Theses supervised by Doç. Dr. Erhan Güneyisi
15 theses · Gaziantep University
Characteristics of self-compacting concretes with tire rubber wastes
In this experimental study, the self-compacting rubberized concretes were produced at constant water-to-binder ratio of 0.35 and binder content of 520 kg/m3. Class F fly ash was incorporated into the self-compacting concrete production as 30% of total binder content by weight. Two types of waste scrap tire rubber, crumb rubber and tire chips, were utilized instead of natural fine and coarse aggregates at various levels. The tire chips and three different graded crumb rubbers (No.18, No.5, and mixed crumb rubber) and six designated rubber contents of 0%, 5%, 10%, 15%, 20%, and 25% were considered as experimental parameters. In total, 21 self-compacting rubberized concrete mixtures were produced. The workability properties of self-compacting concrete mixtures were performed regarding to slump flow diameter, T50 slump flow time, V-funnel flow time, L-box height ratio, and L-box T20 and T40 flow times as well as the rheological behaviour of these concretes was investigated by using the ICAR rheometer. The hardened properties of the concretes were tested for the compressive strength, splitting tensile strength, modulus of elasticity, flexural strength, fracture energy, and bond strength. The results revealed that the utilization of rubber waste negatively affected the fresh properties of self-compacting concretes as well as compressive strength and increasing the rubber content increased the coefficients of the Herschel-Bulkley and the modified Bingham models, which is the indication of the shear thickening.
Effect of metakaolin and silica fume on the mechanical property, shrinkage, and gas permeability of high performance concrete
Using mineral admixtures as substituting additives in concrete has a tendency to increase by the future in order to provide greater sustainability in construction industry. The issues regarding the cost, recycling the industrial wastes, rehabilitation in durability and mechanical performance of concrete will therefore put a pressure on utilization of such materials. This study investigates the effectiveness of metakaolin (MK) and silica fume (SF) in contribution to the mechanical, shrinkage, and gas permeability of high performance concretes. Replacement levels of 5 and 15% of MK or SF by the weight of cement were considered in this study. The other experimental parameter investigated in the study was water-to-cementitious material ratios (w/cm) which were 0.25 and 0.35. The performance characteristics of the plain and mineral admixture incorporated concretes were evaluated by measuring the compressive strength, splitting tensile strength, static modulus of elasticity, drying shrinkage, restrained shrinkage, water sorptivity, and gas permeability. Test results revealed that replacement level of MK and SF had significant effects on the mechanical and especially durability characteristics of high performance concretes.
Corrosion resistance of reinforcement steel embedded in chloride contaminated concrete with and without metakaolin
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 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 very effective in inhibiting the active corrosion of concrete even at severe chloride contamination levels.
Contribution of steel fiber and metakaolin in enhancing mechanical behavior of high strength concretes
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 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 used 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 combined effects 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. Correlation between the measured parameters was also carried out to better understand the interaction between mechanical properties of the concretes. Moreover, the microstructure of plain and steel fiber reinforced concretes incorporated with MK was observed by scanning electron microscopy (SEM). The results indicated that incorporation of MK and use of different types of steel fibers significantly affected the mechanical behavior of the concretes, irrespective of w/b ratio.Keywords: Bonding strength; Compressive strength concrete; Metakaolin; Steel fiber; Tensile strength
Use of shrinkage reducing admixture and steel fiber to control shrinkage cracking of lightweight concretes
ABSTRACTUSE OF SHRINKAGE REDUCING ADMIXTURE AND STEEL FIBER TO CONTROL SHRINKAGE CRACKING OF LIGHTWEIGHT CONCRETESMOHAMADAMEEN, AlaaM.Sc. in Civil EngineeringSupervisor: Associated. Prof. Dr. ERHAN GÜNEYİSİJuly 2012, 91 PagesThis thesis presents the results obtained from an experimental study conducted to investigate the effect of shrinkage reducing admixture (SRA) and steel fiber addition on some of the properties of lightweight aggregate concrete (LWAC). A 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 amounts of SRA used in the mixes were 0.75%, 1.5 % and 3 % by weight of cement. Ring type specimens were used for the restrained shrinkage cracking test. Free shrinkage weight loss, compressive and split tensile strength tests were also undertaken. The results demostrated that the use of steel fibers has little effect on compressive strength but it enhances the split tensile strength. The addition of SRA diminishes compressive strength without influencing 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.Keywords:Lightweight concrete, Mechanical properties, Shrinkage cracking, Shrinkage reducing admixture, Steel fiber.
