Papers by Ramazan Demirboga
Based on ACI 306R-88, the minimum temperature necessary for maintaining concretehydration and str... more Based on ACI 306R-88, the minimum temperature necessary for maintaining concretehydration and strength gaining is 50C. If the atmosphere weather becomes lower than 50Csome preserve measurements should be taken in order to prevent decrease in the rate ofhydration and to prevent fresh concrete from freezing. Most of the cold weather livingcountries spend annually plenty of money in order to facilitate concrete placing in the coldweather and to extend the construction season. It has been tried to carry out the behavior of fresh and hardened concrete contained calcium nitrate at different curing temperatures below freezing temperature of water and compare the results with the both control samples and real Erzurum winter conditions. For this reason, calcium nitrate is used at level of 6% by weightof cement dosage in the mixes. After casting, one group of concrete samples were cured in the different deepfreezes at -5,-10,-15,-200C for 7, and then that same samples were cured inwater for 2...
Construction and Building Materials
Sustainable Concrete Made with Ashes and Dust from Different Sources, 2022
In this article, in order to estimate concrete strength reinforced by GFRP and pozzolanic materia... more In this article, in order to estimate concrete strength reinforced by GFRP and pozzolanic material or non-reinforced concrete, ANN method has been used. Hence, applied materials specifications, produced concrete properties before and after the fire have been considered as system inputs. Some of the mentioned properties are the ratio of w/c, using or non-using GFRP, amount of applied pozzolanic materials and concrete water absorption. Utilized w/c ratios are 0.3, 0.35, 0.4 and the quantity of pumice or expanded perlite is 10%, 20%, 30% of fine aggregates volumes. The temperatures of experiments have been 25 0 C or 600 0 C.The result of article shows the reasonable coincidence between the output of the program and outcome of the experiment. Consequently, Artificial Neural Network (ANN) can be used as an effective method to predict the concrete strength exposed/unexposed to fire.
The compressive strength of core concrete is affected by many parameters and one of them is the s... more The compressive strength of core concrete is affected by many parameters and one of them is the strength of the concrete, which affects the strength of the core compressive strength. This is achieved by using correction factors present in several standards such as ASTM C 42/C 42M-04, but this standard was not considered for high and very high strength concrete (HSC). In this study, a beam of (1x 4x 0.2) m constructed with 100 MPa target strength for core samples. Four different core diameters (25-50-75-100) mm and for each diameter different core length-diameter ratios(λ=l/d) (2-1.75-1.5-1.0) were extracted from the beam for assessing the strength in both casting directions. The relationship between the strength of concrete with respect to reference samples and different cores size with different slenderness ratio, length to diameter (λ) were investigated. The Ultrasonic Pulse Velocity (UPV) was conducted for all samples and the relationship between UPV and strength of cores were de...
Journal of Building Engineering, 2021
Abstract Conventional Portland cement-based composites are inherently weak under tensile stresses... more Abstract Conventional Portland cement-based composites are inherently weak under tensile stresses , due to its high brittleness quotient, and the problem gets further aggravated in geopolymer composites due to pozzolanic effect of precursors like fly ash, GGBFS, etc. Fiber reinforcement in conventional Portland cement concrete have been adopted, for quite some time, to remodel its character from brittle to ductile or quasi-ductile along with significant enhancement in mechanical as well as durability characteristics. With the global emphasis on partial or full replacement of Portland cement-based products in the construction industry and with the advent of “geopolymer” composite as potential replacement, efforts have been made to use fiber reinforcement in geopolymer composites to enhance its performance and service life. The development of fiber reinforced geopolymer composite (FRGC) being relatively new, the paper envisages to contribute to overall understanding and assessment of fiber utility in geopolymer materials. Against this background, a comprehensive database is developed based on past research work and pin-point research gaps for further study and analysis. Analytical assessment of past research reveals that FRGCs possess immense potential as a viable substitute for Portland cement-based composites with a scope for providing better mechanical, durability and structural performances, besides being more environmentally friendly. Further research is required to streamline its database, codes and practical design standards with different fibers, parameters and conditions.
Construction and Building Materials, 2020
h i g h l i g h t s An updated and comprehensive review of geopolymer composites with critical pa... more h i g h l i g h t s An updated and comprehensive review of geopolymer composites with critical parametric assessment. Review paper based on more than 300 research papers spanning over more than 26 years. Microstructure analysis of geopolymer composites presented in simplified form. Evaluation of important parameters involved in geopolymer synthesis. Evaluation based on impact on fresh, mechanical, durability properties and thermal resistance. Consolidation of data base detailing geopolymer mix proportioning, impact of particle size distribution, additives & curing regimes. Identification and elaboration of research gap.
Structural Concrete, 2018
This article presents the results of a study dealing with the concrete resistance to repeated cyc... more This article presents the results of a study dealing with the concrete resistance to repeated cycles of freezing and thawing of nonair entrained, fine lightweight aggregate (LWA) and air‐entrained concrete when tested in accordance with ASTM C 666, procedures A and B. The water‐to‐binder ratios (w/b) of the mixtures ranged from 0.25 to 0.35, and the percentage of cement replacement by silica fume were 7% on a weight basis and constant throughout study. Binder dosage was 500 kg/m3 and constant. LWA was pumice aggregate (PA) and expanded perlite aggregate (EPA). PA and EPA were replaced by 10, 20, and 30% of total volume of 1 m3 as a fine aggregate (0–2 mm fine aggregate fraction). Also one group was produced with air entraining agent by 0.1% ratio of binder dosage. The 200 freeze–thaw cycles were carried out according to ASTM C666/C666M‐15, procedure A and B. The compressive strength, ultrasonic pulse velocity, relative dynamic modulus of elasticity and dry unit weight of mixtures we...
