Accelerated Mortar Bar Test Research Articles

Analysis of waste glass as a partial substitute for coarse aggregate in self-compacting concrete: An experimental and machine learning study

With the growing environmental burden to minimize debris and recycle, the concrete industry has replaced wasted glass with concrete composition elements in multiple ways. This study provides a comprehensive analysis of integrating waste glass aggregate (WGA) at various proportions (0 %, 5 %, 10 %, 15 %, and 20 %) as substitutes for coarse aggregates along with a consistent 20 % silica fume (SF) as cement replacement in self-compacting concrete (SCC). In addition to determining the mechanical, durability and microstructural properties of SCC, this research also uses advanced machine learning (ML) techniques to predict the mechanical properties accurately. By employing slump flow, j-ring flow and v-funnel time the rheology of fresh SCC was evaluated. Mechanical properties were assessed through the evaluation of compressive, splitting tensile, and flexural strength, whereas electrical resistivity, water permeability, rapid chloride permeability (RCPT), and accelerated mortar bar test (AMBT) were employed to evaluate durability. The microstructure was further examined using scanning electron microscopic (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. The replacement of WGA with a constant SF in SCC improved flowability while lessening its passing ability. Furthermore, the study indicated that adding 5 % WGA along with 20 % SF to SCC resulted in a slight decrease of 4.53 % in compressive strength and 3.61 % in flexural strength compared to the reference mix containing 0 % WGA and 20 % SF after 28 days, which yields a favorable outcome. Findings from further assessments revealed that SCC's durability characteristics were enhanced by adding WGA and SF. Expansion of the Ca/Si ratio observed in EDS analysis significantly impacts the strength, while voids and cracks patterns detected in SEM analysis, result in an inferior microstructural performance with the incorporation of WGA. Notwithstanding both the ML models exhibiting excellent regression coefficients (R2), the random forest model showed superior accuracy and reliability in its results.

Alkali-Silica Reaction and Residual Mechanical Properties of High-Strength Mortar Containing Waste Glass Fine Aggregate and Supplementary Cementitious Materials

This paper presents the influence of supplementary cementitious materials (SCMs), such as fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), and waste glass fine aggregate (GA), on the alkali-silica reaction (ASR) in high-strength and normal-strength mortar using an accelerated mortar bar test (AMBT). Residual mechanical properties and scanning electron micrographs were used to assess the changes in the matrix. GA reduced the mechanical properties of both normal-strength (NGA_OPC) and high-strength mortars (HGA_OPC), contributing to a decline in overall performance. This phenomenon was a result of the slipping of the GA from the matrix owing to its smooth surface. However, the inclusion of reactive SF and GGBS in the HGA improved the slip phenomenon of the GA, leading to a significant enhancement in its mechanical properties. Following the ASR expansion measurement, HGA_OPC demonstrated an ASR expansion rate approximately three times higher than that of NGA_OPC. This was attributed to the dense structure of HGA_OPC, which resulted in greater expansion than that of NGA_OPC. However, with the incorporation of SCMs into both HGA and NGA, a significant reduction in ASR expansion was observed. This was attributed to the delayed ASR of GA due to alkali activation or the pozzolanic reaction of the SCMs. Continuous exposure to the AMBT environment can lead to the destruction of GA. This was caused by the inner ASR that originated from the surface crack of the GA, which resulted in a reduction in the flexural strength of the mortar. The HGA with SF exhibited the highest resistance to ASR expansion and residual mechanical properties’ degradation. Therefore, various durability and long-term performance-monitoring studies on ultra-high-performance concrete or high-strength cementitious composites with very high SF contents and GA can be conducted.

Evaluation of Nepali Aggregates for Alkali-silica Reactivity Using Accelerated Mortar Bar Test Method

In many countries, large concrete structures needed to be replaced by new structures because treatment of Alkali Silica Reaction (ASR) was not feasible. Availability of amorphous or poorly crystalline silica is a necessary condition for ASR and it has been a common problem in several countries located in cold geographical regions. Some Nepali rocks also comprise amorphous silica as detected in Sanjen Hydropower Project (SHP) and Tanahu Hydropower Project (THP) during the examination of aggregate through various tests. ASR kinetics and the resulting expansion are observed to be enhanced with an increase in temperature and humidity. Accordingly, the risk of ASR is expected to be prominent in Nepal where temperature and humidity are relatively high. However, systematic research on ASR in Nepal is scarce and the possibility of ASR is little known. This paper determines the reactivity of potential aggregate sources considered for some large infrastructures in Nepal. Accelerated mortar bar test based on the guidelines of ASTM C1260 was performed on aggregate specimens collected from the Pokhara Regional International Airport Project (PRIAP), THP, and SHP. 14-day longitudinal expansion of the mortar bar prepared from the aggregated collected from PRIAP, THP, and SHP was 0.1%, 0.17%, and 0.06% respectively. The aggregate collected from THP is deleterious, whereas aggregate collected from PRIAP and SHP is non-reactive. This study demonstrates that Nepal may have many sources of aggregates that are reactive.

