Alkali-carbonate Reaction Research Articles

The Risk of Alkali–Carbonate Reaction and the Freeze–Thaw Resistance of Waste Dolomite Slag-Based Concrete

The alkali–carbonate reaction (ACR) is a type of alkali–aggregate reaction (AAR) that may lead to serious damage in concrete construction. There is sufficient research on the effect of the ACR on dolomite limestone; however, research on the effect of the ACR on pure dolomite is absent, and there are a large number of dolomite resources that cannot be effectively utilized in civil engineering. This study aims to investigate whether the ACR occurs in pure dolomite spoil and to determine the freeze–thaw resistance of pure waste dolomite slag-based concrete (PWDSC). In this study, X-ray diffraction (XRD) and the lithofacies method (LM) confirmed that the tested samples were pure dolomite. The rock cylinder method (RCM) and rapid preliminary screening testing for carbonate aggregates (AAR-5) were employed to determine the alkali activity of pure dolomite: the RCM indicated a variation of −0.09% in length during the 84-day test period, the AAR-5 exhibited a length expansion rate of 0.03% within 28 days, and the expansion rates were less than 0.1%. These findings suggest that pure waste dolomite slag (PWDS) does not possess alkali activity. The freeze–thaw cycle test showed no significant spalling on the concrete surface, the inside of the cement produced few micro-cracks according to scanning electron microscopy (SEM), and the uniaxial compressive strength (UCS) test showed a decrease of approximately 20% after 200 freeze–thaw cycles. The results verified that ACR does not occur in PWDS and that it can withstand freeze–thaw damage, to a certain extent, when used as concrete coarse aggregate.

Assessment of Potential Alkali-Carbonate Reactivity and Petrographic Analysis of Limestone from Samana Suk Formation Dhamtaur Area, District Abbottabad, Pakistan to Use as Aggregate

A detailed Limestone from the Samana Suk Formation in Dhamtaur, Pakistan, was studied to assess itspotential as a construction aggregate. The limestone contains variable amounts of dolomite, which can be harmful toconcrete. Petrographic analysis and ACR tests showed that the dolomite content is low and the limestone has low alkalireactivity. Engineering laboratory tests confirmed that the limestone meets ASTM and AASHTO standards foraggregate properties. Therefore, the limestone from Dhamtaur can be used as an aggregate in concrete and asphaltworks. The results of the engineering laboratory tests indicate that limestone from the Samana Suk Formation, locatedin the Dhamtaur area, exhibits specific gravity (2.84g/cm3), water absorption (0.0781%), Los Angeles abrasion value(20%), and sulfate soundness (2.23%). These findings strongly support the viability of utilizing these rocks asaggregate, aligning with the established standards of ASTM and AASHTO. A petrographic examination indicates thepresence of dolomite in a minor proportion (2-15%) with a Porphyrotopic-S type texture. Analysis of ACR resultsdemonstrates a slight expansion in the limestone (0-0.01%), implying low reactivity to alkali. Consequently, it isreasonable to propose the utilization of these rocks as a source of aggregate in concrete and asphalt projects.

Damage Generated and Propagated by the AAR Reactive Aggregate from Kingston, Ontario, Canada.

It remains unclear in the literature what the cause of the so-called alkali-carbonate reaction (ACR) damage to concrete is. However, expansion and cracks as distress features are often attributed to the alkali-silica reaction (ASR). Therefore, this work aims to assess the damage to concrete generated and propagated by the so-called ACR-susceptible reactive aggregate through mechanical testing (i.e., the direct shear test), microscopy (the damage rating index-DRI), and other techniques. Distinct induced expansion levels (i.e., 0%, 0.05%, 0.12%, and 0.20%) were selected to compare the distress caused by ACR to concrete affected by ASR. The results show that the behavior of ACR, namely, as captured through the DRI, is inconsistent with that of ASR, thus attesting to ACR being a distinct distress mechanism. The damage captured through mechanical testing does not distinguish ACR from ASR; however, microscopy reveals that cracks in the cement paste are the main damage mechanism. The proportions of cracks in the cement paste are 40-50% of the total number of cracks, whereas open cracks in the aggregates normally characterizing ASR represent only up to 20% of the total cracks.

