Deleterious Alkali-silica Reaction Research Articles

Laboratory and field investigations of alkali-silica reaction prevention by supplementary cementitious materials: Influence of the free alkali loading

Performance tests are often used to evaluate the effect of supplementary cementitious materials (SCMs) on alkali-silica reaction (ASR). However, these tests may be quite demanding, thus other approaches may be more efficient to identify the materials that are worthwhile testing further. This paper presents ASR expansion data obtained from outdoor exposure (2.5 years) and three accelerated laboratory tests: ASTM C1567, TI-B 51, and RILEM AAR-10. A reactive sand containing porous flint, which caused damage in structures after only a few years, was tested with Portland cement and a wide range of SCMs: fly ash, two biomass ashes, two calcined clays, sewage sludge ash, crushed brick, and glass beads. Expansion data were compared with free alkali loadings determined on companion paste samples. It was observed that no expansion occurred below around 2.4 kg/m3 free Na2Oeq in AAR-10 and outdoors (so far). Conversely, no clear trend was found with ASMT C1567 and TI-B 51 results, probably because the outcomes of these immersion tests depend on the transport properties of the specimens and interactions with the surrounding solutions. Since expansions in AAR-10 and outdoors correlate, the free alkali loading seems a promising parameter for screening how SCMs influence the risk of deleterious ASR.

ASR performance of concrete at external alkali supply – effects of aggregate mixtures and blended cement

ABSTRACT The long-term durability of concrete pavements in wet-freeze climate is influenced by deicing salts used for winter maintenance of roads. Alkaline deicers could also be an external source of alkalis, therefore, their role in respect to the development of deleterious alkali-silica reaction (ASR) should be considered. The performance of mineral aggregate mixtures in concrete was studied using RILEM test procedure ‘60°C concrete test with external alkali supply’. Air-entrained concrete specimens were exposed to cyclic temperature changes, wetting-drying and NaCl solution immersion. Tests revealed the development of concrete expansion in time and associated changes of its elastic modulus for 31 mixtures of fine and coarse aggregate and Portland and fly ash or slag blended cements. The expansive behaviour of air-entrained concrete was strongly influenced by the presence of micro- and cryptocrystalline silica in aggregates. A replacement of nonreactive limestone sand by moderately reactive quartz sand resulted in a substantial enhancement of concrete expansion by a factor of three. The observed reduction of elastic modulus was correlated with more abundant presence of alkali-silica reaction products in concrete. Effects of cement type (CEM I, CEM II/A-V, CEM II/B-S) on the ASR performance of concrete with crushed coarse aggregate and quartz sand are discussed.

Reliability of AMBT and CPT in testing the effectiveness of SCM to mitigate alkali–silica reaction of field concrete

This paper examines the reliability of the Australian Standards accelerated mortar bar test (AMBT) and concrete prism test (CPT), AS 1141.60.1 and 60.2, respectively, and the potential for extending these standard test methods to the determination of the type and dosage of supplementary cementitious materials (SCMs) required to mitigate deleterious alkali-silica reaction(ASR) in a similar manner to the corresponding ASTMC1567 and CSAA23.2-28A. Both AMBT and CPT have their strengths and limitations, however, their overwhelming value is in the availability of laboratory test results and their correlation with long-term performance (up to 20 years) of large concrete blocks and structural elements. Since Australia has no existing field exposure site, this paper uses reported data from CANMET’s and Ontario Hydro’s outdoor exposure sites in Ottawa and Kingston, respectively, in Canada and the 18-year exposure site data from the BRE site in the UK to demonstrate the efficacy of the AMBT and CPT approaches to evaluation of ASR reactivity and ASR mitigation using SCM blended cements. Good correlations are observed for moderately–reactive and highly reactive aggregates used with low-alkali cement and cement with alkali contents up to 0.9 % Na2Oeq. The assessment of reported research demonstrates that both AMBT and CPT have the capacity to predict the long–term performance of structural concrete. In addition, AMBT and 2-year CPT test results for eight Australian reactive aggregates are reported showing the influence of SCMs (fly ash and slag) on mitigation of expansion. Whilst both AMBT and CPT demonstrated their potential for assessing SCMs in mitigation of ASR, AMBT was found to be more conservative than CPT and higher SCM dosages were required to achieve a non-reactive classification. The accelerated test data reported coupled with the correlation of AMBT and CPT to the prediction of long term performance of concretes strongly supports the extension of the Australian test methods AS1141.60.1 and 60.2 for the assessment of ASR mitigation using SCMs.

