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This paper presents the effect of activator ratio and silica fume additive on physical and mechanical properties in slaked lime-based alkali-activated mortars which are limited in literature. The binder, which was formed by slaked lime and adding 5%, 10%, 15% silica fume into slaked lime, was activated with sodium hydroxide. The concentration of activator was chosen between 10 and 15 mol. The water/binder ratio was determined to be 0.55, and the binder/sand ratio was chosen as 1/3. After the produced mortar samples were placed in the mold, they were kept at 105 degrees C for 24 h at the activation temperature. The samples taken out of the oven were kept at room temperature (22 +/- 2) oC for up to 28 days. As a result of the experiments, in the samples containing 85% slaked lime and 15% silica fume, a compressive strength value of 36.46 MPa was determined. Compared with the control samples, it was observed that the flexural strength of the alkali-activated mortars produced with slaked lime increased by 3.72-fold and the compressive strength increased by 5.9-fold. As a result of the regression analysis, sodium hydroxide amount providing optimum flexural and compressive strength was determined as 14.28 mol, silica fume ratio as 10.03%.

© 2021 fib. International Federation for Structural Concrete.This paper reports an experimental study of the influence of elevated temperature on alkali activated slag (AAS) and slag-metakaolin (MK) systems. The residual compressive and flexural tensile strengths, ultrasonic pulse velocity (UPV) and porosity and water absorption ratios of AAS and AAS-MK composites after subjected to elevated temperatures of 200, 400, 600, 800, and 1000°C were investigated. Two different procedures were applied for cooling the specimens. The changes in the microstructure of the composites after subjected to high temperature were examined with scanning electron microscope and X-ray diffraction. Test results reveal that depending on the increasing temperature, the residual compressive strength, flexural tensile strength, and UPV values of the specimens decreased, and porosity and water absorption ratios increased. The minimum strength results of AAS and AAS-MK specimens were observed at 800 and 600°C, respectively. In particular, there have been significant changes in the internal structure of AAS and AAS-MK specimens exposed to 1000°C and new reaction products were observed. Test results have shown that AAS specimens are a new alternative that can be developed for use in environments exposed to high temperatures. Since this new composite contains only slag binder and slag aggregate, it can be an economical product that use fully recycled material and these properties can increase the application areas of environmentally friendly material.

There are very few studies in the literature on the usage of CKD in cementitious systems. This article presents the laboratory study results on the influence of cement kiln dust (CKD) on the properties of mortar made with cement kiln dust and Portland cement. The article aims to prevent CKD's (known as a hazardous waste product) damage to nature by utilizing CKD in cementitious systems and contributing to sustainability by reducing cement amount in the cementitious system. For this purpose, 5%, 10%, 15%, and 20% of CKD were replaced with cement and binary cementitious systems were formed. For all mortar mixes, the water/binder ratio was kept constant at 0.5, and the sand/binder ratio was 3. Workability, dry unit weight, water absorption ratio and porosity, flexural strength, compressive strength, abrasion, carbonation, and high-temperature resistance tests were performed on the mortar specimens. Based on the results of laboratory work, it was observed that the replacement of CKD with cement reduces the workability of fresh mortar. Compressive and flexural strengths of CKD-added mixtures were found to be equivalent or insignificantly lower than that of the control sample. The addition of CKD had a negligible effect on water absorption and porosity of samples. Besides, the residual compressive strength determined after the elevated temperature test for the sample made with CKD were found to be equivalent or higher compared to the control sample. Present laboratory studies showed that utilization of CKD in cementitious mortar system is feasible in terms of testing conducted.

It is known that nano-and microparticles have been very popular in recent years since their advantages. However, due to the very small size of such materials, they have very high tendency to agglomeration particularly for nanoparticles. Therefore, it is critical that they are properly distributed in the system to which they are added. This paper investigated the effects of dry particle coating with nano-and microparticles to solve the agglomeration problem. For a clear evaluation, paste samples were preferred to detemine the compressive strength. Nano-SiO2and nano-CaCO3, micro-CaCO3and micro-SiO2, also known as silica fume, were selected as particulate additives. It was studied by the addition of various percentages (0.3, 0.7, 1, 2, 3 and 5%) of nano-and microparticles in cementitious systems, replacing cement by weight with and without dry particle coating. Dry particle coating was made by using a high-speed paddle mixer. Portland cement and additive particles were mixed at 1500 rpm for 30 seconds in high-speed powder mixer designed for this purpose. The 3-day compressive strength of the cement-based samples to which particles were added at the specified rates was determined and the effect of the dry particle coating on the early strength was investigated. According to the results, it was observed that the production of paste with the dry particle coating technique gave higher compressive strength compared to the production of paste directly in early period. Especially with dry particle coating, compressive strength increased more than 100% in paste samples containing 0.3% nano-SiO2compared to direct addition without coating.

In this study, some durability properties of alkali-activated slag (geopolymer) mortars were investigated. In determining these durability properties, a series of test procedures such as high temperature, abrasion, rapid chloride permeability and wetting and drying cycles were performed. For the slag activation, sodium metasilicate was used at three sodium concentrations, 4%, 8% and 12% by mass of slag. Prismatic specimens with 40 x 40 x 160 mm dimensions were prepared from geopolymer mortars for the tests. After 24 h, the specimens were demolded and cured in three different ways until the test time: curing in an oven at 75 degrees C for 1 day, curing in air for 28 days and curing in water at 22 +/- 1 degrees C. The results obtained from the tests were compared with the control mortar made with ordinary Portland cement (OPC).The findings revealed that the resistance of alkali-activated slag mortars under aggressive media investigated within the scope of this work was higher than that of OPC mortar.

In this study, it was proposed a novel prediction model to predict compressive strength of mortar samples having different properties. For this purpose, 8 different fly ashes were used in mortar mixture as a replacement of cement by weight. Mortars including different ashes were prepared with addition of 10%, 20%, 30% and 40% fly ash. Compressive strength of the produced mortar samples were evaluated at 1, 3, 7, 28, 90 and 365 days. Totally 196 test samples were produced and mechanically tested. The relation between compressive strength values (dependent value) and SiO2 + Al2O3 + Fe2O3 content, age, and fly ash replacement ratios (independent values) were predicted by machine learning techniques such as Artificial Neural Networks (ANN) and Adaptive-Network Based Fuzzy Inference Systems (ANFIS). The findings were compared with traditional statistical method Multi-Linear Regression (MLR) to prove proposed models. According to test results it has an incentive effect for future studies to know that GA based Antis model produce better results to estimate compressive strength using chemical composition of fly as in terms of SiO2 + Al2O3 + Fe2O3, fly ashsubstation ratio in the mortar and age of the sample. (C) 2020 Elsevier Ltd. All rights reserved.

