Effect of false set related anomalies on rheological properties of cement paste mixtures in the presence of high range water reducing admixture

felekoglu, burak/0000-0002-7426-1698WOS: 000561439400001There are many studies related to the fresh state properties of the cementitious systems in the literature. However, there is no specific study about the effects of false set formation on fresh state properties of these systems. in this study, the effect of false set formation on fresh state and rheological properties of the cement paste mixtures containing high range water reducing (HRWR) admixture was investigated experimentally. For this aim, two different commercial CEMI 42.5 R. type cements produced by different companies were used. in order to investigate the effect of false set formation related anomalies on fresh state properties, paste mixtures were prepared with different mixing times. in the mixtures where false set related anomaly was the case, rheological properties were positively affected by prolonging the mixing time.Turkish Cement Manufacturers AssociationTurkish Cement Manufacturers Associatio

THE ROLE OF NA(2)O(EQ )RATIO ON THE FLOWABILITY AND STRENGTH DEVELOPMENT OF CEMENTITIOUS SYSTEMS IN THE PRESENCE OF A POLYCARBOXYLATE ETHER-BASED ADMIXTURE

###EgeUn###In this study, the effect of equivalent Na2O(Na2Oeq) ratio of cement on fresh properties and compressive strength of paste and mortar mixtures containing polycarboxylate ether-based high range water reducing (HRWR) admixture was investigated. A low and a high alkali cement were used. Five mixtures having five different Na2Oeq ratios were prepared with increasing alkali content of the cement by incorporating three different amounts of NaOH solution to the low alkali cement-bearing mixtures. Irrespective of the absence or presence of HRWR, Na2Oeq content of the mixtures was found to have a considerable adverse effect on the fresh properties of the mixtures, particularly on their flow loss. NaOH addition increased 1-day compressive strength of the mortar mixtures, however, reduced the compressive strength at later ages. In spite of having a lower fineness and a longer setting time, low alkali cement showed slightly higher 1-day strength than high alkali cement. This seems to have occurred, to some extent, from the higher HRWR admixture demand (0.4 wt.%) of the high alkali cement-bearing mixture than that of the mix containing low alkali cement (0.25 wt.%). At later ages, both of the cements showed equivalent strength values.Turkish Cement Manufacturers AssociationThe authors would like to thank Baticim and Oyak cement plants for their kind assistance in providing the cements and determining the chemical composition of the cements. The first author would like to acknowledge the scholarship provided by Turkish Cement Manufacturers Association during his PhD study

Agrega hacminin ultra yüksek performansli betonun büzülme, reolojik ve mekanik özelliklerine etkisi

Rheology and shrinkage are the key features that should be controlled to perform a successful casting process and obtain a durable ultra-high performance concrete (UHPC). It is anticipated that cast-in-situ applications of UHPC will increase in the near future, so the studies on early-age properties of UHPC have come into prominence. However, there is still no standardized method for mix design of UHPC that can ensure the desired performance. High amount of cement and low water/binder ratio increase the shrinkage values, which also increase the crack formation risk especially at early-age. The basic variable of mix proportions that determines the rheological and shrinkage properties is aggregate volume and accordingly paste volume. In the scope of this experimental study, influence of volume fraction of quartz aggregate on rheological, shrinkage, and mechanical properties of UHPC was investigated. The results showed increasing the aggregate volume led to sharpen pseudoplastic behaviour of UHPC. To be able to produce a self-compacting UHPC, upper limit of aggregate volume was found 45%. Both autogenous and drying shrinkage can be limited by increasing the aggregate volume. Early-age autogenous and drying shrinkage are far more than the shrinkage measured after demoulding during 90 days. Necessary precautions, thus, should be taken as of casting stage.Materials and Environmen

Sulfate resistances of different types of Turkish Portland cements by selecting the appropriate test methods

WOS: 000238875500025The sulfate resistance of 5 different types of Turkish portland cements were compared using ASTM C 452 and ASTM C 1012 standards. All of the cements, except for sulfate resisting cement, were prepared from the same clinker. As it was expected, ASTM C 452 test was found to be insufficient for determining the sulfate resistance of blended cements. ASTM C 1012 test is more realistic than C 452. It was observed that the addition of some mineral admixtures in small amounts to an ordinary portland cement having a moderate sulfate resistance (< 8% C(3)A content) may have negligible or even adverse effect on its sulfate resistance. This may be arisen from the applied test conditions. (c) 2005 Elsevier Ltd. All rights reserved

