The influence of intergrinding of cement and fly ash on concrete durability

2010 ◽  
pp. 673-679
Keyword(s):  
Fly Ash ◽  
Concrete Durability

Comparative Investigations of some Properties Related to Durability of Cement Concretes Containing Different Fly Ashes

2014 ◽  
Vol 1054 ◽  
pp. 154-161 ◽  
Author(s):  
Wojciech Kubissa ◽  
Barbara Pacewska ◽  
Iwona Wilińska
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Low Permeability ◽  
Concrete Durability ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chloride Migration ◽  
Good Workability

The results of research of mechanical properties and selected other characteristics influencing durability of cement concretes containing cement substitutes were presented. Cement concretes performed with conventional fly ash, fluidised fly ash and their mixture were investigated. The obtained results were compared with findings registered for two types of concrete performed without cement replacements and with cement concrete containing silica fume. The results have shown that cement concrete with predetermined 28-day compressive strength of about 50 MPa and good workability may be obtained using different cement replacements. Generally, these cement concretes exhibited also favorable properties related to concrete durability, i.e. low permeability and sorptivity, and significant reduction of chloride migration coefficient. Favourable results were obtained for cement concrete containing mix of conventional and fluidised fly ashes: good workability, compressive strength after 28th day exceeding 50 MPa, low permeability of water, and low sorptivity, as well as low coefficient of chloride migration. These features were similar as for cement concrete containing silica fume.

Influences of Initial Curing Conditions on the Microstructure of Fly Ash Cement System

2010 ◽  
Vol 168-170 ◽  
pp. 532-536 ◽  
Author(s):  
Guo Li ◽  
En Li Lu ◽  
Peng Wang ◽  
Ou Geng ◽  
Yong Sheng Ji
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Mortar ◽  
Early Age ◽  
Concrete Durability ◽  
Cement Concrete ◽  
Hydration Degree ◽  
Curing Conditions ◽  
Cement System ◽  
C 30

In order to study the influences of initial curing conditions on fly ash (FA) cement concrete durability, fly ash cement samples with 30% replacement ratio were fabricated and cured in water at 10°C, 20°C, 30°Cand 40°C for 3d, 7d, 14d and 28d respectively. Hydration degrees of fly ash at early age were measured using the selective dissolve method. Correspondingly the pore structure and morphology of FA-cement mortar and compared cement mortar were studied by using MIP and SEM methods. Then early age compressive strengths of FA-cement concrete and compared normal cement concrete were tested. Experimental results show that initial curing temperatures and ages are important factors to fly ash early age hydration degree, FA-cement system microstructure, morphology and early age compressive strength etc. High curing temperatures and longer curing time can lead higher fly ash hydration degree, and then higher compressive strength of FA-cement concrete, and make the micro-structures of fly ash-cement system denser.

Sulfate Resistance of Alkali Activated Cements

2016 ◽  
Vol 865 ◽  
pp. 95-106 ◽  
Author(s):  
Pavlo Kryvenko ◽  
Sergii Guzii ◽  
Oleksandr Kovalchuk ◽  
Volodymyr Kyrychok
Keyword(s):  
Corrosion Resistance ◽  
Fly Ash ◽  
Protective Coatings ◽  
Resistance Coefficient ◽  
Cement Stone ◽  
Concrete Durability ◽  
Sulfate Resistance ◽  
Repair Materials ◽  
High Sulfate ◽  
Alkali Activated

One of the most important questions of concrete durability is increasing of corrosion resistance of cement stone and materials on his basis. Perspective way of solving such problems is using of alkali activated binders.Two cement systems were investigated to obtain different materials for different application - geocement system for repair materials and protective coatings and fly ash alkali activated hybrid cement for corrosion resistant common cements and concretes.It was studied sulfate resistance of fly ash alkali activated cements after 3 years of storing in aggressive environments like 5 and 10 % solutions of sodium sulfate, 2 and 4 % solutions of magnesium sulfate and sea salt solution. It was shown that fly ash containing cements are characterized by high corrosion resistance (coefficient of corrosion resistance after 3 years of storing in aggressive environment is in the ranges 0.8...1.0) comparing with clinker cements (0.45...0.88). Shown, that high sulfate resistance of cements under study in time is caused by graduate structure development and crystallization of new formations with compacting structure of material that effect on service properties of materials.High corrosion resistance of geocement compositions (coefficient of corrosion resistance 0.9-1.05) in sulfate environment is possible because of formation of faujasite, chabasite, mordenite and nozean phases in the structure of materials. Optimal composition of geocement compositions were developed according mathematical planning of experiments and tested.