In this study, blast furnace slag geopolymer mortars were prepared in prism molds with the size of 4 x 4 x 16 cm by alkali activating powdered sodium meta silicate (Na2SiO3). The mortar mixtures prepared to contain sodium in different proportions were cured with 3 different curing methods, and 300 cycles of freeze-thaw were applied, and strength and weight losses were examined. Control samples prepared with PC were also exposed to freeze-thaw cycles and the results were compared with each other. It was observed that 8% sodium added geopolymer mortars significantly preserved their compressive strength and weight. Especially, the compressive strength of the samples produced with 8% sodium and exposed to freeze-thaw cycle after 28 days of air curing increased by around 32%.

The paper presents the results of research of high-strength geopolymer mortars, prepared from two types of siliceous fly ash. Sodium hydroxide and mixtures of sodium hydroxide and sodium silicate in the form of solutions were used as activators. The activator was added in amounts ranging from 6 to 15% NaOH in relation to the ash mass. After preparation, the mortars were cured at the temperature of 60 degrees C, 80 degrees C or 100 degrees C for various times, from 24 hours to 7 days. Increasing the addition of sodium or a higher curing temperature increase the flexural and compressive strength of the tested mortars. The best results - compressive and flexural strength of 100 MPa and 20 MPa, respectively, were obtained for mortar activated with 15% sodium hydroxide, cured at 100 degrees C for 24 hours. Blended activator - sodium silicate and sodium hydroxide also allowed to obtain high strengths, but lower than sodium hydroxide alone. Extending the curing time at high temperature beyond 24 hours did not produce favourable results in most cases. Fly ash geopolymer mortar, activated with 15% NaOH by mass of ash, cured at 100 degrees C for 24 hours, showed about 18% reduction in greenhouse gas emissions compared to common Portland cement mortar.

Lightweight concretes with thermal insulation properties and good compressive strength can be produced by the replacement of normal aggregate of cement mixture with low-density materials. In this study, sand in a cement mixture has been replaced totally with silica aerogel powder as well as replacement of cement with fly ash. Furthermore, nano silica and silica-fume were added and incorporated into the concrete matrix. The most obvious finding to emerge from this study was that a lighter sample with no sand contributed to the lowest thermal insulation reduction by 58% of the reference sample and reduction in density to 22.8%, with reduced compressive strength of 27.11 MPa at 28 days. Obtaining of a lighter concrete by using aerogel, a chance of reduced building cooling and heating energy consumption and enhanced indoor comfort with the reduction of mold and condensation on buildings wall was obtained.

This study presents the resistance of sodium meta-silicate activated ground granulated blast furnace slag (GGBFS) to acidic and basic mediums.Geopolymer mortars were prepared with GGBFS activated by sodium meta-silicate activator having 4, 8, and 12% sodium concentrations by mass ofslag. These mortars were exposed to two types of acid solutions, H2SO4 and HCl with a 5% concentration of acid-water solution. Similarly, somespecimens were exposed to a basic medium composed of 25% NaOH solution with water. Exposure time for the acidic and basic mediums was setto one year. Comparison of results obtained from slag based geopolymer mortar was made with normal Portland cement control mortar. Normalcontrol samples lost compressive strength significantly after exposure to acidic and basic medium in comparison to alkali activated slag mortar.Particularly, after exposure to H2SO4, the compressive strength of the normal control samples decreased by about 40%. Contrary to this, the slagbased geopolymer mortar gained compressive strength after exposure to the acidic or basic mediums. An up to 21% strength increase was observedfrom the alkali activated slag mixtures made with 4% and 8% Na content.&nbsp

In the current study, heat cured fly ash (FA)/ground granulated blast furnace slag (GGBFS) blend geopolymer mortars activated with sodium hydroxide (NaOH) were investigated. For this reason, 'Combined Design' method of Experimental Design has been introduced for the first time as an exceptional tool for the evaluation of the simultaneous effect of the parameters affecting different properties of the mortars. Empirical models were developed to predict the mortars flow workability, compressive strength and flexural strength as well as to find the optimum levels for the most relevant conditions. For this purpose, 40 design points with different FA/GGBFS ratios ranging from 0/450 g to 450/0g; water 180-225 g, NaOH 50-150 g and curing temperature 50-100 degrees C were generated. For each of the 40 design points, mortars flow workability, flexural and compressive strength were tested and investigated. In the end, Scanning Electron Microscopy (SEM) analysis of three optimal mortar samples, representative of 100% FA, similar to 55/45 FA/GGBFS and 100% GGBFS was performed and analysed for the physical properties such as unit weight, water absorption and porosity. The generated models shows excellent correlation coefficients such as R-2 = 0.95 for flow workability and R-2 = 0.98 for compressive strength. The SEM analysis and physical test results comply with the model results, which show that "Combined Design" method is a very effective and timesaving method to reach very accurate results in the design of geopolymer mortars. (C) 2018 Elsevier Ltd. All rights reserved., In the current study, heat cured fly ash (FA)/ground granulated blast furnace slag (GGBFS) blend geopolymer mortars activated with sodium hydroxide (NaOH) were investigated. For this reason, 'Combined Design' method of Experimental Design has been introduced for the first time as an exceptional tool for the evaluation of the simultaneous effect of the parameters affecting different properties of the mortars. Empirical models were developed to predict the mortars flow workability, compressive strength and flexural strength as well as to find the optimum levels for the most relevant conditions. For this purpose, 40 design points with different FA/GGBFS ratios ranging from 0/450 g to 450/0g; water 180-225 g, NaOH 50-150 g and curing temperature 50-100 degrees C were generated. For each of the 40 design points, mortars flow workability, flexural and compressive strength were tested and investigated. In the end, Scanning Electron Microscopy (SEM) analysis of three optimal mortar samples, representative of 100% FA, similar to 55/45 FA/GGBFS and 100% GGBFS was performed and analysed for the physical properties such as unit weight, water absorption and porosity. The generated models shows excellent correlation coefficients such as R-2 = 0.95 for flow workability and R-2 = 0.98 for compressive strength. The SEM analysis and physical test results comply with the model results, which show that "Combined Design" method is a very effective and timesaving method to reach very accurate results in the design of geopolymer mortars.&nbsp

The energy sector is one of the biggest polluters of environment in Kosovo. More than 40 million tons of ash and about 400 hectares of arable land are occupied from the landfill of Kosovo-A and Kosovo-B power plants. On the other hand, the use of fly ashes with proper characteristics, as pozzolanic material in concrete production is a well-known fact. In this context the effect of the partial replacement of Portland cement with Kosovo fly ash in cement pastes and mortars has been investigated. For that purpose, six different series of (0/100, 5/95,10/90,15/85.20/80 and 25/75) fly ash to cement ratios (FA/PC) have been studied. Normal consistency, initial and final setting time of the cement pastes, and water absorption, flexural strength, compressive strength and shrinkage deformation of the mortar specimens were investigated. Test results show that Kosovo fly ash has good parameters that improve the compressive strength of cement mortars and concrete by replacing the Portland cement up to 10%. On the other hand, it increases slightly the water absorption capacity of the mortars. Nevertheless, it can be concluded that the use of Kosovo fly ash in concrete could be a good alternative to be used as a pozzolanic material. Future studies should be focused on the durability effect of Kosovo fly ash on concrete. Article DOI: https://dx.doi.org/10.20319/mijst.2017.33.125141 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

