Comparison of short- and long-term ASR test methods on cementitious composites

Concrete has a significant place in construction structures, is a material that can be easily damaged due to incorrect design, incorrect material selection. Concrete may be damaged by physical and chemical factors. One of these factors is the alkali-silica reaction (ASR). ASTM C1260, is a short-term test method, and ASTM C227, is a long-term test method, are used to measure effect of alkali-silica reaction. In this study, the effect of fly ash additive use with 0, 5, 10, 15, and 20 wt.% replacement of cement was investigated in short- and long-term ASR test methods. For this purpose, while samples prepared for ASTM C1260 were kept in NaOH solution 14-days, samples prepared for ASTM C227 were waited 360-days in normal water solution. As a result; mortar bars with 20% fly ash additive ratio were classified as harmless for ASR in both test methods

Mechanical and Physical Properties of Autoclaved Aerated Concrete Reinforced Using Carbon Fibre of Different Lengths

In this study, series of tests have been conducted to indicate the mechanical and physical properties (compressive strength, flexural strength, dry density, thermal conductivity and shrinkage) of autoclaved aerated concrete (AAC) reinforced with carbon fibres of different lengths. AG2/350 AAC block specimens without carbon fibre were prepared as a control specimen. The mixtures were prepared by replacing 0.5% weight of cement in the AAC with 4 mm, 6 mm, 12 mm length carbon fibres and these mixtures were poured into moulds and subjected to 58 °C for 4 hours to expand until reaching workable hardness. After preliminary curing, the produced AAC specimens were subjected to 180 °C and pressure of 11 bar for 6 hours in a steam cure until required hardness. The mechanical and physical properties of the reference and the fibre reinforced AAC specimens were determined and compared to each other. As a result, the use of 12 mm fibre reinforcement in AAC gave the best performance in comparison to the other fibre reinforcements of different lengths by increasing compressive strength for 10.63%, flexural strength of 31.48% and thermal conductivity up to 4.23% while reducing the shrinkage ratio to 51.47%. Herein for the specimen using 0.5% replacement of the AAC in weight with 12 mm carbon fibre is recommended

Mechanical properties and microstructure of cement multicomponent systems containing pozzolan materials under sulfate attack

Sulfates are a significant chemical components that may lead to failures of cement concrete composites. The present study is dedicated to analyzing the effects of sulfate on the microstructure of cement composite mortars. For this purpose, cementing composite specimens were prepared with 20% pozzolan mixture [fly ash + granulated blastfurnace slag + bottom ash] by mass of cement, together with the reference additive-free specimen of cement concrete, without any mineral admixtures. These cementing composite mortar specimens were then treated for 2, 7, 28, 90, and 360 days in tap water and 10% sodium sulfate solution. The microstructure of the additive-free mortar and composite cement mortar, partially replaced with 20% pozzolan, was then investigated using a scanning electron microscope. The results showed that increasing curing time also increases the formation of C-S-H [calcium silicate hydrate] gel in the cement mortar, when the microstructural changes in the cement are explored in detail. Ettringite formation [3CaO center dot Al2O3 center dot 3CaSO(4)center dot 32H(2)O] in the specimens cured in 10% Na2SO4 was also noticed, in the present experiments

Determination of compressive strength of perlite-containing slag-based geopolymers and its prediction using artificial neural network and regression-based methods

This study has two main objectives: (i) to investigate the parameters affecting the compressive strength (CS) of perlite-containing slag-based geopolymers and (ii) to predict the CS values obtained from experimental studies. In this regard, 540 cubic geopolymer samples incorporating different raw perlite powder (RPP) replacement ratios, different sodium hydroxide (NaOH) molarity, different curing time, and different curing temperatures for a total of 180 mixture groups were produced and their CS results were experimentally determined. Then conventional regression analysis (CRA), multivariate adaptive regression splines (MARS), and TreeNet methods, as well as artificial neural network (ANN) methods, were used to predict the CS results of geopolymers using this experimentally obtained data set. Root mean square error (RMSE), mean absolute error (MAE), scatter index (SI) and Nash-Sutcliffe (NS) performance statistics were used to evaluate the CS prediction capabilities of the methods. As a result, it was determined that the optimum molarity, curing time, and curing temperature were 14 M, 24 h, and 110 celcius, respectively and 48 h of heat curing did not have a significant effect on increasing the CS of the geopolymers. The highest performances in regression-based models were obtained from the MARS method. However, the ANN method showed higher prediction performance than the regression-based methods. Considering the RMSE values, it was seen that the ANN method made improvements by 24.7, 2.1, and 13.7 %, respectively, compared to the MARS method for training, validation, and test sets

