Self Compacting Concrete

The early-age hydration (B48 h) of a series of self-compacting concretes and corresponding mortars and one traditionally vibrated concrete and mortar is monitored in a continuous way using ultrasonic testing and isothermal calorimetry. The mixtures differ in type of mineral addition, superplasticizer, cement, cement-to-powder ratio and water-to-powder ratio. The influence of these different mixture compositions on the kinetics of the hydration during the first days of the hydration is characterized by the heat production rate q and the evolution of the p-wave velocity, which is a consequence of the microstructural changes. The variations in the acceleration caused by mineral additions and the deceleration caused by superplasticizers lead to a significantly different behavior. Separating the impact of each of the affecting factors is not always possible due to their combined actions. The nature of the acceleration due to limestone additions and the deceleration caused by polycarboxylate ether superplasticizers can be distinguished clearly, but cannot be quantified. The correlation between the ultrasonic and isothermal calorimetric results is investigated based on parameters related to the start and the end of the setting and reveals the meaningfulness of these parameters when assessing the hydration of self-compacting mixtures with continuous ultrasonic techniques.

Ce papier présente les résultats d'une étude expérimentale sur l'influence de la rhéologie sur l'orientation des fibres métalliques et par suite sur le comportement en flexion et compression des bétons de fibres. Plus précisément, on étudie l'influence de l'orientation d'un volume de 0.5 % de fibres sur les propriétés mécaniques d'un béton ordinaire fluide, d'un béton autoplaçant (seuil de cisaillement faible < 50 Pa) et d'un béton à hautes performances plastiques (seuil de cisaillement élevé >100 Pa).

Self-Compacting Concrete is a special type of concrete that is able to flow and compact under its own weight and can occupy all the spaces in the form without any vibration and at the same time it is cohesive enough to be handled without bleeding or segregation. In recent years, self-compacting concrete has been gaining a wide range of application for placement in congested reinforced concrete structures with difficult casting conditions. For such applications, the fresh concrete must possess high fluidity and good cohesiveness. The use of additive materials such as industrial wastes as mineral admixtures can ensure the required concrete properties. The initial experimental study aims at producing and evaluating SCC for ternary blends incorporating fly ash, GGBS, sugarcane bagasse ash and alccofine as partial replacement of cement. Five number of SCC mixes were investigated in this study. The self-compacting mixes have cement replacement with different percentages of mineral admixtures while keeping cement quantity fixed for 360kg/m 3 .The tests such as slump flow test, V funnel test, T500 slump flow test, J ring test, and V5min test were carried on fresh properties of SCC mixes to check the prerequisites mentioned in EFNARC, the mechanical properties of hardened concretes such as compressive strength, split tensile strength were also carried on all the mixes. Incorporating these mineral admixtures resulted in producing economical concrete and the workability requirements of SCC were satisfied, the strength obtained was maximum when alccofine and GBBS were added in the concrete.

Les bétons autoplaçants (BAP) s'écoulent sous l'effet de leur poids propre sans recours à aucune vibration, cette propriété nécessite une très grande fluidité (sans risque de ségrégation) en incorporant dans le béton une quantité élevée de fines, et en réduisant le rapport E/P par l'introduction des superplastifiants. La qualité des granulats est un paramètre très important, elle influe sur les propriétés rhéologiques et mécaniques des bétons. Cette étude traite l'influence du sable de dune en guise de granulat fin (un sable caractérisé par son homométrie, sa nature siliceuse, sa finesse et sa surface spécifique très élevée exigeant ainsi une importante quantité d'eau de gâchage pour leur mouillage), en variant le rapport E/C (0.50 et 0.55) et par l'introduction d'un superplastifiant présentant plusieurs dosages (1%, 1.5%, 1.75% et 2%). Les résultats obtenus montrent que la maniabilité des BAP est améliorée par l'ajout des superplastifiants, par contre les résistances mécaniques sont affectées. 1. Introduction Le BAP peut être considéré comme un matériau de haute performance, qui s'écoule sous l'effet de son poids propre sans recours à aucune vibration mécanique. Cette mise en place sous seul effet de la gravité, nécessite une très grande fluidité des matériaux mais il est aussi indispensable que le béton conserve une stabilité satisfaisante et une parfaite homogénéité. Ces deux propriétés sont obtenus par une quantité élevée de particules fines, Un rapport (Eau/Poudre) faible et un dosage élevé de super plastifiant et d'un agent stabilisateur de viscosité [1, 2, 3]. Les BAP formulés dans le monde sont très riches en quantité cimentaire, par conséquent, la teneur importante du ciment provoque un accroissement de la température des bétons due à la chaleur d'hydratation et engendre en plus l'augmentation de son prix. Il est raisonnable donc de remplacer une partie du ciment par un ajout minéral tel que : le laitier du haut fourneau, la pouzzolane ou les fillers calcaires [4, 5]. Le sable est le constituant inerte entrant dans la composition des mortiers et des bétons, son utilisation permet d'assurer une continuité granulaire entre le ciment et le gravier afin d'obtenir un squelette plus résistant et plus compact. Les études faites sur les sables de dunes dans les dernières décennies, sont multipliées afin de quantifier les caractéristiques physico – chimiques de ce genre de sable qui est, d'origine éolienne, caractérisé par sa finesse, son horométrie et son diamètre maximal qui n'excède pas 5 mm. Les grains de ce sable sont de forme arrondie où anguleuse et visibles à l'oeil, se caractérisent par une porosité inter granulaire et une surface spécifique élevées [6, 7]. Ces propriétés spécifiques vont jouer un rôle majeur dans les caractéristiques du béton à l'état frais et durci : maniabilité médiocre, compacité réduite et résistance mécanique affectée [8]. L'augmentation du taux de sable de dune dans le mélange de béton fait accroître la demande en eau en comparaison avec un béton

