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Çimento, yapı malzemesi üretiminde bağlayıcı malzeme olarak oldukça yüksek oranlarda kullanılmaktadır. Doğal kaynak tüketimi ve atmosfere salınan CO2 miktarı göz önüne alındığında, çimento kullanım oranının düşürülmesi amacıyla alternatif bağlayıcı malzeme arayışı ile geopolimer kompozit üretimi gerçekleşmiştir. Atık malzemeler ile uygun kimyasal malzemelerin bir araya getirilmesi sonucu oluşan geopolimer, sunduğu birçok avantaj nedeniyle malzeme alanı için oldukça umut vericidir. Bu çalışmada, hafif geopolimer harçların mekanik özelliğini yansıtan basınç dayanım testi ile şekil değiştirme durumunu yansıtan rötre testi sonucunda elde edilen verilerin istatistiksel analiz ve modelleme işlemleri genetik ekspresyon programlama (GEP) ve çoklu doğrusal regresyon (ÇDR) kullanılarak gerçekleştirilmiştir. Hafif geopolimer harçların basınç dayanımı ve rötre değerlerine ulaşılması amacıyla sodyum hidroksit molaritesi, alkali/uçucu kül oranı, sodyum silikat/sodyum hidroksit oranı ve yaş girdi parametreleri dikkate alınarak oluşturulan GEP modelleri ile laboratuvar verilerine oldukça yakın sonuçlar elde edilmiştir. Basınç dayanımı ve rötre parametreleri için hedef değerler ile tahmin değerleri arasındaki ilişkiyi gösteren korelasyon katsayıları sırasıyla 0.94 ve 0.97 olarak elde edilmiş olup, diğer istatiksel değerlendirmeler sayesinde de oluşturulan modelin uygunluğu desteklenmiştir.

Recycling end-of-life tires is a global problem that requires an urgent solution. Storing and preserving these tires is a challenge that delays facing potential problems instead of solving the problem. In this context, recycling waste tires without harming the environment and at low costs has been the focus of many researchers. For a few decades, the possibility of these tires to be granulated to the size of aggregate for concrete and then be replaced with natural aggregate has been a subject of research by scientists studying in this field. In this regard, this study aims to experimentally investigate the influence of waste rubber aggregate on some engineering properties of concrete, such as, ultrasonic pulse velocity-based quality assessment, abrasion resistance, and thermal conductivity characteristics as well as the mechanical performance, namely, compressive strength. Another significant side of the study was to establish a statistical relationship and correlation between the w/c ratio and substitution level of waste rubber aggregate and the experimental outputs. The experimental study indicated that the waste rubber aggregate decreased the compressive strength of the concretes whereas it improved the thermal conductivity characteristics and abrasion resistance of the concretes manufactured in this study. On the other hand, the statistical analysis revealed that the input parameters have meaningful effects on the engineering properties of the concretes, and there is a strong correlation between these properties.

Kullanım ömrünü tamamlamış araç lastiklerinin geri dönüştürülmesi çözüm bekleyen global ölçekte bir sorundur. Bu lastiklerin depolanarak muhafaza edilmesi sorunu çözmek yerine olası problemlerle yüzleşmeyi geciktiren bir durumdur. Bu bağlamda atık lastiklerin çevreye zarar vermeden ve düşük maliyetlerle geri dönüştürülmesi birçok araştırmacının ilgili odağı olmuştur. 21. yy.ın başından buyana, bu lastiklerin öğütülerek beton üretiminde kullanılan agrega boyutlarına getirilip sonrasında beton üretiminde doğal agrega yerine kullanılabilirliği bu alanda çalışan bilim insanlarının araştırma konusu olmuştur. Literatürde bu konu ile ilgili çalışmaların sayısı da her geçen gün artmaktadır. Bu çalışma da temelinde bu alandaki son gelişmeleri derleyerek literatüre kazandırma amacına sahiptir. Bilindiği üzere betonun hem taze durumdaki hem de sertleşmiş durumdaki özellikleri çok geniş bir yelpazeye sahiptir. Buradaki çalışmanın amacına uygun bir şekilde sunulabilmesi için de atık lastiklerden elde edilmiş lastik agregalarının betonun taze özelliklerinden işlenebilirlik ve reolojik davranışı, sertleşmiş özelliklerinden ise basınç ve çekme dayanımı, elastik modül, kırılma parametreleri ve aşınma direnci üzerindeki etkisi araştırılmıştır. Derlenen bilgilerden elde edilen bulgular neticesinde lastik agregasının beton üretiminde kullanılması genel olarak betonun bahsedilen özelliklerini kötüleştirdiği sonucuna varılmıştır. Ayrıca, bu özelliklerin ne derece etkilendiği de lastik agreganın şekli, boyut, yüzey özellikleri ve ikame seviyesi ile ilişkilidir. Bundan dolayı bu tür betonların yapısal betonlarda kullanımı önerilmemekle beraber yapısal olmayan, kentsel peyzaj yapılarında, yol banket kenar bordürleri, kilit taşları, satıh kaplamaları vb. üretimlerde kullanılmasının iyi bir geri dönüşüm alternatifi olacağı vurgulanmaktadır.

The main target of this study is to experimentally investigate the possibility of recycling of low-density polyethylene (LDPE) pellets as aggregate in pervious concrete manufacturing to achieve sustainable pervious concrete and contribute to plastic waste management. Therefore, two aggregate-to-cement ratios of 7 and 6 are chosen to produce two different pervious concrete series. Natural aggregate and LDPE pellets utilized in the production of pervious concrete are in a single size that remained on a 4.5-mm sieve and passed from 9.5-mm sieve. Natural aggregate was substituted with LDPE pellet at contents of 0, 10, 20, 30, 40, and 50% of total aggregate volume. Totally, 12 pervious concrete mixtures were designed. Basic engineering characteristics of pervious concrete were investigated in terms of permeability and compressive strength. Moreover, abrasion resistance and splitting tensile strength of concrete mixtures were also examined. Additionally, fresh/dry densities and void contents of produced pervious concrete mixtures were determined during the experimental study. The results showed that abrasion resistance of pervious concrete was enhanced by substituting natural aggregate with LDPE pellet whereas strength characteristics were adversely affected. In addition, reductions in fresh and dry densities, void content, and percolation rate of pervious concretes were observed due to the inclusion of the LDPE pellet.