Fracture behavior of high strength concretes containing silica fume and metakaolin
The study presented in this thesis reports the findings of an experimental study conducted on fracture behavior of high strength concretes incorporating metakaolin (MK) and silica fume (SF). The concrete mixtures with water-to-binder (w/b) ratio of 0.28 and 570 kg/m3 binder content were designed for the experimental study. MK or SF modification was achieved through replacing Portland cement (PC) with mineral admixture by 5% and 15% of the total binder content. Moreover, a plain concrete mixture was produced as control for comparison. The effectiveness of MK and SF incorporation on the compressive strength, splitting and flexural strengths, modulus of elasticity, fracture energy, and characteristic length of concrete were monitored at the end of 28 days of water curing. The results have revealed that the utilization of mineral admixtures provided improvement in fracture properties such as increased fracture energy. Moreover, the results obtained for SF concretes demonstrated a similar trend to the ones incorporating MK. Increasing the replacement level from 5% to 15% resulted in relatively better performance for the concretes including mineral admixture.
Effect of volcanic pumice on properties of plain and silica fume based self compacting concretes
In this thesis, an experimental study conducted on the effects of volcanic pumice powder (VP) on the fresh and hardened properties of self compacting concretes (SCCs) with and without silica fume (SF) was investigated. In the first group, SCCs without SF were produced with 0%, 5%, 10%, and 20% replacement levels of VP. However, for the second group, SF incorporation was achieved by a constant SF replacement level of 8%. The investigated fresh properties of the concretes were slump flow diameter, T500 mm slump flow time, V-funnel flow time, and L-box height ratio. The hardened properties, on the other hand, were compressive strength development, gas permeability, water absorption, water sorptivity and rapid chloride permeability. The tests on the hardened properties of concretes were carried out at the end of 28 and 90 days of water curing. Moreover, statistical study, namely general linear model analysis of variance (GLM-ANOVA), was performed in order to see the significance of the critical parameters such as inclusion of SF and replacement level of VP on the properties of SCCs. The use of volcanic pumice powder resulted in increase in fluidity of SCCs in fresh state while SF increased the viscosity. The results have also revealed that SF incorporation compensated the deterioration of hardened properties of concretes due to increasing amounts of VP, at varying magnitudes.Keywords: Fresh properties, Hardened characteristics, Self compacting concrete, Silica fume, Volcanic pumice powder.