DOI: 10.7764/RDLC.16.1.167 Carbon fibers (CFs) in the cement mortars are used in order to improve characteristics properties of the composite materials such as mechanical properties. Moreover, the uniformity of fiber dispersion is significant aspect for improvement of the composites. Computed Tomography (CT) imaging is a fully nondestructive technique to view features in the interior of opaque solid objects to obtain digital information on their properties. In this study, firstly, flexural test was conducted were investigated for 4×4×16 cm samples incorporated with carbon fiber at 2- and 7-days curing. Secondly, the images that were obtained by using multi-slice CT technique. Finally, the compressive strength properties of the mortars mixed with carbon fiber were discussed. According to the test results, the dispersion and orientation of CFs in the samples have a remarkable impact on mechanical properties of the composites.

U radu se analizira alkalno aktiviranje mješavina morta koje sadrže mljevenu granuliranu zguru iz visokih peći i leteći pepeo, pri čemu se aktivacija odvija pomoću natrijevog metasilikata. Analiziraju se dvije serije te je izmjerena tlačna čvrstoća. Rezultati dobiveni za prvu seriju pokazuju da se tlačna čvrstoća bitno smanjuje sa smanjenjem omjera zgure i letećeg pepela. Trodnevna tlačna čvrstoća morta njegovanog pri temperaturi 100 °C donekle se povećava do omjera 60/40, ali se bitno smanjuje pri omjeru 40/60., The alkali activation of mortar blends containing Ground Granulated Blast Furnace Slag and Fly Ash, with activation based on sodium metasilicate, is investigated in this study. Two series are investigated, and compressive strength is measured. The results of the first series show that the compressive strength decreases considerably with a decrease in the slag and fly ash ratio. The 3-day compressive strength of mortar cured at the temperature of 100°C increases slightly up to the ratio of 60/40, but decreases considerably at the 40/60 ratio.

Mechanical properties of geopolymer mortar made with class F fly ash and class C flyash are evaluated and compared in this paper. Fly ashes were activated with a combinedNaOH and Na2SiO3 alkali solution, and their strength development was observed duringone year. It was observed that compressive strength values were between 10.22 and15.83 MPa for geopolymer mortar mixtures made with class C fly ash. The values of upto 56.44 MPa were obtained for geopolymer made with class F fly ash.

It is known that transport properties of porous materials were important in terms of its durability aspect. In this paper, the effect of activator type, Na amount on the transport properties of geopolymer mortar made with class F fly ash were explored. Two different class F fly ash were employed in producing geopolymer that activated alkaline solutions. As alkali activator, sodium hydroxide solution, and combination of sodium silicate with sodium hydroxide were used. Activator contained 6%, 9%, 12% and 15% of fly ash weight as Na amount. Heat curing regimes were imposed to specimens at 100 degrees C temperature for 24 h duration. Tests were carried out on the geopolymer samples including water absorption, volume of permeable voids, sorptivity, depth of penetration of water under pressure, chloride ion penetration and accelerated corrosion. It is found that the transport properties of geopolymer samples are improved by increasing the Na amounts of mortar mixtures from 6% to 15%. In general, better results were obtained with 15% Na ratio. The mortars produced with only sodium hydroxide have shown better transport properties than mortars made with combination of sodium hydroxide-sodium silicate mixture. (C) 2020 Elsevier Ltd. All rights reserved.

Numerous research studies were conducted to improve the weak properties of recycled aggregate as a construction material during the last two decades. Most of these studies mainly focused on minimizing the undesired characteristics of the recycled aggregate through various treatment techniques to strengthen the attached old mortar or remove it from the recycled aggregate. Mechanical Treatment Methods (MTMs) used to remove the attached mortar from the aggregates were evolved over the years. Among available methods of treatments in the literature, the number of studies investigated the MTMs with an optimization process is limited. In lack of proper optimization process with rubble quality identification, mechanical treatment methods may be ineffective to provide concretes with sufficient properties, and they may yield to extra energy consumption and carbon emission. In other words, the optimization of treatment methods and determination rubble quality are two essential steps for having satisfactory results on the recycled aggregate. In this study, an optimization process is applied using the Los Angles test machine through the conducted Ball Milling Method (BMM). During the BMM process, various combinations of rotation (R) (100–200-300-400-500) and the steel ball (S) (0-2-5-7-10-12) applied to the recycled aggregate. Analysis results demonstrated the effectiveness of reducing the 8.95% water absorption value of the untreated recycled aggregate to 0.84% after the optimization process of BMM. Then, seven concrete specimens including 0-20-40-60% recycled aggregate (RA) and improved recycled aggregate (RA-i) mixes produced in the framework of the experimental study. For comparison purposes, engineering properties of 28 days concrete are determined. The use of RA-i up to 60% in concrete has not influenced the physical and mechanical properties, distinctively. After the optimization process, the RA use in concrete increased up to 60% which is twofold of the optimum RA value in the literature. As a result, optimized BMM improved the mechanical and physical characteristics of RA and increased the use of RA ratio in concrete mixes without any trade-off.

Behaviour of construction materials i.e. steel, concrete and mortar under elevated temperature is important. In the study, the variations in mass loss, and strengths of polypropylene fiber reinforced mortar subjected to elevated temperatures were examined. Mortar was made with CEM I 42.5R Portland cement, monofilament polypropylene fiber, fine aggregate and drinkable water. The sand-cement and water-cement ratio were chosen 3:1 and 1:2 for all mixtures, respectively. Mixes containing 0, 0.1, 0.2 and 0.3% polypropylene fiber in volume of solid matter of mixture were prepared. Mortars were exposed to 100, 200, 400, 600 and 800 degrees C temperatures and cooled down 23 +/- 2 degrees C in air and water. There was a difference between the temperatures at which the important reductions observed for flexural tensile and compressive strength. Significant reduction was observed at 400 degrees C for compressive strength and while it was 200 degrees C for flexural strength. No difference was observed between air cooling and water cooling regimes up to 600 degrees C; however, at 800 degrees C the residual compressive and flexural strength of water cooled mortar was about 40% of the air cooled mortar. Mortar containing polypropylene fiber presented better behaviour to elevated temperature in terms of relative residual strengths up to 400 degrees C.