In this study, a research on the effectiveness of artificial lightweight aggregate (A-LWA) on the fresh and hardened properties of geopolymer mortars is presented. The main aim of this study is to propose a relatively newer means of recycling of FA through geopolymer mortar production. Therefore, firstly, artificial lightweight aggregate (A-LWA) was produced through the cold-bonding pelletization process of FA. Then, FA based geopolymer mortars were produced with this aggregate. The geopolymer mortars manufactured in this study had constant source material and alkaline activator quantities of 600 and 300 kg m-3, respectively. The proportion of Na2SiO3-to-NaOH was 2.5 and the molarity of NaOH was 12 M. The A-LWA sand was replaced partially with river sand up to 100%. The compressive strength, ultrasonic pulse velocity, fresh and dry densities of the geopolymer composites were measured at the age of 7 days and the flow table test was conducted to indicate the consistency of the geopolymer mixtures. The results indicated the A-LWA utilization enhanced the workability of the geopolymer mixtures and the highest increase of flow diameter of %20 was obtained using 100% A-LWA. Compressive strength values of geopolymer mortars varied between 4.28 and 32.3 MPa. A systematical decrease in the compressive strength and revealed with respect to the increasing level of A-LWA due to the softness and weakness of the A-LWA particles. Ultrasonic pulse velocity results of geopolymer mortars ranged from 1479 to 2596 m s-1 with related the replacement level of A-LWA., Bu çalışmada, yapay hafif agreganın (YHA) geopolimer harçların taze ve sertleşmiş özellikleri üzerindeki etkisi üzerine bir araştırma sunulmaktadır. Bu çalışmanın ana amacı, geopolimer harç üretimi yoluyla UK'nin geri dönüşümü için nispeten daha yeni bir alternatif önermektir. Bundan dolayı, UK kullanılarak soğuk bağlama yöntemiyle YHA üretilmiştir. Sonra bu agregalar ile UK esaslı geopolimer harçlar üretilmiştir. Bu çalışmada üretilen geopolimer harçlar, sabit miktarda 600 kg m-3 UK ve 300 kg m-3 alkali aktivatör miktarları kullanılarak üretilmiştir. Na2SiO3/NaOH oranı 2.5 ve NaOH molaritesi 12 M olarak alınmıştır. YHA, dere kumuyla hacimce %100’e kadar kısmi olarak yer değiştirilerek kullanılmıştır. Geopolimer harçların basınç dayanımı, ultrasonik dalga hızı, taze ve kuru birim ağırlıkları 7 günlük süre sonunda ölçülmüştür. Taze karışımların kıvamını belirlemek için geopolimer harçlarda akış tablası deneyi yapılmıştır. Sonuçlar YHA kullanımının geopolimer karışımlarının işlenebilirliğini arttırdığını ve % 20'lik en yüksek akış çapı değerinin % 100 YHA kullanılarak elde edildiğini göstermiştir. Geopolimer harçların basınç dayanımı değerleri 4.28 -32.3 MPa arasında değişen değerler elde edilmiştir.. YHA parçacıklarının boşluklu ve zayıf yapısı nedeniyle YHA artış miktarına bağlı olarak basınç dayanımında sistematik bir azalma görülmüştür. Geopolimer harçların ultrasonik ses geçiş hızı sonuçları, YHA’nın ikame seviyesi ile ilişkili olarak 1479 ile 2596 m s-1 arasında değişen değerler elde edilmiştir

This paper presents the results of an experimental program to determine the properties of glass fiber reinforced geopolymer mortar which is a mixture of fly ash, alkaline liquids, fine aggregates, and glass fibers. The effects of inclusion of glass fibers on density, compressive strength, splitting tensile strength, absorption and sorptivity of hardened geopolymer composite (GPC) was studied. Alkaline liquid to fly ash ratio was fixed as 0.33. NaOH and NaSiO3 solutions were used as alkaline liquids for activation of fly ash. The alkaline liquid combination ratio of 2.5:1 were used for Na2SiO3:NaOH. Glass fiber was added to the mixes in 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% by volume of mortar. A curing regime of 48 hours with 60 ˚C temperature was applied. The experimental results indicated that inclusion of the glass fibers resulted in a decrease in the workability, yet, an improvement in compressive strength and splitting tensile strength of fly ash based GPC was obtained by increasing the fiber content. However, the inclusion of glass fiber did not indicate a remarkable change in the water absorption and sorptivity of GPCs.

Dayanıklılık, ekonomik üretim ve hızlı uygulama olanağı sunan silindirle sıkıştırılmış beton (SSB) son yıllarda ülkemizde yol uygulamalarında ön plana çıkmıştır. SSB malzemesinin ileri düzeyde gelişmesi ile beraber bu uygulamaların daha yaygın hale gelmesi ülkemizin ihtiyacı olan yolların daha ekonomik ve hızlı yapılmasına olanak sağlayacaktır. Bu çalışmada, makro sentetik elyaf miktarının silindirle sıkıştırılmış betonun eğilme dayanımı, aşınma ve kayma direnci özellikleri üzerindeki etkisi araştırılmıştır. Beton hacminin %0, %0.2, %0.4 ve %0.6 oranlarında makro sentetik elyaf kullanılan numunelerin karışım oranları zemin sıkıştırma metoduna göre belirlenmiştir. Bu çalışma sonunda, %0.4 makro sentetik elyaf orana kadar elyaf miktarındaki artışın SSB’nin eğilme dayanımını önemli ölçüde arttırdığı görülmüştür. Ayrıca elyaf miktarındaki artışa bağlı olarak numune içerisindeki boşluk miktarı arttığından dolayı elyaf kullanımının SSB’nin aşınma direncini azalttığı belirlenmiştir. Numune yüzeyindeki elyaflar sürtünmeyi azalttığından kaymaya karşı direncin de elyaf miktarı arttıkça azaldığı gözlemlenmiştir.