Alkali-silica reactivity of lightweight aggregates in alkali-activated slag cement and ordinary Portland cement systems

For alkali-activated slag cement (AAC), an environmentally-friendly material, high-alkalinity activators are normally utilized for activation, which can lead to possible concrete degradation owing to alkali-silica reaction (ASR) when alkali-active aggregates were used. This study explored the effectiveness of lightweight aggregates in mitigating ASR behaviors of the AAC system. Alkali-reactive expanded perlite and non-alkali-reactive expanded shale were used as lightweight aggregates to compare ASR behaviors in ordinary Portland cement (OPC) and AAC systems. The formation of ASR gel in the expanded perlite was expansive, whereas the higher Ca/Si ratio calcium-aluminate-silicate-hydrate (C-A-S-H) in the non-alkali-reactive expanded shale did not cause expansion. In contrast with the OPC system, the larger amount of lower Ca/Si ratio ASR gel caused more deleterious ASR expansion and cracks in the AAC system. Furthermore, replacing expanded perlite with expanded shale effectively mitigated the ASR expansion. Discussion on the ASR mitigation mechanism of lightweight aggregates was provided for predicting the influence on the concrete.

Recycling waste glass aggregate in concrete: Mitigation of alkali-silica reaction (ASR) by carbonation curing

Concerns on low rate of glass recycling are rising due to the environmental issues caused by landfills of waste glass. Glass utilization in concrete is a promising approach to vastly improve the glass recycling rate. However, the glass in concrete causes deleterious alkali-silica reaction (ASR), which cracks the concrete and weakens its durability and is the biggest challenge for this approach. To address this challenge, this study proposes the use of carbonation curing to mitigate ASR of mortar prepared with recycled glass (named glass mortar, GM) for the first time. The effects of glass content and carbonation curing regime on mechanical properties and the resistance to ASR-induced volume change of GM were experimentally investigated. It was found that although the increase of glass content had negative impact on compressive strength and resistance to ASR of GM, with optimized carbonation curing, the 28-day compressive strength was improved by up to 40%, and the ASR-induced expansions was significantly reduced by up to 85%. In addition, the underlying mechanisms of ASR mitigation by carbonation curing were further elucidated through characterization tests including thermogravimetric analysis, pore structure analysis, and pore solution analysis. The test results demonstrated that carbonation curing mitigated the ASR in GM by reducing calcium hydroxide content and the volume of pore solution, densifying the microstructure, and reducing the pH and free alkali metal content in the pore solution. This research is hopeful to promote the application of recycling glass in the concrete industry.

Correlating field and laboratory investigations for preventing ASR in concrete – The LNEC cube study (Part I – Project plan and laboratory results)

As part of the Norwegian R&D project “ASR - Reliable concept for performance testing (KPN-ASR)” and of the RILEM TC 258-AAA activities, a study was launched in 2015 with the aim of correlating the results of field and laboratory investigations for selecting appropriate preventive measures against deleterious alkali-silica reaction (ASR) in concrete. Three coarse aggregates, i.e. New Mexico polymictic gravel, Ottersbo cataclasite, and a non-reactive limestone aggregate, were used to manufacture cubes (300×300×300 mm3) from air-entrained, control (high-alkali cement; normal alkali cement) and ASTM Class F fly ash (20 and 30 % replacement levels of the high-alkali cement) concrete mixtures. The cubes were then shipped to be placed on the study participants’ outdoor exposure sites, where they are being monitored for long-term expansion and cracking development (Canada; France; Germany; Iceland; Norway; Portugal; USA). Companion laboratory cubic specimens (for compressive strength and air-void spacing factor determination on hardened concrete) and test prisms were cast from the above mixtures. The prisms were subjected to RILEM AAR–3.1 and RILEM AAR-4.1 testing at LNEC's laboratory; their expansion was monitored over 205 and 28 weeks, respectively. Selected control and fly ash mixtures, without air-entrainment, were repeated at SINTEF following the 38 °C Norwegian concrete prism test (NCPT, prism size 100×100×450 mm3) and RILEM AAR-4.1. This paper, the first of the LNEC cube study, gives an overview of the project, lists the project's main objectives, provides a summary of the activities already developed in the project, and presents and discusses the results obtained thus far in the laboratory investigations. As expected, excessive expansions were obtained for the control high-alkali concretes, whereas addition of fly ash reduced the expansion to a low level. However, the expansion attained for the fly ash mixtures depended on the CPT procedure used.