The demand forcement usage increases in the world, currently. It is known that using industrial waste materials in concrete as cement or aggregate replacement as part of waste management as well as conserving natural resourcesis getting wider. Due to thesefacts, in this work, an investigation was carriedout on the utilization of waste marble powders as cement replacement mineral materials. In this context, marble powder replaced cement at 5%, 10%, 15% and 20% in mass basis, and mortars were produced. In mortar mixtures, water-binder ratio was chosen as 0.5, and sand-binder ratio was taken as 3. Workability of fresh mortar was measured. Unit weight, water absorption,and porosity, compressive and flexuralstrengths, abrasion, carbonation and drying shrinkage measurements testing were carried out on hardened mortar specimens. Influence of elevated temperature on hardened mortar mixture was also investigated. As a result of laboratory study, it is concluded that replacing marble powder with cement result with a favourable contribution to workability of freshmortar, as well as resistance to elevated temperature. It also reduced drying shrinkage of mortar in comparison to reference mortar made without marble powder. However, it influenced water absorption, abrasion,and carbonation resistance of mortar, unfavourably. For short term curing duration, replacement of marble powder with cement reduced compressive strength insignificantly for 5% and 10%marble powder replacement, but,reduced itsignificantly for 15% and 20%. However, at long term curing at 90 days, the difference between strength of reference mortarand marble containing mortar was diminished, particularly formortar containing 5% and 10% marble powder

This study investigates the effect of ground granulated pumice (GGP) on workability, compressive/flexural strength and abrasion/fire resistance of mortars. Mortar mixture was prepared by replacing cement with GGP at five different replacement ratios (0, 5, 10, 15 and 20%). The sand-to-binder and water-to-binder ratios of the produced mortars were 3.0 and 0.50, respectively. Compressive/flexural strength and horizontal Bohme abrasion tests were conducted on mortar specimens at 28 days. Mortar specimens were also exposed to elevated temperatures of 300, 600 and 900 $$^{\circ }\hbox {C}$$ for a duration of 1 h to measure residual compressive strength. Test results showed that the use of GGP reduced the flow/workability of fresh mortars. It was also observed that the use of 10% GGP content slightly improved strength, abrasion and fire resistance of mortars compared to control normal Portland cement mortar.

Portland çimentosunun icadından önce mineral katkılar sönmüş kireçle karıştırılarak harç imalinde bağlayıcı olarak kullanılmıştır. Günümüzde de mineral katkılar, ekonomik olduklarından ve özellikle taze ve sertleşmiş beton ile harcın bazı özelliklerinde faydalı değişiklikler sağladıklarından, çimentoyla birlikte kullanılmaktadır. Çalışmada, Portland çimentosuna yüksek oranda kalsiyum içeren uçucu kül ve aktifleştirici susuz sodyum sülfat (Na2SO4) ilaveleriyle üretilmiş harç numunelerinin dayanımları incelenmiştir. Uçucu kül, çimento ile ağırlıkça % 10, % 20, % 30 ve % 40 oranlarında ikame edilerek kullanılırken, sodyum sülfat ise toplam bağlayıcı miktarının % 0, % 2 ve % 4 oranlarında kullanılarak kum/çimento oranı 2,75 ve su/çimento oranı ise 0,485 olan harç numuneleri üretilmiştir. Uçucu kül katkılı harç numunelerine susuz sodyum sülfatın aktivatör olarak ilavesinin, harç numunelerinin boşluk oranlarına ve basınç ile eğilmede çekme dayanımlarına etkileri 3, 7, 28 ve 90 günlük kür süreleri sonunda tespit edilmiştir. Bulgular, uçucu külün % 20 ikame oranına kadar kullanılabileceğini, erken yaş dayanım kayıplarının ise bağlayıcı miktarının en fazla % 2’si kadar Na2SO4 kullanılarak telafi edilebileceğini göstermiştir., Prior to the invention of Portland cement, mineral admixtures had been used by blending with calcium hydroxide in the production of mortar mixtures. Today, since the mineral admixtures are economic and ensure useful alterations in some properties of fresh and hardened concrete and mortar, they have been used with Portland cement. In this study, the strengths of cement mortars containing high calcium fly ash and sodium sulfate (Na2SO4) as activator were examined. While fly ash was used at 10%, 20%, 30% and 40% replacement by weight of cement, sodium sulfate was used 2% and 4% by mass of binder. The mortar mixture proportions were 1:2.75:0.485 by weight of cement, sand and water, respectively. The effects of addition of sodium sulfate into cement mortars were investigated through the porosity, compressive and flexural strength tests at 3, 7, 28 and 90 days. The findings showed that fly ash could be used in the cement mortars up to 20% replacement ratio, and that the early term strength losses could be compensated by using 2% sodium sulfate in the mixture.

In this study, the influence of a pre-rest period before heat curing (as a new parameter), on the physical properties, flexural and compressive strength, and microstructure of geopolymer mortars and pastes produced with alkali activation of fly ash were investigated. In this context, geopolymer mortar and paste samples were prepared and pre-rested under laboratory conditions for 0, 1, 2, 3, 7, 14, and 28 days before heat curing. After the pre-rest period, the samples were subjected to heat curing at 75°C in an oven, for 2 days. Mortar and paste samples exposed to a pre-rest period while in the fresh state before heat curing were compared with control samples without pre-resting. Water absorption, porosity, specific gravity, capillarity, flexural strength, compressive strength, and abrasion resistance tests were conducted on the geopolymer mortar samples. A reaction kinetics study using an isothermal calorimeter, XRD, and SEM analyses were performed on the geopolymer paste samples for microstructural investigations. Based on the results obtained, it was observed that the mechanical strength of the samples subjected to the pre-rest period before heat curing increased considerably compared to the reference (without pre-resting) samples. In addition, because of pre-resting, the capillarity coefficient, water permeability, and porosity of the samples decreased compared to the reference samples, and it was concluded that pre-resting improves durability-related properties. Moreover, the reaction kinetics and SEM analysis results, supporting the above findings, showed that a pre-resting period increases the geopolymeric reaction products and causes a denser microstructure.

In this study, changes occurring on the thermal and mechanical properties of the mortar samples depending on different storage conditions, which were prepared by replacement of 60% vol of the cement with aerogel, 50% w of the sand with fly ash, and by the addition of nano-silica in various concentrations (1-3% w), have been investigated. Findings indicated that the used best storage method is the method that specimens are kept in water for a week and then in air until the end of 28 days. The compressive strength values of the samples cured with the second method for 28 days were found to be in the range between 31 and 29.3 MPa. As for in the third method, which the samples were kept in water 28 days, the values have changed in the range between 28.9 and 26 MPa. On the other hand, it can be seen that the lowest values in compressive strength vary between 27.2 and 20.9 MPa, belong to the samples produced in the first storage condition which temperature, humidity and time are respectively 25 degrees C, 50% and 7 days. In the first method, following the first stage, the samples were then kept in the air-dried condition until the 28th day. Among thermal conductivity values, the lowest values were obtained for the samples produced with the first method, ranging between 0.762 and 0.865 W/m.K. and the highest values 0.918 1.051 W/m.K belong to the group conditioned in the third method. (C) 2018 Elsevier Ltd. All rights reserved.