Structural Concrete, 2018
The aim of this work is to experimentally investigate the effect of properties of nano‐CaO in cem... more The aim of this work is to experimentally investigate the effect of properties of nano‐CaO in cement‐based materials. Mortars and paste samples were produced by using nano‐CaO in 2.5, 5, and 7.5% ratios instead of cement. The initial and final setting times and volumetric autogenous shrinkage tests of paste samples and 7, 28, and 360 days’ compressive strength, the ultrasonic pulse velocity, heat of hydration, and linear autogenous shrinkage of mortar samples were determined. In addition, the micro‐structures of paste samples were characterized by X‐ray‐diffraction and SEM. As a result, the shrinkage and setting times were reduced with the increase of nano‐CaO content. CaO with nano size increased the compressive strength (about 10–22%) and the heat of hydration. The compressive strength of mixture containing 7.5% nano‐CaO was lower than that of 2.5 and 5% nano‐CaO at 360 days of curing duration. The heat of hydration increased for all the mixtures containing nano‐CaO at an early st...
Structural Concrete, 2018
This paper investigates the effects of expanded perlite aggregate (EPA) on the properties of mort... more This paper investigates the effects of expanded perlite aggregate (EPA) on the properties of mortar and concrete. A volume of 10, 20, and 30% EPA were used instead of 0–2 mm fine aggregate. Water/binder ratio of 0.30 was constant for all the mortar and concrete mixtures. The compressive strength, ultrasonic pulse velocity (UPV), and linear autogenous shrinkage tests were performed on both mortar and concrete mixtures. Furthermore, the heat of hydration test was only made for mortar mixtures and restrained shrinkage test was only employed to measure cracking time and strain for concrete mixtures. For both mortar and concrete mixtures, the experiments show that the compressive strength, UPV, and linear autogenous shrinkage were generally decreased with increasing the amount of EPA according to control sample, while the heat of hydration is generally increased. However, the reduction ratios in the compressive strength of mortar and concrete samples gradually decreased with increasing t...
Construction and Building Materials, 2017
The nano-MgO improves the properties of the cementitious materials over time. The nano-MgO increa... more The nano-MgO improves the properties of the cementitious materials over time. The nano-MgO increases the hydration heat and compressive strength of mortar. The autogenous shrinkage decreases with the increasing of nano-MgO content. The nano-MgO developments the microstructure of the mortar.
ACI Materials Journal, 2017
ACI Materials Journal, 2017
ACI Materials Journal, 2016
Construction and Building Materials, 2016
h i g h l i g h t s Cores with different h/d were extracted from a slab block of HSC. Molded samp... more h i g h l i g h t s Cores with different h/d were extracted from a slab block of HSC. Molded samples from the same mixes were also prepared. Correction factors were changed between 1.06 and 1.21 for slab. A comparative study was made using the adaptive neuro-fuzzy techniques. Outcomes were assessed statistically to evaluate the performance of ANFIS models.
Fire and Materials, 2016
SummaryThe mechanical properties and thermal conductivity of concretes including pumice aggregate... more SummaryThe mechanical properties and thermal conductivity of concretes including pumice aggregate (PA) exposed to elevated temperature were analyzed by thermal conductivity, compressive strength, flexure strength, dynamic elasticity modulus (DEM) and dry unit weight tests. PA concrete specimens were cast by replacing a varying part of the normal aggregate (0–2 mm) with the PA. All concrete samples were prepared and cured at 23 ± 10C lime saturated water for 28 days. Compressive strength of concretes including PA decreased that reductions were 14, 19, 25 and 34% for 25, 50, 75 and 100% PA, respectively. The maximum thermal conductivity of 1.9382 W/mK was observed with the control samples containing normal aggregate. The tests were carried out by subjecting the samples to a temperature of 0, 100, 200, 300, 400 500, 600 and 700 °C for 3 h, then cooling by air cooling or in water method. The results indicated that all concretes exposed to a temperature of 500 and 700 °C occurred a signi...
1St International Balkans Conference on Challenges of Civil Engineering, Jun 7, 2013
This research was conducted to determine the thermal conductivity coefficients of concretes made ... more This research was conducted to determine the thermal conductivity coefficients of concretes made up with different mixtures of expanded perlite and pumice aggregates. To determine the effect of silica fume and fly ash on the thermal conductivity of lightweight concrete, silica fume and fly ash were added into the mixture with the replacement of cement, by decreasing the cement weights in the ratios of 10, 20 and 30 percent in weight. The highest thermal conductivity was observed for the examples consisted of only pumice aggregate and plain cement, which is 0.3178 W/mK. It decreased with the increase of silica fume and fly ash as replacement of cement. The lowest value of thermal conductivity, which is 0.1471 W/mK, was obtained with the samples prepared with expanded perlite aggregate replacement of pumice aggregate, and 70% cement and 30% fly ash replacement of cement. Both silica fume and fly ash had decreasing effect on thermal conductivity. Expanded perlite aggregate (used instead of pumice) is also decreased thermal conductivity of concrete, decreased Under the light of these findings, it was concluded that silica fume and fly ash can be used in construction industry to improve thermal isolation, and therefore to decrease environmental pollution caused by these wastes, decrease.
Cement and Concrete Research, 2004
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Papers by Ramazan Demirboga