Spalling of concrete caused by ASR – a review

A very well-known fact is that cracks in concrete members can allow water to enter the member, thus jeopardizing the concrete member integrity by changing the chemical composition of concrete and causing the aggregates to expand. This initiates the consequent chemical reactions that may evoke spalling of concrete thus creating a cycle of undesirable occurrences in concrete. As a final result, the concrete member can be deteriorated affecting the serviceability, but sometimes even leading the reduction of its load bearing capacity. An overlooked cause of concrete spalling of a chemical nature is the spalling caused by the Alkali-aggregate reaction. This is colloquially known as “concrete cancer”. It is a specific type of a reaction between alkali hydroxides and specific types of aggregate that occurs in concrete. Two main types of alkali-aggregate reactions are the alkali-silica reaction (ASR) and the alkali-carbonate reaction (ACR). The main goal of this research was to review the alkali-silica reaction in concrete as well as the mechanism of aggregate expansion it causes, which ultimately results in concrete spalling. Finally, the ways of prevention the alkali-silica reaction were reviewed and discussed.

PETROGRAPHIC INVESTIGATION OF LIMESTONE OF THE LAKI FORMATION USED IN CONSTRUCTION SECTOR FROM JAMSHORO AND THATTA DISTRICTS, SINDH, PAKISTAN

Limestone belonging to the Laki Formation is well exposed at Nooriabad, Jhampir, and Makli Hills. Representative samples of the Laki Formation limestone were collected from different locations such as Jamshoro, Bolhari, Makli Hills, and Nooriabad. The four crush plants i.e. Afridi Crush Plant and New Hazara Crush Plant (Makli, Thatta District), Shah Rahim Crush Plant and Bhatti Crush Plant (Nooriabad, Jamshoro District) were selected for sampling. The Petrographic investigation as per ASTM- C295-03 (1) was performed using standard thin sections. The megascopic and microscopic study results reflect no hindrance in using the studied limestone. For cement concrete, this limestone can be used for the low-strength concrete and aggregate base course and sub-base. Variation in lithology, stratification and non-homogeneity was observed, however, the aggregate from the New Hazara crush plant is found fractured in nature and therefore, its use as concrete material is not suggested. The studied limestone of all crushed plants does not show any potential for Alkali Silica Reaction (ASR) and Alkali Carbonate Reaction (ACR). Based on the present study, it is concluded that the studied limestone of the Laki Formation from the above-mentioned locations is suitable for construction purposes and industrial use. For cement concrete, this limestone can be used for the low strength concrete and pavement (sub-base & base coarse) as well as aggregate base course. In the stockpile of crushed aggregate on crusher plants, the chalky limestone was found to be less stable and less durable.

Eocene Kohat Formation suitability as an aggregate from Kohat Range, Sub-Himalayas, Pakistan, based on outcrop, petrographic and geotechnical properties

This paper evaluates the physicochemical and mechanical characteristics of the Limestone of the Kohat Formation. The Eocene Kohat limestone is generally exposed in the Kohat, Hangu, and Bannu districts. Kohat Formation limestone is well exposed throughout the Northern Kohat fold and thrust belt at Togh Bala village. It is cream to grey, hard, compact, well-bedded and fossiliferous. Kohat Formation has been identified into two lithofacies which are from base to top calcareous shale lithofacies with large benthic foraminifera and limestone lithofacies. The faunal assemblage indicates that the Kohat Formation was deposited in an inner to middle shelf environment. The petrographic analyses of samples of the Kohat Formation depict that it principally consists of calcite (60-90%) with a small to trace assemblage of dolomite (0-3%), ungraded quartz (0-1.5%), opaque minerals (0-1.2%) and fossils (8-40%). Aggregate physical properties like water absorption (0.88%), specific gravity (2.69), soundness (2.55%), Los Angeles abrasion value (23.06%), aggregate crushing value (11.56%), aggregate impact value (12.68%), flaky index (9.90%), elongation index (12.76%) and coating and stripping values (96.27%) conform to available standards. Our results indicate that Kohat Limestone is safe in terms of Alkali Carbonate Reactivity (ACR) and Alkali-Silica Reactivity (ASR). The facies, thin section study, geochemical, and geotechnical understanding of Kohat Formation indicate that these aggregate deposits are potential aggregate sources for ballast (railway), road, building material, concrete, mortar and other mega projects for connecting Asia and Europe.