This study examines the influence of the physico-mechanical properties of the intact rock of aggregate materials on the strength performance of a concrete. For this aim, nine different aggregate types were produced from nine different intact rocks, and they were used in the production of nine different concretes. The physical and mechanical properties of the corresponding rocks were varied between 7.8 and 123.3 MPa, 13.30 and 26.40 kN/m3, 2.29 and 34.43%, and 1.30 and 4.34 km/s, for compressive strength (CSr), unit weight (UWr), porosity (nr), and ultrasonic pulse velocity (UPVr), respectively. During the making of the concretes, water–binder ratios were kept between 0.28 and 0.55 based on the slump and workability. According to 28-day compressive strengths, strong correlations were obtained from the physico-mechanical properties of the corresponding aggregate rocks and the compressive strength of the concretes (CSc). While the increasing the Young’s modulus (Er), CSr, UWr and UPVr of corresponding aggregate rocks increased the strength of concretes, the increase in the nr of corresponding aggregate rocks decreased the strength of concrete. The results obtained from this study indicated that knowing any physical or mechanical property of rock used for producing aggregate could be used to estimate the compressive strength of concrete. © 2018, Shiraz University., Istanbul Üniversitesi, Acknowledgements The authors would like to thank to Scientific Research Projects Coordination Unit of Istanbul University for supporting this research (Project Number: 30744).

Roller-compacted concrete pavement (RCCP) is an economic and durable rigid pavement. Although about half century has passed since the first RCCP was implemented, information about this type of concrete is still limited. RCCP as a zero-slump concrete, has lower cement content than conventional vibrated concrete. Therefore, the quality of the aggregates has a significant impact on the properties of concrete. For this reason, the quantity of coarse and fine aggregates in RCCP should be optimized. This study investigates the effect of coarse to fine aggregate (C/F) ratio on the fresh and hardened properties of two RCCPs with cement contents of 9% (204 kg/m(3)) and 12% (268 kg/m(3)). Compressive strength, splitting tensile strength, flexural tensile strength, Vebe time and porosity tests were carried out. The test results demonstrate that increasing the C/F ratio from 0.6 to 1.8 increased the Vebe time threefold, while increasing the cement content from 9% to 12% decreased the Vebe time by 12%. In addition, increasing the C/F ratio from 0.6 to 1.2 significantly decreased the porosity of RCCP, to about 60% for RCCP with 9% cement and 38% for RCCP with 12% cement. Generally, the most suitable C/F ratio for RCCP appeared to be from 1.2 to 1.4. Thus, to attain a workable, high-strength and durable RCCP, a mix with 12% cement and 1.2C/F ratio is recommended. (C) 2018 Elsevier Ltd. All rights reserved.

In this study it was investigated the behavior of class F fly ash based geopolymer mortars subjected to elevated temperatures. Geopolimer composites were prepared with CEN-sand, water, fly ash as the binder, nSiO2Na2O and NaOH mixture combination as alkali activator. After mixing fresh geopolymer mixture, prismatic specimens were prepared using 40 mm × 40 mm × 160 mm prism molds. After molding, fresh geopolymer mortar samples with their mold were subjected to heat curing at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C and 100 °C temperature for 48 hours in an oven. After 48 hours initial heat curing, the hardened samples were taken out of their mold. Then, they were further cured by leaving them in laboratory environment at about 22 ± 2 °C temperature, until 28 days together with heat curing duration. At the end of 28 days, geopolymer mortar samples developed flexural strength values between 2,9 MPa and 8,51 MPa. Geopolymer mortar samples developed compressive strength values between 7,63 MPa and 50,64 MPa. High temperature experiments were conducted to observe behaviour of geopolymer mortars at elevated temperatures. The control cement mortar mixtures were also prepared and subjected to high temperature exposure in comparison to geopolymer mortar mixtures. Control cement mortars were cured at laboratory environment for 28 days without initial temperature curing. Control cement mortar mixtures and geopolymer mortar mixtures were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C temperature. The unit weight, ultrasonic pulse velocity, flexural and compressive strength of all mixtures were measured before and after high temperature exposure. Scanning electron microscope (SEM) images of the mixtures were taken and X-ray fluorescence (XRF) spectrometer analyses were carried out. It was observed that there was an increase in the flexural and compressive strengths of some geopolymer mortars after high temperature exposure. In general, geopolymer mortars exhibited better performance at elevated temperatures in comparison to control cement mortar mixture. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18829

In the study, the influence of heat curing duration and rest period after heat curing duration on the strength and transport characteristics of alkali activated fly ash (AAFA) mortar were investigated. A local class F type fly ash, CEN reference sand, sodium hydroxide and potable water were used in preparation of cement-less fresh geopolymer mortar mixture. Mixture ratios (in mass basis) were 3, 1, 0.29, and 0.1 for sand, fly ash, water and sodium hydroxide, respectively. Some samples were cured at 75 degrees C temperature for 4 h, 1, 2, 3 and 7 days; then, they were tested after heat curing period. Additionally, some of the equivalent samples were kept in the laboratory at 23 +/- 2 degrees C temperature with 50 +/- 5% relative humidity, until 28 days after their initial heat curing period. Then, they were tested at 28 days for combined curing conditions. The measured properties of AAFA mortar were unit weight, porosity, capillary water absorption, water absorption capacity, flexural-bending and split tension strength, compressive strengths and abrasion resistance. It was observed that the strengths of mortar were significantly increased with the increase in heat curing duration. A significant strength development was also observed after rest period. As a result of the study, high strength and abrasion resistant AAFA geopolymer mortar was produced. However, transport properties of AAFA geopolymer mortar found to be not as good as mechanical properties. (C) 2017 Elsevier Ltd. All rights reserved.

In this study, the carbonation depths of slag mortars activated by sodium silicate (water glass), sodium hydroxide and sodium carbonate were investigated and the results were compared to those of control mortar with CEM I 42.5 R normal Portland cement. In the mixture, the sand/binder ratio was 2.75 and the water/binder ratio was 0.50. Na concentrations in the mixture proportions were determined as 4%, 6%, and 8% for all the activators. For liquid sodium silicate activator, SiO2/Na2O ratios (Ms) of 0.75, 1, 1.25, and 1.5 were also chosen. Prismatic specimens having 40 x 40 x 160 mm dimensions were prepared from both fresh Portland cement and slag mortar mixtures for the measurements. The day after the mortar casting, the prisms were demolded and placed in a humidity cabinet at 65% ± 5 relative humidity and 22 ± 2 °C temperature. The carbonation tests of mortars were conducted at 7, 28, 90 and 180 days. It was observed that the carbonation resistance of slag mortars activated by alkalis was lower than that of control mixture with Portland cement. However, it was also seen that an increment in the Na dosage of activator improved the resistance of the activated slag mortars to carbonation.