Alkali-silica reaction of sanitary ware ceramic wastes utilized as aggregate in ordinary and high-performance mortars

Waste management has been the foremost concern in the last decades. Utilizing sanitary ware ceramic (SWC) wastes in concrete has been found to be beneficial in terms of sustainability and cost in previous studies; however, deleterious alkali-silica reaction (ASR) potential of this waste aggregate, albeit it’s high SiO2 content, has not been taken into account. This study aims to examine ASR potential of SWC wastes as well as the effects of permeability, w/c ratio, and reactive powder content of mixtures on the ASR-induced expansions in detail. Accelerated mortar bar, total and capillary water absorptions, and chloride ion penetration tests were conducted for %20, %40, %60, %80, and %100 replacement ratios at the first part of the study. The SWC aggregate showed ASR-induced expansions in “pessimum proportions”. With a 9-day delay, similar patterns (trends) of ASR expansions were observed in the mixtures with a w/c ratio of 0.3 as compared with those of 0.5 w/c ratio. While the ASR expansions had meaningful relations with the water absorption tests and w/c ratio, there was no noteworthy correlation with the rapid chloride ion penetration test results, since the SWC aggregate effected the properties of pore solution. The effect of the finer grains of the SWC aggregate on ASR was investigated in the second part of the study. For this purpose, the SWC aggregate finer than 250 µm was replaced with same sized limestone aggregate. The results revealed that the finer grains of SWC aggregate were responsible for the reductions observed in the first part of the study not due to “pessimum effect” phenomenon but rather to the pozzolanic activity of the finer grains.

Chemical stability of hollow glass microspheres in cementitious syntactic foams

Recent studies have shown cementitious syntactic foams (CSF) to have great potential as a low density and high strength structural material. However, CSFs are made with hollow glass microsphere (HGM) inclusions and cementitious materials with amorphous silica inclusions such as glass are known to have a potential for the deleterious alkali silica reaction (ASR). In this study, CSFs containing HGMs are tested for ASR expansion and compressive strength along with solid particles of soda-lime and borosilicate glass to compare. Results show that in the 30–90 μm average particle size range, only solid borosilicate particles lead to more than 0.2% expansion of the composite material in an accelerated ASTM C1260 lab test for ASR, which is considered as the limit for deleterious effects. Similarly, compressive strength tests show that only solid borosilicate particles lead to reduced compressive strengths (from ~95 to ~40 MPa) in the long term, while CSFs showed no sign of loss of compressive strength even at extremely alkaline conditions. Scanning electron microscopy investigations suggest that CSFs are safe from ASR expansion of the composite and internal stresses due to their hollow geometry, which provides reservoir space for the alkaline silica gel expansion and mitigates the ASR effects.

