Alkali Silica Reaction Deterioration Research Articles

Influences of composition and reaction conditions on molecular structure, hygroscopicity, and swelling behavior of alkali-silica reaction gels

Alkali-silica reaction (ASR) gel, a product of the reactions between the dissolved silica from aggregate and the alkalis from cement, governs the destructiveness of ASR and concrete deterioration. The influences of chemical composition and reaction conditions of ASR gel on its structure and properties remain unclear. In this work, the correlations between the molecular structure, hygroscopicity, and swelling behavior of ASR products were uncovered by investigating six CaO–SiO2-M2O systems with varying alkali/Si and Ca/Si ratios under two reaction conditions. The results indicate that the low-alkali gels have a layered silicate structure dominated by Q1 and Q2 sites similar to calcium silicate hydrate (C–S–H), whereas the high-alkali gels showed coexistence of tobermorite-type C–S–H and alkali-silicate hydrates featured with Q3 polymerization. The 29Si nuclear magnetic resonance (NMR) results showed that the mean chain length (MCL) and degree of polymerization (DP) decrease with alkali/Si and Ca/Si ratios but increase with moisture. Under 97 % RH, decreased crystallinity and enhanced formation of ASH and Q3 sites are obtained along with increased polymerization and d-spacing. The moisture uptake and swelling of the high-alkali gels showed a reverse correlation with the Ca/Si ratio, which confirms the role of calcium in suppressing the formation of ASH and the dominant role of Q3 sites in determining the hygroscopicity of ASR products.

Structural assessment of an ASR-affected reinforced concrete bridge

ASR (alkali-silica reaction) has long been acknowledged as a key consideration when designing concrete structures in South Africa. This study raises awareness of the influence of ASR on the structural behaviour of reinforced concrete bridge structures. Aggregate type plays a role in how the ASR develops over the structural life cycle. Greywacke aggregate is found to be prominent in ASR-affected structures within the Western Cape region, and in the structure that was investigated. ASR decreases concrete tensile strength, compressive strength, and E-modulus over time. To develop a standardised approach that can be replicated on other bridge structures, a simply supported rectangular reinforced concrete bridge deck slab was analysed. The slab was modelled according to the construction drawings, including the reinforcement detailing, to determine the ultimate shear and moment resistance according to the code (BS 1972) used for the original design, and current Eurocode standards, for both unaffected and ASR-affected concrete. Traffic load was determined from the relevant TMH7 standard, and from weigh-in-motion data collected at a station on the high-traffic-volume route crossing the bridge. Due to compressive strength being the least affected material property by ASR deterioration, the ultimate resistance to original design loads was found to be sufficient.

The Impact of Distinct Superplasticizers on the Degradation of Concrete Affected by Alkali-Silica Reaction (ASR).

The effect of two superplasticizers (SPs) with various equivalent (eq.) alkali contents (i.e., with 0.00009% and 4.1% of Na2Oeq, respectively) on the development of an alkali-silica reaction (ASR) was investigated through the use of multilevel assessment. This testing protocol showed promising results for evaluating concrete damage due to ASRs based on mechanical and microscopical testing protocols, specifically the stiffness damage test (SDT) and the damage rating index (DRI). Concrete specimens that incorporated the aforementioned SPs and distinct reactive aggregates (coarse and fine) were manufactured and then stored in conditions that enabled ASR development and were monitored over time. Upon reaching the desired expansion levels of this study, the concrete specimens were prepared for the multilevel assessment. The results show that the SP-incorporated concrete specimens with lower and higher alkali content yielded lower and higher deterioration results, respectively. This clearly confirms that while SP-incorporated concrete that contains SPs with a higher alkali content could increase the risk of ASR deterioration, those SPs with a very low amount of alkali content could act as a mitigation strategy against ASRs. Finally, an investigation into the influence of distinct SPs on the chemical composition of an ASR gel was conducted, which confirmed that the SP with a higher alkali content had the highest potential for further deterioration.

High-contribution of strip glass waste in buckling-strengthening of slim GLARC columns at once avoiding ASR deterioration problems in concrete materials

The important thing about axially loading slim columns is buckling stability. However, very limited researches were found, especially using glass-reinforced concrete. An ASR (alkali silica reaction) deterioration problem only occurs when particles are very fine. The utilization of glass as a particle was avoided, and bigger dimension of glass strip waste was utilized instead because cement cannot penetrate deep into the glass piece. A series of axial loading tests of GLARC (glass-reinforced concrete) slim columns were carried out on arrangement types; glass strips, homogenous and randomly pieces reinforced to explore their buckling performance. All axial GLARC columns capacity results better than glassless columns reinforcement. The best reinforcement was longitudinal horizontal strip arrangement since they have consistent strength contribution hence allow the GLARC columns to resist higher axial loads to avoid buckling failures. The tests results in a good performance and hence GLARC columns have potential chances to be used extensively as structural compression members.

