scholarly journals Reducing Damage Due to Chemical Reactions in Concrete Exposed to Sodium Chloride: Quantification of a Deleterious Chemical Phase Change Formation

2019 ◽  
Vol 271 ◽  
pp. 07004 ◽  
Author(s):  
Fadi Althoey ◽  
Yaghoob Farnam
Keyword(s):  
Fly Ash ◽  
Sodium Chloride ◽  
Phase Change ◽  
Dilution Effect ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Scanning Calorimetry ◽  
Chemical Phase ◽  
Potential Formation ◽  
Negative Effect

It has been shown that sodium chloride can react with the tricalcium aluminate (C3A) and its hydrates, leading to a formation of a deleterious chemical phase change during thermal cycling. It is believed that this chemical phase change is implicated in the premature deterioration of concrete pavements in the cold regions. This work examines the potential formation of the deleterious chemical phase change in several cementitious pastes made using different types of portland cement and supplementary cementitious materials (SCMs). The amount of the chemical phase change was quantified using a low-temperature differential scanning calorimetry. The results indicated that the formation of the chemical phase change can be reduced by using cements with low C3A content. The addition of SCMs showed different effects on the chemical phase change formation. Slag and Class F fly ash could reduce the amount of the chemical phase change due to only the dilution effect whereas silica fume could significantly reduce the amount of the chemical phase change due to the dilution effect as well as pozzolanic reactions. Adversely, the addition of Class C fly ash showed a negative effect through increasing the formation of the chemical phase change.

Use of Fly Ash to Minimize Deicing Salt Damage in Concrete Pavements

2017 ◽  
Vol 2629 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Prannoy Suraneni ◽  
Vahid J. Azad ◽  
O. Burkan Isgor ◽  
W. Jason Weiss
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Concrete Pavements ◽  
Scanning Calorimetry ◽  
Deicing Salt ◽  
Performance Specification ◽  
Hydrated Cement Paste ◽  
Deicing Salts ◽  
Damage In Concrete

Premature damage has been observed at the joints in numerous concrete pavements where calcium chloride and magnesium chloride deicing salts have been used. This damage results from a reaction between the deicing salt and the calcium hydroxide (CH) in the hydrated cement paste. This reaction leads to the formation of an expansive product known as calcium oxychloride (CAOXY). The use of supplementary cementitious materials as a replacement for cement has been proposed to reduce the CH that is available in the mixture to react with the deicing salts. Reducing the CH can reduce the amount of CAOXY that forms. In this study, mixtures representative of paving concrete were made with cements and fly ashes from across the country. CH amounts were determined by using thermogravimetric analysis, and CAOXY amounts were determined by using low-temperature differential scanning calorimetry. Various replacement levels of fly ash were used to demonstrate that the main parameter that influences the amounts of CH and CAOXY that form is the replacement level of fly ash. This paper proposes that a prescriptive specification requiring 35% cement replacement by volume with fly ash would reduce the damage caused by CAOXY formation and further proposes a performance specification to limit the CAOXY formation to below 15 g/100 g paste.

Effect of ground granulated blast funrnace slag and fly ash on strength, permeability, and under-water abrasion of fine-grained concrete

2020 ◽  
Vol 71 (7) ◽  
pp. 775-788
Author(s):  
Quyet Truong Van ◽  
Sang Nguyen Thanh
Keyword(s):  
Fly Ash ◽  
Concrete Strength ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Permeability ◽  
Cement Replacement ◽  
Fine Grained ◽  
Granulated Blast Furnace Slag ◽  
Compressive Strength Test ◽  
Economic Ground