PETROGRAPHY AND AGGREGATE ANALYSIS OF THE CARBONATES FROM THE BABUZAI AREA, PAKISTAN

This study is conducted to evaluate aggregate characteristics and potential of carbonates rocks of the Kashala Formation, Babuzai area Khyber Pakhtunkhwa Pakistan. Physical and chemical tests were performed to assess aggregate suitability. Laboratory tests reveal Los Angeles Abrasion values of 17%, Flakiness and Elongation Index of 13% and 19.7% respectively, and Clay lumps and friable value of 0.12%. Stripping and Coating value greater than 95%, Specific gravity value (2.7-2.9). The aggregate soundness value was logged at 1.28. These parameter values were evaluated through the ASTM (American Society for Testing and Materials) and BS (British Standards) which specify that the Kashala Formation (KF) of the Alpurai group can be the potential source for dimension stone i.e., natural rock material in form of blocks or slabs quarried for commercial purposes, road, and concrete aggregates. The petrographic studies of the selected samples have majorly 70 to 75% of Calcite with an insignificant amount of 20 to 25% dolomite, 5 to 8% quartz along with ores of 1 to 2%. The small number of quartz grains and ore minerals indicate that sample formation is composed of dolomitic marble having a limited amount of deleterious content such as quartz, dolomite, and clays, which suggests that the carbonates have an insignificant threat of ACR (Alkali carbonate reaction) and ASR (Alkali silica reaction). The study indicates that the carbonates of the Babuzai area fall within the standard specification limits and can be used as a source for the indigenous construction industry.

Alkali carbonate reaction (ACR): Investigations on mechanism of dedolomitization of dolomite in dolostones

Alkali-carbonate reaction (ACR) are chemical reactions in concrete which may induce significant damage in concrete structures. Researchers have mainly focused on studies of the symptoms pertaining to the reaction, namely expansion and loss of mechanical properties. Not enough attention has been paid to the processes of dedolomitization in dolomitic rocks, such as migration of alkali and hydroxide ions to the surfaces of dolomite crystals, formation of products and effect of products on further migration of alkali and hydroxide ions to newly generated surface of the reacted dolomite crystals. These processes may significantly affect dedolomitization of dolomite and the resulted expansion of ACR. This paper investigates the alkali ion migration in dolostone and the process of dedolomitization of dolomite in the aggregates. Dolostones were crushed, sieved, and graded. Chemical, physical, and microstructural analysis of dolostones and degree of dedolomitization based on X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and laser scanning confocal microscopy (LSCM) of dolostones. Three of the key outcomes of this study provide new insights on the dedolomitization under autoclave conditions: (i) the degree of dedolomitization for large dolostone particles will stop increasing after a period of autoclaving time in 1 mol/L NaOH solutions, (ii) the reaction rim forms a nanofiltration-like structure that, when thick enough, can block the migration of alkali ions and inhibits the dedolomitization process, and (iii) the mechanism of dedolomitization of dolomite is that Mg2+ ions in the dolomite gradually dissolved from dolomite to form brucite with OH− ions, while the rest of dolomite eventually converts to calcite when all Mg2+ is dissolved.

Inhibition of Alkali-Carbonate Reaction by Fly Ash and Metakaolin on Dolomitic Limestones.