Estimating the Importance Degree of Influence Factors on Concrete Durability Based on Rough Set Theory

2014 ◽  
Vol 988 ◽  
pp. 191-194
Author(s):  
Xiao Ping Su ◽  
Hao Yue Sun
Keyword(s):  
Fly Ash ◽  
Set Theory ◽  
Rough Set ◽  
Loss Rate ◽  
Elasticity Modulus ◽  
Rough Set Theory ◽  
Ash Content ◽  
Concrete Durability ◽  
Freeze Thaw ◽  
Air Content

Under the saline soil environment in the western area of Jilin Province, the concrete durability is affected by a lot of factors, which include wet-dry cycles, freeze-thaw cycles, wet-dry and freeze-thaw cycles, salt soaking time, salts concentration, fly-ash content, air content. These factors impact on the durability of concrete is uncertain, and there may be a problem of duplicate action, with some roughness characteristics. In this article, the rough set theory is used to analyze the degree that these seven factors affect the concrete durability, and to calculate weights. In this article, the loss rate of dynamic elasticity modulus is looked as the evaluation index of concrete durability. The results show that: the importance degrees of 7 factors influencing the loss rate of concrete dynamic elasticity modulus in order are: wet-dry and freeze-thaw cycles > wet-dry cycle > freeze-thaw cycles > multiple salts concentration > air content > long-term soak > fly-ash content.

scholarly journals Performance of a Fly Ash Geopolymeric Mortar for Coating of Ordinary Portland Cement Concrete Exposed to Harsh Chemical Environments

2015 ◽  
Vol 1129 ◽  
pp. 573-580 ◽  
Author(s):  
Walid Tahri ◽  
Z. Abdollahnejad ◽  
Jorge Mendes ◽  
F. Pacheco-Torgal ◽  
José Barroso de Aguiar
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Epoxy Resin ◽  
High Performance ◽  
Ordinary Portland Cement ◽  
High Performance Concrete ◽  
Surface Treatments ◽  
Concrete Durability ◽  
Portland Cement Concrete ◽  
Chemical Attack

Premature degradation of ordinary Portland cement (OPC) concrete infrastructures is a current and serious problem with overwhelming costs amounting to several trillion dollars. The use of concrete surface treatments with waterproofing materials to prevent the access of aggressive substances is an important way of enhancing concrete durability. The most common surface treatments use polymeric resins based on epoxy, silicone (siloxane), acrylics, polyurethanes or polymethacrylate. However, epoxy resins have low resistance to ultraviolet radiation while polyurethanes are sensitive to high alkalinity environments. Geopolymers constitute a group of materials with high resistance to chemical attack that could also be used for coating of concrete infrastructures exposed to harsh chemical environments.This article presents results of an experimental investigation on the resistance to chemical attack (by sulfuric and nitric acid) of several materials: OPC concrete, high performance concrete (HPC), epoxy resin, acrylic painting and a fly ash based geopolymeric mortar. Two types of acids, each with high concentrations of 10%, 20% and 30%, were used to simulate long term degradation by chemical attack. The results show that the epoxy resin had the best resistance to chemical attack, irrespective of the acid type and acid concentration.

scholarly journals Effects of active mineral admixture on mechanical properties and durability of concrete

2021 ◽  
Author(s):  
Chen Xupeng ◽  
Sun Zhuowen ◽  
Pang Jianyong
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Mineral Admixture ◽  
Control Group ◽  
Concrete Durability ◽  
Destructive Effect ◽  
Ordinary Concrete ◽  
Positive Effects ◽  
Optimal Mix

Abstract the purpose of this study is to figure out the effects of the active mineral admixture on the mechanical performance and the durability of the concrete. In this paper, the orthogonal test is adopted to study the effects of the Metakaolin, the ultra-fine fly ash, and the silica fume on the compressive strength and the splitting tensile strength of the concrete at various curing ages, and to further determine the optimal mix ratio. After that, the ordinary concrete is taken as the control group, the Na2SO4 solution and the MgSO4+NaCl solution are taken as the corrosive medium, and the dry-wet alternation method is used to make comparison and micro-analysis on the durability degradation processes of both the admixture concrete with optimal mix ratio and the ordinary concrete in the two solutions as mentioned above. The results show that: as for the concrete mechanical performance, the Metakaolin shows the biggest positive effects on the concrete cured for 7d-14d, while the silica fume affects the concrete with 28d curing age most. The mechanical performance of concretes at various curing ages reach their optimal levels under the conditions of being added with 10% Metakaolin, 15% ultra-fine fly ash, and 3% silica fume. For the concrete durability, the way of adding mineral admixture could greatly improve the concrete capability in resisting the SO4 2- corrosion. However the complex ion has destructive effect on the mineral admixture concrete. Compared with the ordinary concrete, it shows the most significant growth of corrosion product M-S-H, faster reduction of mechanical performance, and loose and porous micro-structure.

