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2020 | Book

External Sulphate Attack – Field Aspects and Lab Tests

RILEM Final Workshop of TC 251-SRT (Madrid - SPAIN, 2018)


About this book

This volume gathers contributions from the final workshop of the RILEM TC-251-SRT "Sulfate Resistance Testing" on External Sulfate Attack (TESA 2018), held on May 24-25, 2018 at IETcc-CSIC, Madrid, Spain. One of the Technical Committee’s main events, it addressed various aspects of external sulfate attack in concrete structures and test methods. The workshop promoted technical discussions and debates on ideas on these topics, with a focus on evaluating the resistance of concrete exposed to ESA. It also provided a forum for participants from around the globe to share their experiences and research on concrete structures affected by external sulfate attack and on test methods. The book discusses the latest advances in research related to ESA and new developments in test methods, and features real-world case studies of concrete structures affected by external sulfate attack in various countries. It also presents new studies linking field cases and lab tests, including 12 contributions on 3 main themes: mechanisms of alteration in external sulfate attack; field aspects of external sulfate attack; and testing to evaluate the resistance of concrete to external sulfate attack.

Table of Contents


Field Aspects

Field Performance of Portland Limestone Cement Concretes Exposed to Cold-Temperature Sulphate Solutions
This paper presents data from a field test program to evaluate the sulphate resistance of concrete produced with varying limestone contents (0–15%) and supplementary cementitious materials (SCM) contents in order to evaluate the risk of thaumasite formation, which is expedited at cold temperatures (0–10 ℃). Concrete specimens were placed in one of three sulphate solutions (Na2SO4, MgSO4, CaSO4), which were buried approximately 2 m below ground (temperature varying from 4 to 13 ℃). Specimens were retrieved annually to measure expansion, resonant frequency, mass loss and to conduct visual rating. Following six years of exposure, concrete with higher w/cm exhibited an increased level of expansion; however, minimal differences were found between varying limestone contents. The addition of fly ash or silica fume to Portland limestone cement produced concretes with better sulphate resistance than Type MS (moderate sulphate) cement concretes and mirrored the performance of ordinary Portland cement with fly ash and silica fume.
A. Hossack, M. D. A. Thomas, E. Moffatt
Review of the Incidence of the Sulphate Attack in Spain. Evaluation of Field Concrete Cases
In this research, an analysis of the damage caused by sulphate attack in various hardened concrete structures, located in Spain, is carried out. This work is showing a summarization of field concretes affected by sulphate attack (external or internal) in the last twenty years based on the experience of the Eduardo Torroja Institute. For the damage assessment, a set of parameters that directly influence the degree of aggressiveness of the attack are taken into account. Parameters related to risks are assessed, such as the environmental conditions of exposure and the characteristics of the materials of the structure itself. The effects of degradation, related to the consequences of this damage, are also analysed. Likewise, these parameters are also related to the type of structures affected. In several regions of Spain, geological characteristics of the soils and climatic conditions that directly influence the processes of attack by sulphates in concrete structures and promote the occurrence of cases of concrete structures attacked by sulphates are presented. These conditions are well known and sulphate resistant cements are commonly used in Spain. Even so, in Spain there are several concrete structures affected by sulphate attack. A number of 17 cases have been analysed according to the experience with sulphate attack in structures and concrete elements at IETcc-CSIC team in the last 20 years.
E. Menéndez, R. García-Rovés, B. Aldea, Y. Salem

Combination of Actions

Investigation on the Combined Interaction of Sulphate and Acidic Attack on Concretes Exposed to Aggressive Environments
The study presented the results about the sulfuric acid corrosion, at very low pH, of a concrete containing blast furnace slag and fly-ash as SCM. Since no standard method are present regarding the acid corrosion, the comparison of the results between different laboratories is strongly related to the experimental conditions. In this research two methods were compared based on the complete concrete immersion in a sulfuric acid solution with different approaches to keep the pH 2 constant. The evolution of damage was followed by the loss of mass (kg/m2); moreover, the microstructure was observed by electron-scanning microscopy and the elastic modulus was performed as non-destructive test (NDT). The rate of degradation after 35 days of exposure, according the loss of mass due to the calcium dissolution of cement paste, is comparable between the two methods. The influence on the experimental parameters and the relation with the combined sulphate and acidic attack is discussed.
M. C. Alonso, K. Villar, D. Qvaeschning, S. Irico, G. Pérez
External Sulphate Attack on Recycled Concrete: Assessment of the Influence of Recycled Aggregate
The performance of recycled aggregate concrete (RAC) under external sulphate attack (ESA) has not been fully clarified yet. The attached mortar on recycled aggregate particles increases the content of hydration products from Portland cement that are able to react with external sulphates. In addition, it increases the porosity of the resulting material, facilitating the penetration of ions. In this paper, we present experimental results focusing on the evaluation of the potential reactivity of recycled aggregates themselves. Weight and length variations of mortar bars made with fine recycled aggregates obtained from crushing concretes containing high and low C3A Portland cements were determined after exposure to sulphate solution at 38 °C. In addition, concrete cores with 25 and 75 mm in diameter exposed to sulphate solution at 20 °C were also evaluated. The results show no indication of significant reactivity of recycled aggregates with external sulphate.
L. R. Santillan, Y. A. Villagrán Zaccardi, C. J. Zega