Portland çimentosu, harç ve beton yapımında yaygın olarak kullanılmaktadır. Ancak çimento harcı ve betonun gecikmiş priz süresi, düşük çekme dayanımı, yüksek kuruma büzülmesi ve düşük kimyasal direnç gibi bazı dezavantajları vardır. Polimerler bu dezavantajları ortadan kaldırmanın yanı sıra, betonun işlenebilirliğini ve geçirimsizliğini arttırmak amacıyla katkı maddesi olarak kullanılabilmektedirler. Bu çalışmada, Stiren-Bütadien Kauçuk lateksinin kütlece farklı ikame oranlarını (%0, %5, %10, %15 ve %20) içeren harçların erken yaştaki (14 gün) sertleştirilmiş özellikleri incelenmiştir. Taze harç için yayılma ve birim ağırlık ölçümleri yapılırken, sertleşmiş harç üzerinde birim ağırlık, basınç dayanımı, eğilme dayanımı, su emme ve kapiler su emme testleri yapılmıştır. Sonuç olarak harç karışımlarında lateks miktarı arttıkça dayanım değerlerinin azaldığı görülmüştür. Lateks kullanımına bağlı olarak eğilme dayanım değerlerinde düşüş gözlenirken, %10 oranında lateks kullanımı kontrol karışımına kıyasla numunelerin eğilme dayanımı değerlerinde %3 oranında küçük bir artış sağlamıştır. Taze ve sertleşmiş harç numunelerinin birim ağırlıkları kontrol numunesine göre artmıştır. Kullanılan lateks, harçların işlenebilirliği, su emme ve kılcal su emme değerleri üzerinde olumlu bir etkiye sahip olmuştur., Portland cement has been widely used in mortar and concrete construction. However, there are some disadvantages such as, delayed setting time of cement mortar and concrete, low tensile strength, high drying shrinkage, and low chemical resistance. In addition to eliminating these disadvantages, polymers can be used as concrete admixtures to enhance the workability and impermeability of concrete. In this study, fresh and hardened properties of mortars containing different replacement ratios of Styrene-Butadiene Rubber latex by mass (0%, 5%, 10%, 15%, and 20%) at early age (14 days) were examined. The flow and fresh unit weight measurements were made for fresh mortar, while compressive strength, flexural strength, unit weight, water absorption, and capillary water absorption tests were conducted for hardened mortar. As a result, it was observed that the strength decreases as the amount of latex increases in the mortar mixes While a decrease was observed in the flexural strength values due to the use of latex, the use of 10% latex resulted in a small increase of 3% in the flexural strength values of the samples compared to the control mixture. The unit weights of the fresh and hardened mortar samples increased compared to the control sample. The latex addition used has a positive effect on workability, water absorption, and sorptivity of the mortars.

In the first stage of the paper, the effect of binder content, curing temperature and curing time on the compressive strength of light-weight geopolymer mortar (LWGM) was investigated. The base materials used for LWGM are ground granulated blast furnace slag (GGBFS) and fly ash (FA). The main components of LWGM are lightweight pumice aggregate and alkali activated FA or GGBFS binder. Effectiveness of aforementioned parameters was examined in terms of variation of the compressive strengths of LWGMs. The experiments were performed on LWGM cubes under curing temperatures of 60, 80, 100 and 120 degrees C with curing period of 2, 6, 8, 24, 48 and 72 h. The alkaline activator is a mix of 12 M NaOH solution with sodium silicate in ratio of 1:2.5. The ratio of alkaline solution to binder was taken as 0.50. 7 binder contents were taken between 650 to 1250 kg/m(3) with 100 kg/m(3) increment. Full factorial experimental program was adopted to observe compressive strength development of LWGMs. Therefore, 336 data samples were obtained. The second stage of the paper is to optimize those experimental parameters through response surface method. Test results indicate that the increment in the binder content increases the compressive strength of LWGM. The strength increases with the increase of curing temperature and curing period of LWGM. The experimental verification indicated a good agreement with optimized results. (C) 2017 Elsevier Ltd. All rights reserved.

The fresh and hardened characteristics of concrete reinforced with basalt fiber (BF) have been investigated in the presented study. The chopped micro BF with the length of 12 mm are included in concrete mixes at 0.2%, 0.4%, 0.6% and 0.8% of total volume along with the variation of water to cement ratios (w/c) of 0.47 and 0.59. Mechanical features of concrete incorporating BF are specified using the parameters obtained from static modulus of elasticity, compressive, flexural and splitting tensile strength tests. The multi objective optimization analyses using response surface method (RSM) is performed by the parameterization of the minimized cost and the maximized performance based on the dependent parameters presented. Test results reveal that the mechanical properties are improved while the workability of concrete is remarkably deteriorated by BF incorporation. The optimization analysis has inferred that the BF content of 0.356% provides the optimum result with the w/c ratio of 0.47.

Bu calismada, makro sentetik elyaf miktarinin silindirle sikistirilmis betonun (SSB) optimum su icerigine ve mekanik ozelliklerine etkisi arastirilmistir. Makro sentetik elyaf beton hacminin %0, %0.2, %0.4 ve %0.6 oranlarinda kullanilmis olup her bir karisim dort farkli su icerigine sahip olacak sekilde toplam on alti SSB karisimi uretilmistir. Zemin sikistirma yontemi kullanilarak her bir elyaf orani icin SSB’nin maksimum kuru birim agirligina karsilik gelen optimum su icerigi belirlenmistir. Ayrica, belirlenen optimum su icerigi kullanilarak 4 farkli SSB karisimi daha uretilmis olup bu karisimlarin kivamini belirlemek icin modifiye Vebe deneyi yapilmistir. Elyaf miktarinin SSB’nin mekanik ozellikleri uzerindeki etkisini incelemek icin basinc dayanimi ve yarmada cekme dayanimi deneyi yapilmistir. Deneysel calismanin sonunda, SSB’de makro sentetik elyaf kullaniminin karisimin su ihtiyacini arttirdigi gorulmustur. Ayrica makro sentetik elyaf miktarindaki artisin SSB karisimlarin basinc dayanimini onemli olcude etkilemedigi ve %0.4 makro sentetik elyaf kullaniminin SSB’nin yarmada cekme dayaniminda onemli olcude artis sagladigi sonucuna varilmistir.

In this research, an experimental study was conducted to evaluate freeze–thaw behaviour of fiber reinforced geopolymer mortars. To build up an extensive experimental program, three different fiber types of basalt fiber (BF), steel fiber (SF), and glass fiber (GF) with two different lengths, three fiber volume fractions of 0.4, 0.8, and 1.2%, and three freeze–thaw cycles of 100, 200, and 300 were chosen as the experimental parameters. Here, the solid binding component was the fly ash with a fixed dosage of 550 kg/m3 while the alkaline activators were Na2SiO3 and NaOH solutions. A fixed alkaline activator-to-binding material (solid binding component) ratio of 0.5 was assigned. In total, 13 different fly ash-based geopolymer mixtures were designed. Based on the results of the experimental program it was found out that the workability of the geopolymer mortars was adversely affected by the fiber addition. A continuous increase in both compressive and flexural strengths was achieved when the volume fraction of the BF and SF type fibers were increased. Another critical finding is that utilization the fiber decreased the damage of the freeze–thaw cycles. Therefore, it was proved that the use of fiber can be an effective way to increase the durability of the geopolymer mortar against the freeze–thaw cycles. The mortars manufactured in this study maintained their integrity even after being subjected to the 300 freeze–thaw cycles. In order to provide a better assessment, the experimental program was supported by visual inspection of the specimens at each 100 freeze–thaw cycles.