In this paper, the dolomitic limestone determined as alkali–carbonate-reactive by various methods is used as an aggregate. Inhibition experiments were carried out on the basis of the concrete microbar method (RILEM AAR-5 standard), in which 10%, 30%, and 50% fly ash and metakaolin were used to replace cement. Thermogravimetric–differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM-EDS) were used to analyze the inhibition mechanism of fly ash and metakaolin on ACR. The results show that the expansion of samples at the age of 28 days are less than 0.10% when the fly ash contents exceed 30% and the metakaolin contents exceed 10%, which proves that the ACR is inhibited effectively. Meanwhile, the Ca(OH)2 content of the samples was reduced and the pore structure of the samples was optimized after adding fly ash and metakaolin. The dolomite crystals in the samples containing 50% fly ash and metakaolin are relatively complete.

Experimental Method for Evaluating the Reactivity of Alkali-Carbonate Reaction Activity.

The main aim of this study was focused on the Method of testing alkali-carbonate reaction activity to avoid alkali-carbonate reaction damage. In this paper, the alkali-carbonate reaction activity and alkali-silica reaction activity of ten kinds of aggregates were determined and analysed by existing standards and methods, by making specimens with aggregates of 2.5–5 mm and 5–10 mm particle size, cured in 1 mol/L tetramethyl ammonium hydroxide solution at 60 °C and 80 °C. Tetramethyl ammonium hydroxide solution was used to exclude the expansion caused by alkali-silica reaction. Effects of aggregate particle size and curing temperature on the expansion of samples were systematically investigated to determine alkali-carbonate reactivity of aggregates. In order to explore the relationship between stress and strain of aggregates, these aggregates were prepared into compacted bodies to test their stress and try to discover the pattern. The results showed that the expansion of the mould specimen prepared by the aggregate of 5–10 mm particle size, cured in 1 mol/L tetramethyl ammonium hydroxide solution at 80 °C was greater than 0.1% after 42 days, which could be used as a reference criterion to determine the alkali-carbonate reaction activity of the aggregate. In addition, the expansion stress test suggest that the alkali-carbonate reaction can generate expansion stress. The expansion stress of aggregates with alkali-carbonate reaction activity were much larger than that of aggregates without alkali-carbonate reaction activity. Through SEM and EDX analysis of the products of the alkali-carbonate reaction, it was shown that the dolomite crystals in the dolomitic aggregates reacted with the TMAH solution and resulted in alkali-carbonate reaction, forming calcite and brucite.

A case study for exploring the alkali-aggregate reactivity of Cyprus aggregates

Concrete is the most commonly used construction material in Cyprus Island as it is all around the world. Even though thousands of tons of concrete are manufactured in both North and South Cyprus, the alkali-aggregate reactivity (AAR) of the crushed (quarried) aggregates has not been previously investigated in a systematic way. The lack of information on the AAR likelihood of Cyprus aggregates in the related literature has caused a lack of awareness about this durability problem in the island and hence, sufficient controls for taking necessary levels of precautions could not be made over the past decades. Two aggregate samples from North Cyprus and another type of aggregates from South Cyprus were obtained from active quarries and tested within this case study for the first time with RILEM tests in order to verify the likelihood of both alkali-silica and alkali-carbonate reactivities of Cyprus Aggregates. The results obtained from RILEM tests and the supplementary SEM analysis showed that both the North (limestone) and South (diabase) Cyprus aggregates exhibit significant levels of alkali-silica reactivity when they are used with composite cement, which is commonly preferred for its advantages. Results also indicated that the mortar batch including the second type of North Cyprus aggregates (dolomitic limestone) with the mentioned cement is potentially reactive for alkali-carbonate reaction as well. The experimental information provided for the first time with this case study is critical both for further Cyprus durability research studies to be carried out and also for improving the quality of local construction activities.

