Long-term alkali-silica mitigation of high-alkali concrete with cement replacements

Concrete Prism ◽

Different Temperatures ◽

Concrete Blocks ◽

High Alkali ◽

Mortar Bar ◽

The impact of high-alkali Portland cements on the prescribed level of supplementary cementitious materials required in the Canadian standard for akali-silica reaction mitigation was evaluated. Based on the results, for concretes containing aggregates exhibiting moderate reactivity, the maximum allowable cement alkali limit was raised from 1.00% to 1.15%. For all levels of aggregate reactivity, cement alkali contents could be allowed up to 1.25% provided the recommended level of mitigation by supplementary cementitious materials was increased. In the initial laboratory study, mortar bars and concrete prisms were cast and monitored using two different reactive aggregates and recommended levels of fly ash and slag. For the concrete prism tests, the alkali contents of the cements were increased to 1.25%, as per the standard, or were increased by 0.25%. Instrumented outdoor exposure concrete blocks, along with additional concrete prisms stored at different temperatures, were cast from numerous mixtures made with cement alkali equivalents ranging up to 1.22%. This paper report on the long-term performance of the prisms and concrete blocks after 12 and 27 years. The performance of the outdoor blocks is also compared to predicted performance based on the accelerated mortar bar and concrete prism test results.

Analysis of Mortar Long-Term Strength with Supplementary Cementitious Materials Cured at Different Temperatures

ACI Materials Journal ◽

10.14359/51663857 ◽

2010 ◽

Vol 107 (4) ◽

Keyword(s):

Cementitious Materials ◽

Term Strength ◽

Different Temperatures

Performance of cement mortar with waste ground clay brick

MRS Advances ◽

10.1557/adv.2018.291 ◽

2018 ◽

Vol 3 (34-35) ◽

pp. 2041-2050

Author(s):

Mohammed Si-Ahmed ◽

Said Kenai ◽

Elhem Ghorbel

Keyword(s):

Cement Hydration ◽

Thermo Gravimetric Analysis ◽

Cementitious Materials ◽

Partial Substitution ◽

Gravimetric Analysis ◽

Thermo Gravimetric ◽

Cement Production ◽

ABSTRACTAn effective way to reduce the impact of cement production on the environment is to use supplementary cementitious materials (SCM) as a partial substitution to cement. In addition to the reduction in cost and energy saving, the use of SCM in cement for the manufacture of mortar and concrete offers technical advantages. In this paper, cement was partially substituted by fines obtained from crushed recycled bricks recovered from a brick plant. The level of substitution was either 0%, 5%, 10% or 15% by weight of cement. The results show that cement substitution by brick fines resulted in a slight loss of workability with the increase of the substitution rate. Substitutions rates of 5% and 10% produced at long-term comparable strength as control mortars. The differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) results show cement hydration improved significantly with different rates of substitutions at 28 and 180 days of age.

Divergence between Performance in the Field and Laboratory Test Results for Alkali-Silica Reaction

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120913288 ◽

2020 ◽

Vol 2674 (5) ◽

pp. 120-134

Author(s):

Jussara Tanesi ◽

Thano Drimalas ◽

Krishna Siva Teja Chopperla ◽

Mengesha Beyene ◽

Jason H. Ideker ◽

...

Keyword(s):

Cementitious Materials ◽

Test Methods ◽

Long Term Results ◽

Alkali Silica Reaction ◽

Lithium Nitrate ◽

Concrete Prism ◽

Laboratory Test Results ◽

Mortar Bar ◽

Concrete Prism Test

The most common test methods used to evaluate alkali-silica reaction (ASR) are the concrete prism test (CPT) and the accelerated mortar bar test (AMBT). However, these tests were not found to be entirely reliable in predicting the performance of concrete under field conditions, especially when supplementary cementitious materials (SCMs) are used. Recently, two new test methods, the miniature concrete prism test (MCPT) and the concrete cylinder test (CCT), have been proposed but still need to be benchmarked with results from outdoor exposed blocks. In this paper, the results from the MCPT, CCT, CPT and exposed blocks are compared and their ability to properly evaluate the expected behavior of these mixtures in service with regard to ASR is discussed. Here, the results of mixtures made with four reactive aggregates: Spratt, Placitas (coarse aggregates), Wright, and Jobe (fine aggregates) and SCMs (fly ashes Classes F or C, slag cement, or silica fume) at different levels of cement replacement or lithium nitrate are presented. For these mixtures, only the MCPT was capable of properly classifying the efficiency of the ASR preventive measures, as compared with the long-term results obtained from the exposed blocks.