WOS: 000393002700019, In this paper, bond strength and abrasion resistance of alkali activated concretes (AAC) were examined experimentally by using the central composite design (CCD) method. AAC were designed and produced considering the sodium concentration (SC), silicate modules (SM), curing temperature (CT) and exposed curing time (ECT) as the CCD's independent parameters. Twenty-one AAC mixtures were established depend on the various combinations of independent parameters in CCD at 95% confidence level. Effects of each independent parameter on the dependent parameters were statistically analyzed using experimental measurements and best possible combination of the independent parameters were defined for the maximization of the compressive strength, split tensile strength, UPV and bond behavior of AAC and for the minimization of abrasion value of AAC by solving the multi-objective optimization problems which is generated using the proposed regression models for the dependent parameters. Test results demonstrate that all studied independent parameters have the noteworthy effect on the properties of AAC statistically; however, the most effective independent parameter is SC. The optimum values of the parameters studied were defined as CT of 66 degrees C, ECT of 14.76 h, SC of 5.72% and SM of 1.0 for the defined multi-objective optimization problem. (C) 2016 Elsevier Ltd. All rights reserved., Turkish Scientific and Technical Research Council [MAG-214M035]; Scientific Research Division of Mustafa Kemal University [13700], This research was supported financially by Turkish Scientific and Technical Research Council (MAG-214M035) and Scientific Research Division of Mustafa Kemal University (13700). Authors thank to TUBITAK and Mustafa Kemal University.

Yapılmış olan bu laboratuvar çalışmasında, silis dumanı katkılı harçların karbonatlaşma ve rötre özellikleri araştırılmıştır. Deneylerde hazırlanan harç numunelerin bağlayıcı/kum oranı 2,75'tir. Normal Portland çimentosunu (PÇ 42.5) ağırlık bazında %10, 15, 20 ve 40 oranında silis dumanı ile ikame edecek şekilde hazırlanan harç karışımlarının su-bağlayıcı oranları 0,25, 0,30, 0,40, 0,50 ve 0,60 olarak belirlenmiştir. Yapılan deneyler sonucunda, bütün su-bağlayıcı oranlarında 28, 90, 180 günlük zaman dilimlerinde karbonatlaşma değerlerinin arttığı görülmüştür. %10 ve %15 oranlarında silis dumanı kullanımı karbonatlaşma değerlerini düşürürken %40 oranında silis dumanı kullanımı ise karbonatlaşma değerlerini arttırmıştır. Silis dumanı katkılı harçlarda kuruma rötresinin, silis dumanı ikame oranından ve su-bağlayıcı oranından oldukça etkilendiği görülmektedir. Su-bağlayıcı oranının 0,25 ve 0,30 olduğu harçlarda, %40 silis dumanı ilavesi hariç diğer ikame oranlarında rötreyi azaltıcı etkisi belirgin olarak görülmektedir. Ancak su-bağlayıcı oranının artması ile silis dumanının rötreyi azaltıcı etkisi düşük seviyelerde kalmıştır., In this laboratory studies, carbonation and shrinkage properties of mortars with silica fume additive were investigated. In the tests, binder/sand ratio of prepared mortars was 2.75. Water/binder ratios of mortars produced with silica fume replaced with ordinary Portland cement (PC 42.5) with 10, 15, 20 and 40% by weight were determined as 0.25, 0.30, 0.40, 0.50 and 0.60. According to the tests results, carbonation values were increased for all water/binder ratios at 28, 90 and 180 days. While, the usage of silica fume with the quantities of 10% and 15% were decreased the carbonation values, the usage of silica fume with the quantity of 40% was increased the carbonation value. It was seen that, replacement ratio of silica fume and water/binder ratio in mortars were relatively effected the drying shrinkage. In the mortars with water/binder ratios of 0.25 and 0.30, addition of silica fumes was decreased shrinkage for all replacement ratios of silica fumes except 40%. However, the effect of silica fume on shrinkage was decreased with the increase of water/binder ratios.

This study investigated the dual effect of freeze-thaw cycles with sodium sulfate solution on the performance of non-air-entrained Engineering Cementitious Composites (ECCs) with high volumes of slag. ECC specimens containing three different levels of slag content as a replacement for cement (55%, 69% and 81% by weight of total cementitious material) were exposed to aggressive sodium sulfate solution under freezing-thawing cycles. The load-deflection response associated with ultimate mid-span deflection and flexural strength/stiffness was determined, along with crack development behavior. For comparison purposes, the freezing-thawing resistance (in water) of control ECC specimens was also evaluated. Modified point count method air-void parameters, compressive strength, porosity, water absorption and sorptivity tests were also conducted on the virgin ECC specimens (those not exposed to freezing-thawing cycles in water or aggressive sodium sulfate solution). The test results for the virgin specimens revealed that increased slag content (S/PC) improved the ductility, hardened air content, water absorption, porosity and sorptivity of ECC, while marginally decreasing the compressive and flexural strengths. Freeze-thaw cycles in water or sodium sulfate solution showed that the ductility of ECC specimens decreased remarkably, irrespective of slag content and applied freezing-thawing process. Reduction in mass loss was at minimal levels and no significant behavior change was monitored between the specimens undergoing freeze-thaw cycling in water and the aggressive sodium sulfate solution. Moreover, the decrease in flexural stiffness was more evident than the reduction of the flexural strength for all ECC mixtures. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.

WOS: 000385154900022, This study presents the mechanical and transport properties of milled cut steel fiber reinforced concretes (MCSFRC). Properties studied include unit weight, workability, compressive strength, flexural strength, splitting tensile strength, bond strength, water absorption, water porosity, water sorptivity, rapid chloride ion permeability and drying shrinkage of concrete. Mixtures with a waterbinder ratio of 0.40, total binder content of 500 kg/m(3) and milled cut steel fiber content of 0, 0.25, 0.50 and 1.00% by concrete volume were produced and tested. The laboratory results showed a slight reduction in compressive strength with the use of milled cut steel fiber. On the other hand milled cut steel fibers significantly improved the tensile strength and decreased the drying shrinkage. Although no significant increase was observed in the absorption, porosity and sorptivity, chloride ion permeability increased drastically with the increase of milled cut steel fiber content.

WOS: 000385319300027, A laboratory study is performed to evaluate the influence of elevated temperature on the strength and microstructural properties of high strength concretes (HSCs) containing ground pumice (GP), and blend of ground pumice and metakaolin (MK) mixture. Twelve different mixtures of HSCs containing GP and MM were produced, water-to-binder ratio was kept constant as 0.20. Hardened concrete specimens were exposed to 250 degrees C, 500 degrees C and 750 degrees C elevated temperatures increased with a heating rate of 5 degrees C/min. Ultrasound pulse velocity (U-pv), compressive strength (f(c)), flexural strength (f(fs)) and splitting tensile strength (f(sts)) values of concrete samples were measured on unheated control concrete and after air-cooling period of heated concrete. The crack formation and alterations in the matrix, interface and aggregate of HSCs were examined by X-ray diffraction (XRD), scanning electron microscope (SEM) and polarized light microscope (PLM) analyses. XRD, SEM and PLM analyses have shown that, increasing target temperature result with decrease in mechanical properties i.e. U-pv, f(c), f(fs) and f(sts) values. Elevated temperature also results with crack formation, and increasing target temperature caused more cracks. Alterations in the matrix, interface and aggregate were, also observed by these analyses. The experimental results indicate that concrete made with MK + GP blend together as a replacement of cement in mass basis behaved better than control concrete made with cement only, and concrete containing only GP as a cement replacement. (C) 2016 Elsevier Ltd. All rights reserved.