Testing and Parameters of Testing

Influence of Temperature and Aggressive Solutions in the Formation of Thaumasite and Ettringite in Standard and Commercial Mortars
Formation of thaumasite or ettringite is depending on the temperature and the presence of carbonates, apart from the sulphate concentration. Although in the field exposition, these conditions may vary during the service life. In addition, not always is possible to control the composition of the commercial mortars or concretes. In the present work, seven different mortars are studied under two temperatures and three external solutions. The temperatures are 5 ºC and 20 °C. The solutions are water, sodium sulphate and sodium sulphate plus calcium carbonate. The aggregates are calcareous in the commercial mortars, and calcium carbonate, quartz and opal plus quartz in the standard mortars. The aspect, expansion and weight variation are analysed with time. The mortars with alkali reactive aggregates (opal plus quartz) show alteration under all conditions with variable damage. On the other hand, the expansion and the formation of thaumasite or ettringite is favored by low temperature and solution combination.
E. Menéndez, B. Aldea, M. Formoso, R. García-Roves, S. Ruiz, J. de Frutos
Influence of Thermal Preconditioning on the Mechanism of External Sulphate Attack
During external sulphate attack, the penetration of sulphates within the material is the rate-limiting step. Thus laboratory tests can last a few years before giving usable results. It is possible to shorten the response time by stimulating the penetration of sulphates. One way to achieve that is to dry the material at 60 °C then to saturate it with a sulphate solution before the test. The impact of this thermal pre-conditioning on the sulphate attack phenomenology still remains unclear. Two external sulphate attack tests have been set on two mortar cylinders each. The monitoring of the degradation process made it possible to investigate the influence of the thermal pre-conditioning. The mechanism of external sulphate attack appeared similar for the two tests. Although the mortar cylinders with thermal pre-conditioning showed stronger degradation earlier according to certain parameters (mass, volume, radius), there was no difference regarding the beginning of the expansion.
S. Boudache, E. Rozière, A. Loukili, H. Colina
Influence of Specimen Size on the Expansion of Portland Cement Mortars Immersed in Sodium Sulphate Solution
This paper explores the role of specimen size on the rate of length change in sodium sulphate attack. Prismatic cement mortar specimens of size cross sections 10 mm × 10 mm and 20 mm × 20 mm with length of 160 mm and standard size (ASTM C1012) of 25 mm × 25 mm × 285 mm, were continuously immersed in 50 g/l sodium sulphate solution, and the change in length was monitored periodically. The expansion was seen to be dependent on the surface area to volume ratio. Quantification of the attack using the depth of alteration in the specimens was studied by X-ray microtomography. The information from the microstructural analysis was used to assess the impact of specimen size, with a view of connecting laboratory specimens to actual structural elements in sulphate-rich environments.
M. F. Suma, M. Santhanam
An Alternative Method to Evaluate the Sulphate Resistance of Cementitious Binders
Although there have been a number of studies with proposed methods to evaluate sulphate resistance of cementitious mixtures, ASTM C1012 is still the most widely accepted performance method. However, the test often requires measurements that last from 6 months to a year, making it a very unpopular among practitioners. This paper presents a new method that is two to three times faster than the current ASTM test by accelerating the penetration and diffusion of sulphates, and inciting the chemical reactions between the hydrated cement paste and sulphate ions. Degradation was assessed on mortar specimens immersed in sodium sulphate solution (5% Na2SO4) by monitoring the variation in mass and the length change over time. When compared to the current ASTM method, the new method showed a significant acceleration in the rate of expansion with severe visual deterioration observed on the mortar bars in less than one-half the time.
F. Aguayo, O. J. Funez, T. Drimalas, K. J. Folliard, R. D. Lute
New Approach for Testing SR Cements
Flat mortar prisms are used for the assessment of SR cements in Germany. As in other countries, relative length change is the relevant test criterion. But often it was observed that also CEM I-SR cements caused high length changes. Therefore, the significance of the test results was critically questioned. With a modified test method, significantly better test results could be achieved for cements with known high and low sulphate resistance. The modifications include i.a. cylindrical instead of flat mortar specimens and a test solution containing 3.0 instead of 30 g sulphate/L, consisting of a defined mixture of calcium, magnesium and sodium sulphate. The test method provides meaningful results for cements with various main constituents, especially for cements containing limestone, slag and fly ash.
K. Lipus
A Fast Testing Method for Discriminating Hardened Cement Paste Reactivity with External Sulphate
Civil engineering structures exposed to external sulphate are widely encountered in the world. Usual laboratory experiments used to characterize sulphate attack require long periods of time (e.g., for months). We have adapted a test already available in the literature: ground compacted materials placed in an oedometric cell are flushed with a sodium sulphate solution. The test was optimized by injecting a stoichiometric amount of sulphate in a single injection, whose duration and flow rate are controlled. We first analyzed the testing method in terms of permeability before and after compaction, of expansion behavior after sulphate injection, and of sulphate uptake during injection. Experimental results showed that the amount of sulphates retained in the sample is correlated to the duration of the injection. Reactive transport calculations simulating the injection/expansion periods highlighted the significance of mechanisms occurring at different time scales: flow of water, sorption of sulphate on C-S-H, and formation of secondary ettringite and diffusion of sulphate within the compact. Eventually, expansions of various cement pastes (namely, CEM I, CEM I + 20% limestone filler and CEM-III/C) correlate with results obtained on stress-free concrete samples made of those same paste. This testing strategy is promising to discriminate the sensitivity of various cements to sulphates with a laboratory experiment lasting on the order of a week.
S. Meulenyzer, B. Huet, H. Raqen, F. Bégaud, N. N. Bui, M. Vandamme, J. M. Pereira