Being a relatively newer material in construction sector, geopolymer based building materials have been of large interest for last decade. This study presents a comprehensive experimental study for assessment of the effectiveness of mix parameters and compound characteristics of the ingredients on the engineering properties of lightweight geopolymer mortar (LWGM). The investigated fresh properties are rheology and flow behavior of LWGMs. Mechanical properties of hardened LWGMs were monitored in terms of compressive and flexural strength as well as ultrasonic pulse velocity. Acidic pumice aggregate was used to reduce the unit weight of the mortar. The mix parameters taken into account are molarity of NaOH solution, the mass ratio of NaOH and Na2SiO3 solutions to fly ash (S/FA), proportions of Na2SiO3/NaOH (SS/SH), and the oxide compositions, which are percentage of Na2O, the ratios of H2O/Na2O, SiO2/Na2O, and H2O/Solid. The results indicated that SS/SH and S/FA significantly affected viscosity behavior and the fresh mortars were observed to conform well to Herscel-Bulkley rheological model with shear thinning tendency. The mechanical properties of hardened LWGMs demonstrated strong correlation with oxide compositions.

Composite columns have superior strength and ductility performance, and they have become more widely accepted in the engineering applications. However, the filled tubular columns require more attention. This study aims to present a new formulation for the axial load carrying capacity (N u ) of circular concrete filled steel tubular (CFST) short columns having various geometrical and material properties. Although there have been some empirical relations for predicting N u in the literature, genetic algorithm based explicit formulation is not available. In the current study, 314 comprehensive experimental data samples presented in the previous studies were examined to prepare a data set for training and testing of the prediction model. The prediction parameters were selected as outer diameter of column (D), wall thickness (t), length of column (L), compressive strength of concrete (f c ), and yield strength of steel (f y ). The prediction model was obtained by means of gene expression programming (GEP). The proposed model was compared with available ones presented in the current design codes (ACI, Australian Standards, AISC, AIJ, Eurocode 4, DL/T, and CISC) and some existing empirical models proposed by researchers. The prediction performance of all models were also evaluated by the statistical parameters. The results indicated that the GEP model was much better than the available formulae, yielding higher correlation coefficient and lower error.

In this study, the effects of micro-steel fiber, pelletized fly ash lightweight aggregate and microsilica content on the fresh and hardened properties of high-performance cementitious composite (HPCC) were experimentally investigated. Micro-steel fibers having a length of 6 mm were used in the production of mixtures at the level of 0%, 1% and 2% by total volume. Besides, artificial lightweight aggregate produced by the pelletizing method was employed in the mixture production by 0% and 20% of total aggregate volume. 0% and 25% of the total binder content were designated as microsilica. Thus, a total of 12 different HPCC mixtures were obtained. The water-to-binder ratio of 0.2 was chosen in the design of all HPCC mixtures. A high-rate water-reducing chemical admixture is used to give a suitable flow for the fresh mixtures. The mechanical properties of HPCC mixtures are evaluated in terms of compressive and flexural strengths and elastic modulus. In addition to these, total water absorption and capillary water absorption tests were performed to evaluate the pore structure and permeability. The drying and autogenous shrinkage values were determined during the 60-day drying period. Thus, the effects of fiber content, microsilica addition, and artificial lightweight aggregate content were examined. The results of the experiment showed that the mechanical properties of HPCC and shrinkage behavior have been improved with the increase of steel fiber volume fraction. Furthermore, the negative effects of artificial lightweight aggregate can be eliminated by microsilica.

The aim of the study is to determine the impact of various NaOH molarities, sodium silicate-to-sodium hydroxide ratios, binder amounts and the age on the compressive strength and free shrinkage of fly ash based lightweight geopolymer mortars. After experimental evaluation, the data were used to model and optimize mix proportions of lightweight geopolymer mortars through response surface method. NaOH molarities were determined as 6 M, 8 M, and 10 M. sodium silicate-to-sodium hydroxide ratios were chosen as 0.5, 1.5, and 2.5 and binder amounts were used as 600, 700, and 800 kg/m3. For the same variables, except the binder amount, the compressive strengths of geopolymer pastes were also determined. The usage of lightweight aggregate as a replacement of river sand (25%) affected the results due to pore structure and its strength. Thus, it was concluded that strength and shrinkage of the samples reduced in comparison to the geopolymer mortars only including sand. The increase of molarity improved compressive strength of pastes and mortars. However, higher sodium silicate-to-sodium hydroxide ratio resulted in lower strength values. Geopolymer mortars with higher binder amounts and NaOH molarities showed a lower drying shrinkage strains, while resulted in increase of the autogenous shrinkage. The effect of sodium silicate-to-sodium hydroxide ratios were also observed in both shrinkage types. Besides, the optimum variables based on maximum strength and minimum shrinkage strain values were reached in optimisation study conducted with response surface method (RSM). The optimum values for the parameters of NaOH molarity, binder amount and sodium silicate-to-sodium hydroxide ratio were specified as 9.892 M, 600 kg and 0.5, respectively. The corresponding desirability value for this optimisation was obtained as 0.833 within the acceptable range.

The paper presented herein investigates the mechanical performance of concrete involving lightweight and normal weight aggregates with similar compressive strength. For this, two compressive strength values, 25 and 45 MPa, were considered for the concretes produced by normal and lightweight aggregates. Therefore, four concrete mixtures were designed at different water-to-cement ratios and cement contents. The lightweight aggregate utilized in this study was produced through cold bonding pelletization of fly ash and cement at ambient temperature in a specially designed tilted pan. The artificial lightweight aggregate used as a substitution of natural aggregate had similar particle size distribution to that of natural aggregate. The same mixing procedure was adopted to produce concrete and the testing specimens attained from each mixture were cured at the same circumstances. After the 28-day curing period, the specimens were tested for compressive strength and modulus of elasticity, splitting tensile and flexural strengths. Moreover, advanced mechanical properties such as fracture parameters, bond strength between embedded reinforcement and the concrete were also investigated. The test results indicated that it is possible to produce the lightweight aggregate concrete having similar compressive strength with the natural aggregate concrete, however, the utilization of artificial lightweight aggregates significantly influenced the investigated mechanical and fracture properties of the concretes despite having the similar compressive strengths. But, it was also observed that the utilization of lightweight aggregate made the concrete more ductile.

