alkali content of concrete mix water and aggregates
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Alkali Content of Concrete Mix Water and Aggregates

2019-4-22  Alkali Content of Concrete Mix Water and Aggregates Introduction Alkali silica reaction (ASR) is a chemical reaction between some types of aggregate and the highly alkaline pore water present in all Portland cement concretes. When the concrete contains sufficient moisture, alkalis and reactive aggregate the reaction produces

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CONCRETE TECHNOLOGY Diagnosis and Control of

2014-9-29  • In many concrete mixtures, the alkali content of the concrete is low ... aggregates, admixtures, and mix water.When the alkali and silica react, they form the gel reaction product. External alkalies can come from a number of sources, but the predominant source is anti-icing or deicing chemicals. Exact composition

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Alkali Aggregate Reaction in Concrete - Types, Causes, and ...

2019-7-16  Alkali aggregate reactions (AAR) occur when aggregates in concrete react with the alkali hydroxides in concrete producing a hygroscopic gel which, in the

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Properties of alkali-activated concrete (AAC ...

2021-7-15  dissolved in 1000 ml of water. Alkaline solution was prepared by mixing determined quantities of NaOH solution and Na 2SiO 3 solution, 1 h before the production mix. Concrete mixtures were prepared in a pan mixer. Prior to mixing, all the aggregates were kept in

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Evaluation of alkali-silica reaction in recycled ...

Three CPT mixes were produced to compare with ASTM C 1260 results, all using CEM I 42.5R: one with CRA-Rna, one with CRA-Raa and another with CNA-R. NaOH was added to the mixing water of CPT mixes in order to adjust the alkali content to 1.25% (by cement wt.), according to RILEM AAR-3 . An innocuous non-reactive fine NA (FNA-NR) was used in the ...

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Design and properties of seawater coral aggregate alkali ...

2021-8-2  Design and properties of seawater coral aggregate alkali-activated concrete, Journal of Sustainable Cement-Based Materials, DOI: 10.1080/21650373.2021.1913659 To link to this

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Assessment of Alkali-Silica Reactivity of Aggregates by ...

A new accelerated concrete prism expansion test at 38 °C (accelerated CPT) is proposed for assessing the alkali-reactivity of concrete aggregates. In this test, concrete prisms with a standardized mix composition and different alkali contents are immersed in alkaline solutions with compositions simu

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Aggregate Reaction - an overview ScienceDirect Topics

Mark G Alexander, in Developments in the Formulation and Reinforcement of Concrete (Second Edition), 2019. 4.1 Introduction. Alkali– aggregate reaction (AAR) 1 is a chemical reaction between alkalis in the concrete and reactive components of the aggregates. It was first observed in the United States in the 1920s and initially researched by Stanton in 1940. AAR is a type of internal chemical ...

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THE ALKALI- SILICA REACTION: A STUDY OF REACTIVE ...

2019-2-2  THE ALKALI- SILICA REACTION: A STUDY OF REACTIVE AGGREGATES AND PRODUCTION OF EXPANSIVE CONCRETE SPECIMENS By : Thesis directed by : ROBB SPARKS. PROF. VICTOR E. SAOUMA. 15 th April, 2016. University of Colorado, Boulder

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THRESHOLD ALKALI CONTENTS FOR EXPANSION OF

this article investigates the threshold alkali contents for expansion of concretes containing certain british aggregates. the concretes investigated were all of constant mix proportions, with water/cement ratio of 0.5; aggregate/cement ratio of 4.6, and cement content of 400 kg/cubic metre.

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Alkali-Aggregate Reaction - cement

Alkali-silica reaction (ASR) is of more concern because aggregates containing reactive silica materials are more common. In ASR, aggregates containing certain forms of silica will react with alkali hydroxide in concrete to form a gel that swells as it adsorbs water from the surrounding cement

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Alkali-Aggregate Reaction in Reinforced Concrete ...

5. The alkalis in the concrete come mainly from the cement. An effective means of reducing the risk of AAR includes proper control on the amount of cement used in the concrete mix, use of a low alkali cement, and appropriate use of cement replacement such as pulverised fuel ash (PFA). 6. In 1992, a programme of studies on AAR was started by the Public Works Laboratories of the Hong Kong ...

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Aggregate Reaction - an overview ScienceDirect Topics

Mark G Alexander, in Developments in the Formulation and Reinforcement of Concrete (Second Edition), 2019. 4.1 Introduction. Alkali– aggregate reaction (AAR) 1 is a chemical reaction between alkalis in the concrete and reactive components of the aggregates. It was first observed in the United States in the 1920s and initially researched by Stanton in 1940. AAR is a type of internal chemical ...

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INVESTIGATION OF ALKALI THRESHOLD LIMITS AND

2019-10-22  AAR-3.2 (Nixon Sims 2016b) with an additional alkali content of 5.25 kg/m3 incorporated into the test programme to mimic the 1.25% alkali content used in AS 1141.60.2. These alkali contents were achieved by adding high purity NaOH to the concrete mix water. Due to the longer timeframe required to undertake CPT at 38°C (12 months), AS 1141.60 ...

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(PDF) Alkali-Aggregate Reaction (AAR) of Concrete ...

Alkali-Aggregate Reaction (AAR) of Concrete Structures Outline • What is AAR? ... Sub-Committee under SCCT was set up • Hong Kong Specification • WBTC 14/94 issued 3 Kg/m³ limit on reactive alkali content in concrete • Quality Scheme for the Production and Supply of Concrete (QSPSC) Cl. 7.1.1(e) Use of chemical method ASTM C289 ...

