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    Comparative analysis of long-term and high temperature performances of OPC based high strength mortar and silica fume based high strength geopolymer mortars
    (Elsevier Science Inc, 2024) Saridemir, Mustafa; Celikten, Serhat; Bulut, Metehan; Deniz, Suvat
    The effects of Class C fly ash (FA) contents on the performance of silica fume (SF) based high strength geopolymer mortars (HSGM) subjected to high temperatures up to 1000 degrees C are investigated. The percentages of FA substitution by SF are 10%, 15%, 20% and 25% by weight. The alkali activators used consist of sodium silicate (SS) and sodium hydroxide (SH) and are used in mixtures with SH/SS ratios of 0.3, 0.4, 0.5 and 0.6. In order to compare SF based HSGMs, ordinary Portland cement (OPC) based high strength mortar (HSM) as a control mortar is also produced with the same dosage and water content. The results at environmental temperature show that higher mechanical properties are obtained from SF based HSGMs compared to OPC based HSM. The optimum replacements of Class C FA and SH/SS ratios are 15 % and 0.3 or 0.4 in terms of mechanical properties. At 28 days, SF based HSGMs with flexural strength (ffs) of 15 MPa and compressive strength (fc) of 100 MPa can be produced without thermal curing. High reductions in the mechanical properties are seen on the OPC based HSM and SF based HSGMs subjected to high temperatures. In addition, SF based HSGMs with fc values above 25 MPa can also be obtained after exposure to 1000 degrees C. Alterations in the microstructure of OPC based HSM and SF based HSGMs under the influence of high temperatures are also examined with XRD, FTIR, SM, and FESEM/EDX analyses. Particularly, a spongy structure with volumetric expansion is seen with the formation of the glassy phase in the matrix of SF based HSGMs subjected to a temperature of 1000 degrees C.
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    Effect of calcined perlite content on elevated temperature behaviour of alkali activated slag mortars
    (Elsevier, 2020) Celikten, Serhat; Saridemir, Mustafa; Akcaozoglu, Kubilay
    In this paper, the influence of calcined perlite on the elevated temperature behaviour of alkali activated slag (AAS) mortars is researched. The diversity parameters of mortars are the levels of calcined perlite (CP) replacement (0, 25 and 50% by volume), the molecular silicate modulus (0.25, 0.50, 0.75, 1.00 and 1.25) and the levels of elevated temperature (400 degrees C, 600 degrees C and 800 degrees C). The flexural strength (f(f)), compressive strength (f(e)) and mass loss of mortars produced according to these diversity parameters are determined. Moreover, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analyses are performed on the samples from the mortars exposed to ambient and elevated temperatures. The experimental results prove that the initial f(f) and f(e) results of mortars at ambient temperature significantly reduce with the increase of CP content. This decrease in the f(f) and f(e) results of mortars is confirmed by the mass losses and microstructure analysis. On the other hand, the experimental results prove that there are significant improvements in the residual strengths of mortars at elevated temperatures with the increase of CP content.
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    Effect of high temperature, acid and sulfate on properties of alkali-activated lightweight aggregate concretes
    (Elsevier Sci Ltd, 2022) Saridemir, Mustafa; Celikten, Serhat
    The primary aim of the present study is to research the effect of binary blended on the mechanical, microstructural and durability properties of alkali activated lightweight aggregate concretes (AALWACs) used basaltic pumice (BP) as lightweight aggregate. Ground granulated blast furnace slag (GGBFS) and fly ash (FA) as precursors are activated with the mixtures of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) in diverse SiO2/Na2O ratios (Ms). The unit weight, compressive strength (f(c)), flexural strength (f(fs)) and splitting tensile strength (f(sts)) and water absorption of AALWACs are determined. Moreover, the f(c) and weight loss of AALWACs exposed to high temperature, acid and sulfate effects are determined separately. The results show that higher strength can be obtained from the AALWACs compared to the control concrete (C) produced with only Portland cement. The effects of high temperatures on the microstructures of AALWACs are examined by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and polarized light microscope (PLM) analyses. As the temperature exposed to the AALWACs increases, SEM and PLM analyses indicate that the deterioration, alteration, discoloration, pore and crack in their microstructures increase.
