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© 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.

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.

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.

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

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.

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.

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.

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 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.

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.

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.

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.

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.

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.

The potential of a concrete for carbonation can be assessed effectively by measuring its carbonation depth using an accelerated carbonation testing. This paper reports the findings of a laboratory study including compressive strength, accelerated carbonation depth, and porosity properties of concrete mixtures made with fly ash and normal portland cement. The study involves two replacement ratios of fly ash, various water-to-cement ratios, use of superplasticizer, two curing conditions, and four concrete ages. Statistical models that relate accelerated carbonation depth to strength and porosity are presented.

This paper presents the fresh, mechanical, transport, and durability performances of self-consolidating rubberized concretes (SCRCs). Fresh concrete properties were determined with slump flow, V-funnel, J-ring, and L-box tests. Mechanical, transport, and durability properties were determined by measuring compressive, flexural, and splitting tensile strengths; bond strength characteristics; water porosity; water absorption; water sorptivity; rapid chloride-ion permeability; and freezing-and-thawing and corrosion resistance. SCRC mixtures with a water-binder ratio (w/b) of 0.32; total binder content of 500 kg/m(3) (842 lb/yd(3)); and crumb rubber content of 0, 10, 20, and 30% by fine aggregate volume were produced and tested. Fresh properties testing revealed that the use of crumb rubber as a fine aggregate diminished the filling and passing ability of SCRC. A gradual reduction in mechanical properties was also observed with an increase in crumb rubber content; however, the rate of compressive strength reduction was more evident than that of tensile strength. Despite the fact that water porosity, water absorption, and chloride-ion permeability increased slightly with the use of crumb rubber, a remarkable decrease was observed in the initial and secondary water sorptivity of SCRC. No significant decrease was observed in the freezing-and-thawing and corrosion resistance of SCRC with 10% crumb rubber. Beyond that level, however, durability performance was significantly affected.

The aim of the present study is to investigate some properties of alkali-activated mortars containing slag at different replacement levels. Ground granulated blast furnace slag was used at 0%, 20%, 40%, 60%, 80% and 100% replacement by weight of cement, and liquid sodium silicate having three different Na dosages was chosen as the alkaline activator. In this research, carbonation resistance measurements and compressive and flexural strength tests were performed on the mortar specimens with size of 40 x 40 x 160 mm. The findings obtained from the tests showed that carbonation depth values of the mortars decreased with the increase of activator dosage. Additionally, compressive and flexural strength values increased with the increase in activator concentration and slag replacement level. Portland cement/slag mortars activated by liquid sodium silicate exhibited lower strength than the slag alone activated by the same activator. (C) 2011 Elsevier Ltd. All rights reserved.

WOS: 000292664700032, In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)-binder ratio (WPLA/b) was 0.60; the water-binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural-tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural-tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects. (C) 2011 Elsevier Ltd. All rights reserved., Cukurova University [MMF2006D23], The authors would like thank Cukurova University Scientific Research Projects Directorate that supported the present work (Project number: MMF2006D23).

In this study, the strength properties of polypropylene (PP)-fibre-reinforced fly-ash concrete were investigated experimentally and statistically. Three control factors (amount of fly ash, amount of PP fibre and curing time) were used for this study. The fly ash content that was used was 0, 60 and 120 kg/m3 and the fibre content was 0, 0·45, 0·90 and 1·80 kg/m3. The specimens were cured in standard curing conditions at temperature 23 ± 2°C for periods of 7, 28, 90 and 365 days. At the end of the curing period, the average of three specimens was tested to measure each of the concrete strength properties (compressive strength, flexural tensile strength and splitting tensile strength). Furthermore, the level of importance of these parameters on the strength properties was determined by using the analysis of variance (Anova) method.