The utilisation of supplementary cementitious materials (SCMs) is widespread in the concrete industry because of the performance benefits and economic. Ground granulated blast furnace slag (GGBFS) and fly ash (FA) have been used as the SCMs in concrete for reducing the weight of cement and improving durability properties. In this study, GGBFS at different cement replacement ratios of 0%, 20%, 40% and 60% by weight were used in fine-grained concrete. The ternary binders containing GGBFS and FA at cement replacement ratio of 60% by weight have also evaluated. Flexural and compressive strength test, rapid chloride permeability test and under-water abrasion test were performed. Experimental results show that the increase in concrete strength with GGBFS contents from 20% to 40% but at a higher period of maturity (56 days and more). The chloride permeability the under-water abrasion reduced with the increasing cement replacement by GGBFS or a combination of GGBFS and FA

scholarly journals New Approach for the Determination of Radiological Parameters on Hardened Cement Pastes with Coal Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 475
Author(s):  
Ana María Moreno de los Reyes ◽  
José Antonio Suárez-Navarro ◽  
Maria del Mar Alonso ◽  
Catalina Gascó ◽  
Isabel Sobrados ◽  
...  
Keyword(s):  
Fly Ash ◽  
Activity Concentration ◽  
Gamma Ray ◽  
Coal Fly Ash ◽  
Cementitious Materials ◽  
New Method ◽  
Supplementary Cementitious Materials ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Activity Concentrations

Supplementary cementitious materials (SCMs) in industrial waste and by-products are routinely used to mitigate the adverse environmental effects of, and lower the energy consumption associated with, ordinary Portland cement (OPC) manufacture. Many such SCMs, such as type F coal fly ash (FA), are naturally occurring radioactive materials (NORMs). 226Ra, 232Th and 40K radionuclide activity concentration, information needed to determine what is known as the gamma-ray activity concentration index (ACI), is normally collected from ground cement samples. The present study aims to validate a new method for calculating the ACI from measurements made on unground 5 cm cubic specimens. Mechanical, mineralogical and radiological characterisation of 28-day OPC + FA pastes (bearing up to 30 wt % FA) were characterised to determine their mechanical, mineralogical and radiological properties. The activity concentrations found for 226Ra, 212Pb, 232Th and 40K in hardened, intact 5 cm cubic specimens were also statistically equal to the theoretically calculated values and to the same materials when ground to a powder. These findings consequently validated the new method. The possibility of determining the activity concentrations needed to establish the ACI for cement-based materials on unground samples introduces a new field of radiological research on actual cement, mortar and concrete materials.

scholarly journals Long-term mechanical and shrinkage properties of cementitious grouts for structural repair

2019 ◽  
Vol 4 ◽  
pp. 9-15
Author(s):  
Md Shamsuddoha ◽  
Götz Hüsken ◽  
Wolfram Schmidt ◽  
Hans-Carsten Kühne ◽  
Matthias Baeßler
Keyword(s):  
Fly Ash ◽  
Flexural Strength ◽  
Cementitious Materials ◽  
Response Surfaces ◽  
Supplementary Cementitious Materials ◽  
Strength Development ◽  
Structural Repair ◽  
Positive Effects ◽  
Micro Silica

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

Effect of w/cm and Composition on Correlations of Concrete Electrical Resistivity and Chloride Migration Coefficients

2016 ◽  
Vol 711 ◽  
pp. 21-28
Author(s):  
Francisco J. Presuel-Moreno
Keyword(s):  
Electrical Resistivity ◽  
Steady State ◽  
Fly Ash ◽  
Laboratory Experiments ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Ion Migration ◽  
Resistivity Measurements ◽  
Chloride Migration

The performance with regard to chloride penetration of specimens made with three base compositions (supplementary cementitious materials: 20% fly ash, 20% fly ash + 8% silica fume, and 50% slag replacement by weight of cement), and water-to-cementitious ratios of 0.35, 0.41, or 0.47 were investigated here. In this investigation, laboratory experiments were carried out to study the correlation between electrical resistivity and non-steady state chloride ion migration coefficients (Dnssm) of concrete. NT Build 492 was used to determine chloride migration coefficients. Rapid migration tests and resistivity measurements were performed several times over two years, and the non-steady state migration coefficient (Dnssm) vs. resistivity values were correlated. Experimental results show that a good correlation was found between electrical resistivity and Dnssm. Based on the relationships developed from this investigation, it appears that the correlations are age and composition dependent.

