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1
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The Effect of Boron Compound to Cement Hydration and Controllability of this Effect

100%
Davraz M.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-26-B-33
EN
The use of boron compounds as composites of cementitious, except for the limited usage conditions like setting retarder has not become widespread because of the hardening and the related problems. In this study, the effects of the boron compounds into hydration process of the different cement types and controllability of these effects was investigated. Portland cement, boron modified active belite cement, and calcium aluminate cement were used in the mortar mixtures as binder material. Except for the control mixture, boric acid (BA) was used at the ratios of 0.25-1.00% of weight of cement in mortar mixtures with Portland cement. Setting times dependent on pH, EC and T changes of fresh mortars were measured. With increasing BA concentration, setting times of the mortars rather increased, pH, electrical conductivity, and T values of the mortars significantly reduced. To suppress the affect of BA on the hydration process, the two various stabilizers were used in the mortars, setting times, pH, electrical conductivity, and T values of these mortars were measured again. As a result, the optimum workability times and the parameters of the hydration reaction taking into account, the most suitable type and usage ratio of stabilizer were determined for mortars with BA.
2
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Determination of Radiation Shielding of Concrete Produced from Portland Cement with Boron Additives

51%
Davraz M., Pehlıvanoğlu H., Kilinçarslan Ş., Akkurt İ.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 3
702-704
EN
Concrete is a material which is widely used for neutron shielding in such building constructions as nuclear power stations, particle accelerators and medical hospitals. Concrete is very significant for neutron shielding, because is contains some elements which help to moderate very penetrative fast neutrons. Boron increases the neutron shielding effectiveness of concretes. Boron can be added to concrete in different ways, by addition of boron to the water, used in concrete, or by addition of boron containing natural minerals. In this study, three samples of concrete were produced using B₂O₃ additives material, boron-modified active belite and Portland cement. Neutron absorption coefficients of the produced three different types of concrete samples were obtained through experiments. It is concluded that the addition of boron to concrete is an alternative option to be used for the purposes of neutron shielding.
3
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Investigation of Relationships between Ultrasonic Pulse Velocity and Thermal Conductivity Coefficient in Foam Concretes

51%
Davraz M., Kilinçarslan Ş., Koru M., Tuzlak F.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 1
469-470
EN
In this study, using type CEM I 42.5 R Portland cement, limestone powder, polypropylene fibers and super plasticizer, additive foam concrete specimens were produced. 28 days compressive strengths, dry densities, ultrasonic pulse velocities and thermal conductivity coefficient of these samples were determined. Analysing test results, it was noticed that there underlies a strong relationship between ultrasonic pulse velocity and thermal conductivity coefficient in the foam concrete. It is possible to estimate thermal conductivity by ultrasonic pulse velocity method, easy and credible method.
4
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Predicting the Poisson Ratio of Lightweight Concretes using Artificial Neural Network

51%
Davraz M., Kilinçarslan Ş., Ceylan H.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-184-B-186
EN
Artificial neural network is generally information processing system and a computer program that imitates human brain neural network system. By entering the information from outside, artificial neural network can be trained on examples related to a problem, so that modeling of the problem is provided. In this study, compressive strength, Poisson ratio of the lightweight concrete specimens, which have different natural lightweight aggregates, were modeled with artificial neural network. The data which were provided by artificial neural network model were compared with the data obtained from experimental study and a good agreement was determined between the results.
5
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The Effects of Accelerating Admixture on the Mechanical Properties of Boric Acid Added Mortars

51%
Davraz M., Kılınçarslan Ş., Pehlivanoğlu E.
|
|
vol. 125
|
issue 2
263-267
EN
Use of boron compounds has not become widespread because of the hardening and the other related problems in cementitious composites. The boron compounds as an additive material can be used widely in the production of cement and concrete in case of the elimination of these negative conditions. Thus the control of workability and hydration process of fresh concrete and mortar, some technological properties such as fire resistance, the radiation impermeability of hardened concrete and mortars can be enhanced. In this study, the effects of accelerating admixtures to the mechanical properties of boric acid added mortars were investigated. In order to determine of these effects and the results obtained to compare with those of control mortars, prismatic mortar samples were prepared in accordance with TS 196-1. Boric acid was added to mortar samples by up to 1% from 0.25% by weight of cement. Boric acid was not added to control mortar samples. Portland cement, boron modified active belite cement and calcium aluminate cement as binding material were used in mortar samples. 2, 7, 28 day compressive strengths and 28 day flexural strengths of 315 prismatic samples which were prepared in accordance with the design of 35 different mixes were determined. Results of boric acid added mortar samples were compared with control samples produced by using Portland cement, BAB cement and CAC cement. 2, 7, and 28 day compressive/flexural strength of mortar samples which were added 1% boric acid was determined as 0/0, 12.8/2.90, 40/6 MPa, respectively. Other hand, 2, 7, and 28 day compressive/flexural strength of mortar samples which were added 1% boric acid and 2% sodium aluminate was determined as 14.2/3.07, 27.2/5.57, 34.2/5.97 MPa, respectively. As a result, the retarding effect of the boric acid in terms of early strength of concrete was suppressed using sodium aluminate.
6
Content available remote

Investigation of Properties of Foam Concretes Produced Using Pumice at Different Ratios

51%
Kilinçarslan Ş., Davraz M., Koru M., Ekıztaş F.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 3
708-709
EN
Foam concrete is a type of light weight concrete having self-compacting properties. It can be obtained by mixing the foam, formed by the foaming agent, with a mixture consisting of cement, water and aggregate. It contains independent closed pores with a volume of 75-80% within its body. In this study, three series of foam concrete were produced using different ratio of pumice. Compressive strength, splitting tensile strength and thermal conductivity of foam concrete samples were determined for each density set. It is found that, pumice ratio has a linear relationships with dry bulk density, compressive strength, tensile strength and thermal conductivity. It can also be concluded that strong relationship exist between higher correlation coefficients and pumice ratio.
7
Content available remote

Mechanical Performances of Artificial Aggregated Lightweight Concrete

51%
Davraz M., Ceylan H., Kılınçarslan Ş.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1246-1250
EN
In this study, some physical and mechanical performances of artificial aggregated lightweight concretes were compared. Special empirical models were developed to estimate the elasticity modulus of lightweight aggregate concrete (LWAC). Five different natural aggregates and one artificial lightweight aggregate material were used throughout the research. Mixture proportions were kept as constant values in all concrete mixtures. All mixtures were cast into cubic, prismatic and cylindrical concrete standard moulds and they were cured at the same curing conditions. A series of physical and mechanical properties, such as density, compressive strength and elasticity modulus for LWAC were experimentally determined. According to the research findings a few empirical models were statistically developed for estimating the elasticity modulus and Poisson's ratio of LWAC and a new diagram practically to be used for estimating the Poisson's ratio of LWAC was also proposed.
8
Content available remote

Influence of High Temperature on Concrete Produced from Portland Cement with Boron Additives

51%
Davraz M., Pehlıvanoğlu H., Kilinçarslan Ş.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 3
872-874
EN
The boron compounds have been widely used as additives in the production of cement and concrete to enhance their engineering properties. In this study, three series of concrete specimens were produced using B₂O₃ additive materials, boron modified active belite cement and Portland cement. After 28 days of curing period the specimens were exposed to temperatures of 250, 500 and 750°C. Mass loss and compressive strength were determined and recorded after the specimens were cooled to room temperature. It was concluded that the effect of the boron becomes more apparent at high temperatures.
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