Influence of waste tire rubber powder, polypropylene fiber and their binary blends on mitigating alkali-silica reaction

This work aims to investigate the inhibitory effect and inhibitory mechanism of waste tire rubber powder (abbreviated as WRP) and polypropylene fiber (PPF), and their binary blends on mitigating the alkali-silica reaction (ASR). To achieve this, mortar bars containing either WRP, PPF, or WRP + PPF were prepared for the accelerated mortar bar test (AMBT). The mechanism of ASR inhibition was illustrated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray computed micro-tomography (X-ray CT). The results indicated that the combination of WRP and PPF showed excellent synergistic effect on improving the compressive strength of the mortar cubes. In addition, WRP could effectively alleviate ASR, but the effect depended on the particle size of WRP, with the inhibition effect of 120 mesh WRP being the best. The addition of WRP + PPF exhibited an excellent synergistic effect on the inhibition of ASR expansion, and 120 mesh WRP and PPF with a length of 9 mm and a dosage of 0.8 kg/mm3 showed the best inhibition effect when they were incorporated together. Moreover, the inhibition mechanism of WRP and PPF on ASR was physical effect: WRP consumed the swelling energy generated by water absorption of the gel through deformation, and PPF applied its own bridging effect to suppress crack propagation. Finally, the analysis of the X-ray CT scanning results showed that adding WRP and PPF to the slurry increased the porosity. With the progress of ASR, the gel filled the pores and decreased the expansion. This further revealed more about how WRP and PPF could work together to reduce the damage caused by ASR effectively.

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.

Comparative study of the efficacy of fly ash and reactive aggregate powders in mitigating alkali-silica reaction

This study investigates the ability of reactive aggregate powders to mitigate alkali-silica reaction (ASR) in comparison with fly ash using the accelerated mortar bar test (AMBT). ASR expansion results confirm that the reactive aggregate powders can mitigate ASR, although fly ash still has better mitigating efficacy. Microstructural characterization post-AMBT shows presence of extensive cracking in the plain OPC mortar, few cracks in the mortar with 25% reactive aggregate powders and negligible cracking in the mortar with 25% fly ash. Elemental analysis shows that the reactive aggregate powders are able to increase the Si/Ca and Al/Si ratio of C–S–H composition similar to fly ash. 25% fly ash replacement however results in much higher Si/Ca and Al/Si ratio which likely explains its better efficacy in mitigation. Thermogravimetric analysis results demonstrate that the reactive aggregate powders are pozzolanic like fly ash and that a reactive aggregate powder with better pozzolanic properties has better efficacy to mitigate ASR. The reactive aggregate powders however unlike fly ash do not contribute to compressive strength development of the mortars.

Estimation of non-traditional supplementary cementitious materials potential to prevent alkali-silica reaction using pozzolanic reactivity and bulk resistivity

Relationships between supplementary cementitious material (SCM) pozzolanic reactivity, bulk electrical resistivity, and alkali-silica reaction expansion were examined for traditional and non-traditional SCMs using the modified R3 test, bulk resistivity measurements, and the accelerated mortar-bar test (AMBT), respectively. The SCMs included pozzolanic pumice and glass powder and latent hydraulic slag, with cement and limestone fillers being tested as controls. For mixtures with SCMs, as fineness, reactivity, or replacement level increased, bulk resistivity increased, and the ASR expansion decreased; this was not the case for limestone. Strong correlations between pozzolanic reactivity, bulk resistivity, and ASR expansion suggest the ability to estimate expansion based on reactivity and resistivity, although ASR expansion is a more complex phenomenon. By increasing the curing temperature, 1-day bulk resistivity measurements could be used to estimate ASR expansion. Threshold values for bulk resistivity and pozzolanic reactivity were proposed for screening materials and mixtures, including novel ones, for ASR durability.