Long-term mechanical and shrinkage properties of cementitious grouts for structural repair

RILEM Technical Letters ◽

10.21809/rilemtechlett.2019.82 ◽

2019 ◽

Vol 4 ◽

pp. 9-15

Author(s):

Md Shamsuddoha ◽

Götz Hüsken ◽

Wolfram Schmidt ◽

Hans-Carsten Kühne ◽

Matthias Baeßler

Keyword(s):

Fly Ash ◽

Flexural Strength ◽

Cementitious Materials ◽

Response Surfaces ◽

Strength Development ◽

Structural Repair ◽

Positive Effects ◽

Micro Silica

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

Materials and Structures ◽

10.1617/s11527-021-01644-7 ◽

2021 ◽

Vol 54 (2) ◽

Author(s):

Marlene Sakoparnig ◽

Isabel Galan ◽

Florian R. Steindl ◽

Wolfgang Kusterle ◽

Joachim Juhart ◽

...

Keyword(s):

Binding Capacity ◽

Cementitious Materials ◽

Chloride Penetration ◽

Conventional Concrete ◽

Sprayed Concrete ◽

Carbonation Resistance ◽

Negative Environmental Impact ◽

The Impact ◽

Positive Effect

AbstractThe reduction of clinker use is mandatory to lower the negative environmental impact of concrete. In shotcrete mixes, similarly to the case of conventional concrete, the use of supplementary cementitious materials (SCMs) and proper mix design allow for the substitution of clinker without compromising the mechanical properties. However, the impact of the substitution on the durability of shotcrete needs to be further assessed and understood. The results from the present study, obtained from real-scale sprayed concrete applications, show a reduction of the Ca2+ leaching and sintering potential of clinker-reduced shotcrete mixes due to the presence of SCMs. This positive effect, crucial for low maintenance costs of tunnels, is mainly related to a reduced portlandite content, which on the other hand negatively affects the carbonation resistance of shotcrete. Additionally, the hydration of SCMs positively influences the chloride penetration resistance presumably due to a combination of microstructural changes and changes in the chloride binding capacity. Differences found in the pore size distribution of the various mixes have low impact on the determined durability parameters, in particular compared to the effect of inhomogeneities produced during shotcrete application.

Implementation of natural and artificial materials in Portland cement

Hemijska industrija ◽

10.2298/hemind191216014d ◽

2020 ◽

Vol 74 (3) ◽

pp. 147-161

Author(s):

Pero Dabic ◽

Damir Barbir

Keyword(s):

Portland Cement ◽

Cementitious Materials ◽

Environmental Benefits ◽

Hardened Concrete ◽

Cement Composites ◽

Artificial Materials ◽

Waste Container ◽

Almost All ◽

For the preparation of modern cement and concrete, supplementary cementitious materials (SCM) have become essential ingredients. The technical, economic and environmental advantages of using SCM have become unquestionable. The main technical reasons for their use are the improvement of the workability of fresh concrete and durability of hardened concrete. Actually, SCM affect almost all concrete properties, while environmental and economic reasons may be more significant than technical reasons. These ingredients can reduce the amount of Portland cement used in cement composites, resulting in economic and environmental benefits. In addition, many of the SCM are industrial by-products, which can otherwise be considered as waste. This paper presents a literature review of the present knowledge on the impact of natural zeolite, waste construction brick and waste container glass on physical, chemical and mechanical properties of Portland cement as the most commonly used cement in the world.

Production of Ultra-High-Performance Concrete with Low Energy Consumption and Carbon Footprint Using Supplementary Cementitious Materials Instead of Silica Fume: A Review

Energies ◽

10.3390/en14248291 ◽

2021 ◽

Vol 14 (24) ◽

pp. 8291

Author(s):

Mays A. Hamad ◽

Mohammed Nasr ◽

Ali Shubbar ◽

Zainab Al-Khafaji ◽

Zainab Al Masoodi ◽

...

Keyword(s):

Energy Consumption ◽

Silica Fume ◽

High Performance ◽

High Performance Concrete ◽

Cementitious Materials ◽

Ultra High Performance Concrete ◽

Cement Production ◽

Granulated Blast Furnace Slag ◽

The increase in cement production as a result of growing demand in the construction sector means an increase in energy consumption and CO2 emissions. These emissions are estimated at 7% of the global production of CO2. Ultra-high-performance concrete (UHPC) has excellent mechanical and durability characteristics. Nevertheless, it is costly and affects the environment due to its high amount of cement, which may reach 800–1000 kg/m3. In order to reduce the cement content, silica fume (SF) was utilized as a partial alternative to cement in the production of UHPC. Nevertheless, SF is very expensive. Therefore, the researchers investigated the use of supplementary cementitious materials cheaper than SF. Very limited review investigates addressed the impact of such materials on different properties of UHPC in comparison to that of SF. Thus, this study aims to summarize the effectiveness of using some common supplementary cementitious materials, including fly ashes (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ashes (RHA) in the manufacturing of UHPC, and comparing the performance of each material with that of SF. The comparison among these substances was also discussed. It has been found that RHA is considered a successful alternative to SF to produce UHPC with similar or even higher properties than SF. Moreover, FA, GGBS and MK can be utilized in combination with SF (as a partial substitute of SF) as a result of having less pozzolanic activity than SF.

