Civil Engineering / İnşaat Mühendisliği
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Article Citation - WoS: 19Citation - Scopus: 22Influence of Thixotropy Determined by Different Test Methods on Formwork Pressure of Self-Consolidating Concrete(Elsevier Ltd., 2018) Tuyan, Murat; Ahari, Reza Saleh; Erdem, Tahir Kemal; Andiç Çakır, Özge; Ramyar, KambizIn this experimental study, the influence of thixotropy determined by different test methods on the formwork pressure of self-consolidating concrete (SCC) with varying compositions was investigated. In order to determine the effect of water/binder (w/b) ratio, slump flow diameter and coarse aggregate/total aggregate (CA/TA) ratio on thixotropy and formwork pressure of SCC, fifteen concrete mixtures were prepared. Four different test methods i.e., “structural break-down area” (SBDA), “break-down percentage” (BDP), “drop in apparent viscosity” (DAV) and “yield value at rest” (YVR) were performed to determine the thixotropy of the SCC mixtures. Test results showed that the SBDA, DAV and YVR methods were more appropriate to evaluate the thixotropy of SCC than the BDP method. A strong correlation between thixotropy and formwork pressure was found using SBDA, DAV and YVR methods in SCC mixtures having low w/b ratio. There was a strong relationship between thixotropy determined by SBDA, BDP and DAV methods and formwork pressure in low slump flow SCC mixtures, while thixotropy determined by the YVR method showed good correlation with the formwork pressure in SCC mixtures having high slump flow values. Finally, new models were developed to estimate the formwork pressure of all kinds of mixtures as a function of thixotropy and time. The models were found to be successful for each of the thixotropy measurement method.Article Citation - WoS: 123Citation - Scopus: 140Effect of Various Supplementary Cementitious Materials on Rheological Properties of Self-Consolidating Concrete(Elsevier Ltd., 2015) Saleh Ahari, Reza; Erdem, Tahir Kemal; Ramyar, KambizIn design of self-consolidating concrete (SCC) for a given application, the mixture's rheological parameters should be adjusted to achieve a given profile of yield stress and plastic viscosity. Supplementary cementitious materials (SCM) can be useful for this adjustment in addition to their other advantages. In this study, the rheological properties of 57 SCC mixtures with various SCM were investigated for a constant slump flow value. For this aim, various amounts of silica fume (SF), metakaolin (MK), Class F fly ash (FAF), Class C fly ash (FAC) and granulated blast-furnace slag (BFS) were utilized in binary, ternary, and quaternary cementitious blends in three water/binder ratios. Results showed that SF and BFS decreased plastic viscosity and V-funnel time values in comparison with mixtures containing only Portland cement (PC). However the opposite tendency was observed when MK, FAC and FAF were incorporated with PC. Substitution of PC with SF, MK and FAC increased high range water reducer (HRWR) demand in the SCC mixtures having constant slump flow. Use of SCM in SCC mixtures increased yield stress values. Good correlations were established between plastic viscosity and V-funnel flow time values for all w/b ratios.Article Citation - WoS: 27Citation - Scopus: 30Time-Dependent Rheological Characteristics of Self-Consolidating Concrete Containing Various Mineral Admixtures(Elsevier Ltd., 2015) Saleh Ahari, Reza; Erdem, Tahir Kemal; Ramyar, KambizThe study herein was intended to evaluate the influence of elapsing time on rheological properties and thixotropy of self-consolidating concrete (SCC) mixtures containing various mineral admixtures. For this purpose, variation of T50 flow time, torque plastic viscosity, apparent yield stress and thixotropy were investigated as a function of time in a standstill condition. Various amounts of silica fume (SF), metakaolin (MK), Class F fly ash (FAF), Class C fly ash (FAC) and granulated blast-furnace slag (BFS) were utilized in binary, ternary and quaternary cementitious blends in 17 different SCC mixtures having a constant slump flow value. The results showed that SCC mixtures containing various mineral admixtures were highly stable or moderately stable (VSI between 0 and 1) at 0 min according to ASTM C 1611. However, mixtures containing FAC, FAF and BFS exhibited some bleeding and segregation at 50 min. In a standstill condition, apparent yield stress and thixotropy increased significantly with time while torque plastic viscosity values changed only in a limited range. In addition, with elapsing time, MK and FAC were found to have more influence on torque plastic viscosity and yield stress values in comparison with the other admixtures. However, increase in the yield values were more pronounced in comparison with the torque plastic viscosity values. Increase in thixotropy with time for the SF and MK blended mixtures were higher when compared to the control mixtures and mixtures containing the other mineral admixtures.Article Citation - WoS: 111Citation - Scopus: 132Thixotropy and Structural Breakdown Properties of Self Consolidating Concrete Containing Various Supplementary Cementitious Materials(Elsevier Ltd., 2015) Ahari, Reza Saleh; Erdem, Tahir Kemal; Ramyar, KambizAbstract In this study, thixotropy and structural breakdown of 57 self-consolidating concrete (SCC) mixtures containing various supplementary cementitious materials (SCM) were investigated by different approaches. The effects of SCM type and content on high range water reducer demand and plastic viscosity were also studied. For these purposes, various amounts of silica fume (SF), metakaolin (MK), Class F fly ash (FAF), Class C fly ash (FAC) and granulated blast-furnace slag (BFS) were utilized in binary, ternary, and quaternary cementitious blends in three water/binder (w/b) ratios. Results showed that except BFS, use of SCM in SCC mixtures increased thixotropy values in comparison with the mixtures containing only portland cement (PC). Good correlations were established between structural breakdown area and drop in apparent viscosity values for all w/b ratios. The different methods used to evaluate the thixotropy and structural breakdown got more consistent with each other as w/b decreased.