Alkali−Silica Activity and Inhibition Measures of Concrete Aggregate in Northwest China

The alkali−silica reaction (ASR)-induced expansion of mortar bars containing four types of aggregates originating from different regions in northwest China was studied. The chemical composition, mineral composition, vitreous and amorphous substances, and expansion rates were determined using X-ray fluorescence, X-ray diffraction, polarizing microscope images, and the accelerated mortar bar test (AMBT). The inhibitory effects of fly ash and silica fume on the aggregate activity were evaluated. The binary mortar mixes were produced and tested, containing cement and fly ash or silica fume as the partial cement replacement. The microstructure and composition of the ASR products were analyzed by scanning electron microscope energy dispersive spectroscopy (SEM–EDS). The results show that all four types of aggregates exhibited an alkali activity, and that all expansion rates on the 14th day were higher than the standard of 0.1%. The lowest and highest values were 0.2% and 0.3%, respectively. The primary constituent in the chemical compositions of these aggregates was found to be silica. Polarization microscopy also confirmed that they contained alkali-active cryptolites. Fly ash and silica fume could both inhibit alkali activity expansion and the silica fume exhibited a superior inhibition effect. When the fly ash and silica fume contents were 20% and 10%, respectively, the expansion rates of the mortar bar on the 14th day were all less than 0.03%.

Alkali-silica reaction in volcanic rocks: a worldwide comparative approach

The potential alkali-silica reactivity (ASR) of volcanic aggregates, especially basalts, remains a source of debate in the scientific community. When evaluating the potentially deleterious character of this type of aggregate, different laboratory testing methods may produce contradictory data; this is particularly evident when using the accelerated mortar bar test (AMBT). In order to better understand such discrepancies, this study applied several methods of characterizing potential aggregate alkali reactivity, including the accelerated mortar bar test (AMBT), petrographic characterization, and the concrete prism test (CPT). Moreover, this study assessed volcanic aggregate samples from sites around the world, including the Azores, Brazil, Canada, the Canary and Hawaiian Islands, Iceland, Japan, Mozambique, New Zealand, Norway, and Turkey. The results obtained contribute to accurately assessing the potential alkali reactivity of volcanic aggregates and enhance the understanding of their different behaviours.

Influence of aggregate crushing on the results of accelerated alkali-silica reactivity tests

This study aimed to evaluate the influence of the crushing process of natural aggregates on the results of accelerated alkali reactivity tests. Thus, two crushers, jaw and roll, were used to crush two aggregates, Vitória and Jaboatão, generating four samples (JV, JJab, RV, RJab), and the morphology of the produced particles was analyzed. Moreover, petrographic analysis, accelerated mortar bar test (AMBT), and miniature concrete prism test were conducted. The results indicated differences in expansion for different crushers, particularly in the AMBT, where the expansion of aggregate Vitória was approximately 2.6-fold higher when crushed with jaw crusher compared with roll crusher. We conclude that the type of crusher is an important parameter in the analysis of the results of the reactive potential of an aggregate using the AMBT and may even lead to erroneous classifications.

Impact Assessment of Pozzolanic Material Coupled with River Bed Aggregate on Expansive Behavior of High Strength Concrete

High strength concrete is widely used in engineering structures. Present work is an effort for suitability assessment of river bed aggregates in high strength concrete to be used at structural units of Dam (Spillway & Powerhouse) and the vulnerability of placed concrete expansion. Multiple sizes of coarse aggregate (5-20mm, 20-40mm, and 40-80mm) from Beor river bed material have been tested for physical (water absorption, crushing index, soundness, shape, and bulk density), and mineralogical characterization. Concrete Mix Design (CMD) for Spillway has been optimized using Fly ash and river aggregate that achieved the Unconfined Compressional Strength (UCS) up to 32.5 MPa. The accelerated mortar bar test (AMBT) has been introduced to gauge the reactive aggregates used in CMD.. Expansive properties of concrete were observed at the age of 7 days and 28 days that demonstrate more expansion of the specimen with slag rather than the Fly ash. Results of AMBT suggest that a minimum proportion of GGBS (40%) is needed to limit the AMBT expansion to less than 0.1% for crushed river bed aggregate and sand from the Beor source. The petrographical characterization of coarse aggregate shows the presence of deformed quartz in the coarse aggregate, which directly relates to water absorption (Wa), suggesting its suceseptility to Alkali-Silica Reaction (ASR). Modifications in Pozzolanic additives in CMD indicates that 30% mixing of Fly ash can reduce the expansion rate of concrete up to 96.15%.