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    Effects of elevated temperatures and cooling regimes on the waste andesite dust-based geopolymer mortars
    (Elsevier Sci Ltd, 2024) Celikten, Serhat; Saridemir, Mustafa; Sologlu, Mustafa
    In this study, the geopolymer mortar mixtures were manufactured by activating andesite stone cutting waste dust with sodium silicate. The sodium silicate content in the mixtures was determined to contain 6%, 8% and 10% Na2O by weight of waste andesite dust (WAD). The produced mixtures were subjected to thermal curing at three different temperatures (60 degrees C, 75 degrees C and 90 degrees C), and in two different periods (8 hours and 24 hours). Flexural strength (fs) and compressive strength (fc) tests of 1, 28 and 56 days were carried out on the specimens obtained from the geopolymer mortar mixtures. The effects of Na2O content, thermal curing temperature and time on the strength values of the geopolymer mortars were investigated. Moreover, the geopolymer mortar samples produced with 8 hours of thermal curing were exposed separately to 400 degrees C, 600 degrees C and 800 degrees C. The specimens, which were kept for 1 hour at 400 degrees C, 600 degrees C and 800 degrees C, were exposed to three different cooling conditions (slow-cooled in air, fast-cooled in air and water-cooled). The fs and fc tests were carried out on the cooled geopolymer mortars, and the effects of high temperatures and cooling conditions on the strength properties of the geopolymer mortars were evaluated. In addition, the changes in the microstructures were examined by performing XRD and SEM/EDAX analyses on the selected geopolymer mortars. The fs and fc values of the watercooled geopolymer mortars significantly decreased.
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    Influence of calcined diatomite content and elevated temperatures on the properties of high strength mortars produced with basalt sand
    (Ernst & Sohn, 2020) Saridemir, Mustafa; Celikten, Serhat; Ciflikli, Murat; Karahancer, Mustafa
    In this paper, the effect of calcined diatomite (CDT) content on the mechanical, microstructural, and mineralogical properties of high strength mortars (HSMs) exposed to 25, 400, 600, 800, and 1,000 degrees C temperatures is investigated. The percentages of CDT that replace Portland cement (PC) in this work are 0, 5, 10, 15, and 20%, by weight. The researched properties of the HSMs are the unit weight (U-w), ultrasonic pulse velocity (U-pv), flexural strength (f(s)), compressive strength (f(c)) and the analyses of X-ray powder diffraction, polarized light microscopy, and scanning electron microscopy/energy dispersive spectroscopy. The experimental results show that the CDT has a potential to be successfully employed as a partial replacement of PC in the HSMs exposed to elevated temperatures. The optimal replacement level of PC by CDT is determined as 15% from strength tests. Besides, the U-w, U-pv, f(s), and f(c) values progressively reduce as the temperatures subjected to the HSMs increase. The CDT has a positive effect on the f(s) and f(c) values the HSMs after exposure to elevated temperatures.
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    Investigation of fire and chemical effects on the properties of alkali-activated lightweight concretes produced with basaltic pumice aggregate
    (Elsevier Sci Ltd, 2020) Saridemir, Mustafa; Celikten, Serhat
    This paper evaluates the properties of alkali-activated lightweight concretes (AALWCs) produced with basaltic pumice aggregate. The AALWC mixtures using the replacement ratios of 0, 25 and 50% blast furnace slag (BFS) by weight of fly ash (FA) are produced in addition to a reference lightweight concrete (RLWC) produced by only Portland cement. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) are employed as activating agents in the AALWC mixtures. The experimental studies are performed to investigate the properties of AALWCs. In these studies, the strength properties like compressive strength (f(c)), flexural strength (f(fs)) and splitting tensile strength (f(sts)) are determined. Moreover, the durability properties such as water absorption, acid and sulfate attacks resistance, and behaviour at elevated temperatures are studied. The residual f(c) and mass loss of lightweight concretes (LWCs) including the RLWC are examined after the durability tests. The results of AALWCs are compared with each other and RLWC. The change in the microstructures of LWCs due to the elevated temperatures are researched by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) spot, X-ray diffraction (XRD) and polarized light microscope (PLM) analyses. The results show that the AALWCs have superior durability properties than the RLWC. Moreover, the recovery of wastes such as BFS and FA contributes to both reducing environmental pollution and reducing CO2 emissions. (C) 2020 Elsevier Ltd. All rights reserved.
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    Mechanical and microstructural properties of alkali-activated lightweight mortars exposed to high temperatures
    (Elsevier, 2021) Saridemir, Mustafa; Celikten, Serhat; Ayaydin, Gunay
    The influence of the curing conditions (ambient curing or heat-curing), and concentration of the activating agent (8, 10, 12, 14, 16, 18 and 20 Molar sodium hydroxide solution) on the properties of alkali-activated lightweight mortars (AALWMs) containing ground granulated blast furnace slag (GGBFS) as sole binder is reported in this study. AALWMs are exposed to elevated temperatures (150, 250 and 500 degrees C) at the age of 28 days. The investigated properties of AALWMs at ambient and high temperatures are the unit weight (U-w), ultrasonic pulse velocity (U-pv), flexural strength (f(s)), compressive strength (f(c)) and the analyses of X-ray powder diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The best strength results have been achieved on the ambient-cured AALWMs activated with 8 M NaOH solution.