The Uses of Finely Ground Materials to Mitigate the External Sulphate Attack (ESA) on Cementitious Materials
External sulphate attack (ESA) is a term used to describe various chemical reactions between sulphate ions and hydrated cement compounds. Thus, the chemical composition of the binder is extremely important on the durability of concrete structures and structural members exposed to sulphate environments. This paper aims to evaluate physical (i.e. induced expansion and compressive strength) and mineralogical (i.e. X-ray diffraction) properties of eight mortar mixtures presenting distinct compositions (i.e. OPC, Quartz and Limestone Fillers, Red-Clay Waste, Fly Ash, Metakaolin, Silica Fume and Rice Husk Ash) and exposed to two different 0.7 M sulphate solutions (i.e. sodium and magnesium). The results show that the remaining portlandite in the system plays an important role on the sulphate attack deterioration process and seems to be dependent on the type of sulphate attack. Moreover, the overall ESA damage was found to increase with the use of binders containing aluminum-silicate compounds.
D. J. De Souza, M. H. F. Medeiros, J. Hoppe, L. F. M. Sanchez
Evolution of Damage Due to Sulphate Attack in Cement Mortar with and Without Ground Coal Bottom Ash
Siliceous coal bottom ash is a residue originated in thermo-electrical power stations as a result of the hard coal combustion. It is expected that some characteristics of the coal bottom ash would be similar to those of the coal fly ash formed together in the same boiler. Coal bottom ash has a larger size than coal fly ash. Then, the first one was ground to achieve a particle size similar to the cement size. Therefore, to assess the sulphate resistance of cement-based materials made of ground coal bottom ash, sixteen Portland cement mixes were prepared by combining a cement CEM I 42.5 N according to the European standard EN 197-1:2011, a ground coal bottom ash and a coal fly ash. Both ashes were formed in the same boiler. The expansion measurements are considered to be an adequate parameter to assess damage due to sulphate attack of continuously submerged specimens. This procedure is the basis of the American standard ASTM C-1012/C1012 to evaluate the resistance of Portland cement and other cementitious materials to sulphate attack wherein the expansion measurements are taken with a standardized length comparator along the time. In this research program, the extent of sulphate attack was quantified by the percentage expansion of slender bars submerged in 5% sodium sulphate solution according to the ASTM C-1012 standard. This standard specifies an expansion limit of 0.01% for ordinary Portland cements CEM I and 0.035% for blended cements after a period of one year of exposure. The Portland cement CEM I 42.5 N made without ashes exhibited the largest expansion at 330 days (0.09%); whereas a cement with 10% of coal ash, CEM II/A-V, the expansion was much lower (0.03%) for both types of ashes. The expansion decreases when the ash content increases. In this property, no difference was found between ground coal bottom ash and coal fly ash provided by the same thermo-electrical power station.
E. Menéndez, C. Argiz, M. A. Sanjuán
External Sulphate Attack – Field Aspects and Lab Tests
Dr. Esperanza Menéndez
Dr. Véronique Baroghel-Bouny
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