ALKALI-SILICA REACTIVITY OF SOME GRANITIC ROCKS IN KUMASI, GHANA: IMPLICATIONS FOR USE OF ROCK AGGREGATES FOR CONSTRUCTION

This paper seeks to assess the potential of Alkali-Silica Reaction on some granitic rocks in Kumasi in Ghana. Alkali-Silica reactions occur over time between alkaline cement paste and silica contained in rock aggregates as a result of the swelling due to the reaction of certain constituents in the rock aggregates with alkali hydroxides. Alkali-Silica reactions become potentially harmful when they cause significant expansion. Aggregates used for this research were sought from three different quarries, namely, Consar Stone Quarry in Barekese, Nnagot Quarry in Kona and Modern Granite Quarry in Buoho. To achieve the objectives of this project, two test methods were employed such as Accelerated Mortar Bar test (ASTM C1260) and Petrographic analysis. Presence of strained quartz is an indicator for the occurrence of Alkali-Silica Reaction. Samples from Kona contained quite an appreciable amount of strained quartz and exhibited an expansion above the ASTM C 1260 specification, implying that it is potentially reactive and thus not useful for construction works, whilst samples from Barekese, and Buoho were innocuous and may be used for construction works. Supplementary cementing materials such as pozzolans (which are readily available) can be added to concrete mixtures with aggregates from Kona to reduce the harsh effects of ASR.

Evaluation of alkali-silica reaction in recycled aggregates: The applicability of the mortar bar test

Alkali-silica reaction (ASR) is considered one of the most concrete degrading agents causing expansion due to a gel formation that swells in contact with water. In this regard, this study investigates ASR through an expansion test of mortars produced with recycled aggregates (RA). The RA were prepared by crushing source concrete (SC) mixes that were previously produced with alkali reactive natural aggregates (NA). SC mixes were exposed to different environments to accelerate ASR. The mortars were tested using the ASTM C1260 accelerated mortar bar test (AMBT). For comparison purposes, the aggregates were also tested using the RILEM AAR-3 concrete prism test (CPT). As for mortars with NA, changes were needed to optimize the mix production procedure to obtain a mouldable mortar and more trustworthy values. For this purpose, RA-mortars were produced with RA obtained from primary or secondary crushing, different water adjustment types, including the addition of constant volumes of water to maintain a mouldable slump, the addition of 50% of the total absorption water, and pre-saturation of RA. The results showed that the adjustment type of RA absorption water in the mix highly influenced the expansion results. The addition of constant volumes of water to maintain a mouldable slump led to the more trustworthy values. The expansion limits of ASTM C1260 seems be too high for fine RA’s evaluation.

Influence of Limestone Mineral Addition in Cements on the Efficacy of SCMs in Mitigating Alkali-Silica Reaction Assessed by Accelerated Mortar Bar Test

AbstractThis study evaluates the effect of limestone mineral addition in cement on the efficacy of supplementary cementitious materials (SCMs) in mitigating alkali-silica reaction (ASR) using the a...

Petrographic method to semi-quantify the content of particles with reactive components and residual mortar in ASR-affected fine recycled concrete aggregates

A petrographic method is proposed to semi-quantify the content of particles with reactive phases in fine recycled concrete aggregates (FRCA) affected by the alkali-silica reaction and the residual mortar (RM) adhered to them. This method is compared to the image analysis method. Quartered FRCA samples are studied by three petrographers, and the results are compared. Finally, the potential reactivity of the samples is evaluated by the accelerated mortar bar test (AMBT). According to the AMBT and petrographic method, the samples are qualified as potentially reactive, with a low degree of reactivity. The method is easy to perform and fast (compared to image analysis), but the results obtained by three petrographers show some differences that can mainly be attributed to the visual estimation of RM. Although more studies are needed to verify the effectiveness of the proposed method, the implemented technique shows great potential to semi-quantify reactive components in FRCA particles.

ASR mitigation using binary and ternary blends with waste glass powder

Alkali silica reaction (ASR), commonly referred to as “concrete cancer”, is a major durability problem in concrete structures. ASR is a chemical reaction that occurs between the reactive amorphous silica from the natural aggregates and the alkalis in cement in the presence of moisture. This reaction causes undue expansion and cracks in hardened concrete which over time results in deterioration. The use of supplementary cementitious materials (SCMs) has been proven effective to minimize ASR distress. In this study, a synergistic function of glass powder was evaluated in binary and ternary blends with conventional SCMs (slag and silica fume) for ASR mitigation. The ASR mitigation was evaluated using the accelerated mortar bar test (AMBT) and miniature concrete prism test (MCPT) methods. Additional testing including the flow test, strength activity index (SAI), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive x-ray spectral analysis (EDS) was conducted to examine the pozzolanic activity, microstructural analysis, and chemical composition. The results demonstrated that the use of SCMs along with glass powder reduce ASR expansion substantially. The binary or ternary blends of 20% replacement of glass powder, slag, or silica fume can be utilized for ASR mitigation without compromising other concrete properties. Also, the ternary system containing glass powder with other conventional SCMs performed better compared to individual use of SCMs to mitigate ASR. These results were also supported by the findings of the microstructure and chemical analysis, in which the glass powder and SCMs were found to reduce the cracks due to ASR expansion.