Thermal and Compressive Strength Properties of Sepiolite Substituted Autoclaved Aerated Concrete

Gazbeton gözenekli hafif betondur. Bu araştırmada, Sepiyolitin gazbeton üretiminde hammadde olarak kullanılan kuvarsit yerine ikamesinin gazbetonun ısıl ve basınç dayanım özelliklerine etkisi araştırılmıştır. Araştırmada, duvar elamanı olarak kullanılan ve ticari olarak üretimi yapılan G2/04 sınıfı gazbeton üretimi esas alınmıştır. Eskişehir Sivrihisar maden sahasından alınan Sepiyolitin, hammadde olarak kullanılan kuvarsit yerine %5, %10, %15, %20 ve %25 oranlarında ikame edilerek gazbeton örnekleri üretilmiştir. Üretilen örnekler 60 ºC sıcaklıkta 4 saat kürde bekletildikten sonra 180 ºC'de 11 bar basınçta 6,5 saat otoklavda küre tabi tutulmuştur. Üretilen örneklerin basınç dayanımı ve ısıl iletkenlik özellikleri belirlenmiştir. Sonuç olarak sepiyolit oranının arttırılması sonucu basınç dayanımında azalma olurken ısıl iletimde iyileşme gözlenmiştir.Aerated concrete is a lightweight concrete which has porous structure. In this study, effects of usage of sepioliteas a raw material instead of quartzite on the thermal and compressive strength properties of aerated concrete were investigated.G2/04 class aerated concrete, which has been commercially produced as a wall component, has been focused. Aerated concrete samples have been prepared by substitution of sepiolite instead of quartzite in %5, %10, %15, %20 and %25. Sepiolite has been provided from Eskişehir mine field. After 4 hours cure at 60ºC, samples moved to treat in autoklave in the temperature of 180ºC and pressure at 11 bar for 6.5 hours. Thermal conductivity and compressive strength properties of samples were determined. As a result, increasing the rate of sepiolite in aerated concrete decreases the compressive strength and increases the thermal conductivity

The mechanical properties of Alkali-silica reactive mortars containing same amounts of silica fume and fly ash

Bu çalışmada, çimento yerine aynı oranlarda silis dumanı (SD) ve Uçucu kül (UK) içeren karışımların Alkali- silika reaksiyonu (ASR) etkisi araştırılmıştır. ASR nedeniyle oluşan genleşmenin kontrol altına alınması için kullanılan SD ve UK’nın genleşme ve mekanik özellikleri üzerine etkisi belirlenmiştir. Araştırmada, SD ve UK % 0, 5,0, 10,0, 15,0 ve 20,0 oranlarında çimento yerine ikame edilmiştir. Agrega ve çimento karışımlarının reaktifliğini belirlemek için ASTM C 1260 deney standardı kullanılmıştır. Deneysel çalışmada, ASR etkisinde bırakılan örneklerin morfolojisi ve kimyasal kompozisyonu taramalı elektron mikroskobu (SEM) ve Enerji yayıcı X-ışını analizörü (EDX) kullanılarak incelenmiştir. Deney sonuçlarına göre, 14 günlük ölçümler sonucunda, ortalama en yüksek boy uzamasının kontrol harç çubuklarında %0,34, ortalama olarak en düşük boy uzamasının ise %20 SD ikamesi yapılan harç çubuklarında %0,04 olduğu gözlenmiştir. ASR etkisine maruz kalan harçlarda en az dayanım kaybı %20 SD ikamesi yapılan harçlarda olmuştur. ASR etkisinde bırakılan % 0–20 ikameli SD’li harçlar UK’lı harçlara göre %18 daha iyi eğilme dayanımına ve basınç dayanımına sahip olduğu görülmüştür. SEM görüntüsünde ASR çatlaklarının yoğun ve geniş çatlaklı olduğu bölgelerde yapılan EDX’larda kalsiyum oranı yüksek silis oranı düşük oluşmuştur.In this study, the Alkali silica reaction (ASR) effects on the mortars containing the same proportions of silica fume (SF) and fly ash (FA) instead of cement were investigated. SF and FA, used to control the expansion caused by ASR, were seen to have effects on the expansion and mechanical properties. In the study, SF and FA were substituted for cement in the proportions of 0.5.0%, 10.0%, 15.0% and 20.0%. ASTM C 1260 standard was used to determine the reactivity of aggregates and cement mixtures. In this experimental study, the morphology and chemical composition of the samples exposed to the effects of ASR were analyzed by using a scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX). The results of 14-day experimental measurement showed that the average maximum length of extended control mortar bars was observed to be 0.34% while the lowest average 20% increase of the length SF replace was seen to be 0.04% in the mortar bar. The least strength loss in the mortars exposed to ASR was in those which had 20% SF substitution. Exposed to the effects of ASR, the mortars with 0%-20% SF substitution had a 18% better flexural strength and compressive strength compared to the mortars with FA. As observed on the SEM images, EDX done on the dense and wide ASR cracked areas showed high calcium and low silica percentage