Effects of Curing Method on Properties and Salt-Scaling Resistance of Concrete under Lab Testing

10.32920/16732855.v2 ◽

2021 ◽

Author(s):

Greg Richards ◽

Medhat Shehata

Keyword(s):

Fly Ash ◽

Cementitious Materials ◽

Alkali Concentration ◽

Salt Scaling ◽

High Calcium ◽

Curing Methods ◽

Curing Method ◽

High Alkali ◽

Scaling Resistance

This paper presents a study of the effect of curing on the salt-scaling resistance of concrete containing supplementary cementitious materials (SCMs) under lab conditions. Two curing methods were examined: moist curing and wrapping in a tight plastic sheet. Wrapping concrete slabs in plastic was adopted to represent curing methods that do not supply the concrete with additional water. The two curing methods produced different scaling results; however, the outcomes did not change in terms of meeting or failing the acceptance limit. Curing in plastic wraps produced higher carbonation depth prior to exposing the sample to the salt solution. This could have contributed, partly, to the higher scaling obtained in wrapped samples, other than the sample with 40% high-calcium fly ash. For this sample, there is evidence that curing using plastic wraps maintained high alkali concentration in the surface concrete, which could have enhanced the pozzolanic activity of the fly ash at the surface.

Pozzolanic Reaction of Supplementary Cementitious Materials and Its Effects on the Strength of Mass Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.505 ◽

2010 ◽

Vol 168-170 ◽

pp. 505-511 ◽

Cited By ~ 2

Author(s):

Hua Shan Yang ◽

Kun He Fang ◽

Sheng Jin Tu

Keyword(s):

Cementitious Materials ◽

Pozzolanic Reaction ◽

Mass Concrete ◽

X Ray Diffraction ◽

X Ray ◽

Slag Powder ◽

Phosphorous Slag ◽

Better Than

The present study aims to investigate the opportunity to largely substitute low heat Portland cement of mass concrete with supplementary cementitious materials. The pozzolanic reaction of two types of supplementary cementitious materials, phosphorous slag powder and fly ash , were determined by X-ray diffraction, differential thermal analysis–thermogravimetry and scanning electron microscopy from 28 to 90 days. The properties of mortar and mass concrete containing 30% of supplementary cementitious materials were also investigated. Results showed that supplementary cementitious materials could decrease the amount of calcium hydroxide, fill the capillary pores, thus making the mortar and mass concrete more compact and durable. Long-term strength of mass concrete containing 30% of supplementary cementitious materials were comparable (or even better) than the control concrete (without supplementary cementitious materials) at constant workability, while the Young’s modulus was lower than the control concrete.

Long-Term Mechanical Properties of Fiber Reinforced Polymer Bars Exposed to Alkali Environment: Experimental Investigation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.722.27 ◽

2016 ◽

Vol 722 ◽

pp. 27-32

Author(s):

František Girgle ◽

Lenka Bodnárová ◽

Anna Matusikova ◽

Vojtěch Kostiha ◽

Jan Prokeš ◽

...

Keyword(s):

Mechanical Properties ◽

Concrete Structures ◽

Steel Reinforcement ◽

Advanced Composite Materials ◽

Long Time ◽

Frp Reinforcement ◽

High Alkali ◽

The Impact ◽

Whole Life Cycle

This paper deals with actual issues concerning the design and the utilization of modern composite reinforcement (FRP) in concrete structures. These advanced composite materials are, especially if the whole life cycle of the structure is considered, gradually becoming a convenient alternative to ordinary steel reinforcement. The structure reinforced with FRP reinforcement (as well as the structure reinforced with steel reinforcement) has to be designed with regard to sufficient endurance, serviceability and durability. The long-term material properties of FRP reinforcement embedded in concrete, which are influenced by temperature, load magnitude and ambient environment, must be considered during design of the structure. A high alkali environment of concrete with pH higher than 12.0 acts mainly on glass fibres which degrade and their mechanical properties are reduced consequently. The used matrix creates a barrier which insulates the bearing fibres against alkali ions attack. The main objective of the paper is therefore to describe behaviour of composite as a whole. The experimental approach and results which were reached during the tests are also presented. An effort was to specify the impact of alkali environment on the long-time properties of developed reinforcement which could be used in durable concrete structures.