However, as most of other alkali activated cements, alkali activated phosphor slag cement is with much lager shrinkage than portland cement, which will result in cracking of cement paste and concrete, and is one of the main barriers for their wide application 14. Using eccentrically sample to find the relationship. All relevant mechanical properties of alkaliactivated concrete will be considered, like compressive strength and softening behaviour, tensile strength, flexural strength, elastic modulus, bond behaviour, shear strength, tension stiffening, creep, drying shrinkage, autogeneous shrinkage, restrained shrinkage and early age cracking. Using eccentrically sample to find the relationship between. Cracking tendency of alkaliactivated slag concrete. Durability assessment of alkali activated slag aas concrete. Compressive strength, tensile strength, and drying shrinkage of alkali activated slag paste and mortar were measured with various liquid slag ratios, sand slag ratios, curing ages, and curing temperatures. Drying shrinkage of alkali activated slag concrete aasc can be 1. Heat progression in aasf systems was characterized by means of isothermal calorimetry. Corrosion of reinforcing bars embedded in alkaliactivated. In this study, the effect of restrained shrinkage cracking on the chloride penetration of high. Ordinary portland cement opc was also tested for comparative purposes and exposed to the same solution.
Magnesia modification of alkaliactivated slag fly ash cement. Cracking tendency of alkaliactivated slag concrete subjected. The high drying shrinkage of aasc, which translates into a greater cracking tendency than ordinary portland cement concrete opcc, is not reported in the literature. However, the cracking tendency of aasc under drying conditions, when restrained, is. The objective of employing the escf is to give a new method determining cracks of concrete at early age. The concrete itself must be properly proportioned, and properly mixed. The aim of this study is to investigate the strengths and drying shrinkage of alkali activated slag paste and mortar. The effect of the curing temperature and naoh content on cracking tendency and compressive strength for naoh slag geopolymers is reported in relation to 29si and mas nmr structural analyses and xrd phase quantitative analysis. Shrinkage performance of fly ash alkaliactivated cement. Read durability assessment of alkali activated slag aas concrete, materials and structures on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The aim of this study was to determine the effects of partial fly ash substitution in to a series of alkaliactivated concrete based on a highmgo blast furnace slag bfs. Alternative concrete based on alkaliactivated slag. Cracking tendency of alkali activated slag concrete subjected to restrained shrinkage frank collinsa, j.
Investigation of high performance concrete containing slag under restrained shrinkage conditions. Cracking tendency of alkaliactivated slag concrete 1. Influence of activator on the strength and drying shrinkage. Ringtype tests were performed for studying restrained shrinkage cracking of highperformance concrete.
The development of cracks due to a restrained shrinkage is studied using ring tests. This is due to the evaporation of excess mixing water. Significant drying shrinkage is one of the main limitations for the wider utilization of alkaliactivated slag aas. The shrinkage of concrete pulls the slab apart showing it as cracks on surface. Wei and hansen studied the early age strainstress development in uniaxially restrained cement pastes and concretes with a specially designed testing frame 38. Cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage. However, these studies were mainly focused on sra based on polypropylene glycol, while as it is shown in this paper, the behavior of sra based on 2.
Effect of polypropylene fiber on properties of alkali. Assessing the autogenous shrinkage of alkaliactivated slag. The concrete prepared using alkali activated cement has low tendency to bleeding and higher resistance to plastic shrinkage, also, the viscosity and yield stress of the alkali activated cement paste were relatively higher when compared to those of ordinary portland cement paste. The cracking time of all the samples occurred within a reasonable experimental period thus the novel plastic ring is a convenient method for predicting concretes crack potential. Aasc has lower elastic modulus, higher creep, and higher tensile strength than opcc, and the combined effects of these can affect the cracking tendency of aasc. Jul 07, 2015 all results were compared to those obtained for a control opc mortar. Alkali activated slag concrete aasc has higher drying shrinkage than ordinary portland cement concrete opcc. However, the cracking tendency of aasc under drying conditions, when restrained, is unreported. Jan 01, 2020 alkali activated slag aas is one of the most important cementitious materials which is made by slag and alkaline activator completely replacing the cement. Effects of dosage of alkaliactivated solution and curing. The results indicate that the setting time of this cement is similar to that of the ordinary commercial cements. A total of 6 mixtures were tested under both shrinkage tests.