In this experimental study, the influence of using fly ash, polypropylene fiber, and steel fiber in concrete on abrasion resistance is presented. Seven concrete mixtures containing 0, 10, 15, 20, 25, 30, and 45% fly ash as cement replacement in mass basis were prepared. Another, seven fiber-reinforced portland cement concrete mixtures containing 0.25, 0.5, 1, and 1.5% steel fiber, and 0.05, 0.1, and 0.2% polypropylene fiber in volume basis were prepared. These seven fiber-reinforced Portland cement concrete mixtures were modified by replacing 15 and 30% fly ash with cement in mass basis, consequently, 14 fiber-reinforced fly ash concrete mixtures were prepared. Water-binder ratio was kept constant at 0.35 for all concrete mixtures. Bohme surface abrasions of the concrete mixtures were measured at 28 days. The results of the laboratory work showed that replacement of fly ash with cement reduced abrasion resistance of concrete; however, inclusion of the steel fiber improved the abrasion resistance of concrete. Using polypropylene fiber did not improve abrasion resistance of concrete made with or without fly ash. The comparison between the relation of abrasion to compressive strength and abrasion to flexural tensile strength, made in terms of R 2 of the linear regression on log scale, showed that a stronger relation existed between abrasion and flexural tensile strength than between abrasion and compressive strength of the concrete containing either fly ash or fibers, or both.

This paper reports on a comprehensive study on the properties of concrete containing fly ash and steel fibers. Properties studied include unit weight and workability of fresh concrete, and compressive strength, flexural tensile strength, splitting tensile strength, elasticity modulus, sorptivity coefficient, drying shrinkage and freeze-thaw resistance of hardened concrete. Fly ash content used was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.25%, 0.5%, 1.0% and 1.5% in volume basis. The laboratory results showed that steel fiber addition, either into Portland cement concrete or fly ash concrete, improve the tensile strength properties, drying shrinkage and freeze-thaw resistance. However, it reduced workability and increase sorptivity coefficient. Although fly ash replacement reduce strength properties, it improves workability, reduces drying shrinkage and increases freeze-thaw resistance of steel fiber reinforced concrete. The performed experiments show that the behaviour of fly ash concrete is similar to that of Portland cement concrete when fly ash is added. (C) 2007 Elsevier Ltd. All rights reserved.

WOS: 000255086900005, This paper examines the influence of aggregate type on the strength characteristics and abrasion resistance of high strength silica fume concrete. Five different aggregate types (gabbro, basalt, quartsite, limestone and sandstone) were used to produce high strength concrete containing silica fume. Silica fume replacement ratio with cement was 15% on a mass basis. Water-binder ratio was 0.35. The amount of hyperplasticizer was 4% of the binder content by mass. Gabbro concrete showed the highest compressive and flexural tensile strength and abrasion resistance, while sandstone showed the lowest compressive and flexural tensile strength and abrasion resistance. High abrasion resistant aggregate produced a concrete with high abrasion resistance. Three-month compressive strengths of concretes made with basalt, limestone and sandstone were found to be equivalent to the uniaxial compressive strengths of their aggregate rocks. However, the concretes made with quartsite and gabbro aggregate showed lower compressive strength than the uniaxial compressive strength of their aggregate rocks. (c) 2007 Elsevier Ltd. All rights reserved.

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of ground granulated blast-furnace slag (GGBFS) concrete studied under dry and wet curing conditions. In the study, a total of 45 concretes, including control normal Portland cement (NPC) concrete and GGBFS concrete, were produced with three different water-cement ratios (0.3, 0.4, 0.5), three different cement dosages (350, 400, 450 kg/m(3)) and four partial GGBFS replacement ratios (20%, 40%, 60%, 80%). A hyperplasticizer was used in concrete at various quantities to provide and keep a constant workability. Twelve cubic samples produced from fresh concrete were de-moulded after a day, then, six cubic samples were cured at 22 +/- 2 degrees C with 65% relative humidity (RH), and the remaining six cubic samples were cured at 22 +/- 2 degrees C with 100%RH until the samples were used for compressive strength measurement at 28 days and three months. Three cubic samples were used for each age and curing conditions. The comparison was made on the basis of compressive strength between GGBFS concrete and NPC concrete. GGBFS concretes were also compared within themselves. The comparisons showed that compressive strength of GGBFS concrete cured at 65%RH was influenced more than that of NPC concrete. It was found that the compressive strength of GGBFS concrete cured at 65%RH was, at average, 15% lower than that of GGBFS concrete cured at 100%RH. The increase in the water-cementitious materials ratios makes the concrete more sensitive to dry curing condition. The influence of dry curing conditions on GGBFS concrete was marked as the replacement ratio of GGBFS increased. (c) 2006 Elsevier Ltd. All rights reserved.

