appropriate to neglect the contribution of mineral admixtures in carbonation resistance of SLWAC. It is also concluded that even with pastes of moderate quality, the carbonation mechanism should not be relevant to the durability of SLWAC.

High-Performance Grouting Mortar Based on Mineral Admixtures

A study on high-performance grouting mortar is reported. The common mortar was modified by mineral admixtures such as gypsum, bauxite, and alunite. The effects of mineral admixtures on the fluidity, setting time, expansion, strength, and other properties of mortar were evaluated experimentally. The microstructure of the modified mortar was characterized by X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. Moreover, the expansive performance and strength of the grouting mortar were verified by anchor pullout test. The results show that the best conditions for gypsum-bauxite grouting mortar are as follows: a water-to-binder ratio of 0.3, a mineral admixture content of ~15%, and a molar ratioKof 2. The ultimate bearing capacity of the gypsum-bauxite grouting mortar anchor increased by 39.6% compared to the common mortar anchor. The gypsum-bauxite grouting mortar has good fluidity, quick-setting, microexpansion, early strength, and high strength performances.

부순모래를 사용한 습식 숏크리트의 광물성 혼화재료 혼입에 따른 내구성 평가

The purpose of this dissertation was to investigate the effect of mineral admixtures, such as fly ash, blast furnace slag powder, meta kaolin and silica fume, on the basic properties and durability of crushed sand shotcrete, selecting a series of shotcrete mixtures with a variable admixture. Compressive strength increased as the content of mineral admixtures increased, specially it was the most effective when using meta kaolin both at sample specimen and core after shotcreting. Rapid chloride ion permeability test and sulfuric acid resistance test showed that both durability increased as the substitute rate of mineral admixture increased. In air void analysis with image analysis, the targeted the spacing factor and specific surface were not satisfied because air-entrained agent was not used.

Effects of Fly Ash and Granular Blast-Furnace Slag on Development Rate of Strength of Concrete

Fly ash (FA) and granular blast-furnace slag (GBFS) are usual mineral admixtures to conventional concrete, and their contents substituted for Portland cement definitely affect development rate of strength of concrete. C30 and C60 concrete samples with FA and/or GBFS were prepared to study the influence of substitution content of the mineral admixtures on 3 d, 7 d and 28 d strength. The results reveal that the development rate of strength in period from 3 d to 7 d gets slow with increasing content of mineral admixtures except for concrete with only GBFS less than 20%. In the case of substituting FA as the only mineral admixture for part of cement, the development rate of strength of C30 concrete in period from 7 d to 28 d keeps roughly constant even that of C60 concrete increases. When substituting mineral admixtures in the presence of GBFS for cement within experimental range, the development rate of strength in period from 7 d to 28 d gets fast with increasing substitution content. The enhancing effect of combining FA and GBFS occurs in period from 7 d to 28 d for both C30 and C60 concretes (FA+GBFS≤40%), even occurs in period from 3 d to 7 d for C60 concrete. Based on 7 d strength and the development rate, 28 d strength of concrete can be predicted accurately.

Chloride ion penetration into concrete under hydraulic pressure

The lining concrete of subsea tunnel services under combined hydraulic pressure, mechanical and environmental loads. The chloride ion and water penetrations into concrete under hydraulic pressure were investigated. The experimental results indicate that the water penetration depth, chloride ion transportation depth, and the concentration of chloride ion ingression into concrete increase with raised hydraulic pressure and hold press period. But the chloride ion transportation velocity is only 53% of that of water when concrete specimens are under hydraulic pressure. The chloride transportation coefficient of concrete decreases with hold press period as power function. And that would increase 500%-600% in chloride transportation coefficient when the hydraulic pressure increases from 0 to 1.2 MPa. The hydraulic pressure also decreases the bound chloride ion of concrete to about zero. Besides, the low water-cementitions materials and suitable content of mineral admixture (including fly ash and slag) improve the resistance capacity of chloride penetration, and binding capacity of concrete under hydraulic pressure.

Reutilization of RFA of Construction Waste in Cement Mortar

The effect of some factors(dosage and grain size of recycled fine aggregate of construction waste, content of mineral admixture) on the properties of cement mortar was studied. The results indicated that when recycled fine aggregate particles gradation was areaⅡ, replacement percentage (sand) was 60%,dosage of mineral admixture was 36%, compared with blank sample, the 28d flexural strength and the compressive strength of cement mortar samples were increased by 30.7% and 37.2%, respectively. Micro-morphology of section on cement mortar was observed by SEM. Identifying the hydration products through XRD was carried out.