Kiremit ve hafifbeton tozu kullanımının betonda alkali-silika reaksiyonuna etkilerinin deneysel olarak araştırılması

Proje -- Kırıkale Üniversitesi2007/320087303

The Effect of Magnetized Water on Mechanical, Thermal Conductivity, Microstructure and Bond Formation Properties in Hybrid Blast Furnace Slag and Powder Perlite Binder Lightweight Geopolymer Composites

Geopolymer concretes are studies to reduce the use of cement and conventional concrete. These studies, which are widespread today, are of great importance in terms of the development of new generation binders. Thanks to the production of cement-free geopolymers, will ocur reductions in CO2 emissions. In addition, with the use of artificial pozzolans, positive effects can be achieved on environmental protection, recycling of waste materials and sustainability. One of the most important problems in the production of geopolymer concrete is workability. Workability plays a key role in the production, placement and compaction of mortars or types of concrete. If a concrete with difficult workability cannot be properly placed in the mold and compressed, the durability of the concrete will be adversely affected by this situation. The strength values will remain at low levels if the mortar and concrete voids are more than normal, and if sufficient compression cannot be made during the placing of the mold. In this study, light geopolymer composites will be produced by using expanded perlite as aggregate, blast furnace slag (YFC) as binder, and raw perlite powder (powder perlite) brought to the cement fineness size in different proportions. In the study, the production of lightweight geopolymer composite will be done with a fixed molarity value. Sodium hydroxide (NaOH) solution will be used as the activator. In the production of lightweight geopolymer composites, preliminary studies will be carried out on the curing temperature and curing times, and work will continue on the optimum values obtained. Sand and aggregate form the skeletons of mortars and concretes. Approximately 70% to 85% of mortar and concrete consists of sand and aggregates. When the concretes are examined according to their weights in the literature, it is seen that they are classified as light concrete, normal concrete and heavy concrete. Here, the most important element that makes the concrete light, normal or heavy is aggregate. In this study, expanded perlite will be used as aggregate, which is obtained from the factory as an approximate maximum grain diameter of dmax≌ 4.75 mm after the expansion process. In addition, 3% by volume (8mm in size) fiber will be used in the base part to improve the flexural strength of lightweight geopolymer composites, and 0.5% by volume (4mm in size) will be used in the mixture to prevent the formation of shrinkage cracks and increase the compressive strength. Concrete, cement mortar, composite... etc. One of the important features that enable to make comments and make decisions about the samples produced as For this reason, flexural and compressive strength analyzes of geopolymer mortars and fibrous/non-fibrous lightweight geopolymer composites will be performed. According to the results of this analysis, three designs that give the best results in geopolymer mortars and fibrous/non-fibrous lightweight geopolymer composite sample groups will be selected; These three designs will be reproduced with magnetized water obtained at different magnetic field and flow velocity values, and the stage of improving their mechanical and insulation properties will be started. For this purpose, the water to be used in the production of geopolymer mortars and fibrous/non-fibrous geopolymer composites that give the best three results will be converted into magnetized water by passing through the device designed to apply different magnetic fields at different flow rates. Magnetized water field constant 600 millitesla (mT) and 1000 mT (0.6T (Tesla) and 1.0T); flow rate will be 9 liters/minute (lt/min) and 18 liters/minute. Thermal conductivity, mercury porosimetry, SEM, EDS, XRD, FTIR analyzes will be made for the mixtures obtained by using magnetized water. As a result, in this proposed project, it is aimed to produce a material with a low thermal insulation coefficient. One of the most important elements in the production of lightweight geopolymer is to bring the workability and mechanical strength to the desired level. It is aimed to improve the workability and mechanical properties by using magnetized water in the light geopolymer mixture. In addition, it will be possible to reduce the dead loads of the structures with the production of lightweight composite materials. Thus, the self-loads of the existing elements in the building will decrease and it will be possible to reduce the effects of the earthquake on the structure. Thanks to the use of perlite as aggregate, a new area of use will be created for the perlite reserves in Turkey. In the study, it is aimed to produce lightweight composite materials with alternative binders to cement-binding materials by using YFC and powder perlite. In addition to these, it is aimed to reduce carbon dioxide (CO2) emissions, energy consumption from cement production and the negative effects on the environment due to these situations

