scholarly journals RILEM TC 247-DTA round robin test: sulfate resistance, alkali-silica reaction and freeze–thaw resistance of alkali-activated concretes

2020 ◽  
Vol 53 (6) ◽  
Author(s):  
Frank Winnefeld ◽  
Gregor J. G. Gluth ◽  
Susan A. Bernal ◽  
Maria C. Bignozzi ◽  
Lorenza Carabba ◽  
...  
Keyword(s):  
Fly Ash ◽  
Round Robin ◽  
High Reactivity ◽  
Rilem Technical Committee ◽  
Alkali Silica Reaction ◽  
Experimental Conditions ◽  
Freeze Thaw ◽  
Sulfate Resistance ◽  
Durability Testing ◽  
Alkali Activated

AbstractThe RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted.

Sulfate Resistance of Alkali Activated Cements

2016 ◽  
Vol 865 ◽  
pp. 95-106 ◽  
Author(s):  
Pavlo Kryvenko ◽  
Sergii Guzii ◽  
Oleksandr Kovalchuk ◽  
Volodymyr Kyrychok
Keyword(s):  
Corrosion Resistance ◽  
Fly Ash ◽  
Protective Coatings ◽  
Resistance Coefficient ◽  
Cement Stone ◽  
Concrete Durability ◽  
Sulfate Resistance ◽  
Repair Materials ◽  
High Sulfate ◽  
Alkali Activated

One of the most important questions of concrete durability is increasing of corrosion resistance of cement stone and materials on his basis. Perspective way of solving such problems is using of alkali activated binders.Two cement systems were investigated to obtain different materials for different application - geocement system for repair materials and protective coatings and fly ash alkali activated hybrid cement for corrosion resistant common cements and concretes.It was studied sulfate resistance of fly ash alkali activated cements after 3 years of storing in aggressive environments like 5 and 10 % solutions of sodium sulfate, 2 and 4 % solutions of magnesium sulfate and sea salt solution. It was shown that fly ash containing cements are characterized by high corrosion resistance (coefficient of corrosion resistance after 3 years of storing in aggressive environment is in the ranges 0.8...1.0) comparing with clinker cements (0.45...0.88). Shown, that high sulfate resistance of cements under study in time is caused by graduate structure development and crystallization of new formations with compacting structure of material that effect on service properties of materials.High corrosion resistance of geocement compositions (coefficient of corrosion resistance 0.9-1.05) in sulfate environment is possible because of formation of faujasite, chabasite, mordenite and nozean phases in the structure of materials. Optimal composition of geocement compositions were developed according mathematical planning of experiments and tested.

scholarly journals Strength, Fracture and Durability Characteristics of Ambient Cured Alkali—Activated Mortars Incorporating High Calcium Industrial Wastes and Powdered Reagents

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1167
Author(s):  
Dhruv Sood ◽  
Khandaker M. A. Hossain
Keyword(s):  
Elastic Modulus ◽  
Fly Ash ◽  
Calcium Hydroxide ◽  
Ultrasonic Pulse ◽  
Industrial Wastes ◽  
Freeze Thaw ◽  
High Calcium ◽  
Alkali Activated ◽  
Ambient Curing ◽  
Class F