Research findings have reported a behavioural relationship between the splitting tensile strength and compressive strength of concretes. This work studied both the experimental and analytical relationships that exist between splitting tensile strength and compressive strength of both vibrated concrete (VC) and self compacting concrete (SCC) of similar grades. Both concrete types were designed to achieve target compressive strength of 20 N/mm 2 , 30 N/mm 2 and 40 N/mm 2 at 28 days. The compressive and splitting tensile properties were measured on cylindrical concrete specimens of 150 mm diameter  300 mm length at 28-days using a compression testing machine. The analytical work tested seven different reported models relating the two measured parameters for VC on SCC, while the Welch 2 sample t-test statistical technique was adopted to check the normality and equality of variance of the results. Experimental findings revealed that the ratio of the splitting tensile to compressive strengths for VC and SCC decreases with increasing compressive strength, and the analytical study revealed that similar analytical model could be adopted for both concrete types as there is no statistically detectable difference between their results.

The study has conducted to determine the workability and compressive strength of the self –compacting concrete. The sand has replaced with quarry dust with the proportion of 10, 20, 30 and 40% and super plasticizer was added 0.9%. The experiments were carried out at the Infrastructure University Kuala Lumpur (IUKL) concrete laboratory. Slump flow, J-Ring tests were carried out to determine the workability of self-compacting concrete and compressive strength test was conducted on 7 days and 28 th days of curing period. A finding of the study shows that workability and compressive strength has increased by addition of quarry dust. It is concluded that addition of quarry dust up to 30% improve the workability of the self-compacting concrete and further addition of quarry dust decrease the workability. Additionally, compressive strength of the quarry dust modified self-compacting concrete shows the trend of higher compressive strength up to 30% addition of quarry dust with sand replacement and further addition decrease the compressive strength.

An attempt was carried out to develop some properties of self-compacted concrete (SCC) by adding waste plastic fibers (WPF) resulting from cutting beverage bottles. Many tests were conducted to investigate the effect of adding WPF on the fresh properties, whereas other tests were applied on that kind of concrete to study the effect of this type of waste on hardened properties. For this reason, different self-compacting concrete mixtures were designed at constant water-to-binder ratio of 0.35 and 490 kg/m3 of binder content. The class F fly ash was replaced with cement as 25% by weight. The eighth designated plastic fiber contents of 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75  and 2% by volume. The workability properties of self-compacting concrete mixtures were performed to slump flow diameter, T50 slump flow simultaneously, V-funnel flow at the same time, and L-box height ratio. The 7,14 and 28-day compressive strengths of self-compacting  concretes were also measured. Moreover, the 7, 14 and 28-day flexural strengths of concretes were also measured. The test results showed that the plastic fibers have adverse effect on the fresh properties of self-compacting concrete and improvement by hardened properties.

In this paper the properties of Self Compacting Concrete (SCC) was investigated using white cement and lime stone powder as fine aggregate instead of sand. All mixtures were proportioned with constant amount of (cement, lime stone powder, coarse aggregate and silica fume). While the glass powder, ceramic powder and glue were used as additives in different proportions from cement weight. The study focuses on comparison of fresh properties for self compacting concrete using two types of testing flow test and J-ring test. Whereas the hard concrete properties tests limited to compressive strength.
The results leading to some developing in fresh properties and hard properties of self compacting concrete due to adding the additives. The best spread ability obtained at adding glue (4%) from cement weight. While the glass powder and ceramic powder affect to hard properties, adding ceramic powder increased the compressive strength at rates between (10-20) % from cement weight and adding glass powder modified the compressive strength at rates more than (20)% from cement weight.