Effects Of Alkali-silica Reaction Research Articles

Effect of alkali silica reaction on the performance of hooked bars

The Alkali-silica reaction (ASR) is a deterioration phenomenon that causes undesirable expansion and cracking in hardened concrete. This reaction usually occurs between certain types of reactive aggregates and high-alkali cement and is reported in a notable number of reinforced concrete (RC) structures worldwide, for which assessing the residual performance is critical. Many of these structures employ hooked bars to provide anchorage, especially in their joint regions. This paper examines the pull-out behavior of hooked bars in RC beam-column joints affected by ASR to help assist with safety evaluation of RC structures impacted by this reaction. A set of 7 full-scale RC columns was fabricated with concrete containing reactive fine aggregates, which incorporated different hooked bar diameters and amounts of transverse reinforcement. The specimens were subjected to pull-out of their hooked bars either in control conditions or after curing in a relative humidity of 100 % and a temperature of 50°C for up to 303 days to achieve different levels of ASR-induced expansions. Results showed that up to an unrestrained uniaxial expansion level of 0.2 %, the ASR-affected hooked bars showed an increase by up to 22 % in their ultimate pull-out capacity but a notable reduction in their ductility. Despite distributed cracking in ASR-affected specimens, their failure mode was relatively similar to that in the control specimen and remained a combination of side and front failure.

Effect of alkali-silica reaction on the flexural behavior of beams with tensile lap splices

A series of 19 beam specimens, with varying stirrup spacing and tensile lap splice lengths, were tested at the National Institute of Standards and Technology (NIST) under four-point loading to investigate the impact of alkali silica reaction (ASR) on the flexural strength and bond behavior of reinforced concrete members. The beams contained highly reactive aggregates, were cured in an environmental chamber at high relative humidity and temperature, and were tested in batches at regular intervals in time. The development of strains in the deformed bar reinforcement was monitored in five beam specimens to provide an assessment of the level of ASR expansion achieved prior to testing. The strain development in the tensile reinforcement bars and stirrups was generally similar between the specimens, despite differences in stirrup spacing and lap splice length. Strains in the transverse stirrups due to ASR-induced expansion at the time of testing were roughly twice the strains recorded in the longitudinal tensile reinforcement, reaching a maximum value of approximately 0.002 mm/mm prior to testing. The concrete mixture studied exhibited expansions in the range of 0.2% and the tested beams exhibited randomly oriented surface cracking with no localized spalling or general loss of section at the time of testing. The effects of ASR included reductions in the compressive strength and modulus of companion cylinders of up to 15% and 50%, respectively. A rigorous statistical analysis of the measured data was performed to quantify the influence of ASR-induced expansion, splice length, and stirrup spacing on the beams’ flexural capacity and the maximum achieved average bond strength. Results indicated that in the range of expansions, stirrup spacings, and lap splice lengths studied, there was no evidence that the moment capacity or the maximum average bond strength was reduced by the effects of ASR. Tested beams constructed with ACI 318 code compliant splice lengths achieved or exceeded the nominal flexural strength of the section, regardless of the degree of ASR-induced expansion observed.

The Effect of Alkali-Silica Reaction (Asr) on the Mechanical Properties of Concretes Containing Trass

The Effect of Alkali-Silica Reaction (Asr) on the Mechanical Properties of Concretes Containing Trass

Time-Dependent Deformation of a Concrete Arch Dam in Thailand - Numerical Study on Effect of Alkali Silica Reaction on Deflection of Arch

Time-Dependent Deformation of a Concrete Arch Dam in Thailand - Numerical Study on Effect of Alkali Silica Reaction on Deflection of Arch

Effect of ASR expansion on mechanical properties of concrete

In this experimental study the effect of alkali silica reaction [ASR] on the mechanical properties of concrete namely compressive strength, fl exural strength, splitting tensile strength, modulus of elasticity and pull-out strength is presented. The effect of the specimens’ geometry on ASR expansion has also been studied. The results confirm that ASR expansion of over 0.04% causes significant losses in the mechanical properties of concrete, albeit at differing rates. Moreover, this study proves that the specimen geometry has an important role on ASR expansion rate.