The Optimum Amount of Waste Glass Aggregate that can Substitute Fine Aggregate in Concrete

The study that is reported in this paper was carried out to study the effects of glass sand on the properties of concrete and determine the optimum amount of waste glass aggregate that can effectively replace fine aggregate in cement concrete. The objectives of the study were to prepare concrete specimens containing various amounts of glass sand as partial replacement for fine aggregate and to determine the properties of fresh and hardened concrete specimens so produced. It was found that glass sand does not have significant effect on the workability of concrete. The density of concrete containing glass sand was slightly lower than the density of normal concrete by a factor of 1-2%. The presence of glass sand did not alter the established strength-time relation of concrete. The strength of concrete containing glass sand increased progressively with curing time. Glass sand had significant effect on the strength of concrete. A plot of concrete strength and glass sand content was a parabola curving downward. The peak strength, obtained at 10% glass sand content, was 1.2 times the target strength of 25 N/mm2. The study concluded that the optimum amount of glass sand that can effectively substitute river sand in grade C25 concrete is 16% of the proportion of fine aggregate in the concrete. For plain concrete, glass sand alone can be used as fine aggregate. It was recommended that supplementary cementitious materials should be incorporated in the concrete to suppress the deleterious alkali-silica reaction that may take place when glass concrete is exposed to moisture.

Tackling the issues of self‐compacting concrete containing high volume of waste glass aggregate by zeolite

AbstractThe use of waste glass in concrete can bring significant economic and environmental benefits due to reduction of landfills and demand for natural aggregates. This paper presents a comprehensive investigation on the feasibility of using high volume of waste glass as fine aggregate in self‐compacting concrete (SCC). A detailed investigation on fresh behavior of mixtures was performed by evaluating filling ability, stability, passing ability, and viscosity of SCC mixtures. Compressive strength and electrical resistivity experiments and scanning electron microscope analysis were also performed to investigate the strength and durability of the concrete mixtures. Furthermore, alkali silica reaction (ASR) potential of different size ranges of the used glass was assessed. The obtained results revealed that excessive bleeding and segregation and deleterious ASR expansion are possible challenges of incorporating fine glass aggregates in SCC. Interestingly, there was no evidence that glass has a considerable impact on the mechanical performance of concrete whereas it increased the electrical resistivity of concrete. Utilizing high volume of waste glass in SCC up to 600 kg/m3 became feasible when a part of portland cement was substituted with zeolite.

ASR potential of nickel slag fine aggregate in blast furnace slag-fly ash geopolymer and Portland cement mortars

Utilizing nickel slag as aggregates in concrete production proposes an economic option for recycling this industrial by-product, and meanwhile preserves the natural rock aggregate resources. Thus, there is an urgent need to further explore the potentially alkali-silica reaction (ASR) nature. This study investigates the ASR of high-magnesium nickel slag (HMNS) fine aggregate in the fly ash-blast furnace slag geopolymer and Portland cement (PC) mortars. No obvious ASR product is observed in the mortars with HMNS fine aggregate, which exhibit lower ASR expansion than the mortars with ASR reactive sand. In the geopolymer mortars, the reactive Al species initially dissolved from HMNS promote the formation of aluminum-containing alkalis silicate gel layer covered on the surface of HMNS grains. This provides a diffuse barrier to protect the inner silica against further attack of alkalis, and consequently mitigates the deleterious ASR. In the PC mortars, the pozzolanic reaction of HMNS improves the consumption of portlandite in the pore solution to reduce the alkalinity and calcium content, resulting in a suppression to the ASR degradation. The accelerated mortar bar test shows that HMNS is reliable for the utilization without deleterious ASR expansion risk.

Alkali-Silica Reactivity of High Density Aggregates for Radiation Shielding Concrete.

Long-term exposure of concrete to nuclear reactor environments may enhance the ageing phenomena. An investigation concerning a possible deleterious alkali-silica reaction (ASR) in concrete containing high-density aggregates is presented in this paper. The scope of this investigation was limited to heavy aggregates that could be used for the construction of the first Polish nuclear power plant (NPP). Five different high-density aggregates were selected and tested: three barites, magnetite, and hematite. Mineralogical analysis was conducted using thin section microscopic observation in transmitted light. The accelerated mortar beam test and the long-time concrete prism test were applied to estimate the susceptibility of heavy aggregates to ASR. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted on aggregates and mortars. The quartz size in aggregate grains was evaluated using image analysis. Application of the accelerated mortar beam method confirmed the observations of thin sections and XRD analysis of high-density aggregates. The microcrystalline quartz in hematite aggregate and cristobalite in one of barite aggregate triggered an ASR. The composition of ASR gel was confirmed by microscopic analysis. The long-term concrete test permitted the selection of innocuous high-density aggregates from among the other aggregates available, which showed practically no reactivity.