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Alkali Release from Aggregates in Long-Service Concrete ...

This paper proposes a simple model for predicting the development of deleterious expansion from alkali-silica reaction (ASR) in long-service concrete structures. This model is based on some composition and reactivity parameters related to ASR, including the long-term alkali contribution by aggregates to concrete structures. This alkali

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B-TC 106-3-Detection of potential alkali-reactivity of ...

2006-8-4  CONCRETE MIX DESIGN ANNEX For aggregates with a 'normal' density (approxi- (comments relate to clauses as numbered in the method) mately 2.6 to 2.75), the weight proportions below will give a close approximation to the volume proportions in clause 6: A4.1 Moulds cement content 440 kg/m 3 free (effective) water content 200 kg/m 3 The use of ...

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ALKALI-SILICA REACTIVITY OF PORTLAND-COMPOSITE

2019-2-23  limiting the effective alkali content in the cement and concrete; use of supplementary cementing materials (fly ash, slag, etc.) in the cement or as an addition; verification of the suitability of a concrete mix in a performance test. The concrete aggregates from the Lithuania gra-vel deposits contain about (2 - 4%) reactive silica mi-

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Alkali Silica Reactivity - TechConsults

2020-5-9  Introduction– Alkali-silica reactivity (ASR) is an expansive reaction between reactive forms of silica in aggregates and potassium and sodium alkalis, from cement, aggregates, admixtures water (moisture), and pollution of land, air, water (environmental degradation) ASR is considered as “concrete cancer”, as it crawls slowly inside the poured and hardened concrete, and mat take 10years ...

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THRESHOLD ALKALI CONTENTS FOR EXPANSION OF

this article investigates the threshold alkali contents for expansion of concretes containing certain british aggregates. the concretes investigated were all of constant mix proportions, with water/cement ratio of 0.5; aggregate/cement ratio of 4.6, and cement content of 400 kg/cubic metre.

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Sess ion A 7: ALKALI -AGGREGATE REACTIONS 161

2017-8-17  due to an increase in alkali content in the concrete. Key words : Alkali-silica reaction, aggregate, alkali content, durability. 1. INTRODUCTION. ASR is a complex physical and chemical reaction between water, alkali in the concrete pore solution and reactivesilica minerals in aggregates [1]. The reaction demands an alkaline environment which is ...

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EVALUATION OF ALKALI-SILICA ... - Home ICAAR

2020-11-6  a high-alkali cement content of 420 kg/m3 and a water-to-cement ratio of 0.45. In order to accelerate the ASR reaction in concrete prisms, the alkali content of the concrete mixture was boosted up to 1.25% Na2Oeq. by weight of portland cement by adding reagent grade NaOH pellets into the mix water. Also, to avoid alkali

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Quality of Water for Concrete - CivilWeb Spreadsheets

Quality of Recycled Water Used in Concrete. Water recycled from the processing of returned concrete, wash water and rain water harvested at the concrete plant can be used as mixing water so long as it meets the requirements of BS EN 1008. One method of reclaiming water and aggregates from returned concrete is shown in the below diagram.

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THE ALKALI- SILICA REACTION: A STUDY OF REACTIVE ...

2019-2-2  THE ALKALI- SILICA REACTION: A STUDY OF REACTIVE AGGREGATES AND PRODUCTION OF EXPANSIVE CONCRETE SPECIMENS By : Thesis directed by : ROBB SPARKS. PROF. VICTOR E. SAOUMA. 15 th April, 2016. University of Colorado, Boulder

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Mix-design and Properties of Mortars from Alkali-activated ...

2020-11-20  Alkaline Activators. The sodium silicate solution used was a viscous liquid produced for the cement industry with a water content of 56 wt%, the SiO 2 /Na 2 O oxide composition ratio of 2.07 and a density of 1.53 g/cm 3.An 8 M water solution of sodium hydroxide was used.

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Strength and Durability Evaluation of Recycled Aggregate ...

2015-5-14  The concrete mixes had the same water to cement ratio (w/c) and cement content. Several mixes were prepared utilizing four grades, grades 1, 2, 4, and 5 of the recycled aggregate. Mixes were identified according to the grades used in each mix, for example, Mix 1,2,5 indicates that grade 1, grade 2 and grade 5 were used in that mix.

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Research Article The Effect of Variation of Molarity of ...

2019-7-31  proportions of ne aggregate contents. e measurements of N-sand, M-sand, and QD used in the mixtures are given in Table . e binder was mixed with the ne aggregates at slow speed ( ± r/min) in the mixture. e alkaline activator was then added with binder and ne aggregates. e addi-tional water was gradually added to the mixture for good workability.

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RILEM Recommended Test Method: AAR-4.1—Detection

2015-10-1  The amount of water added to the mix to achieve the prescribed free water content of 220 kg/m 3 is then calculated, taking into account both the water absorption and the measured water content of the fine and coarse aggregates. The water absorptions of most fine aggregates will be less than the intended water content (i.e. 5 ± 2 %).

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The Effect of Variation of Molarity of Alkali Activator ...

The effect of molarity of alkali activator, manufactured sand (M-sand), and quarry dust (QD) on the compressive strength of palm oil fuel ash (POFA) and fly ash (FA) based geopolymer mortar was investigated and reported. The variable investigated includes the quantities of replacement levels of M-sand, QD, and conventional mining sand (N-sand) in two concentrated alkaline solutions; the ...

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