The mechanical and microstructural properties of Li2SO4, LiNO3, Li2CO3 and LiBr added mortars exposed to alkali-silica reaction

Demir, Ilhami/0000-0002-8230-4053WOS: 000317443100010Aim of this study intends analyzing the effects of lithium additives on fresh and hardened cement mortars. In this study, mortar specimens were prepared by adding four types of additives (Li2SO4, LiNO3, Li2CO3 and LiBr) to the mixing water of the cement at 0.5%, 1%, 1.5%, 2%, 2.5% and 3% proportions by weight. The Alkali-silica reaction (ASR) of these mixtures was explored. The effects of Li2SO4, LiNO3, Li2CO3 and LiBr, which are used to control ASR induced expansion, on expansion and mechanical properties were determined. ASTM C 1260 experiment standard was used to find out the reactivity of aggregate and cement mixtures. In this experimental study, the morphology and the chemical composition of specimens exposed to ASR effect was examined by means of scanning electron microscope (SEM) and Energy Dispersive Spectroscopy (EDS). Fourteen-day readings conducted in the experimental study showed that the average maximum length change of the reference mortar bar was 0.34%, whereas the lowest average length change was 0.023% of the mortar bar with 3% Li2CO3 additive. Among the mortars that had undergone ASR, mortars containing 3% LiNO3 experienced the least strength loss. As observed in the SEM image, EDX done on dense and wide ASR cracked areas pointed to high ratios of calcium oxide and silica oxide. (C) 2013 Elsevier Ltd. All rights reserved

The usage properties of Kaman (Kırşehir, Turkey) granites as crushed stone aggregates

Bu araştırmada; Kırşehir-Kaman yöresi dört farklı bölgedeki taş ocaklarından elde edilen granit kayaçların mühendislik özellikleri incelenmiştir. Çalışmada, yöredeki kayaçların mineralojik yapısı, basınç dayanımı, çekme dayanımı, elastisite modülü, yüzey sertliği, birim hacim ağırlığı, ağırlıkça su emme ve görünür gözeneklikleri belirlenmiştir. Deneylerden alınan sonuçlara göre; bu kaya örneklerinin mineral yapıları ve sertlikleri benzerdir. Birim hacim ağırlıkları ve basınç dayanımları yüksek, su emmesi düşük olan kayaların elastisite modülü değeri de yüksektir. Sonuç olarak; Kaman yöresindeki kayaçların kırmataş agrega olarak uygun olduğu ve en iyi özelliklerin de Ömerhacılı sahasına ait olduğu görülmüştür.In this research; the engineering properties of granitic rocks taken from the stone quarries in Kaman were investigated. The rock samples were taken from four different stone quarries in the region and the minerological structures, compresive strength, tensile strength, elasaticity module, surface hardness, unit weight, water absorbtion and apperent porosity properties of these samples were determined. Experiment results showed that the mineral structures and hardness of these samples were similar. It was found that the rocks with higher unit weight and compresive strength but lower water absorbtion had higher elasicity module value. It was seen that the rocks in Kaman region were appropriate to be used as crushed aggregate and that the rocks with best properties belonged to ömerhacılı region