Potential use of Jordanian volcanic tuffs as supplementary cementitious materials

Ten Volcanic tuffs collected from several locations in the northern region of Jordan were investigated for potential use as supplementary cementitious materials. The volcanic tuffs were subjected to screening tests which evaluated their chemical composition, morphology and pozzolanic activity. The more promising tuffs were evaluated further as partial (10–40 wt.%) replacement for Portland cement. Their effects on the fresh mix workability, and hardened material strength and susceptibility to alkali-silica reactions were examined. Volcanic tuffs with higher SiO2 content produced higher early-age compressive strengths, and those with higher CaO contents produced improved long-term strength development qualities. Partial replacement of Portland cement with the selected volcanic tuffs reduced the susceptibility to deleterious alkali-silica reactions.

Three decades of international RILEM activities to combat deleterious Alkali-Silica Reactions (ASR) in concrete.

Since 1988, the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) Technical Committees (TCs) have been seeking to establish universally applicable test methods for assessing the alkali-reactivity potential of aggregates, and from later on, for concrete mixes. TC 106 (1988 – 2001) focused on accelerated aggregate tests. The successor committee TC 191-ARP (2001 – 2006) also included work on diagnosis/appraisal & specification. TC 219-ACS (2006 – 2014) introduced work on performance testing & modelling. The major recommendations were published as a RILEM State-of-the-art Report in 2016. In 2014, TC 258-AAA was established, scheduling to finish the work on performance-based assessment in 2019. This current TC is focusing on the following Work Packages; WP1Performance based testing concepts, WP2 Relationship between results from laboratory and field and the establishment of field exposure sites, WP3 Testing of potential alkalis released from certain types of aggregates and measurement of internal concrete alkali content, and eventually; WP4 Verification of alkalis released from aggregates.

Risk of ASR in coating mortars incorporating glass aggregates and a Portland–limestone cement

As the cement content is one of the parameters that control alkali–silica reaction (ASR), this study examined its influence on the expansion of glass mortars. The mortars had volumetric ratio of 1:4 (cement: aggregate) and various aggregate compositions, obtained using replacement ratios of natural sand with waste glass, of 0, 20, 50 and 100%. A volumetric ratio 1:4 was chosen because it is a current composition for cementitious coating mortars. In fact, mortar mixes with increased cement content can lead to erroneous conclusions for in situ mixtures with reactive aggregates. It is concluded that it is feasible to produce glass mortars without deleterious ASR expansion depending on the amount of cement used. For normal cement/aggregate ratios for coating mortars (1:4, in volume), a CEM II/B-L 32.5 N mortar with glass incorporation has a low ASR risk.

A combined synchrotron radiation micro computed tomography and micro X-ray diffraction study on deleterious alkali-silica reaction

Synchrotron radiation micro computed tomography (SR Micro CT) and micro X-ray diffraction (SR Micro XRD) were used to investigate the deleterious effects of alkali-silica reaction (ASR) in mortar bars. The samples were prepared by mixing ordinary Portland cement and chert, the latter consists of quartz crystals known to be potentially alkali-silica reactive; then they are aged in a NaOH solution at 80 °C according to RILEM AAR-2 for ASR to occur. A characterization of the microstructural features (cracks, voids due to dissolution, aggregate detachment) due to ASR was performed by SR Micro CT and a detailed mineralogical characterization of the weathering layer growing at the cement paste-aggregate interface was conducted by SR Micro XRD. When ASR occurs, we observe the dissolution of the quartz belonging to aggregate followed by the precipitation of new crystals of quartz. On the other hand, when ASR aging increases the quartz dissolution is almost complete and a halo diffuse scattering dominates the XRD patterns. Furthermore, the ASR generated a widespread microcracking associated with irregular voids due to aggregate dissolution and a general detachment at the cement paste-aggregate boundary is observed.