Improvement of Concrete Durability by Composite Cement

2009 ◽  
Vol 405-406 ◽  
pp. 14-18 ◽  
Author(s):  
Nai Qian Feng ◽  
Quan Lin Niu ◽  
Chong Zhi Li
Keyword(s):  
Reinforced Concrete ◽  
Fly Ash ◽  
Natural Zeolite ◽  
Composite Powder ◽  
Concrete Structures ◽  
Chloride Ion ◽  
Reinforced Concrete Structures ◽  
Concrete Durability ◽  
Positive Role ◽  
Composite Cement

Mineral powders play positive role in improving the durability of concrete subjected to alkaline and saline corrosion, where sulphate ion and chloride ion coexisted may cause serious deterioration to the reinforced concrete structures. Metakaolin, slag, fly ash and natural zeolite mixed in appropriate proportion were tested in inhibiting the deterioration. It is found that the composite powder might decreased AAR and the charge passed of concrete effectively，the while the 7d and 28d strength of cement and concrete are improved as well.

The Research-Technology Interface in the Fly Ash-Concrete Regime

1985 ◽  
Vol 65 ◽  
Author(s):  
G. M. Idorn
Keyword(s):  
Fly Ash ◽  
Research Society ◽  
Hardened Cement ◽  
Concrete Durability ◽  
Dense Matrix ◽  
Research Activity ◽  
Fly Ash Concrete ◽  
Research Technology ◽  
Materials Research ◽  
Fly Ash Utilization

ABSTRACTOpportunities for development of the use of fly ash in blends with Portland cement by improvement of the relevant research are discussed in view of the currently modest growth of the fly ash utilization, despite copious research activity during the past decade. Refined characterization is suggested of the decisive parameters of the chemistry, mineralogy and granulometry of both the components of the reacting, blended system, and also of the effects induced by chemical admixtures. Effective dispersion of the finest particle fractions in the fresh paste, and monitored integral hydration are indispensable successive precursors for the creation of a blended, hardened cement paste which acts as a “microconcrete”, having dense matrix consisting of fully hydrated, finest fractions of both source materials and coarser unhydrated particles representing “microaggregates”. Surface chemistry and energetics are emphasized as essential scientific regimes to apply for the explanatory research having as their aim substantial increases of the replacement ratios of fly ash to cement in concrete.The Materials Research Society (MRS) is a possible instrument for activity to encourage development of research planning and management methods, which are used in other fields of materials research, to strengthen research as an instrument for effective recovery of the chemical energy inherent in fly ash and for improvement of concrete durability.

scholarly journals Experimental Investigation of Neutralisation of Concrete with Fly Ash as Fine Aggregate in Freeze-Thaw Environment

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Dongsheng Zhang ◽  
Mingjie Mao ◽  
Qiuning Yang ◽  
Wenbo Zhang ◽  
Pengfei Han
Keyword(s):  
Fly Ash ◽  
Mathematical Expression ◽  
Influence Coefficient ◽  
Fine Aggregate ◽  
Concrete Durability ◽  
Freeze Thaw ◽  
Composite Damage ◽  
Variation Characteristics ◽  
Deterioration Mechanism ◽  
Highly Correlated

To study the durability of concrete with fly ash as fine aggregate under alternate freeze-thaw and carbonation, freeze-thaw and carbonation cyclic tests are conducted to explore variation characteristics such as relative dynamic modulus of elasticity and neutralisation depth. The influence coefficient (λC) of carbonation on concrete freeze-thaw damage and the influence coefficient (λF) of freeze-thaw on concrete neutralisation are introduced. In addition, scanning electron microscopy is performed to reveal the deterioration mechanism of the alternating effect. Finally, through a regression analysis of test data, the mathematical expression of the composite damage coefficient kF under alternate freeze-thaw and carbonation is obtained. Based on these findings, a prediction model of the neutralisation depth of concrete is established with number of freeze-thaw cycles and water-cement ratio as parameters. The values calculated through this model and the values measured in the tests are highly correlated. This provides a theoretical reference and basis for the analysis of concrete durability in a multifactor environment.

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