Effect of anions on behavior of mortar exposed to alkali–silica reaction

To investigate the effect of alkali–silica reaction (ASR) on concrete structures in saline and alkaline service environments, mortar containing reactive aggregates is immersed in 5% and 10% NaCl solutions, 5% and 10% NaOH solutions, and deionized water for 210 d. The mortar’s mechanical properties and durability are thereafter tested, and their relationships are analyzed. The results show that external hydroxyl ions negatively affect the aforementioned properties, whereas the effect of chloride ions is minimal. Based on the linear relationship between compressive strength and water permeability, this study proposes a method to evaluate the ASR deterioration of concrete structures.

Experimental Behavior of Large Reinforced Concrete Specimen with Heavy ASR and DEF Deterioration

AbstractSlight and moderate amounts of deterioration caused by alkali silica reaction (ASR)/delayed ettringite formation (DEF)-induced expansion in reinforced concrete specimens do not markedly or ...

Reduced alkali-silica reaction damage in recycled glass mortar samples with supplementary cementitious materials

Recycling waste glass aggregate into concrete can reduce environmental impacts but also may lead to serious alkali silica reaction (ASR) damage. This study aims to characterize ASR damage development in the mortar samples containing reactive glass aggregates and investigate the damage reduction effect of the waste supplementary cementitious materials (SCMs), including recycled glass powders and fly ash. The recycled glass aggregate mortar samples with/without SCMs were prepared in this study. The length change tests were first conducted with the prepared mortar samples based on the ASTM C1260 standard. The results demonstrated the added SCMs can largely decrease early-age ASR expansion rate. The optical microscope and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) were further conducted to characterize the ASR damage in mortar samples and investigate the damage mitigation mechanism with added SCMs. The combined SEM imaging and chemical analysis indicated added SCMs can decrease both the alkali and calcium content of the generated ASR gel. In addition, the ASR damage development inside mortar samples were monitored with dynamic micron X-ray CT (μCT) over a reaction period of 63 h at the temperature of 80 °C. The scanning patterns demonstrated the ASR damage can be easily developed from the area with initial cracks and sharp corners. The images of glass power and fly ash samples showed significantly reduced ASR damage. This study showed that adding of SCMs can largely reduce ASR deterioration and thus facilitate the recycling glass particles into concrete.

Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions.

Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.

Long-Term Vibration Monitoring of the Effects of Temperature and Humidity on PC Girders with and without Fly Ash considering ASR Deterioration

Structural responses have been used as inputs in the evaluation procedures of civil structures for years. Apart from the degradation of a structure itself, changes in the environmental conditions affect its characteristics. For adequate maintenance, it is necessary to quantify the environment-induced changes and discriminate them from the effects due to damage. This study investigates the variation in the vibration responses of prestressed concrete (PC) girders, which were deteriorated because of the alkali–silica reaction (ASR), concerning ambient temperature and humidity. Three PC girders were exposed to outdoor weather conditions outside the laboratory, one of which had a selected amount of fly ash in its mixture to mitigate the ASR. The girders were periodically vibration tested for one and a half years. It was found that when the temperature and humidity increased, the frequencies and damping ratios decreased in proportion. No apparent variation in the mode shapes could be identified. A finite element model was proposed for numerical verification, the results of which were in good agreement with the measured changes in the natural frequencies. Moreover, the different dynamic performances of the three specimens indicated that the fly ash significantly affected the vibrations of the PC girders under ASR deterioration.

Performance of RC Columns Affected by ASR. II: Experiments and Assessment

AbstractThis paper describes the structural performance and analytical methodology for large-scale column specimens with a lap splice and concentric axial loading affected by varying levels of alkali-silica reaction (ASR) under displacement-controlled monotonic loading. The lap-splice length in the specimens is typical of the Texas DOT practice for the bar size used and is conservative by code standards. The specimens with varying degrees of ASR showed no evidence of bond deterioration within the splice; had similar initial stiffness and behavior up to the first cracking; had a 25–35% increase in postcracking stiffness up to yielding; had a 5–15% increase in yield strength; and showed no overall detrimental effects on the structural response when compared with control specimens without ASR deterioration. This improved behavior can be explained by the resulting volumetric expansion of the concrete because of the ASR that engaged the longitudinal and transverse reinforcement—this is believed to have resulte...

Probabilistic model for steel–concrete bond behavior in bridge columns affected by alkali silica reactions

Past research has shown that in concrete bridges, cements with high alkali content combined with reactive siliceous aggregates can result in alkali silica reaction (ASR) in the presence of sufficient moisture. There is a concern that ASR may form at the steel–concrete interface and weaken the bond behavior in RC columns. This could result in a reduction of the structural capacity of columns and overall bridge reliability. Therefore, to accurately assess the column and bridge reliability over the service life of the structure, it is important to account for the possible effects of ASR on the steel–concrete bond behavior in the lap-splice region. This paper develops a probabilistic model of the steel–concrete bond behavior that considers the effects of ASR. The proposed model is formulated starting from a currently available bond–slip model suggested by CEB-FIP. Unknown parameters in the bond–slip model and their statistics are assessed through a Bayesian approach using available data from the load testing of eight large-scale bridge column specimens constructed to study the effect of ASR on the bond behavior in the lap-splice region. The experimental data do not directly show the bond behavior, but are in terms of the force–displacement response of the full specimens. Therefore, to assess the parameters in the bond–slip model, a finite element model is constructed to obtain the force–displacement responses as a function of the parameters in the bond–slip model. The results show that the bond stiffness and strength tend to increase for the specimens exhibiting moderate ASR deterioration, but decrease as ASR deterioration reaches a certain level.