The Effect of Homogenization Procedure on Mechanical Properties of High-Performance Concrete with Partial Replacement of Cement by Supplementary Cementitious Materials

2019 ◽  
Vol 292 ◽  
pp. 102-107 ◽  
Author(s):  
Josef Fládr ◽  
Petr Bílý ◽  
Karel Šeps ◽  
Roman Chylík ◽  
Vladimír Hrbek
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Water Content ◽  
High Performance ◽  
High Performance Concrete ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Partial Replacement ◽  
Depth Of Penetration ◽  
Cement Additive

High-performance concrete is a very specific type of concrete. Its production is sensitive to both the quality of compounds used and the order of addition of particular compounds during the homogenization process. The mechanical properties were observed for four dosing procedures of each of the three tested concrete mixtures. The four dosing procedures were identical for the three mixes. The three mixes varied only in the type of supplementary cementitious material used and in water content. The water content difference was caused by variable k-value of particular additives. The water-to-binder ratio was kept constant for all the concretes. The additives used were metakaolin, fly ash and microsilica. The comparison of particular dosing procedures was carried out on the values of basic mechanical properties of concrete. The paper compares compressive strength and depth of penetration of water under pressure. Besides the comparsion of macro-mechanical properties, the effect of microsilica and fly ash additives on micro-mechanical properties was observed with the use of scanning electron microscopy (SEM) and nanoindentation data analysis. Nanoindentation was used to determine the thickness and strength of interfacial transition zone (ITZ) for different sequence of addition of cement, additive and aggregate. The thickness obtained by nanoindentation was further investigated by SEM EDS line scanning.

Effect of Curing Temperature on Hardened Concrete Properties

2005 ◽  
Vol 1914 (1) ◽  
pp. 97-104 ◽  
Author(s):  
W. Micah Hale ◽  
Thomas D. Bush ◽  
Bruce W. Russell ◽  
Seamus F. Freyne
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
Curing Temperature ◽  
Supplementary Cementitious Materials ◽  
Cold Weather ◽  
Strength Development ◽  
Hardened Concrete ◽  
Hardened Properties ◽  
Hot Weather ◽  
Materials Used

Often, concrete is not mixed or placed under ideal conditions. Particularly in the winter or the summer months, the temperature of fresh concrete is quite different from that of concrete mixed under laboratory conditions. This paper examines the influence of supplementary cementitious materials on the strength development (and other hardened properties) of concrete subjected to different curing regimens. The supplementary cementitious materials used in the research program were ground granulated blast furnace slag (GGBFS), fly ash, and a combination of both materials. The three curing regimens used were hot weather curing, standard curing, and cold weather curing. Under the conditions tested, the results show that the addition of GGBFS at a relatively low replacement rate can improve the hardened properties for each curing regimen. This improvement was noticeable not only at later ages but also at early ages. Mixtures that contained both materials (GGBFS and fly ash) performed as well as and, in most cases, better than mixtures that contained only portland cement in all curing regimens.

scholarly journals Study of Hydration and Microstructure of Mortar Containing Coral Sand Powder Blended with SCMs

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4248
Author(s):  
Xingxing Li ◽  
Ying Ma ◽  
Xiaodong Shen ◽  
Ya Zhong ◽  
Yuwei Li
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Silica Fume ◽  
Dilution Effect ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Limestone Powder ◽  
Chemical Effect ◽  
Granulated Blast Furnace Slag ◽  
Coral Sand

The utilization of coral waste is an economical way of using concrete in coastal and offshore constructions. Coral waste with more than 96% CaCO3 can be ground to fines and combined with supplementary cementitious materials (SCMs) such as fly ash, silica fume, granulated blast furnace slag in replacing Portland cement to promote the properties of cement concrete. The effects of coral sand powder (CSP) compared to limestone powder (LSP) blended with SCMs on hydration and microstructure of mortar were investigated. The result shows CSP has higher activity than LSP when participating in the chemical reaction. The chemical effect among CSP, SCMs, and ordinary Portland cement (OPC) results in the appearance of the third hydration peak, facilitating the production of carboaluminate. CSP-SCMs mortar has smaller interconnected pores on account of the porous character of CSP as well as the filler and chemical effect. The dilution effect of CSP leads to the reduction of compressive strength of OPC-CSP and OPC-CSP-SCMs mortars. The synergic effects of CSP with slag and silica fume facilitate the development of compressive strength and lead to a compacted isolation and transfer zone (ITZ) in mortar.

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