This article presents the effect of different sodium hydroxide (NaOH) concentrations and sodium silicate-to-sodium hydroxide ( $$\text {Na}_{2}\text {SiO}_{3}$$ /NaOH) ratio on the fresh and some hardened properties of lightweight geopolymer mortar (LWGM). The main components of LWGM are lightweight pumice aggregate, crushed limestone aggregate, and alkali-activated FA or GGBFS. Effectiveness of aforementioned parameters was tested in terms of variation of the workability, fresh unit weight, absorption and strength of LWGM. The curing parameters were taken from a previous study conducted by the authors. The alkaline activator is a mix of 8, 10, 12 and 14 molar (M) of NaOH solution and $$\text {Na}_{2}\text {SiO}_{3}$$ with the following ratios 1:0.5, 1:1, 1:1.5, 1:2 and 1:2.5. The ratio of alkaline solution to binder was taken as 0.50. Full factorial experimental program was adopted to observe strength development, water absorption and sorptivity of LWGM. Therefore, 256 data samples were obtained for strength and absorption properties. Optimum alkaline agent ratios and NaOH molarity were obtained from analysis of the experimental data using response surface method. Test results indicate that the increment in the $$\text {Na}_{2}\text {SiO}_{3}$$ /NaOH ratio up to an optimum value increases the strength and decreases water absorption of LWGM. The increment in NaOH concentration from 8 to 14 M increases the strength and decreases the workability and water absorption of LWGM. The strength of GGBFS-based LWGM with different NaOH concentrations and $$\text {Na}_{2}\text {SiO}_{3}$$ /NaOH ratio is greater than that of FA-based GPLWM.

Bond deterioration between the reinforcement and surrounding concrete is one of the crucial reasons for the structural degradation in the steel–concrete composite structures. The assessment of bond deterioration due to corrosion is of prime importance on this issue. This study aims to present the derivation of analytical formulation of ultimate bond strength τ u at the corroded reinforcement–concrete interface for the reinforced concrete (RC) elements subjected to various levels of corrosion. The modeling technique dealt in this work is gene-expression programming and artificial neural network. The data used for the development of the models are thoroughly selected from the available experimental studies reported in the technical literature. A total of 218 experimental data samples were arranged to obtain training and testing data sets. The critical predictive factors were compressive strength of concrete, concrete cover, steel type, diameter of the steel bar, bond length, and corrosion level. The performances of the proposed empirical models were also evaluated statistically. The results indicated that the soft-computing based models had a satisfactory performance to predict the ultimate bond strength of corroded steel bars in RC elements.

In this study, an artificial neural network (NN) based explicit formulation for predicting the edge breakout shear capacity of single adhesive anchors post-installed into concrete member was proposed. To this aim, a comprehensive experimental database of 98 specimens tested in shear was used to train and test NN model as well as to assess the accuracy of the existing equations given by American Concrete Institute and prestressed/precast concrete Institute. Moreover, the proposed NN model was compared with another existing model which had been derived from gene expression programming by the authors in a previous study. The prediction parameters utilized for derivation of the model were anchor diameter, type of anchor, edge distance, embedment depth, clear clearance of the anchor, type of chemical adhesive, method of injection of the chemical, and compressive strength of the concrete. The proposed model yielded correlation coefficients of 0.983 and 0.984 for training and testing data sets, respectively. It was found that the predictions obtained from NN agreed well with experimental observations, yielding approximately 5 % mean absolute percent error. Moreover, in comparison to the existing models, the proposed NN model had all of the predicted values in ±20 % error bands while the others estimated up to %160 error.

This paper presents the results of an experimental study on the hardened characteristics of the self-compacting concretes made with cold bond fly ash lightweight aggregates. Binary and ternary use of fly ash (FA) and silica fume (SF) blends have been considered in the production of self-compacting cold bonded fly ash lightweight aggregate concretes (SCLWCs). For this, a total of 9 SCLWC mixtures were proportioned having constant water-binder ratio of 0.35 and the total binder content of 550 kg/m(3). The control mixture contained only Portland cement (PC) as the binder while the remaining mixtures having binary and ternary blends of PC, FA, and SF. Properties that include compressive strength and ultrasonic pulse velocity, chloride ion penetration, gas permeability, water absorption by total immersion and by capillary absorption were investigated at two curing ages of 28 and 56 days. Test results have showed that incorporating the mineral admixtures enhanced significantly the permeability characteristics. Moreover, it was observed that the compressive strength of the SCLWCs with SF was much higher than those of the control concrete. (C) 2014 Elsevier Ltd. All rights reserved.

This study evaluates the effect of waste polyethylene terephthalate (PET) granules on the fresh, mechanical and absorption characteristics of self-consolidating concretes (SCCs). Fine aggregates were replaced with different percentages (from 0% to 8%) of PET granules obtained by crushing waste PET bottles. The fresh properties of SCC containing PET granules were determined using slump flow and V-funnel flow time tests. Mechanical properties (compressive strength and splitting tensile strength tests) and absorption properties (sorptivity and water absorption tests) were evaluated. The results indicated that utilization of waste PET granules in production of SCC could be an effective way for recycling purpose. The maximum amount of PET replacement should be limited to 5%. Exceeding 5% of PET content may result in an increase of V-funnel flow time to overpass the limiting value, decrease in compressive strength, reduction in sorptivity and increase in the water absorption. The production of high performance SCC containing 5% PET granules satisfies all the requirements for SCC with satisfactory outputs.

This paper presents the experimental results of a research carried out on the strength and permeability related properties of high performance concretes made with binary and ternary cementitious blends of fly ash (FA) and metakaolin (MK). The replacement ratios for FA were 10% and 20% by weight of Portland cement and those for MK were 5% and 10%. Compressive strength, chloride permeability, water sorptivity, and water absorption properties of concretes were obtained in this study for different testing ages up to 90 days. The influences of fly ash, metakaolin, and testing age on the properties of concretes have been identified using the analysis of variance. The statistical based regression models and the response surface method with the backward stepwise techniques were employed in the multi-objective optimization analysis. That is carried out by maximizing compressive strength while minimizing chloride permeability, water sorptivity, and water absorption. It was observed that fly ash and especially metakaolin were very effective on the aforementioned properties of the concretes, depending mainly on replacement levels and duration of curing. The results indicated that the ternary use of fly ash and metakaolin with the approximate cement replacement values of 13.3% and 10% respectively has provided the best results for the testing age of 90 days, when the optimized strength and permeability based durability properties of the concretes are concerned. (C) 2014 Elsevier Ltd. All rights reserved.