Vzorky, jez byly v pr b hu zrani pono eny ve po celou dobu ve vod. Cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage, cement and concrete research, 30 2000 791798. Some issues of shrinkagereducing admixtures application in. Oct, 2016 consequently, restrained shrinkage crack and setting time results demonstrated that c50 set and cracked the earliest. Effectiveness of fly ash on the restrained shrinkage cracking. The effect of ground granulated blast furnace slag slag. Restrained shrinkage cracking that appears on concrete surfaces during construction, or while concrete in the curing process adversely affect the longterm durability and other performance attributes of concrete basedinfrastructures. Strength and durability properties of alkali activated slag. Oct 01, 2012 read effects of dosage of alkaliactivated solution and curing conditions on the properties and durability of alkaliactivated slag concrete, construction and building materials on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Steel bar embedded in an alkali activated slag aas concrete was tested under complete immersion, in 3. Cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage collins, frank and sanjayan, jg 2000, cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage, cement and concrete research, vol.
The free shrinkage from casting to 400 days of aging of four sccs mixtures based on cem i 52. Based on the literature, the main causes of shrinkage cracking and mitigation strategies were identified. Influence of treated mud on free shrinkage and cracking. Among aas concrete, sc8 exhibited lowest drying shrinkage 320 micro strain but exhibited high shrinkage than opc control mix cm2 270 micro strain and lower shrinkage than opc slag blended mix slg60, which is in agreement. Concrete slabs can shrink as much as 12 inch per 100 feet. Crack width of highperformance concrete due to restrained. Over the last two decades, engineers have developed and introduced high performance concrete hpc to enhance the strength and durability aspects of concrete structures. Sodium silicate and sodium carbonate were used as alkali activators. The results indicated that increasing the proportion of slag led to improvements in the. Cracking and mechanical strength of naoh slag geopolymers.
Alkali activated slag mixtures with comparable strength to opc show a higher autogenous and drying shrinkage. Read influence of activator on the strength and drying shrinkage of alkaliactivated slag mortar, construction and building materials on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Alkaliactivated slag concrete aasc has higher drying shrinkage than ordinary portland cement concrete opcc. Cracking and mechanical strength of naohslag geopolymers. Aasc, however, has lower elastic modulus, higher creep, and higher tensile strength than opcc, and these combined effects can reduce the cracking tendency. Some of those researchers followed the standard procedure for the determination of cementitious materials crack prediction due to restraint as provided under aashto specification 1997 12. Numerical modeling of alkaliactivated slag concrete beams subjected to restrained shrinkage article in aci structural journal 975. Aasc, however, has lower elastic modulus, higher creep, and higher tensile strength than opcc, and the combined effects of these can reduce the cracking tendency. The purpose of this study is to investigate the autogenous shrinkage of alkali activated slag fly ash aasf mortar blends. Slag also known as groundgranulated blastfurnace slag is a byproduct of the blast furnace ironmaking process, and most of the slag is disposed at the landfill 24.
Some issues of shrinkagereducing admixtures application. The cracking of early age concrete was normally caused by the coupled effects of autogenous shrinkage, drying shrinkage and thermal deformation. Concrete shrinkage can be defined as the deformation of a concrete element that is not subjected to any external mechanical stress in a constant thermodynamic environment. Strength and drying shrinkage of alkaliactivated slag paste. This study investigates the effects of earlyage surface cracking on restrained shrinkage concrete made of alkali activated cement. Numerical modeling of alkaliactivated slag concrete beams. Cracking tendency of alkali activated slag concrete subjected to restrained shrinkage collins, frank and sanjayan, jg 2000, cracking tendency of alkali activated slag concrete subjected to restrained shrinkage, cement and concrete research, vol. Influence of polymer additives on mechanical fracture. Experimental and numerical analysis of restrained early. Sceng school of civil, environmental and chemical engineering rmit university melbourne, australia august 2009. The effects of silica fume, fly ash, ground granulated blast furnace slag, and calcium nitrite inhibitor to restrained shrinkage cracking were investigated. For the most part, ggbs can be used as sole binder in production of concrete if activated by alkaline solution of higher ph. This work is aimed to study the possibility of inhibiting the shrinkage of aas mortar by incorporating polypropylene fiber ppf. The goal of this study is to develop mitigation strategies for earlyage shrinkage cracking in concrete bridge decks.