The Development of Highly Durable Concrete Using Classified Fine Fly Ash in Hokuriku District

In the Hokuriku district, the effort toward the production of highly durable concrete mixtures using classified fine fly ash has just started as a part of ongoing countermeasures for the chloride attack and the alkali silica reaction (ASR). At a time when ASR deterioration phenomena are still progressing, the use of fly ash cement in concrete should be recommended and assertively be adopted as a regional approach for the mitigation of ASR problem especially in the Hokuriku District. In order to promote this mutual understanding and cooperation among the electric power companies, the national and local governments, the industrial association of ready-mixed concrete companies and the universities are indispensable. Accordingly, a joint-collaborative industry-academia-government research committee has been set up in January 2011. This paper focuses on the drawing from the current stage of ASR problem in the Hokuriku district and the development of highly durable fly ash concretes as its countermeasures.

Performance of olive waste ash concrete exposed to alkali‐silica reaction

AbstractThis work investigates the effect of olive waste ash (OWA) on the durability of concrete exposed to alkali‐silica reaction (ASR). Three OWA contents were considered in the work: 7, 15 and 22 %, with crushed Pyrex glass used as reactive fine aggregate. The other experimental parameters investigated in the study were: w/c ratio (0.4 and 0.5) and air content (non‐air‐entrained and air‐entrained). The OWA concrete specimens were submerged in 1‐N NaOH solution at 40 °C to accelerate the ASR. The ASR damage was monitored by measuring the expansion of concrete prisms and the decrease in compressive strength.The study demonstrates that OWA concrete is more resistant to ASR deterioration than plain concrete. The durability of OWA concrete with respect to ASR damage improved with the increase in OWA content. The OWA concrete with a w/c ratio of 0.4 exhibited a better performance with respect to ASR deterioration than the OWA concrete with a w/c ratio of 0.5. The air‐entrained OWA concrete exhibited better durability with respect to ASR damage than the non‐air‐entrained OWA concrete.

Alkali-Silica Reactivity of Andesite in Noto Peninsula and Monitoring of Expansion Behavior of Concrete Bridge Piers

A large number of bridge piers in Japan, which were mostly constructed in the 1970s or 1980s, are suffering from serious damages caused by alkali-silica reaction (ASR). The concrete using reactive andesite successively expanded for more than 30years, leading to the serious damage of structural elements of bridge pier. In the case study of Kashima Bridge in Ishikawa Prefecture, the degree of deterioration of bridge pier due to ASR was investigated by both visual inspection of cracking and non-destructive testing. Furthermore, the mechanical properties of concrete and the degree of fracture of steel bars were examined for the purpose of strengthening design of bridge pier. Based on the classification of ASR deterioration level of each element, the steel plate bonding was adopted for the column, after the pillow beam had been totally reconstructed. This paper describes the mineralogical properties of reactive andesite used in concrete and the mechanical properties of concrete cores taken from bridge pier. Furthermore, monitoring and strengthening methods applied for Kashima Bridge pier are introduced together with non-destructive testing by means of ultrasonic wave inspection. In the maintenance of this bridge, a monitoring using crack sensors has been successfully applied in order to ensure the daily safety of bridge.

Thermo-Chemo-Mechanics of ASR Expansion in Concrete Structures

The critical nature of the alkali-silica reaction (ASR) on premature concrete deterioration requires the quantitative assessment, in time and space, of the chemomechanical impact of ASR expansion on the dimensional stability of concrete structures. In particular, the coupled problem of heat diffusion and ASR kinetics can be critical, as the ASR is a thermoactivated chemical reaction. The quantitative analysis of these coupled effects on both material and structural level is the main objective of this paper. Starting from the governing micromechanisms of ASR expansion, a chemoelastic model is developed that accounts for ASR kinetics and the swelling pressure exerted by the ASR reaction products on the skeleton. This chemoelastic model is a first-order engineering approach to capture timescale and magnitude of ASR expansion. It is shown that the realistic prediction of ASR structural effects requires the consideration of two timescales: (a) A latency time associated with the dissolution of reactive silica; and (2) a characteristic time associated with the ASR product formation. In addition, a dimensional analysis of the governing equations reveals that the ASR deterioration of “massive” concrete structures is driven by the simultaneous activation of heat diffusion and reaction kinetics within a surface layer defined by a characteristic ASR heat diffusion length. In turn, in “slender” structures, it is the simultaneous activation of moisture diffusion and ASR kinetics that drives the surface layer delamination. This is illustrated through finite-element case studies of ASR effects in structures of different dimensions: a concrete gravity dam and a bridge box girder.