This paper presents the results obtained from an experimental study conducted to investigate the effect of shrinkage reducing admixture (SRA) and steel fiber addition on the performance properties of lightweight aggregate concrete (LWAC). Total of seven LWAC mixes with SRA or steel fibers were produced at the same water-cement ratio using cold-bonded fly ash coarse aggregates. The percentage of steel fiber volume fractions used in the mixes was 0.25, 0.75 and 1.25. The amount of SRA used in the mixes was 0.75%, 1.5% and 3 % by weight of cement. Ring type specimens were used for the restrained shrinkage cracking test. At the same time, free shrinkage and weight loss of LWACs were measured. Moreover, the compressive and split tensile strength tests were undertaken. The results indicated that the use of steel fibers has little effect on compressive strength but it improves the split tensile strength. The addition of SRA decreases compressive strength without affecting tensile strength. Moreover, the utilization of steel fiber or SRA extends the cracking time and reduces the crack width of LWAC resulting in finer cracks associated with lower free shrinkage. (C) 2013 Elsevier Ltd. All rights reserved.

Circular hollow section (CHS) steel beams are widely used in both mechanical and civil applications. CHS members are mainly subjected to bending. The flexural overstrength factor (namely the ratio between the ultimate bending strength over the plastic bending moment) characterizes the flexural behaviour of steel CHS beams. This paper describes an analytical study aiming to develop a new explicit formulation for predicting the flexural overstrength factor of steel CHS beams. The proposed models were derived from soft-computing techniques based on both neural networks (NNs) and gene expression programming (GEP), respectively. To this aim, experimental data available from scientific literature were analysed and collected to form a comprehensive dataset for developing the prediction models. A total number of 128 samples was considered in order to cover different geometric and mechanical properties. The input variables accounted for the modelling were the external diameter (D), wall thickness (t), shear length (L-v), and steel yield strength (f(y)). The database was arbitrarily divided into two subsets to obtain both training and testing databases for the generation of the models. The prediction capability of the proposed formulations was assessed with respect to the experimental data and the levels of accuracy and performance were also compared with an existing analytical formulation available previously developed for cold-formed sections. The results showed that the novel proposed models derived from NN and GEP methods provide better prediction performances than those obtained by the existing analytical model. (C) 2015 Elsevier Ltd. All rights reserved.

In this paper, effect of steam and water curing on the compressive strength development and transport properties such as water sorptivity, rapid chloride ion permeability, and gas permeability of concretes containing various volumes of lightweight fly ash aggregate (LWA) were investigated. In production of concrete, a fixed amount of lightweight coarse (LWCA) aggregate plus varying amounts of lightweight fine aggregate (LWFA) were used. Utilization of LWFA was achieved by volumetric substitution of fine aggregate with five different replacement levels namely, 0%, 25%, 50%, 75%, and 100%. Therefore, five different concrete mixtures were produced for this experimental study. The produced concretes were divided into two parts one of which was initially steam cured while the other was directly exposed to water curing. After initial steam curing regime, the steam cured (SC) concretes were also transferred to water until testing Mechanical properties of concretes were monitored through compressive strength development over 56 days, while transport properties were measured by means of water sorptivity, gas permeability and rapid chloride permeability tests conducted at 28 and 56 days. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.

This study reports the finding of an experimental study carried out on the durability related properties of the lightweight concretes (LWCs) including either cold bonded (CB) or sintered (S) fly ash aggregates. CB aggregate was produced with cold bonding pelletization of class F fly ash (FA) and Portland cement (PC) while S aggregate was produced by sintering the fresh aggregate pellets manufactured from FA and bentonite (BN). Two concrete series with water-to-binder (w/b) ratios of 0.35 and 0.55 were designed. Moreover, silica fume (SF) with 10% replacement level was also utilized for the purpose of comparing the performances of LWCs with and without ultrafine SF. The durability properties of concretes composed of CB and S aggregates were evaluated in terms of water sorptivity, rapid chloride ion permeability, gas permeability, and accelerated corrosion testing after 28 days of water curing period. The compressive strength test was also applied to observe the strength level at the same age. The results revealed that S aggregate containing LWCs had relatively better performance than LWCs with CB aggregates. Moreover, the incorporation of SF provided further enhancement in permeability and corrosion resistance of the concretes.

In the first stage of the study presented herein, the findings of an experimental study on drying shrinkage behavior of concretes incorporated with high reactivity commercial metakaolin (MK) and calcined kaolins (CKs) were reported. Free shrinkage strain measurements as well as corresponding weight loss were measured over 60 days of drying. Four different types of kaolins obtained from local sources were calcined and used as mineral admixture for concrete production. Moreover, commercial metakaolin of high purity was also used as reference material for comparison. In the second stage of the study, prediction models through gene expression programming (GEP) and multiple linear regression (MLR) were derived. The data set used for training and testing covers the experimental data presented in this study as well as additional ones collected from the literature. The parameters considered for developing the prediction model are related to the characteristic properties of mineral admixture, concrete composition, and drying period. As a result, CK incorporated concretes revealed comparable performance with MK incorporated ones in terms of drying shrinkage and weight loss. Furthermore, the prediction models yielded strong correlation with the experimental results. Statistical analyses also revealed that the proposed models can be handful tools in predicting the drying shrinkage strain of the concretes modified with MK.

This paper reports an experimental study on the mechanical properties of steel fiber incorporated plain and silica fume (SF) concretes produced with cold bonded artificial fly ash aggregates (AFAs). Two concrete series with water-to-binder ( w / b ) ratios of 0.35 and 0.55 were designed. SF incorporation was achieved by 10% replacement of the weight of cement by silica fume. Two types of hooked-end steel fibers with length/aspect ratios of 60/80 and 30/40 were utilized. AFA, produced from cold bonding pelletization of 90% class F fly ash and 10% Portland cement, was used as coarse aggregate in all of the concrete mixtures. The mechanical properties investigated were compressive strength, modulus of rupture, and bonding strength between rebar and concrete. The tests were carried out at the end of 28 day water curing. Analyses of variance of the experimental results were performed and the contributions of the significant factors on the mechanical characteristics of the concretes were determined for statistical evaluations. Moreover, correlation of the experimental data was carried out to monitor the interaction between mechanical properties and bonding strength of the concretes. The results demonstrated that incorporation of SF and utilization of different types of steel fiber reinforcements significantly affected the mechanical properties of the concretes regardless the w / b ratio.