A study on ASR mitigation by optimized particle size distribution

In this study, the effect of alkali-silica reaction on binary cementitious composite systems incorporating fly ash or slag having optimized particle size distribution has been investigated. Specimens have been exposed to ASR effect according to ASTM C227 and ASTM C1260 methods. Test results, which were conducted after ASR exposure, have been discussed in terms of use of additive having optimized particle size distribution. The characterization of specimens was investigated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopic analyzer (EDS), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis instrument (TGA). As a result of the experimental program, it was seen that the ASR effect is reduced with fly ash and slag replacement. Even, fly ash addition has been more effective than slag addition in reducing the ASR effect for the same additive ratio. In addition, addition of fly ash and slag with optimized particle-size distribution were found to be more effective in reducing the ASR effect as compared to addition of fly ash and slag without optimized particle-size distribution.

<b>Effect of Alkali-silica Reaction on Delayed Ettringite Formation in Concrete</b>

<b>Effect of Alkali-silica Reaction on Delayed Ettringite Formation in Concrete</b>

Comparison of short- and long-term ASR test methods on cementitious composites

Concrete has a significant place in construction structures, is a material that can be easily damaged due to incorrect design, incorrect material selection. Concrete may be damaged by physical and chemical factors. One of these factors is the alkali-silica reaction (ASR). ASTM C1260, is a short-term test method, and ASTM C227, is a long-term test method, are used to measure effect of alkali-silica reaction. In this study, the effect of fly ash additive use with 0, 5, 10, 15, and 20 wt.% replacement of cement was investigated in short- and long-term ASR test methods. For this purpose, while samples prepared for ASTM C1260 were kept in NaOH solution 14-days, samples prepared for ASTM C227 were waited 360-days in normal water solution. As a result; mortar bars with 20% fly ash additive ratio were classified as harmless for ASR in both test methods.

Effects of alkali-silica reaction on mechanical behavior of four-pile caps

ABSTRACT: The structural behavior resulting from alkali-aggregate reactions on four-pile caps was numerically studied using software based on the Finite Element Method. The cracking was analyzed in terms of reduction rates in the mechanical properties of the concrete (compressive strength, tensile strength and modulus of elasticity) as a consequence of the expansion induced by the alkali-aggregate reaction (AAR) referred to in the literature. One option for dealing with changes in mechanical properties, reported as influenced by the reactive aggregate type, environmental conditions and stress state, is to directly use the value of the properties of the material tested in the analysis, an approach adopted in the study and implemented in the analysis. From the results found in the analysis program the three main effects of AAR could be better understood: expansion, cracking and degradation of mechanical properties of concrete.

Effect of alkali-silica reaction on the fracture properties of confined concrete

Alkali-silica reaction (ASR), which was recently discovered in nuclear power plant structures commonly without shear reinforcement, has previously been shown to induce anisotropic expansion in confined concrete. The fracture properties (strength, stiffness, and specific fracture energy) of ASR-induced anisotropically-damaged concrete specimens were quantified by varying both the damage level and relative direction of the ASR-induced cracking orientation against the loading direction corresponding to the fracture propagation. The effect of different orientations (0, 45, and 90° relative to the notch of the specimen) of expected ASR-induced cracks on the fracture properties was investigated using a wedge-splitting test (WST). Specimens without ASR expansion generally showed the highest fracture properties; however, the specific fracture energy was highest for ASR-affected specimens in which the expected orientation of ASR-induced cracks was perpendicular to the WST specimen notch. Specimens in which the ASR-induced cracks were parallel to the notch exhibited the lowest strength and fracture energy.