Alkali-activated mortars (AAMs) are developed incorporating binary/ternary combinations of industrial wastes comprising of fly ash class C (FA-C), fly ash class F (FA-F) and ground granulated blast furnace slag (GGBFS) with alkaline reagents and silica sand. The use of high calcium precursors, calcium-based powder form reagents, dry mixing method, and ambient curing with performance characterization based on chemical ratios and fracture properties are some novel aspects of the study. The mechanical (dry density, compressive strength, ultrasonic pulse velocity, elastic modulus, fracture/crack tip toughness and fracture energy), durability (shrinkage/expansion and mass change in water and ambient curing conditions, water absorption and freeze-thaw resistance) and microstructural (SEM/EDS and XRD analyses) characteristics of eight AAMs are investigated. The binary (FA-C + GGBFS) mortars obtained higher compressive strengths (between 35 MPa and 42.6 MPa), dry densities (between 2032 kg/m3 and 2088 kg/m3) and ultrasonic pulse velocities (between 3240 m/s and 4049 m/s) than their ternary (FA-C + FA-F + GGBFS) counterparts. The elastic modulus and fracture toughness for mortars incorporating reagent 2 (calcium hydroxide: sodium sulphate = 2.5:1) were up to 1.7 and five times higher than those with reagent 1 (calcium hydroxide: sodium metasilicate = 1:2.5). This can be attributed to the additional formation of C-S-H with C-A-S-H/N-C-A-S-H binding phases in mortars with reagent 2. Ternary mortars exhibited comparatively lower shrinkage/expansion and initial sorptivity indices than their binary counterparts due to the lower geopolymerisation potential of fly ash class F that facilitated the reduction of matrix porosity. All mortar specimens demonstrated 100% or more relative dynamic modulus of elasticity after 60 freeze-thaw cycles, indicating the damage recovery and satisfactory durability due to probable micro-level re-arrangement of the binding phases. This study confirmed the viability of producing cement-free AAMs with satisfactory mechanical and durability characteristics.

scholarly journals Durability of concrete containing ternary blends of high calcium fly ash and slag

2021 ◽  
Author(s):  
Seyon Kandasamy
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Sulfate Attack ◽  
Alkali Silica Reaction ◽  
Ternary Blends ◽  
Fresh Properties ◽  
Freeze Thaw ◽  
Salt Scaling ◽  
High Calcium ◽  
High Calcium Fly Ash

This thesis investigates the performance of ternary blends containing high calcium fly ash (HCFA) and slag against: sulfate attack, alkali-silica reaction (ASR), salt scaling, and freeze-thaw damage. In addition, compressive strength, permeability and fresh properties were evaluated. In terms of sulfate attack, the performance of HCFA was significantly enhanced when slag was added to the mix, and the same was found for ASR. The high efficacy in resisting ASR of HCFA/slag blends was found to be a result of the blends' ability to bind and retain alkalis. Regarding the salt scaling, the tested ternary concretes failed the Ministry of Transportation Ontario limit, 0.8 kg/m²; however, enhanced performance was achieved when the samples were cured by wrapping with plastic sheets. Ternary blends achieved high resistance to freezing/thawing and less bleeding compared to those of the control mix without slag or HCFA; however, setting time was dragged by about an hour.

Alkali-silica reaction in alkali-activated combined slag and fly ash concretes: The tempering effect of fly ash on expansion and cracking

2020 ◽  
Vol 251 ◽  
pp. 118968 ◽  
Author(s):  
Alexandre Rodrigue ◽  
Josée Duchesne ◽  
Benoit Fournier ◽  
Mathieu Champagne ◽  
Benoit Bissonnette
Keyword(s):  
Fly Ash ◽  
Alkali Silica Reaction ◽  
Alkali Activated

scholarly journals Durability of concrete containing ternary blends of high calcium fly ash and slag

2021 ◽  
Author(s):  
Seyon Kandasamy
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Sulfate Attack ◽  
Alkali Silica Reaction ◽  
Ternary Blends ◽  
Fresh Properties ◽  
Freeze Thaw ◽  
Salt Scaling ◽  
High Calcium ◽  
High Calcium Fly Ash

This thesis investigates the performance of ternary blends containing high calcium fly ash (HCFA) and slag against: sulfate attack, alkali-silica reaction (ASR), salt scaling, and freeze-thaw damage. In addition, compressive strength, permeability and fresh properties were evaluated. In terms of sulfate attack, the performance of HCFA was significantly enhanced when slag was added to the mix, and the same was found for ASR. The high efficacy in resisting ASR of HCFA/slag blends was found to be a result of the blends' ability to bind and retain alkalis. Regarding the salt scaling, the tested ternary concretes failed the Ministry of Transportation Ontario limit, 0.8 kg/m²; however, enhanced performance was achieved when the samples were cured by wrapping with plastic sheets. Ternary blends achieved high resistance to freezing/thawing and less bleeding compared to those of the control mix without slag or HCFA; however, setting time was dragged by about an hour.

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