EFFECT OF CEMENT FINENESS ON PROPERTIES OF CEMENTITIOUS MATERIALS CONTAINING HIGH RANGE WATER REDUCING ADMIXTURE

WOS: 000396529300009The effect of cement fineness on the fresh state and rheological properties as well as compressive strength of cementitious systems was investigated. A CEM I 42.5R portland cement containing 7.92% C(3)A and sulfate resisting cement containing 3.58% C(3)A were used. The cements were ground to 4 different Blaine finenesses, ranging from 2800 to 4500 cm(2)/g. In the absence of water-reducing admixture, the water requirement of mixtures increased with an increase in the cement fineness. Thus, the fresh state properties of the mixtures were affected negatively. However, surprisingly, a reverse behavior was observed in the mixtures containing water-reducing admixtures, that is, an increase of the cement fineness increased the effectiveness of the admixture; consequently, the fresh state properties of the mixtures were improved. This seems to have been caused from the higher adsorption of the admixture on finer cement grains than on the coarser particles. Moreover, as expected, the strength of the mortar and concrete mixtures increased along with the increase in cement fineness and its C3A content.Turkish Cement Manufacturers AssociationThe authors would like to thank Izmir-Cimentas and Akcansa cement plants for their kind assistance in providing the cements and determining the chemical composition of the cements. The first author would like to acknowledge the scholarship provided by Turkish Cement Manufacturers Association during his PhD study

Adsorption properties of polycarboxylate ether-based high range water reducing admixture on cementitious systems: A review

Adsorption of polycarboxylateether-based water-reducing admixtures (PCE) on the cement surface affects many properties of cementitious systems, especially fluidity. One of the most important parameters affecting the adsorption behavior of PCE is the anionic group properties. Therefore, understanding the anionic group properties of PCE is of great importance for cement-admixture compatibility. In this study, the effects of PCE's anionic group variation and cement properties on cement-admixture compatibility, especially adsorption, were reviewed based on the studies conducted in the literature. It was observed that phosphate and organo-silane substituted PCEs at certain rates have a positive influence on the fresh state properties of cementitious systems due to adsorption improvement and sulfate resistance. In addition, the fresh state properties of the cementitious system were negatively affected as the C3A content and the increment in fineness of the cement increased the admixture requirement. It was emphasized that the effect of pozzolan utilization on the adsorption properties of PCE in cementitious systems should be considered. Information was given about the properties of PCE recommended for use in the presence of pozzolan

Assessment of cement characteristics affecting rheological properties of cement pastes

felekoglu, burak/0000-0002-7426-1698WOS:000636189300005In this study, the cement-based parameters affecting CEMI portland cements-polycarboxylate ether-based high-range water-reducing (HRWR) admixtures compatibility were investigated. For this purpose, eight CEMI cements and three commercial HRWR admixtures were used. The rheological properties of 112 paste mixtures with different admixture dosages and water/cement (W/C) ratios were determined in accordance with Herschel-Bulkley model. Then after, using the experimental data, proper models were established to predict the dynamic yield stress and final viscosity of the pastes. in addition to cement characteristics (such as fineness, compound composition and equivalent alkali content), water-reducing admixture content and its solid material content as well as water/cement ratio of the pastes were considered as input data. Multivariate adaptive regression splines (MARS) and multiple additive regression trees (MART) methods were used in the models. Besides, artificial neural network (ANN) and conventional regression analysis (CRA) including linear, power, and exponential functions were applied to determine the accuracy of the heuristic regression methods. Three statistical indices, root-mean-square error, mean absolute error, and Nash-Sutcliffe, were used to evaluate the performance of the models. Modeling findings indicated that the model with the lowest error for both of the rheological variables in the testing set is the MART, followed by ANN, MARS, and CRA-Exponential methods. The most effective cement characteristics causing incompatibility, hence detraction of paste rheological properties, in decreasing order, were determined as cement fineness, C3S, C(3)A and equivalent alkali contents. C(4)AF and C2S contents of the cement were found to have less effect on the cement-admixture incompatibility. It will be possible to determine the rheological properties of mixtures containing different cements without conducting an experimental study by using the model based on MART method.Turkish Cement Manufacturers AssociationThe authors would like to express sincere thanks to Oyak, BatiCim, Cimenta, Akcansa, and Nuh cement plants as well as Draco, BASF, and Inka admixture companies for providing the cements and admixtures used in this study. The first author would also acknowledge the financial support provided by Turkish Cement Manufacturers Association during his PhD study

Effect of gypsum type on properties of cementitious materials containing high range water reducing admixture

WOS: 000373650700003In this study, the effect of cement gypsum type on properties of the properties of cement paste, mortar and concrete mixtures containing high range water reducing admixture (HRWR) was investigated. Two different types of cement prepared from the same clinker but containing either calcium sulfate hemihydrate or dihydrate as retarder were used. The fresh and hardened (compressive strength and drying shrinkage) properties as well as static and dynamic rheological behavior of the mixtures were investigated. Compared to the mixtures containing dihydtate, the fresh and rheological properties of mixtures were negatively affected when cement-containing hemihydrate was used. However, hemihydrate utilization had a positive influence on the early compressive strength. The adverse effects on fresh properties were more significant in paste mixtures. These negative effects decreased in the mortar and concrete mixtures. The presence of hemihydrate in cement was found to increase the drying-shrinkage. (C) 2016 Elsevier Ltd. All rights reserved.Turkish Cement Manufacturers AssociationThe authors would like to thank Izmir-Cimentas cement plant for their kind assistance in providing the cement and determining the chemical composition of the cement. The first author would like to acknowledge the scholarship provided by Turkish Cement Manufacturers Association during his PhD study