This paper reports of a comprehensive study on the durability properties of concrete containing polypropylene fiber and fly ash. Properties studied include unit weight and workability of fresh concrete, and compressive strength, modulus of elasticity, porosity, water absorption, sorptivity coefficient, drying shrinkage and freeze–thaw resistance of hardened concrete. Fly ash content used in concrete mixture was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.05%, 0.10% and 0.20% in volume basis. The laboratory results showed that inclusion of fly ash improves; however, polypropylene fiber decreases the workability of concrete. Moreover, polypropylene fiber addition, either into Portland cement concrete or fly ash concrete, did not improve the compressive strength and elastic modulus. The positive interactions between polypropylene fibers and fly ash lead to the lowest drying shrinkage of fibrous concrete with fly ash. Freeze–thaw resistance of polypropylene fiber concrete was found to slightly increase when compared to concrete without fibers. Moreover, fly ash increased the freeze–thaw resistance more than the polypropylene fibers did.

The development of new binders, as an alternative to traditional cement, by the alkaline activation of industrial by-products (i.e. ground granulated slag and fly ash) is an ongoing research topic in the scientific community [Puertas F, Amat T, Jimenez AF, Vazquez T. Mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres. Cem Concr Res 2003;33(12): 2031–6]. The aim of this study was to investigate the feasibility of using and alkaline activated ground Turkish slag to produce a mortar without Portland cement (PC). Following the characterization of the slag, mortar specimens made with alkali-activated slag were prepared. Three different activators were used: liquid sodium silicate (LSS), sodium hydroxide (SH) and sodium carbonate (SC) at different sodium concentrations. Compressive and flexural tensile strength of alkali-activated slag mortar was measured at 7-days, 28-days and 3-months. Drying shrinkage of the mortar was measured up to 6-months. Setting times of the alkali-activated slag paste and PC paste were also measured. Setting times of LSS and SH activated slag pastes were found to be much slower than the setting time of PC paste. However, slag paste activated with SC showed similar setting properties to PC paste. LSS, SH and SC activated slag mortar developed 81, 29, and 36 MPa maximum compressive strengths, and 6.8, 3.8, and 5.3 MPa maximum flexural tensile strengths at 28-days. PC mortar developed 33 MPa compressive strength and 5.2 MPa flexural tensile strength. LSS and SH activated slag mortars were found to be more brittle than SC activated slag and PC mortars. Slag mortar made with LSS had a high drying shrinkage, up to six times that of PC mortar. Similarly, slag mortar made with SH had a shrinkage up to three times that of PC mortar. However, SC activated slag mortar had a lower or comparable shrinkage to PC mortar. Therefore, the use of SC as an activator for slag mortar is recommended, since it results in adequate strength, similar setting times to PC mortar and comparable or lower shrinkage.

Badly compacted mixtures will develop undesirable properties of low stiffness, bad fatigue resistance, bad durability, etc. that is not expected from a good pavement. This paper is to evaluate the compactibility of hot asphalt mixtures (HAM) made with crump rubber modified bitumen, which was manufactured by incorporating the waste shredded-tire rubber particles in base bitumen in different sizes and concentration. Type of binder and binder viscosity during compaction has a great effect on the compactibility of HAM. Compaction Coefficient (CC), which is variation in porosity line throughout compaction, could be related with the energy needed to compact the mixture. Less energy is needed for the mixture having low CC. Modification of bitumen with rubber makes the mixture less compactable when compared with the mixtures made without rubber. (C) 2007 Elsevier Ltd. All rights reserved.

This study presents the strength properties of alkali activated Ground Granulated Blast Furnace Slag (GGBFS) /Fly Ash (FA) blend mortars prepared with sodium meta-silicate and, sodium hydroxide-silica fume combination mixture. The GGBFS/FA ratios were arranged at (100/0, 80/20, 60/40, 40/60, 20/80, 0/100). Water to “GGBFS+FA” ratio was kept constant at 0.5. Na concentration ratio to “GGBFS+FA” was kept constant at 6%. These ratios were in mass basis. Three different mixture parameters were used. In the first series of mixture, only sodium meta-silicate was used as activator. In second and third series, sodium hydroxide and silica fume combination was used as activator. Sodium hydroxide and silica fume was mixed with water and used directly in preparation of second series of mortar mixtures. For preparation of third series of mortar mixture, sodium hydroxide and silica fume were mixed continuously with water for three days to allow dissolution of silica fume in sodium hydroxide solution. At first, 3-days compressive strengths of all alkali activated mortar mixture were measured. After that due to the very low compressive strength of mortars made with high volume fly ash content, only 100/0 and 80/20 slag/fly ash ratios were investigated for 7, 14 and 28 days compressive and 28 days flexural strength. The results of the 3 days tests show that decreasing the slag/fly ash ratio decreases distinguishably the compressive strength of the mortars. The mortars produced with the mixture of sodium hydroxide and silica fume combination as activator showed satisfactory results when compared with those activated with sodium meta-silicate.

In this laboratory work, high compressive and flexural tensile strength of alkali activated fly ash geopolymer mortars were presented. Class F fly ash was used throughout the study. NaOH was used as alkali medium that provides high pH value. Also, the factors influencing the compressive and flexural tensile strength were investigated. A total of 216 fly ash geopolymer mortar samples were prepared. Heat curing temperature, heat curing duration and alkali (Na) concentration were chosen as the influencing parameters of strengths. Mortar mixture parameters were 3 and 1/3 for sand-binder ratio, and water-binder ratio, respectively. Na concentrations of the mortar mixtures were changed from 4% to 20% with 2% increment step. Heat curing temperatures were changed from 45 to 115 degrees C with 10 degrees C increment step. Heat curing durations were chosen as 24, 48 and 72 h. For each combination of influencing parameter, three prismatic specimens with 40 mm x 40 mm x 160 mm dimensions were prepared using a three-cell mortar cast. After heat curing period in a laboratory oven, the samples were left to cool down to room temperature, then compressive and flexural strengths were measured as described in its respective standard. Very high compressive and flexural tensile strength obtained, which were as high as 120 and 15 MPa respectively. (C) 2015 Elsevier Ltd. All rights reserved.