Resource Assessment of Limestone Based on Engineering and Petrographic Analysis

The China-Pakistan Economic Corridor (CPEC) is a massive in-progress construction project in Pakistan that connects more than 70 countries via multiple trade channels such as highways, railways, roads, and fiber optics. This project also involves the development of local infrastructure and industrial zones in Pakistan, which demands the discovery of new resources of aggregate to facilitate the construction. Therefore, physical characterization research was carried out on the Kirman hill region (Jurassic limestone), District Kurram, Pakistan, to investigate their suitability for utilization as construction materials using site investigation and laboratory studies. The results outline that all typical engineering parameters are within acceptable limits set by international standards like BS, ASTM, and AASHTO. Bituminous tests revealed that Jurassic limestone is appropriate as an aggregate for asphalt wearing coarse. Likewise, the petrographic study performed shows proper matching with engineering tests. The petrographic analysis of Jurassic limestone showed a minute amount of deleterious content; as a result, it is resistant to Alkali silica reaction (ASR) and Alkali carbonate reaction (ACR) expansions. Based on engineering and petrographic analysis, the Jurassic limestone, Kirman hill region, District Kurram, Pakistan is recommended as a potential aggregate for (i.e., base course, subbase course, cement concrete, and asphalt) and other mega and minor civil construction projects. Doi: 10.28991/CEJ-2022-08-03-02 Full Text: PDF

Alkali Carbonate Reaction (Acr): Investigations on Alkali Ions Migration and Dedolomitization of Dolostone Aggregate

Alkali Carbonate Reaction (Acr): Investigations on Alkali Ions Migration and Dedolomitization of Dolostone Aggregate

A case study of distress mechanism(s) in a concrete structure foundation in the saturated zone and above the saturated zone.

In this case study, distress mechanism(s) of a concrete structure in the saturated and unsaturated zones of the foundation were investigated. This research was performed using a stereomicroscope, polarised light microscopy (PLM), and a limited study using a scanning electron microscope (SEM) with backscattered electron (BSE). Results of this study showed that concrete cores extracted from both the saturated and unsaturated zones of the foundation exhibited severe to moderate concrete distress, but the cause of the distress/cracking in the concrete was not related to Alkali-Carbonate Reaction (ACR) as was initially suspected. While the damage to the concrete extracted from the structure above the saturated zone of the foundation was caused by a combination of Alkali-Silica Reaction (ASR) and freeze-thaw deterioration, concrete distress in the saturated zone of the foundation was caused primarily by ASR of shale particles in the natural sand fine aggregate. The sand also contained traces of chert particles with ASR. Limited ASR was seen in the crushed gravel coarse aggregate siliceous limestone, dolomitic limestone, and chert particles. Results of this case study showed that siliceous shale particles in the fine aggregate caused detrimental ASR damage to the concrete, and thus caution needs to be exercised when aggregate containing shale is used in concrete.

Alkali-Silica Reaction as Cause of Distress in Concrete Pavements Made from Purported Alkali-Carbonate Reaction Aggregate

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Geotechnical study on the utilization of Pleistocene Sands in Sohag Basin (Upper Egypt) as a construction raw material

The Pleistocene Sands (Armant and Qena formations, Sohag Basin, Upper Egypt) had been evaluated texturally, minerologically and geotechnically as a construction raw material throughout intensive laboratory examinations. These Sands (fine aggregates) are classified into well-graded sands (SW). Texturally, the Pleistocene Sands are consisting mainly of equi-dimensional angular quartz grains. Rock fragments and feldspars are present with minor amounts. Few mineral grains (dolomite and gypsum) were recorded within the sands of Armant Formation. Whereas, few grains of basement rock fragments were identified in Qena Formation. Armant Formation has a higher content of TDS (total dissolved salts), sulfates, calcium carbonates and chlorides than Qena Formation. Additionally, Armant Formation has active chemically mineral grains (dolomite and gypsum). So, Armant Formation sand samples will be reacted harmfully when used as concrete, mortar and sandy bricks due to alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR) that will be happened on long run of time. The absence of shrinkage in length and collapse failure modes indicates the absence of bleeding and segregation with the fresh mixtures (concrete, mortar and sandy bricks) before stiffness state.