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    Mechanical and microstructural properties of calcined diatomite powder modified high strength mortars at ambient and high temperatures
    (Elsevier, 2020) Saridemir, Mustafa; Celikten, Serhat; Yildirim, Ahmet
    In this experimental work, mechanical and microstructural properties of calcined diatomite powder (CDP) modified high strength mortars (HSMs) at ambient and high temperatures were researched. In the HSM mixtures, Portland cement was replaced with CDP at ratios of 0%, 5%, 10%, 15% and 20%. Several experiments regarding the hardened properties were carried out at 14, 28, 56 and 90 days at the ambient temperature of 25 degrees C. HSMs were heated up to high temperatures of 400 degrees C to 1000 degrees C at the age of 56 days, separately. Then, high temperature resistances of HSMs were quantified in terms of the residual hardened properties and the changes in the microstructural properties after heating. The residual performance was found to be higher in the HSMs modified with CDP than in the reference HSM (R-HSM) which was made 0% CDP. Based on the test results, it was seen that the HSM modified with 15% CDP (15CDP-HSM) exhibited the highest mechanical properties at ambient and high temperatures. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
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    Mechanical properties of SFRHSC with metakaolin and ground pumice: Experimental and predictive study
    (Techno-Press, 2017) Saridemir, Mustafa; Severcan, Metin Hakan; Celikten, Serhat
    The mechanical properties of steel fiber reinforced high strength concrete (SFRHSC) made with binary and ternary blends of metakaolin (MK) and ground pumice ( GP) are investigated in this study. The investigated properties are ultrasonic pulse velocity (U-pv), compressive strength (f(c)), flexural strength (f(f)) and splitting tensile strength (f(st)) of SFRHSC. A total of 16 steel fiber reinforced concrete mixtures were produced by a total binder content of 500 kg/m(3) for determining the effects of MK and GP on the mechanical properties. The design fc was acquired from 70 to 100 MPa by using a low water-binder ratio of 0.2. The test results exhibit that high strength concrete can be obtained by replacing the cement with MK and GP. Besides, correlations between these results are executed for comprehending the relationship between mechanical properties of SFRHSC and the strong correlations are observed between these properties. Moreover, two models in the gene expression programming (GEP) for predicting the f(c) of SFRHSC made with binary and ternary blends of MK and GP have been developed. The results obtained from these models are compared with the experimental results. These comparisons proved that the results of equations obtained from these models seem to agree with the experimental results.
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    Microstructural Analyses of High Strength Concretes Containing Metakaolin at High Temperatures
    (Springer, 2017) Saridemir, Mustafa; Severcan, Metin Hakan; Ciflikli, Murat; Celikten, Serhat
    In this study, the effects of high temperatures on the mechanical and microstructural properties of high strength concretes (HSCs) containing metakaolin (MK) are investigated. For this purpose, the concrete mixtures containing MK were produced with a water-binder ratio of 0.2. The mechanical properties of these concretes at 25, 250, 500 and 750 degrees C temperatures were determined. Besides, the effect of high temperature on the microstructural properties of cementitious matrix, interfacial transition zone between cement and aggregates, and aggregates of concretes were inspected by X-ray diffraction, scanning electron microscope and plane polarized transmitted light (PPTL) analyses. The results indicate that the ultrasound pulse velocity (U-pv), compressive strength (f(c)), flexural strength (f(fs)) and splitting tensile strength (f(sts)) values of these concretes decrease with the increasing of the high temperature especially after 250 degrees C. The heated concrete specimens were also examined at both macro- and micro-scales to determine the discoloration, alteration and cracks of HSC at different temperatures. PPTL analyses show that increasing temperature causes impairing of interfaces between aggregate particles and cementitious materials. The results also show that the partial replacement of 10 % MK with cement has the best performance on the mechanical properties of HSC.
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    The strength properties of alkali-activated silica fume mortars
    (Techno-Press, 2017) Saridemir, Mustafa; Celikten, Serhat
    In this study, the strength properties of alkali-activated silica fume (SF) mortars were investigated. The crushed limestone sand with maximum size of 0-5 mm and the sodium meta silicate (Na2SiO3) used to activate the binders were kept constant in the mortar mixtures. The mortar specimens using the replacement ratios of 0, 25, 50, 75 and 100% SF by weight of cement together with Na2SiO3 at a constant rate were produced in addition to the control mortar produced by only cement. Moreover, the mortar specimens using the replacement ratio of 4% titanium dioxide (TiO2) by weight of cement in the same mixture proportions were produced. The prismatic specimens produced from eleven different mixtures were de-moulded after a day, and the wet or dry cure was applied on the produced specimens at laboratory condition until the specimens were used for flexural strength (f(fs) ) and compressive strength (fc) measurement at the ages of 7, 28 and 56 days. The f(fs) and (fc) values of mortars applied the wet or dry cure were compared with the results of control mortar. The findings revealed that the f(c) results of the alkali activated 50% SF mortars were higher than that of mortar produced with Portland cement only. It was found that the f(fs), and f(c), of alkali-activated SF mortars cured in dry condition was averagely 4% lower than that of alkali-activated SF mortars cured in wet condition.