Characterization and utilization of calcined Turkish kaolins for improving strength and durability aspects of concrete
In this thesis, an experimental investigation on the utilization of calcined impure Turkish kaolins as supplementary cementing material to improve mechanical and durability characteristics of concrete was presented. Microstructural characteristics of the raw kaolins were analyzed and the alteration in microstructural properties were monitored as a result of calcination process. The microstructural features were measured by means of X ray diffraction analysis (XRD), thermal analyses (DTA-TG), scanning electron microscopy (SEM), particle size distribution with laser diffractometer, and Brenaur-Emmet-Teller (BET) nitrogen adsorption specific surface area measurements. Pozzolanic properties of calcined kaolins were evaluated and compared. Furthermore, commercially available high reactivity metakaolin (MK) from Czech Republic was used for comparison. The concretes of different properties including various amounts of calcined kaolins and MK were produced for comparison and evaluation of the effectiveness of the calcined kaolin on the mechanical (compressive and splitting tensile strength) and durability (gas permeability, water permeability, sorptivity, rapid chloride penetration, electrical resistivity, freezing-thawing resistance, drying shrinkage, and corrosion behavior) characteristics of concrete. Finally, an analytical study was carried out to obtain explicit mathematical formulation for estimation of the concrete properties.Keywords: Calcination, Concrete, Durability, Metakaolin, Microstructure, Strength
Effect of cold bonded and sintered fly ash lightweight aggregates on permeability and corrosion behavior of concrete
This thesis reports the finding of an experimental study carried out on the strength and durability related properties of the lightweight concretes (LWC) 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 properties of LWCs were evaluated in terms of compressive strength, water sorptivity, rapid chloride ion permeability, gas permeability, and accelerated corrosion testing after 28 days of water curing period. 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.Key Words: Cold bonding, Corrosion, Permeability properties, Concrete, Sintering
Improving the ductility properties of lightweight concrete by steel fiber addition
In this study, the mechanical and fracture properties of the cold bonded fly ash lightweight aggregate concretes (LWACs) with and without steel fiber were experimentally investigated. The LWAC with a constant water-to-cement ratio of 0.40 and 400 kg/m3 cement content were produced with two different volume fraction of artificial fly ash lightweight aggregates. Three types of hooked-end steel fibers with the aspect ratios of 55, 65, and 80 were utilized with four different volume fractions of 0.35, 0.70, 1.00, and 1.50% of concrete volume. The effectiveness of aspect ratio, steel fiber volume fraction, and lightweight aggregate volume fraction on the compressive, splitting tensile, flexural and bond strengths, modulus of elasticity, fracture energy and characteristic length of concrete were investigated at the end of 28-days of water curing. The results have revealed that utilization of steel fiber enhanced splitting tensile, flexural, bond strengths of LWACs. The compressive strength, however, were not affected significantly by the steel fiber addition. The utilization of steel fiber considerably increased the fracture energy and characteristic length. Moreover, the compressive, splitting tensile, flexural and bond strengths, fracture energy, and characteristic length were significantly influenced by the artificial fly ash lightweight aggregate content.Keywords: Concrete; Fracture properties; Lightweight cold-bonded fly ash aggregate; Mechanical properties; Steel fiber.
Some engineering properties of self compacting lightweight mortars
In this study, lightweight fly ash fine aggregates (LWFAs) were used as a partial replacement of natural fine aggregate to investigate the fresh and hardened states of self compacting mortars (SCMs). For this, a powder mixture of 90% fly ash (FA) and 10% Portland cement (PC) by weight were pelletized in a tilted pan through a cold-bonded agglomeration process. Thereafter, a total of five mixtures of SCMs were prepared in which natural fine aggregate was replaced by LWFA partially started from 0% to 100% by 25% increment. Subsequently, tests carried out on the fresh mortar involved mini-slump flow, mini-V-funnel flow time, and viscosity while the hardened properties of SCMs were evaluated using the compressive strength, ultrasonic pulse velocity, gas permeability, and sorptivity tests. The hardened characteristics of SCMs were determined at different ages up to 56 days. It was observed that the increased percentage of LWFA improved the workability and the flowability of SCMs. On the other hand, some of the engineering properties of SCMs in terms of strength and permeability had a negative effect due to the substitution of LWFAs for natural fine aggregate, especially at higher replacement level.
Use of recycled aggregates in the production of pervious concretes
The objective of this research was to incorporate recycled aggregate into pervious concrete to create a very sustainable concrete product for many applications. The research methodology interested replacing natural aggregate with recycled aggregate in the pervious concrete production at 4 different replacement levels of 25%, 50%, 75% and 100%, with two different water-to-cement ratios of 0.27 and 0.32. Single sized recycled and natural aggregate, passing from 12.5-mm sieve and retained on 9.5-mm sieve, were used in the manufacturing of pervious concrete. Totally ten different concrete mixtures were produced and each of the concrete batches was tested for slump, dry density, porosity, compressive and splitting tensile strengths, water permeability and abrasion resistance. The properties of pervious concrete produced with recycled aggregate were also evaluated by statistical technique, namely GLM-ANOVA. The experimental results showed that the properties of pervious concrete were significantly affected by using recycled aggregate. Substituting the recycled aggregate with natural aggregate resulted in a considerable increment in permeability coefficient. However, it was observed that the mechanical properties of such concretes were adversely influenced up to a certain degree.