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water-cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450kg/m(3)) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20 +/- 2 degrees C with 65% relative humidity (RH), and three other cubic samples were cured at 20 +/- 2 degrees C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water-cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased. (c) 2005 Elsevier Ltd. All rights reserved.

A laboratory investigation was carried out to evaluate the strength properties of high-volume fly ash (HVFA) roller compacted and superplasticised workable concrete cured at moist and dry curing conditions. Concrete mixtures made with 0%, 50% and 70% replacement of normal Portland cement (NPC) with,two different low-lime Class F fly ashes, good and low quality, were prepared. Water-cementitious material ratios ranged from 0.28 to 0.43. The compressive, flexural tensile and cylinder splitting tensile strengths were measured and presented. The relationship between the flexural tensile and compressive strengths was discussed. The influence of loss on ignition (LOI) content of fly ash on water demand and the strength of concrete was also discussed. The influence of moist and dry curing conditions on the high-volume fly ash (HVFA) concrete system was assessed through a proposed simple efficiency factor. The study showed that producing high-strength concrete was possible with high-volume fly ash content. LOI content increased the water demand of fresh concrete. HVFA concrete was found to be more vulnerable to dry curing conditions than was NPC concrete. It was concluded that HVFA concrete was an adequate material for both structural and pavement applications. (c) 2004 Elsevier Ltd. All rights reserved.

This paper presents a part of the results of an ongoing laboratory work carried out to design a structural lightweight high strength concrete (SLWHSC) made with and without mineral admixtures. In the mixtures, basaltic-pumice (scoria) was used as lightweight aggregate. A control lightweight concrete mixture made with lightweight basaltic-pumice (scoria) containing normal Portland cement as the binder was prepared. The control lightweight concrete mixture was modified by replacing 20% of the cement with fly ash. The control lightweight concrete mixture was also modified by replacing 10% of the cement with silica fume. A ternary lightweight concrete mixture was also prepared modifying the control lightweight concrete by replacing 20% of cement with fly ash and 10% of cement with silica fume. Two normal weight concrete (NWC) were also prepared for comparison purpose. Fly ash and silica fume are used for economical and environmental concerns. Cylinder specimens with 150 mm diameter and 300 mm height and prismatic specimens with dimension 100 × 100 × 500 mm were cast from the fresh mixtures to measure compressive and flexural tensile strength. The concrete samples were cured at 65% relative humidity with 20 °C temperature. The density and slump workability of fresh concrete mixtures were also measured. Laboratory test results showed that structural lightweight concrete (SLWC) can be produced by the use of scoria. However, the use of mineral additives seems to be mandatory for production of SLWHSC. The use of ternary mixture was recommended due to its satisfactory strength development and environmental friendliness. © 2003 Elsevier Ltd. All rights reserved. Firat University Scientific Research Projects Management Unit: MMF 2002 BAP 48 The authors thank Çukurova University Scientific Research Projects Directorate that supported this study (Project No: MMF 2002 BAP 48).

In this brief article, the author comments on research undertaken by Long et al (2002) on the compactness and fluidity of binary and ternary compound paste systems containing ultrafine powders such as pulverized fly ash (PFA), pulverized granulated blast furnace slag (PS) and silica fume (SF). In the study, through optimization of the proportions of compositions and applying heat treatment to specimens, a very-high-performance concrete (VHPC) including large quantities of ultrafine powders was made that offers compressive strength up to 200 MPa. This discussion takes the authors to task on eight points regarding the Long et al research: the terminology of very-high-performance-concrete; the chemical oxide composition of fly ash used; the relative density due to lower mean diameter; reductions in water/binder ratio; contradictory results in a table depicting the introduction of fly ash into paste mixture; the lack of information on sand content; the claims regarding the compressive strength of VHPC; and a small syntax error.