Mitigation of autogenous shrinkage in alkali activated slag. A lower elastic stiffness, higher degree of saturation, and potentially higher chemical shrinkage contribute to the high autogenous shrinkage of aas. Shrinkage characteristics of alkaliactivated slag cements. Sbornik alternativni stavebni pojiva by oktaedr issuu. Sanjayan, cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage, cement and concrete research, vol.
Alkaliactivated slag aas is one of the most important cementitious materials which is made by slag and alkaline activator completely replacing the cement. This study aimed to determine the effects of curing regime on shrinkage of alkaliactivated concretes produced from a swedish highmgo blast furnace slag. Cracking of concrete in compositedeck slabs is inevitable, but there are measures you can take to control it installing reinforcing bars in both directions, particularly over beams and girders, will help minimize cracking of compositedeck slabs. Drying shrinkage of alkali activated slag concrete aasc is higher than that of ordinary portland cement concrete opcc. Aastho, standard practice for estimating the cracking tendency of concrete a specification in designation. Slag also known as groundgranulated blastfurnace slag is a byproduct of the blast furnace ironmaking process, and most of the slag is.
The mixes studied were prepared with 400 kg of cement and the fibres were added in proportions of 40 and 120 kg per cubic metre of concrete. Jul 25, 2014 semina alternativni stavebni pojiva 17. Few previous works revealed that it is possible to reduce aas drying shrinkage by the use of shrinkage reducing admixtures sras. Shrinkage appeared not to be affected by the activator type, while the expansion. Cracking tendency of alkali activated slag concrete subjected to restrained shrinkage. Alkali activated slag aas is becoming an increasingly popular building material due to its excellent engineering properties and low co 2 emissions, but its large shrinkage is an important reason to restrict its application and popularization. The mechanical strength and durability properties this alkali activated slag concrete aas were compared to the properties of ordinary portland cement concrete opc with the same proportion of binder, which ranged from 340 to 512 kg per m 3 of concrete. Sanjayanb a maunsell mcintyre pty ltd, level 9, 1 slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. This shrinkage causes forces in the concrete which literally pull the slab. If you use too little cement, you can almost guarantee cracks.
Hydration process and crack tendency of concrete based on. Plastic shrinkage cracking and bleeding of concrete. A comprehensive search was first literature conducted. Adding short steel fibers into slag based geopolymer mortar and concrete is an effective method to enhance their mechanical properties. Proper concrete mix design and use of quality materials. Compared to opc concrete, alkaliactivated slag aas concrete o ers several advantages. Autogenous deformation of alkaliactivated blast furnace. Since the calcium oxide expansive agent used in the present work was deadburnt, the hydration activity was relatively low. Effectiveness of fly ash on the restrained shrinkage. Indeed, deformations can be responsible for cracking, losses in prestressing, redistribution of stress, and sometimes, but more rarely, damage to the structure 5. Sanjayanb a maunsell mcintyre pty ltd, level 9, 161 collins street, melbourne, victoria 3000, australia b department of civil engineering, monash university, clayton, victoria 3168, australia received 20 september 1999.
Its worth remember that shrinkage performance is a very important property for reinforced concrete composites just because a high shrinkage performance is associated to cracking tendency that leads to future durability problems. Aasc, however, has lower elastic modulus, higher creep, and higher tensile. The obtained results showed development of deformations consisting of both shrinkage and expansion. Concrete placed during hot midday temperatures will contract as it cools during the night. Early age strength and workability of slag pastes activated by naoh and na2co3. Alkaliactivated slags represent an alternative to ordinary portland cement due to reducing the environmental impact of the building industry. Mar 12, 2011 a new type of magnesia modification alkali activated cement was prepared, the strength, setting time, shrinkage ratio and cracking behavior, as well as the composition and structure of the hydration product were investigated. With input from the wsdot and based on results from. Manufacture on a commercial basis is underway in the uk, australia, usa and possibly, china.