Efficacy of SCMs to mitigate ASR in systems with higher alkali contents assessed by pore solution method

This study demonstrates the efficacy of supplementary cementitious materials (SCMs) to mitigate alkali-silica reaction (ASR) even when used in conjunction with cement of higher alkali contents (up to 1% Na2Oeq). The expansion of concrete prisms was studied immersed in simulated pore solution in order to address the limitations of conventional ASR testing methods, accelerated mortar bar test (AMBT) and concrete prism test (CPT). Expansion results demonstrate that 25% fly ash and 50% slag are both sufficient to mitigate ASR even with cements with alkali content up to 1% Na2Oeq and that the pore solution method is a viable alternative ASR testing method. Massive amounts of ASR products (~20 μm thickness) were observed in concretes without SCMs consistent with high degree of expansion and extensive cracking. Small amounts of ASR products (≤5 μm thickness) were also observed in concrete with SCMs despite absence of significant expansion.

Rice husk ash as supplementary cementing material to inhibit the alkali-silica reaction in mortars

abstract: Alkali-silica reaction (ASR) is one of the most harmful distress mechanisms that affects the durability of concrete worldwide. Yet, it has been found that ASR-induced expansion and distress may be prevented by the appropriate use of supplementary cementing materials (SCMs). Recent studies suggest that rice husk ash (RHA), a by-product of the rice production, may present promising performances as a pozzolanic material and to enhance the durability of blended mixtures. There are many controversial studies regarding the use of RHA and how its properties directly affect the performance and durability of concretes and mortars. The present study aims to evaluate the influence of the RHA on ASR through the accelerated mortar bar test (AMBT), X-Rays Diffraction (XRD), Thermogravimetric Analysis (TG), Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscopy (SEM). To validate the obtained data, the results were compared with mortars made of a well-known SCM (silica fume) which has distinguished behaviour against ASR. The results indicate that, besides the silica fume mortars have showed better results, the use of RHA suggests promising results to mitigate the ASR, yet, further analysis on concrete prims test should be carried out to fully validate the use of RHA to enhance the durability of the concrete. The RHA finesses and its particle size were the most important properties in the SCM performance.

Parametric study and alkali–silica reactivity-induced expansion model of ASTM C 1260

ASTM C 1260 (accelerated mortar bar test (AMBT)) is the most popular and time-effective method to evaluate the alkali–silica reactivity of an aggregate. In this study, the test specimens (mortar bars) of AMBT were prepared with six aggregate groups having six different rock mineralogies (limestone, dolomite, andesite, dacite, basalt and dolomitic limestone) and three dosages of cement alkalis (0·42, 0·84 and 1·26% equivalent sodium oxide (Na2Oeq)). The bars were immersed in the three strengths (1·0, 0·5 and 0·25 N) of sodium hydroxide (NaOH) solution at 80°C and were tested for changes in length for the test duration of 98 d. This experimental study and analytical approach were used to (a) investigate the three factors of solution concentration, cement alkali and test duration of ABMT on mortar expansion, and (b) propose a model in predicting mortar expansion of each aggregate group. The study showed that the alkali solution contributed significantly to mortar expansion, followed by test duration, and then followed by cement alkali. The predicted mortar expansion evaluated by the proposed models showed a very good agreement with that obtained by the experimental procedure.

Mitigation of alkali-silica reaction by limestone calcined clay cement (LC3)

The study aims to investigate the influence of limestone calcined clay cement (LC3) on the alkali-silica reaction (ASR). Kinetics and sequence of ASR formation were monitored using the model reactant method. Accelerated mortar bar test (AMBT) was also conducted to evaluate the effect LC3 in the ASR expansion. 30 wt% replacement by flash calcined clay and limestone in binder reduced the mortar expansion lower than the limit of Australian Standard. From the model reactant method, the additional calcium rich phases in LC3 model reactant system seem to delay the ASR gel formation or produce high Ca/Si ASR products, relatively rigid C-S-H and C-A-S-H that has less expansive capability. The current results reveal the possibility to utilize model reactant experiments to monitor the formation sequence of ASR gels with the presence of calcined clay and limestone due to the consistent results observed between model reactant experiments and real LC3-based specimens.