An experimental work was carried out to investigate the use of a non-standard high calcium fly ash in concrete. The response of the same fly ash to the accelerated curing was also explored. With three different cementitious material contents, a total of 48 concretes were produced. The water/ cement ratios were varied from 0.40 to 0.87. Compressive strengths of the moist cured cube specimens cast from the concrete mixtures made with 0%, 15%, 30% and 45% replacement of normal Portland cement with fly ash were measured at 28 days and 3 months. Accelerated compressive strengths were also measured using warmwater method and boiling-water method in accordance with the relevant ASTM and Turkish Standards. Despite the fact that the fly ash used was a non-standard, the laboratory test results showed that it could be utilized in concrete production at a replacement level between 15% and 30% by weight basis because fly ash concrete developed comparable or higher compressive strength than that of corresponding normal Portland cement concrete. The laboratory test results also indicated that the accelerated curing could be used to predict the compressive strength of fly ash concrete with 85% correlation coefficient. The amount of fly ash was found to be immaterial in the strength prediction. The relation between warm-water method and boiling-water method was of linear form with 93% correlation coefficient., Se llevó a cabo un trabajo experimental para investigar el uso de una ceniza volante de alto contenido en cal en el hormigón, la cual no cumple las especificaciones recogidas en norma. También, se estudió el comportamiento de la ceniza bajo un curado acelerado. Se elaboraron un total de 48 hormigones con tres proporciones diferentes de material cementante. Las relaciones agua/cemento (a/c) usadas estaban comprendidas entre 0,40 y 0,87. A 28 días y 3 meses de curado, se determinaron las resistencias a compresión de probetas cúbicas de hormigón elaboradas con 0%, 75%, 30%y 45% de sustitución de cemento Portland por ceniza. También, se determinaron las resistencias a compresión de las probetas de hormigón sometidas a curados acelerados: agua caliente y agua hirviendo, de acuerdo con las normas ASTM y Turcas. A pesar del hecho que la ceniza volante usada no cumple con la normativa vigente, los resultados de los ensayos de laboratorio mostraron que pueden utilizarse en la producción de hormigón, con un porcentaje de sustitución entre 15%y 30% en peso, ya que el hormigón con ceniza desarrolló resistencia a compresión similares o superiores al hormigón de referencia. Los resultados de laboratorio también indicaron que los ensayos acelerados pueden usarse para predecir la resistencia a compresión de hormigón con ceniza, con un coeficiente de correlación del 85%. La proporción de ceniza no influye en la predicción de resistencia. La relación encontrada para las resistencias a compresión entre el método de agua caliente y el método de agua hirviendo tiene una forma lineal, con un coeficiente de correlación del 93%.

In this work, the abrasion resistance of high volume fly ash concrete was investigated. Concrete mixtures containing a large amount of fly ash replacing the cement in mass basis at 50 and 70% were prepared with various water-cementitious material ratios. A specially selected superplasticizer was employed to maintain the workability of the concrete. Volume loss of the specimen was considered as the abrasion value measured using a Dorry abrasion machine. Comparisons were made between normal portland cement (NPC) concrete and fly ash concrete. Comparisons were also made between fly ash concretes with 50 and 70% replacement. Investigation results have shown that the abrasion resistance increased as compressive strength increased. Analysis of the results showed that, for high strength grades (>40 MPa), the abrasion resistance of high volume fly ash concrete with 70% replacement with cement was found to be higher than that of counterpart control NPC concrete and concrete made with 50% fly ash. Superplasticizer and curing conditions have no significant influence on the general trend of the abrasion of concrete studied.

This paper presents experimental results obtained from the direct pull-out test using different types of rockbolts having different shape of lugs. These are smooth surface bars, ribbed bars, single conical lugged bars, double conical lugged bars and triple conical lugged bars. It is found that the failure mechanism of the conical lugged rock bolt is different from that of conventional rockbolts, in which the adhesion or the shear strength at the bolt-grout interface provides the load bearing capacity. From the results of experimental study, the use of the conical lugged rock bolts is suggested, because it provides a greater anchorage strength due to wedging effect that is a combination of the shear and compressive strength of the grouting material. © 2003 Elsevier Science Ltd. All rights reserved. The authors would like to thank the Research Fund of Cukurova University for supporting this research. No: MMF. 2001.30.