scholarly journals The Effectiveness of High Quality Supplementary Cementitious Materials for Mitigating ASR Expansion in Concrete with High Alkali Content

2015 ◽  
Vol 5 (5) ◽  
pp. 854-859
Author(s):  
I. Prasetia
Keyword(s):  
Research Work ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Test Method ◽  
Supplementary Cementitious Materials ◽  
Replacement Ratio ◽  
High Quality ◽  
Thin Sections ◽  
Main Research ◽  
Mortar Bar

Alkali silica reaction (ASR) is influenced by external factors such as the surrounding environment of high alkalinity. Countries with cold climate have a high probability to be exposed to high concentrations of NaCl solution by the deicing salt. This condition will lead to serious ASR problems in concrete, if the aggregates contain reactive silica. The main research work in this paper is to investigate the effect of 15% replacement ratio of high quality fine fly ash (FA15%) and 42% replacement ratio of blast furnace slag (BFS42%) on the ASR mitigation in concrete with different alkali amount inside the pore solution. The experiments were conducted according to the accelerated mortar bars experiment following the JIS A1146 mortar bar test method. In addition, post-analysis such as observation of ASR gel formation by the Uranyl Acetate Fluorescence Method and observation of thin sections using a Polarizing Microscope were also conducted. The mortar bar tests show a very good mitigation effect of supplementary cementitious materials (SCMs). The results show that only small ASR expansions, which can be categorized as “innocuous”, occurred for specimens with 1.2% Na2Oeq using FA15% and BFS42%. However, larger alkali amount inside the system will require more SCMs amount.

Application of Modified ASTM C1260 Test for Fly Ash-Cement Mixtures

2003 ◽  
Vol 1834 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Chang-Seon Shon ◽  
Shondeep L. Sarkar ◽  
Dan G. Zollinger
Keyword(s):  
Fly Ash ◽  
Field Performance ◽  
Cementitious Materials ◽  
Rapid Identification ◽  
Test Method ◽  
Supplementary Cementitious Materials ◽  
Track Record ◽  
Alkali Aggregate Reactivity ◽  
Naoh Solution ◽  
Mortar Bar

The ASTM C1260 accelerated mortar-bar test is a commonly used method for rapid identification of potential alkali-aggregate reactivity and may also be used for assessing the effectiveness of supplementary cementitious materials in suppressing alkali–silica reactivity (ASR). A general criticism of this test method is the severity of test conditions. It is not uncommon for aggregates with a good field-performance track record and no history of ASR to test reactive by this method. The purpose of this study was to evaluate the effectiveness of fly ash in controlling expansion due to ASR, using a modified ASTM C1260 test. Three different strengths of NaOH solution were used to test reactive, potentially reactive, and nonreactive aggregates in the presence of Class F and Class C fly ash at 20% and 35% replacement by mass of cement. The other variables included high- and low-alkali cement, extended curing time, and a longer testing period of 28 days. A correlation was drawn between additional evaporable water and expansion due to ASR.

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

Modified Plasters for Restoration and Finishing Works

2014 ◽  
Vol 923 ◽  
pp. 42-47 ◽  
Author(s):  
Myroslav Sanytsky ◽  
Tetiana Kropyvnytska ◽  
Roman Kotiv
Keyword(s):  
Compressive Strength ◽  
Chemical Composition ◽  
Cementitious Materials ◽  
Quality Parameters ◽  
Supplementary Cementitious Materials ◽  
Cement Matrix ◽  
Hydration Products ◽  
High Quality ◽  
Physico Chemical ◽  
White Portland Cement

The paper is devoted to the research and development of modified plasters for restoration and finishing works based on decorative multicomponent cements containing white Portland cement and supplementary cementitious materials (silica fume, metakaolin and fine ground limestone). This cements are similar to Roman cement by their chemical composition. The use of optimal granulometry of decorative multicomponent cements provide directed formation of microstructure of the cement matrix with the formation of stable hydration products. Compositions of modified plasters by the criterions of workability and compressive strength were designed. Physico-chemical modification of plaster by complex air-entraining admixture allows to obtain high-quality modified plasters with improved quality parameters.

scholarly journals Compressive and Flexural Strength Property Enhancement for Fibre Reinforced Standard Concrete (FRSC), High Strength Concrete (FRHSC) and High Performance Concrete (FRHPC) using Foundry Sand (FS) and Crushed Concrete Waste (CCW)

2021 ◽  
Vol 2 (2) ◽  
Author(s):  
Pruthviraj S R ◽  
Ravi Kumar C M ◽  
Yajnodbhavi H M ◽  
Maruthi T ◽  
Raghavendra S
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Research Work ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Specific Test ◽  
Foundry Sand ◽  
Crushed Concrete

Now days, many research works are carried for all grades of concrete to make the concrete most economical and durable there by adding the supplementary cementitious materials and alternative replacement aggregates. In this research work deals with the experimental investigation of mechanical properties of the M30, M50 and M80 grade concrete by replacing the fine and coarse aggregate by foundry sand and crushed concrete waste respectively. Mix design procedures were followed as per IRC44:2017 guidelines and recommendation. Proper dosage of super plasticizer (SP) was maintained in the concrete to make it better performed. In this present investigation, a Poly Propylene fibre (PPF) of 0.3% by weight of the cement is used. Mechanical properties such as Compressive strength and Flexural Strength were determined by preparing the respective mould sizes for specific test and are cured for 7, 14 and 28 days and result obtained for respective days were tabulated and discussed.  

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

2021 ◽  
pp. 1-29
Author(s):  
Douglas Hooton ◽  
Benoit Fournier
Keyword(s):  
Cementitious Materials ◽  
Outdoor Exposure ◽  
Supplementary Cementitious Materials ◽  
Concrete Prism ◽  
Different Temperatures ◽  
Concrete Blocks ◽  
High Alkali ◽  
Mortar Bar ◽  
The Impact

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.

scholarly journals Efficiency Concepts and Models that Evaluates the Strength of Concretes Containing Different Supplementary Cementitious Materials

2019 ◽  
Vol 5 (1) ◽  
pp. 18 ◽  
Author(s):  
Rahul Biswas ◽  
Baboo Rai
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Research Work ◽  
Cementitious Materials ◽  
Mineral Admixture ◽  
Supplementary Cementitious Materials ◽  
Hardened Concrete ◽  
Effective Utilization ◽  
Natural Pozzolans ◽  
Quantitative Understanding

The usage of Supplementary Cementitious Materials (SCM) is very much acknowledged due to the several improvements possible in the concrete composites, and because of the general economy. Research work till date suggests that utilization of SCMs enhance a significant number of the performance characteristics of the hardened concrete. The idea of efficiency can be utilized for comparing the relative performance of different pozzolans when incorporated into concrete. The efficiency concept, which was initially developed for fly ash, can be effortlessly connected to other advantageous s as well, such as silica fume, slag and natural pozzolans. A quantitative understanding of the efficiency of SCMs as a mineral admixture in concrete is essential for its effective utilization. The paper reviews the literature pertaining to the different efficiency concepts and models present to date that evaluates the strength of concretes containing different SCMs. This short survey demonstrates that there is a need for a superior comprehension of the SCMs in concrete for its powerful usage. Also, it is an effort directed towards a specific understanding of the efficiency of SCMs in concrete.

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