Dolomitic filler in self-compacting concrete: a review

The utilization of fine powders as fillers in self-compacting concrete (SCC) application is widespread, particularly in Europe. The incorporation of these fillers to attain the self-compatibility properties of SCC seems to be cheaper than the use of chemical admixtures. Among the wide range of potential fillers, dolomitic powders, particularly generated as by-products from quarry’s processing, are locally available and can be used to produce SCC. Few studies have shown that dolomitic powders can be incorporated in the SCC’s mix design, resulting in acceptable fresh and hardened properties of SCC. The particle size distribution and fineness of the dolomitic powder as well as the level of addition are the key factors affecting those properties. The influence of the chemical nature of the dolomitic powder on the properties of SCC, particularly the durability (e.g. alkali-carbonate reaction), is yet to be investigated. Furthermore, more efforts are still required to investigate the use of dolomitic by-products in the production of SCC.

Reactive Phases in Alkali Carbonate Reaction Reference Aggregate

Reactive Phases in Alkali Carbonate Reaction Reference Aggregate

Expansive behavior of an alkali-carbonate reactive dolostone from Argentina: Proposal of an osmotic theory-based model to explain the expansion caused by the alkali attack

The expansion mechanism of dolomitic rocks in alkaline environments is complex and a current topic of debate, since two different chemical reactions can coexist: one linked with silica attack (alkali-silica reaction, ASR) and the other with dolomite attack (alkali-carbonate reaction, ACR). In previous works, a potentially reactive, fine-grained argillaceous dolomitic rock was identified in Argentina, with similar expansive characteristics to the typical American reactive carbonates. When this rock is used as aggregate in mortars or concretes, the dolomite experiences a clearly expansive dedolomitization reaction, which cannot be controlled by the classical techniques that allow the inhibition of ASR: supplementary cementitious materials (SCMs) (fly ash, natural pozzolan, silica fume, etc.) or Li-based admixtures. Since none of the classical theories proposed by the literature adequately describe the expansive behavior of this rock, an expansion mechanism based on the osmotic phenomenon is proposed in the present work. This mechanism describes the behavior of the Argentine dolostone more appropriately and allows explaining the effect of the main factors involved in the concrete expansion (pH of the pore solution, nature of the alkali cation associated with the OH−, role of water in the expansion, temperature, aggregate particle size, effect of the SCMs, etc.). The basis of the osmotic model is presented, and its advantages are discussed compared with the classical ACR mechanisms proposed by the literature.

The engineering assessments and potential aggregate analysis of mesozoic carbonates of Kohat Hills Range, KP, Pakistan

China-Pakistan Economic Corridor (CPEC) is the ongoing mega construction project in Pakistan. This project provides multi trading routes like roads, railways and fiber optics to more than 70 countries. Additionally, local infrastructure and industrial zones construction in Pakistan is also the part of this project. This construction needs a considerable amount of construction materials. Therefore, the Mesozoic carbonates were studied in the vicinity of Kohat Hills Range, Khyber Pakhtunkhwa province, Pakistan, for the fundamental engineering assessments. The Mesozoic carbonates are extensively exposed in Kohat Hills Range. The petrographic observations reveal that these carbonates are dominantly composed of limestone with subordinate dolomites. The limestone is well preserved and not extensively affected by diagenesis, which affects the aggregate capability, and there was not found any deleterious material which can cause alkali–silica reaction and alkali–carbonate reaction. Likewise, the fundamental engineering tests were performed, which shows proper matching with petrographic observation. The specific gravity, water absorption, soundness, los angeles abrasion value, unite weight, impact value, flakiness and elongation, bitumen coating, and crushing values reveal that these aggregates are well according to the specified limits of the international standards AASHTO, ASTM, and BS. Based on the results obtained, the Mesozoic carbonates of the Kohat Hills rang are recommended as potential aggregate resources for megaprojects like CPEC and other ongoing construction projects.