Preparation of Ultra-High Performance Concrete Using Phosphorous Slag Powder

Reactive powder concrete (RPC) is an ultra-high performance concrete (UHPC). Cement and silica fume content of RPC are generally rather high compared to the conventional concrete. The aim of this paper is to decrease the cement content of RPC by using phosphorous slag powder. Firstly the effect of grinding time on the activity index of phosphorous slag was investigated. And then, the mix proportion design of this UHPC containing phosphorous slag powder and silica fume was done through orthogonal design. The results indicate that the utilization of phosphorous slag powder in RPC is feasible when the dosage of phosphorous slag powder is about 35% (by weight of the binder) and the water-binder ratio is less than 0.18. By substituting phosphorous slag powder for a part of cement and keeping the water-binder ratio at about 0.14, UHPC specimens whose content of mineral admixtures, including phosphorous slag powder and silica fume, was about 40%~50% (by weight of the binder) were obtained after they had been cured in 80 °C water for 72 hours. The compressive and flexural strength of those specimens was more than 150 MPa and 20 MPa respectively.

Effect of Composition of Cementitious Materials on Alkalinity of Pore Solution and Strength of Cement Paste

Alkalinity of the surroundings is the basis to study the MICP technology. Alkalinity of pore solution and strength of cement paste made of various cementitious materials were studied. Results show that the alkalinity of pore solution of cement paste decreased with the increase of sulpho-aluminate cement content. pH value of cement paste was about less than 10 when sulpho-aluminate cement content exceeded 75%. Incorporation of sulpho-aluminate cement decreased compressive strength of paste obviously; however, compressive strength of paste was improved when the addition of sulpho-aluminate cement was more than 75%. Addition of mineral admixtures reduced the alkalinity of pore solution of cement paste and increased its compressive strength. Compressive strength of specimens was decreased when the content of mineral admixtures increased.

Analysis of Concrete Performance Used for Non-Ballasted Track Base Plate Based on the Coupling of Effect of Acid and Carbonization

Combining Shi Wu Passenger Dedicated Line and considering the effect of variety and content of mineral admixtures on concrete performance, the paper has investigated the microscopic structural’s variation of C40 high performance used in non-ballasted track base plate under the coupling conditions of acid rain and carbonization by using micro-testing methods such as SEM and XRD and optimizing mix design.The effect of variation on concrete performance has also been analyzed. Results show that when the concrete was eroded in coupling conditions of acid rain and carbon corrosion, C40 high performance concrete specimens produced a certain amount of acicular and columnar ettringite, the surface structure was loose, and pore increased, in addition, plate Ca(OH)2 crystal content gradually decreased with increasing of age, the concrete strength decreased, the maximum reducing value reached to 27%, what's more, the depth of neutralization increased with age. For different erosion pattern, its influence law was: S mode＜ST mode＜TS mode＜T mode.

Effect of metakaolin content on the properties self-consolidating lightweight concrete

This paper presents the fresh, mechanical and transport properties of expanded shale aggregate self-consolidating lightweight concrete (SCLC) containing metakaolin assessed by means of slump flow, flow time, V-funnel, L-box, compressive, flexural/splitting/bond strength, water absorption, porosity, sorptivity and rapid chloride permeability tests. Metakaolin content based SCLC mixtures were developed by incorporating 0%, 20%, 40% and 60% of as a replacement by weight of fly ash while keeping a constant cement and mineral admixture content of 450kg/m3 and 150kg/m3, respectively. These included four mixtures containing 0%, 5%, 10% and 15% metakaolin content as a partial binder replacement. It was observed that expanded shale aggregates SCLC can be produced with the density lower than 2000kg/m3 which was increased by the addition of metakaolin. Increases in metakaolin content worsened the filling and passing ability of SCLC and by the addition of metakaolin no positive effect on the strength properties on SCLC was monitored. Replacement of 20%, 40% and 60% of metakaolin with fly ash resulted 3%, 8% and 10% decrease in porosity and water absorption with respect to control mixture, respectively. The initial and secondary sorptivity values of SCLC mixtures with metakaolin replacement were equal or lower than the control mixture without metakaolin. Moreover, increases in metakaolin content showed significant improvement in chloride ion penetration resistance of SCLC.

Natural and accelerated carbonation of concrete containing fly ash and GGBS after different initial curing period

This paper presents a study of the carbonation process of concrete with different initial curing periods consisting of fly ash and ground granulated blast furnace slag (GGBS). Both are exposed in a natural indoor environment for 720 days and at accelerated conditions. The relationship between compressive strength and carbonation depth is analysed. The factors affecting the carbonation of high-volume mineral admixture concrete in a natural environment and accelerated conditions are discussed using the orthogonal method. The factors include: water–binder ratio, content of mineral admixtures, total amount of cementitious materials and fly ash–slag ratio. The influence of different initial curing periods at early ages on carbonation depth is also reported. The results show that there is not always a linear rule between compressive strength and carbonation depth of high-volume mineral admixture concrete. Adequate curing at an early age can decrease the carbonation resistance of concrete significantly. For insufficiently cured concrete, the early stage before 56 days is the main developing stage of carbonation in a natural environment. An evident decrease of carbonation depth can be observed after exposure for 180 days and this will make the carbonated area turn to a red colour again when sprayed with phenolphthalein. In order to guarantee the excellent anti-carbonation ability of concrete in field structure, it is very important to ensure the initial curing time, except for restricting the water–binder ratio and the content of mineral admixtures.