Investigation of the effect of alkali silica reaction (ASR) on properties of concrete pavement admixed with cow bone ash (CBA) by electrical resistivity test

The use of concrete in road pavements construction in view of its durability and cost effectiveness over time have gained momentum. Cement concrete pavements however suffer deterioration due to Alkali-Silica Reaction (ASR). This study therefore investigates the use of Cow Bone Ash (CBA) in mitigating the effect of ASR using electrical resistivity test (schlumberger array probe method). The results are then compared with American Society for Testing and Materials (ASTM) standards and relevant literatures. The result of the study showed that the average resistivity at 0%, 5%, 10%, 15%, 20% and 30% CBA replacement are 298.87 Ωm, 306.23 Ωm, 215.02 Ωm, 489.31 Ωm, 382.34 Ωm and 272.53 Ωm respectively. This indicates that the peak resistivity is obtained at 15% CBA replacement which is the optimal replacement level for ASR inhibition in the concrete. The result also shows that the concrete samples are corrosion free with the least resistivity value on the 7th day at 30% CBA addition (163.03 Ωm) and the maximum value at 20% CBA addition on the 56th Day (1069.54 Ωm). The study concluded that ASR and reinforcement corrosion can be effectively controlled between 15% and 20% cement replacement by CBA in concrete/rigid pavements.

Hydro-Thermo-Mechanical Analysis of an Existing Gravity Dam Undergoing Alkali–Silica Reaction

The alkali–silica reaction is a chemical phenomenon that, by inducing expansion and the formation of cracks in concrete, can have a severe impact on the safety and functioning of existing concrete dams. Starting from a phenomenological two-phase isotropic damage model describing the degradation of concrete, the effects of alkali-silica reaction in an existing concrete gravity dam are evaluated and compared with real monitoring data. Considering the real temperature and humidity variations, the influence of both temperature and humidity are considered through two uncoupled diffusion analyses: a heat diffusion analysis and a moisture diffusion analysis. The numerical analyses performed with the two-phase damage model allow for prediction of the structural behaviour, both in terms of reaction extent and increase of crest displacements. The crest displacements are compared with the real monitoring data, where reasonably good agreement is obtained.

Effects of Alkali-Silica Reaction on Concrete Squat Shear Walls

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Effect of alkali silica reaction on the mechanical properties of aging mortar bars: Experiments and numerical modeling

Alkali silica reaction and its effect on concrete and mortar have been studied for many years. Several tests and procedures have been formulated to evaluate this reaction, particularly in terms of aggregate reactivity. However, the data given in the literature concerning the mechanical properties of concrete and mortar are scattered and very little information is available for some properties such as fracture energy. In this study, the mechanical behavior of mortar was evaluated and monitored, under normal and accelerated environmental conditions. Fracture energy, compressive strength and tensile strength were measured for mortar specimens, casted with highly reactive Spratt crushed aggregate, at two different storage temperatures (23℃ and 80℃) and at two different alkali concentrations (immersed in water and in 1 N NaOH solution). Moreover, free expansion tests (according to ASTM C1260) and petrographic observations were performed, in order to relate them to the evolution of the mechanical properties of mortar. Results show a decrease of the mechanical properties associated with specimens at 80℃ in alkali solution and that the deterioration due to alkali silica reaction is counter-balanced by the strengthening of mortar resulting from the hydration process. A multi-physics computational framework, based on the Lattice Discrete Particle Model is then proposed. Numerical simulations based on a complete calibration and validation with the obtained experimental data capture the behavior of mortar subjected to the complex coupled effect of strength build-up and alkali silica reaction at different temperatures and alkali contents.

Effects of alkali-silica reaction on a hydropower structure after 50 years of ongoing deterioration

The Nalubaale hydropower station was constructed between 1949 and 1954. Deterioration of the powerhouse structure was first noticed in 1964 when hairline cracking in the generator floor started to appear. The cracking progressively continued resulting in degradation of the generator floor, upper gallery and structural frame of the powerhouse. It was not until 1990 that alkali-silica reaction (ASR) in the mass concrete elements was identified to be the root cause of the deterioration. The condition of the powerhouse structure was reassessed in 2015 25 years after the investigations in 1990. The assessment comprised the determination of the concrete properties 50 years after ASR had initiated and a comprehensive evaluation of instrumentation data was undertaken to identify the effects of ASR on the powerhouse structure. This paper presents the findings of the condition assessment and provides an update on the concrete properties after more than 50 years of ongoing ASR. It also provides an assessment of the residual life of the structure and proposes rehabilitation methods to control the effects of ASR.