One of the most remarkable drawbacks of the reinforced concrete structural elements is the corrosion of reinforcement. Especially, in marine structures or in such environments where chloride contamination risk exist this issue gains much importance. In this study, chloride contamination of the concrete was implemented by adding 0%, 1.5%, 3%, and 5% NaCl by weight of the total binder content, into concrete. To assess the influence of high reactivity metakaolin (MK) incorporation on the corrosion resistance of the chloride contaminated concrete, 5% and 15% MK replacement levels by the total weight of the binder were assigned in concrete production. The corrosion behaviors of reinforcing bars embedded in concretes were monitored through accelerated corrosion test, corrosion current density and the corresponding corrosion rate by linear polarization technique (LPR). Moreover, the electrical resistivity of concrete was measured. Analysis of the test results indicated that MK was proved to be effective in inhibiting the active corrosion of concrete even at severe chloride contamination levels.

This paper reports an investigation on the effects of metakaolin (MK) and calcined kaolins (CKs) on the compressive strength development of the concrete. For this, non purified ground kaolins obtained from different sources were thermally treated at specified conditions. Moreover, commercially available metakaolin (MK) of high purity from Czech Republic was also used for comparison. Four replacement levels (5%, 10%, 15%, and 20%) of CK and MK were assigned for concrete production. On the other hand, one plain mix without admixture was produced as reference. Compressive strength development of the concretes was observed at 3, 7, 28, and 90 days. The strength development of concretes was evaluated by statistical technique named GLM-ANOVA. Moreover, a prediction model was derived from gene expression programming (GEP) to illustrate and evaluate the parameters affecting the strength. The investigated parameters are SiO2, Al2O3, kaolinite, and alunite contents, fineness of mineral admixture, age of concrete, and replacement level. The results showed that type of thermally treated kaolin, the replacement level, and age are very effective on the strength development of the concretes. The prediction model containing those seven parameters was compared with the experimental results and proved to be a handful tool for estimating compressive strength of concrete incorporated with commercial MK and calcined kaolins.

One of the major environmental concerns is disposal or recycling of the waste materials. Marble processing plants and limestone quarries produce millions of tons waste dust in the powder form every year. Having considerable high degree of fineness in comparison to cement, these materials may be utilized as filler for production of self compacting concretes (SCCs). For this purpose, an experimental program has been conducted to investigate the possibility of using marble powder (M) and limestone filler (LF) in the production of SCCs with and without fly ash. Two series of concrete mixtures containing binary and ternary blends of fine materials were designed and cast with a constant water–binder ratio of 0.35. Test results showed that high replacement level of the filler slightly affected the fresh properties of the SCCs adversely. However, the inclusion of fly ash mitigated such problems. Moreover, mechanical and transport properties were improved by using marble powder and limestone filler.

The 90 experimental data samples previously validated in the current literature regarding the compressive strength of mortars have been collected and evaluated to develop the practical soft-computing model which is presented in this study for prediction of the compressive strength of mortars with blended cements. The presented model provides many economical, technical and environmental benefits to be swiftly implemented into the practice. It is formulated based on the soft-computing techniques of genetic expression programming (GEP) by considering the model factors including as specific weight and surface of cement, water/cement ratio, testing age, the amounts of clinker, limestone, pozzolana and gypsum. Paper explains the validity of the presented model with that randomly selected experimental sub datasets available in the current literature. The findings illustrate that the presented GEP model has a favorable potential for estimating the compressive strength of mortars with blended cements.

This study investigates the effectiveness of metakaolin (MK) on the improvement of durability of concretes to sulfate attack. Experimental parameters of the study were MK replacement levels, water to cementitious materials ratio, initial curing procedure in terms of air curing and water curing, and type of the sulfate exposure regimes such as continuous and drying-immersion cyclic exposures. The degree of sulfate attack was evaluated by the reduction in compressive strength (CS) of concrete. The tests were conducted at specified periods up to 365 days. At the end of initial curing, concrete specimens were divided into three groups such that the first group was transferred into tap water to be used as control in the assessment of CS reduction while the other groups were immersed in 10% Na2 SO4 solution for the period of 365 days under continuous or cyclic exposures. The results indicated that inclusion of MK as modifying agent increased the resistance of concrete against sulfate attack depending mainly on ...

This paper presents the results of an investigation on the use of metakaolin (MK) as a supplementary cementing material to improve the performance of concrete. Two MK replacement levels were employed in the study: 10% and 20% by weight of the Portland cement used. Plain and PC-MK concretes were designed at two water–cementitious materials (w/cm) ratios of 0.35 and 0.55. The performance characteristics of the concretes were evaluated by measuring compressive and splitting tensile strengths, water absorption, drying shrinkage, and weight loss due to the corresponding drying. The porosity and pore size distribution of the concretes were also examined by using mercury intrusion porosimetry (MIP). Tests were conducted at different ages up to 120 days. The results revealed that the inclusion of MK remarkably reduced the drying shrinkage strain, but increased the strengths of the concretes in varying magnitudes, depending mainly on the replacement level of MK, w/cm ratio, and age of testing. It was also found that the ultrafine MK enhanced substantially the pore structure of the concretes and reduced the content of the harmful large pores, hence made concrete more impervious, especially at a replacement level of 20%.

Shrinkage is generally considered as an important durability property of hardened concrete. During the drying process, free and absorbed water is lost from the concrete. When the drying shrinkage is restrained, cracks can occur depending on the internal stresses in the concrete. The ingress of deleterious materials through these cracks can cause decrease in the compressive strength and the durability of concrete. In the first stage of the study, a prediction model through the most popular soft computing method called neural network (NN) was derived. The data set used for training and testing of the prediction model covers the experimental data presented in the literature. In the second stage of the study, the findings of an experimental study on drying shrinkage behavior of concretes incorporated with silica fume (SF) and fly ash (FA) were reported. Free shrinkage strain measurements as well as corresponding weight loss were measured over 40 days of drying. The obtained experimental results were also used for the validation of the proposed prediction models. The highest amount of mineral admixture resulted in high shrinkage strain development. Moreover, the proposed NN model also accurately predicted the values obtained from experimental study. (C) 2015 Elsevier Ltd. All rights reserved.

Reinforced concrete (RC) is one of the most commonly used composite materials in construction industry. Corrosion of reinforcing steel embedded in concrete is a crucial issue leading deterioration of RC structure. In this study, mathematical formulations that predict the time from corrosion initiation to corrosion cracking in RC elements subjected to accelerated corrosion test are presented. For this, the time to corrosion cracking t cr in RC elements is evaluated and developed using soft-computing techniques, namely, genetic algorithms and artificial neural networks. In the models, nine critical estimation parameters were considered. The experimental inputs are mix design properties of the concretes, curing conditions, testing age, mechanical properties of concrete, and cover thickness of RC elements. The dataset was formed by collecting 126 experimental data samples reported in the technical literature. The dataset was randomly separated into three parts for training, testing, and validating the models. Through the numerical study, the influences of various experimental factors on the duration and extent of RC corrosion-induced cracking were shown. It was found that the soft-computing based models gave reasonable predictions of t cr in RC elements. However, the neural network model performed better and the highest correlation coefficient (R) between predicted and experimental t cr values was computed as 0.998.