Application of an innovative methodology to assessing the alkali-silica reaction in concrete

A new methodological approach, based on two innovative parameters such as the threshold alkali level (TAL) of aggregates and the tolerable driving force (Δtol) provided by an inhibitor of the deleterious alkali-silica reaction (ASR), was used for the assessment of the ASR expansivity of concrete mixes made with different alkali-reactive aggregates and different cements (one limestone-Portland (or Portland) cement, three pozzolanic cements and one blast furnace cement). Concrete prism expansion tests were performed under two different test conditions: 38 °C and 100 % RH or 60 °C and 100 % RH. The alkali-reactivity of the aggregates was also evaluated by using the petrographic examination and the ultra-accelerated mortar bar expansion test in 1 M NaOH solution at 80 °C. The test results were interpreted according to the innovative methodological approach, as well as according to a traditional approach based on pass-fail criteria. It was found that the two parameters, TAL and Δtol, are appropriate for both assessing the alkali-reactivity of aggregates (TAL) and comparing the efficacy of blended cements as ASR inhibitors (Δtol). These two parameters may be rapidly evaluated (150 days of testing) by using the accelerated concrete prism expansion test at 60 °C and 100 % RH.

Effect of Waste Oil-Cracking Catalyst Incorporation on Durability of Mortars

This paper presents research on transport properties and alkali-silica reaction (ASR) susceptibility of mortars containing a pozzolanic waste generated in the fluid catalytic cracking (wFCC) unit by the Portuguese oil-refinery. For this purpose, two series of mortars were prepared by partially replacing cement with 5%, 10% and 15% of wFCC catalyst. The main difference between the two series of mortars is the sand reactivity used in their composition. The results revealed that wFCC catalyst blended cement mortars exhibit an increased resistance against capillary water absorption and chloride migration, as well as a considerable inhibition effect on deleterious ASR expansion. However, under the adopted experimental conditions the incorporation of wFCC catalyst in mortars decreases their carbonation resistance.

Microstructure of selected aggregate quartz by XRD, and a critical review of the crystallinity index

Reliable assessment of the potential of quartz in aggregate to develop deleterious alkali–silica reaction (ASR) is essential for the construction of durable concrete. The crystallinity index for quartz (QCI) introduced by Murata and Norman [15] has been applied to predict the ASR potential of quartz. Despite a number of technical shortcomings and omissions in the original paper, the method has arguably become the most popular alternative for the ‘petrography+expansion testing’ combo.This paper investigates the ASR potential of twelve Italian concrete aggregates, by petrography, mortar bar expansion testing, and test the quartz potential reactivity by calculating the QCI and by the line profile analysis of the XRD pattern. The results confirm that a relationship between QCI values and aggregate expansion behavior is absent. Contrary, the microstructural analysis is a powerful method for predicting the ASR-reactivity of quartz. Finally, the method introduced by Murata and Norman [15] is critically reviewed.

Alkali-silica reactivity of foam glass granules in structure of lightweight concrete

Lightweight aggregate concrete (LWAC) made with foam glass granules (FGG) are subjected to alkali silica reactions (ASR) between FGG and cement matrix. The aim of the study was to identify the effect of different cements on the ASR which occurs between FGG and binder. Eight cements with different chemical composition and Na2O equivalent were used for production of LWAC specimens. Loose bulk density, water absorption, material density and porosity were determined for FGG. Properties of fresh LWAC, like density, flow table test and cone slump as well as air content were tested. Mechanical and physical properties, such as flexural and compression strength tests, were performed for 28days old LWAC specimens. Tests with scanning electron microscope and microstructural investigations were performed for foam glass granules and hardened concrete specimens before and after exposure to alkali solution. The ASR test was performed according to RILEM TC 106-AAR testing recommendations. Relative expansion of 0.160-0.205% was detected which does not comply with standard recommendations (0.054%). Moreover, flexural strength reduction up to 73% and compression strength reduction up to 43% were detected due to deleterious ASR. It was detected that Na2Oeq. is only one of the criteria that determine choice of cement for production of sustainable LWAC. Therefore other measurements must be provided to limit deleterious expansions and comply with the standard requirements.