Mixes were activated with various amounts of sodium silicate at alkali modulus mass ratio sio 2 na 2 o values of 1. This study addressed the mechanical behaviour of a steel fibrereinforced alternative concrete made from waterglass na 2 sio 3. Although the data are limited, the restrained shrinkage cracking of concrete containing slag appears to be less than that of concrete without slag. The studied curing procedure included heattreatment, no heattreatment, sealed and nonsealed conditions. Different shrinkage cracking patterns were first produced on concrete slabs subjected to nonrestrained, two. Shrinkage reduction and crack prevention of alkaliactivated phosphorous slag cement ceramics silikaty 60 2 141145 2016 143 added as the alkaline activator. A series of tests was performed to determine the effect of type and dosage of activators on autogenous shrinkage deformation. Selfcompacting concretes with supplementary cementitious. In spite of the numerous advantages of alkali activated slag mortars, alkaliactivated aluminosilicates have big disadvantage high value of shrinkage followed by formation of microcracks. Aasc has lower elastic modulus, higher creep, and higher tensile strength than opcc, and the combined effects of these can affect the. The fracture properties of steel fiberreinforced slag based geopolymer concrete mortar sgcsgm and unreinforced control samples were compared through threepoint bending tpb tests. Significant drying shrinkage is one of the main limitations for the wider utilization of alkali activated slag aas.
Drying shrinkage of alkaliactivated slag concrete aasc is higher than that of ordinary portland cement concrete opcc. Cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage article in cement and concrete research 305. Crack potential and hydration processes of the cement pastes were monitored using an uptodate eccentric steel cracking frame escf, associated with the noncontact electrical resistivity apparatus, independently. Pdf shrinkage cracking of restrained concrete slabs. Many others have considered the crack tendency with restrained shrinkage in their studies for the assessment of concrete cracking problems 10, 11. Investigation of high performance concrete containing slag. Jan 01, 2009 read influence of activator on the strength and drying shrinkage of alkali activated slag mortar, construction and building materials on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Oct 31, 2016 cracking tendency of alkali activated slag concrete 1. Shrinkage performance of fly ash alkaliactivated cement based binder mortars vol. Alkaliactivated slag aas is becoming an increasingly popular building material due to its excellent engineering properties and low co 2 emissions, but its large shrinkage is an important reason to restrict its application and popularization. Dispersion of carbon nanotubes with sds surfactants. Frontiers the effect of blast furnace slagfly ash ratio. All alkali activated cements tend to have lower embodied energycarbon footprints than portland cements up to 8090% but this is pozzolan dependent. In this paper, experimental results about the shrinkage and creep behavior of an alkali.
This effect is caused by both autogenous and drying shrinkage. Pdf cracking tendency of alkaliactivated slag concrete. Deformations of alkaliactivated slag concrete aasc with high mgo and al 2 o 3 content, subjected to variable curing temperature were studied. Alkali activated cementitious material and concrete. Sodium carbonate sc, sodium silicate ss, and their combination were used as alkali activators. Frontiers effects of curing conditions on shrinkage of. The wetter or soupier the concrete mix, the greater the shrinkage will be.
Strength and durability properties of alkali activated slag and fly ashbased geopolymer concrete a thesis submitted in fulfilment of the requirements for the degree of doctor of philosophy andi arham adam m. Evaluation of the thermal and shrinkage stresses in. Cracking tendency of alkaliactivated slag concrete subjected to restrained shrinkage frank collinsa, j. One factor limiting alkali activated slag binders is shrinkage, which is both more substantial in alkali activated slag than in opc and less well understood 35. Mitigation strategies for earlyage shrinkage cracking in.
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