This paper reports the results of an analytical study to predict the edge breakout shear capacity of single adhesive anchors post-installed into uncracked hardened concrete. For this purpose, an experimental database for the adhesive anchors compiled by the ACI Committee 355 was obtained and utilized to construct training and test sets so as to derive the closed-form solution by means of gene expression programming (GEP). The independent variables used for development of the prediction model were anchor diameter, type of anchor, edge distance, embedment depth, clear clearance of the anchor, type of chemical adhesive, method of injection of the chemical, and compressive strength of the concrete. The generated prediction model yielded correlation coefficients of 0.98 and 0.92 for training and testing data sets, respectively. Moreover, the performance of the proposed model was compared with the existing models proposed by American Concrete Institute (ACI) and Prestressed/Precast Concrete Institute (PCI). The analyses showed that the proposed GEP model provided much more accurate estimation of the observed values as compared to the other models. (C) 2014 Elsevier Ltd. All rights reserved.

This study reports the results of an experimental study on mechanical properties of plain and metakaolin (MK) concretes with and without steel fiber. To develop the metakaolin included steel fiber reinforced concrete mixtures, Portland cement was partially replaced with MK as 10% by weight of the total binder content. Two types of hook ended steel fibers with length/aspect ratios of 60/80 and 30/40 were utilized to produce fiber reinforced concretes. Two series of concrete groups were designed with water to binder ratios (w/b) of 0.35 and 0.50. The effectiveness of MK and different types of steel reinforcement on the compressive, flexural, splitting, and bonding strength of the concretes were investigated. All tests were conducted at the end of 28 days of curing period. Analyses of variance on the experimental results were carried out and the levels of the significance of the variables on the mechanical characteristics of the concretes were determined. Moreover, correlation between the measured parameters was carried out to better understand the interaction between mechanical properties of the concretes. The results revealed that incorporation of MK and utilization of different types of steel fibers significantly affected the mechanical properties of the concretes, irrespective of w/b ratio. (C) 2013 Elsevier Ltd. All rights reserved.

In this paper, a soft-computing based study aimed to estimate the available rotation capacity of cold-formed rectangular and square hollow section (RHS-SHS) steel beams is described and novel mathematical models based on neural network (NN) and genetic expression programming (GEP) are proposed. In order to develop the proposed formulations, a wide experimental database obtained from available studies in the literature has been considered. The data used in the NN and GEP models are arranged in a format of eight input iiarameters covering both geometrical and mechanical properties such as width, depth and wall thickness of cross section, inside corner radius, yield stress, ratio of modulus of elasticity to hardening modulus, ratio of the strain under initial hardening to yield strain and shear length. The accuracy of the proposed formulations is verified against the experimental data and the rates of efficiency and performance are compared with those provided by analytical semi-empirical formulation developed by some of the Authors in a previous study. The proposed prediction models proved that the NN and GEP methods have strong potential for predicting available rotation capacity of cold-formed RHSSHS steel beams. (C) 2013 Elsevier Ltd. All rights reserved.

The flexural behaviour of steel beams significantly affects the structural performance of the steel frame structures. In particular, the flexural overstrength (namely the ratio between the maximum bending moment and the plastic bending strength) that steel beams may experience is the key parameter affecting the seismic design of non-dissipative members in moment resisting frames. The aim of this study is to present a new formulation of flexural overstrength factor for steel beams by means of artificial neural network (NN). To achieve this purpose, a total of 141 experimental data samples from available literature have been collected in order to cover different cross-sectional typologies, namely I-H sections, rectangular and square hollow sections (RHS-SHS). Thus, two different data sets for I-H and RHS-SHS steel beams were formed. Nine critical prediction parameters were selected for the former while eight parameters were considered for the latter. These input variables used for the development of the prediction models are representative of the geometric properties of the sections, the mechanical properties of the material and the shear length of the steel beams. The prediction performance of the proposed NN model was also compared with the results obtained using an existing formulation derived from the gene expression modeling. The analysis of the results indicated that the proposed formulation provided a more reliable and accurate prediction capability of beam overstrength.

The ductile design of steel structures is directly influenced by the flexural behaviour of steel beams, which should be sufficient to allow plastic hinges to rotate until the collapse mechanism is completely developed. To guarantee the achievement of such a performance, the beam flexural overstrength must be quantified to appropriately apply capacity design principles. To this aim, analytical formulations to predict the flexural overstrength factor (s) of steel beams with a wide range of cross-section typologies (I and H sections, square and rectangular hollow sections) were developed based on gene expression programming (GEP). An experimental database was gathered from the available literature and processed to obtain the training and testing databases for the derivation of the closed-form solution through GEP. The independent variables used for the development of the prediction models were the geometric properties of the sections, the mechanical properties of the material, and the shear length of the steel beams. The predictions of the proposed GEP-based models were compared with the results obtained using the existing analytical equations proposed in the current literature. Comparative analysis revealed that the proposed formulation provides a more accurate prediction of beam overstrength. (C) 2013 Elsevier Ltd. All rights reserved.

Ground granulated blast furnace slag (GGBFS), a by-product from iron industry, was recycled as artificial coarse aggregate through cold bonding pelletization process. The artificial slag aggregates (ASA) replaced partially the natural coarse aggregates in production of self-compacting concrete (SCC). Moreover, as being one of the most widely used mineral admixtures in concrete industry, fly ash (FA) was incorporated as a part of total binder content to impart desired fluidity to SCCs. A total of six concrete mixtures having various ASA replacement levels (0%, 20%, 40%, 60%, and 100%) were designed with a water-to-binder (w/b) ratio of 0.32. Fresh properties of self-compacting concretes (SCC) were observed through slump flow time, flow diameter, V-funnel flow time, and L-box filling height ratio. Compressive strength of hardened SCCs was also determined at 28 days of curing. It was observed that increasing the replacement level of ASA resulted in decrease in the amount of superplasticizer to achieve a constant slump flow diameter. Moreover, passing ability and viscosity of SCC's enhanced with increasing the amount of ASA in the concrete. The maximum compressive strength was achieved for the SCC having 60% ASA replacement.