Durability properties of polymer-modified lightweight fly ash aggregate concretes
The aim of this thesis is to examine the durability properties of natural rubber latex (NRL) modified lightweight concretes (LWCs). The LWC was produced from lightweight fine and coarse aggregates (LWAs) which are manufactured by cold bonding of class F fly ash. The NRL which is an elastic hydrocarbon polymer was used as an addition in the concrete production as 2% and 5% of the weight of total binder content (400 kg/m3), considering the solid polymer content. The observed properties of polymer modified concretes are evaluated by rapid chloride permeability test (RCPT), soaking, test, and water sorptivity and corrosion current density by linear polarization resistance (LPR) test. Moreover, the LWCs were tested for compressive strength to determine mechanical performance. The tests were carried out at the end of 28 and 90 days of curing. However, the specimens used for soaking test were immersed in NaCl solution after 28 days of curing and tested for chloride ion penetration at different intervals. Moreover, the reinforced LWCs used for LPR test were immersed in NaCl solution and tested at specified periods of chloride exposures. The results indicated that the modification of the lightweight concretes with NRL resulted in improvement of the durability related properties of LWCs.
Effect of metakaolin and calcined kaolin on workability and rhelogical properties of self compacting concrete
In this study, the effectiveness of calcined impure local kaolin (CK) and commercially available high reactivity metakaolin (MK) on the workability and rheological properties of self-compacting concretes (SCCs) were investigated. Moreover, the compressive strength and ultrasonic pulse velocity of hardened SCCs were measured at the end of 28 days of water curing. After proper heat treatment, CK was utilized as a supplementary cementitious material. In order to observe and compare the influences of CK and MK, three replacement levels (0%, 5%, and 10%) were assigned. The SCCs with 0.35 water-to-binder ratio and 550 kg/m3 total binder content were designed for the testing. The workability tests applied were slump flow diameter, slump flow time (T50cm), V-funnel flow time, and L-box height ratio. For the rheological testing of fresh SCCs, ICAR rheometer was used to find the rheological parameters. The flow diameter of the SCCs were adjusted to be in the range of 700±20 mm. The test results indicated that the SCCs incorporating CK had lower loss of workability than MK incorporated ones. However, the hardened properties of SCCs with MK was better than control and CK included ones.
Properties of self-compacting concretes prepared with recycled aggregate
The recycling of construction and demolishing wastes as Recycled Concrete Aggregate (RCA) is an important issue for major urban cities since it provides an alternative mean to the dependence of construction industry on natural aggregates. The use of RCA in Self Compacting Concrete (SCC) is a relatively new research area on which a very limited scientific research has been carried out in the current literature. The drawbacks in widespread commercial use of RCA in SCC are mainly caused by the weak and porous old cement mortar adhered on RCA. In practice, this adverse effect and some hitherto unknown properties of SCC with treated and untreated RCAs prevent the maximum utilisation of RCA in SCC. This thesis aims to overcome this short-coming in the current literature by assessing the properties of SCC using treated and untreated RCAs. Moreover, in this thesis, the potential treatment methods and some important rheological, mechanical and durability properties of SCC with RCA have been investigated. The response surface method was employed in the multi-objective optimization analysis along with the analysis of variance to obtain the best possible resolution of RCA in SCC. The results reveal that the applied RCA treatments of two stage mixing approach and water glass provide better microstructures leading to significant strength improvements of SCC. In addition, Herschel-Bulkley and modified Bingham models provide well defined rheological representations for SCC with RCA.