A laboratory study was undertaken to assess the compressive and flexural tensile strength and drying shrinkage properties of mortar mixtures containing high-calcium nonstandard Afsin-Elbistan fly ash (FA). Possibility of using Afsin-Elbistan FA in cement-based materials as shrinkage-reducing or compensation agent was also discussed. Five mortar mixtures including control Portland cement (PC) and FA mortar mixtures were prepared. FA replaced the cement on mass basis at the replacement ratios of 10%, 20%, 30% and 40%. Water-cementitious materials ratio was 0.4 for all mixtures. The mixtures were cured at 65% relative humidity and 20±2 °C. The compressive and flexural tensile strength and drying shrinkage values of the mortar mixtures were measured. The results show that Afsin-Elbistan FA reduced drying shrinkage of the mortar by 40%. Therefore, it was concluded that Afsin-Elbistan FA can be used as a shrinkage-reducing agent. The mortar containing 40% FA expanded. This indicates that Afsin-Elbistan FA may be utilized to compensate drying shrinkage of cement-based materials. © 2003 Elsevier Ltd. All rights reserved. Firat University Scientific Research Projects Management Unit: MMF2002BAP51, FBE2002D179 The authors thank Cukurova University Scientific Research Projects Directorate that supported the present work (MMF2002BAP51 and FBE2002D179).

An accelerated carbonation test was carried out in order to assess the carbonation of fly ash (FA) concrete. The process of carbonation was accelerated using a controlled environment. The concrete mixtures made with 0, 50 and 70% replacement of normal Portland cement (NPC) with fly ash were prepared. Water-cementitious material ratios were ranged from 0.28 to 0.55. Some concrete mixture was also made with a superplasticizer. Comparisons were made to evaluate the influence of FA on the carbonation of concrete. The laboratory test results showed that FA concrete made with 70% replacement ratio was carbonated more than that of 50% FA replacement concrete and normal Portland cement (NPC) concrete. In contrast, 50% FA replacement concrete showed lower or similar carbonation to NPC concrete. Before exposing the concrete to the accelerated carbonation testing, the longer initial curing period resulted in lower carbonation depth. The effect is more marked with moist curing. The statistical analyses results showed a strong correlation between the carbonation depth and the strength of the concrete. The influence of the superplasticizer on the carbonation was found to be insignificant. (C) 2003 Elsevier Science Ltd. All rights reserved.

The results of nondestructive testing of mortar specimens using a simple and inexpensive microwave measurement system are presented. Temporal dependencies of amplitude of reflection and transmission coefficients at x band for the specimens made with different water-to-cement ratio (w/c) are given. It is shown that there is a strong correlation between the measured results and w/c. The results also demonstrate the influence of curing conditions and the effects of aging.

In this work, a laboratory investigation was carried out to evaluate the strength and particularly the shrinkage properties of concrete containing high volumes of fly ash. The concrete mixtures made with 50 and 70% replacement (by mass) of ordinary portland cement (OPC) with fly ash were prepared. Water-cementitious material ratios ranged from 0.28 to 0.34. Some concrete mixtures were also made with superplasticizer. The strength and shrinkage properties of the-concrete mixtures cured at 20degreesC temperature with 65% relative humidity are reported. The laboratory test results show that high-volume fly ash (HVFA) concrete attained satisfactory compressive and tensile strength at I day of age. It also showed that 50% replacement HVFA concrete developed higher strength than OPC concrete at 28 days and beyond. The inclusion of high volumes of fly ash in concrete with a low water-cementitious material ratio resulted in a reduction in the shrinkage values of up to 30% when compared to OPC concrete. The concrete mixtures made with superplasticizer showed higher shrinkage values of up to 50% when compared to the concrete made with no superplasticizer.

This paper reports the results of an investigation on the influences of admixtures and curing conditions on some properties of Alkali-Activated Slag (AAS) mixtures with no cement. In the study, Shrinkage-Reducing (SRA) and superplasticizing and setretarding (WRRe) admixtures were used. For the slag activation, sodium metasilicate was used at two sodium concentrations, 4% and 6% by mass of slag. Setting time, flow loss of fresh mixtures, and shrinkage strain, carbonation, flexural and compressive strength of hardened mixtures were measured. The test results showed that the admixtures generally had no impact on the setting times of AAS pastes. WRRe increased the flow rate of AAS mortars while SRA partially affected the flow values of AAS mortars. WRRe and SRA did not produce an important difference on the carbonation depths of AAS mortars. However, WRRe and especially SRA admixtures decreased the shrinkage values of AAS mortars. Additionally, curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to Normal Portland Cement (NPC) mortars, and the strength development of AAS mortars at early ages was very fast in comparison with NPC mortars when subjected to elevated temperature.

in this paper, the results of a laboratory investigation conducted with heat evolution of high-volume fly ash (HVFA) concrete are presented. Heat evolution of concrete was studied by measuring the temperature increase in concrete under adiabatic curing condition. Characteristic of heat evolution of fly ash concrete was found to be strongly dependent on the replacement level of fly ash and dosage of superplasticizer used to maintain workability. It was also found that using fly ash as cement replacement resulted in a reduction on the maximum temperature rise. Increasing the replacement level of fly ash caused lower temperature rise in concrete. Superplasticizer caused a delay in peak temperature rise time; this is taken as an indicator that high-dosage superplasticizer used in concrete caused retardation ill hydration of cement. Concretes having similar ingredients showed similar peak temperature rise whether they are superplasticized or not. (C) 2002 Elsevier Science Ltd. All rights reserved.

This paper presents the influence of shrinkage-reducing (SHR) and superplasticizing and set-retarding admixtures (SSRe) on the properties of slag pastes and mortars activated by liquid sodium silicate with different dosage and modulus ratio. Properties in the fresh and hardened state for these binders were investigated by means of measuring some properties including setting time, flowability, flexural strength, compressive strength, carbonation and shrinkage. In this study, fifteen pastes and mortars were prepared. Liquid sodium silicate was used to activate the slag at two sodium concentrations, 4% and 6% by mass of slag. Liquid sodium silicate and sodium hydroxide were blended to obtain 0.75 and 1 modulus ratio of SiO2/Na2O. Results showed that although the higher percentage of sodium in the activator produced a higher strength, workability and setting times rapidly decreased with the higher sodium concentration due to instantaneous reaction and quick hardening of slag activated by liquid sodium silicate. None of the admixtures generally had an impact on the setting times of alkali-activated slag (AAS) pastes. SSRe admixture increased the flow rate of AAS mortars while SHR admixture partially affected the flow values of AAS mortars. SHR admixture exhibited a slight decrease in the carbonation depths of AAS mortars. SSRe and particularly SHR chemical admixtures reduced the shrinkage of AAS mortars. However, the shrinkage values of AAS mortars still were higher than those of ordinary Portland cement (NPC) mortars. Curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to NPC mortars. (C) 2012 Elsevier Ltd. All rights reserved.