The effects of alkali-silica reaction on the mechanical properties of concretes with three different types of reactive aggregate

The effects of alkali-silica reaction on the mechanical properties of concretes with three different types of reactive aggregate

Modelling of Alkali-Silica Reaction Effects on Mechanical Property Changes of Concrete

Alkali-silica reaction (ASR) is a chemical reaction in concrete that alkalis in cement react with reactive silica in aggregate in the presence of water. When ASR takes place, it produces gels that absorb water and expand. Swelling of ASR gels can damage concrete and cause cracking and volume expansion in concrete structure. In this paper, mechanical consequences of ASR on concrete are simulated by a finite element (FE) analysis. An FE model of concrete is built. The evolution of concrete mechanical properties subjected to ASR is achieved by FE analyses. The constitutive model of concrete is attained via the FE analysis. A case study is used to demonstrate the proposed method. The simulated results using the proposed model are in good agreement with the observations of concrete with ASR reported in the literature. The results can be used for a basic research to enhance durability of concrete slab tracks and concrete railway sleepers.

The Effects of Alkali Silica Reaction (ASR) towards Fly Ash Based Geopolymer Concrete

Alkali Silica Reaction (ASR) is a physiochemical reaction which affects the strength and durability of concrete. ASR occurs due to a chemical reaction between alkali oxides presents in the cement paste and reactive silica in aggregate. This reaction could lead to the volume expansion, cracking, loss of strength and potential failure of the concrete. This research aimed to investigate the potential alkali silica reactivity on geopolymer concrete. Specimens were prepared using Class F fly ash as binder while sodium hydroxide and sodium silicate as alkaline activators. ASTM C1260 was adopted to determine potential alkali silica reactivity by measuring the length change of mortar bar as well as the decrease in compressive strength test. Results show that fly ash based geopolymer concrete is less vulnerable to ASR as the expansion of mortar bar is below the threshold of ASTM standard limit which is 0.10% of expansion. This test ensures that the durability of geopolymer concrete is excellent and can withstand a long life span.

Alkali-Silica Reaction in Concrete Engineering Suppression Measures of Inquiry

Local materials was used as raw materials in the test. Test methods are standard test methods. It compared the use of fly ash alone or lithium hydroxide used alone inhibited the effect of alkali-silica reaction, and to a certain percentage of fly ash and lithium hydroxide complex joint effect of inhibiting alkali-silica reaction in the test. The results showed that compound admixtures overcome the shortcomings of the use of fly ash alone or lithium hydroxide inhibition of alkali-silica reaction. It can achieve the goal of complementary advantages.

Investigation of polypropylene fiber effect to the silica fume concrete

Some of the characteristics of concretes of a variety of mineral additives to improve and participate in threads.The optimum amount of heat of hydration to reduce the addition of silica fume concrete, high strength and low permeability to provide the target, the effect of alkali-silica reaction and sulfate provides many benefits like getting under control. Optimum silica fumes may be added to concrete, high strength and low heat in the hidratasyon destination, alkali silica reaction and to provide permeability under control provides many benefits such as receiving the effect of sulfate. Search surface area silica fumes contribution aggregates-paste without spaces and more than high strength concretes. However, there are also negative effects such as silica exposure by being streamed. The amount of the relative values of these effects optimum silica smoke and cement, aggregates, is determined based on the type and quantities such as the terms of maintenance with plasticizer additive factors are also affected. Polymer fibers, giving the best results and to participating in, and the most widely used polypropylene fiber blends. Polypropylene fiber concrete in three dimensions by creating a micro accessory network, reduce the deficit and the presence of natural concrete to be pumped some properties. In this study, exposure to silica, which is a waste material in theindustrial field on theproperties of concrete betonunda and silica exposure by joining concrete to improve the effects of the adverse effects on properties of polypropylene fiberconcrete.