Rheology of fresh concretes with recycled aggregates (original) (raw)

Influence of Recycled Aggregate on the Rheological Behavior of Cement Mortar

Key Engineering Materials, 2014

In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order to generate more homogeneous fine aggregates. The characterization of the natural and recycled sands was carried out through physical tests, X-ray diffraction, scanning electron microscopy (SEM), and image analysis (shape and texture description parameters). A conventional mortar and three mortars containing recycled sands were produced with a sand/cement ratio of 4 and consistency index of 255±5 mm. The consistency was kept constant by ranging the water-cement ratio from 0.58 to 1.14. The rheological study was performed using a rotating viscometer to obtain torque-rotation ratio and to calculate the yield stress and plastic viscosity. The ...

RHEOLOGY OF FRESH CONCRETE -A REVIEW

Journal of Rehabilitation in Civil Engineering, 2021

Concrete is a heterogeneous, complex composite construction material. Fresh properties of concrete, that is, workability is much significance since it has affect the quality, cost of construction, strength and durability. Even to this day the workability of fresh concrete is measured by empirical test, in-spite of its limitations, drawbacks and sometimes with misleading results. Empirical test are single parameter test whereas quantitative fundamental science approach is another method with minimum of two parameters, which is more reliable, suitable and needed for characterizing the flow of fresh concrete. The emergence of concrete rheology as a new technology, based on the well-established fluid rheology is promising, since it provides a scientific description of the flow properties of concrete by two physical parameters namely yield stress and plastic viscosity. Understanding the two fundamental fresh property of concrete allow for more economical and better performing concrete mixes. Generally the rheological properties of fresh concrete calculated by using flow curve method through rheometers. Rheometer is a device to measure the rheological properties of fresh concrete. This paper contributes to bringing out the importance of rheology and also bringing out the advantage and limitations of rheometers pertaining to concrete industry.

Effect of coarse aggregate characteristics on concrete rheology

In the present study, concrete was considered as a two-phase material, consisting of coarse aggregate (CA) and mortar. Coarse aggregate properties were characterized by fineness, uncompacted void and friction angle. The combined effects of CA characteristics and mix design on the rheological properties of the corresponding concrete were investigated using a portable IBB concrete rheometer. Experimental results indicated that a higher CA and fine aggregate content normally result in higher concrete rheological parameters (yield stress and viscosity). For a given type and amount of mortar, concrete yield stress and viscosity generally increase with the uncompacted void content and friction angle but decreased with the size (or fineness) of CA. Well graded CA, generally having low uncompacted void content, provides concrete with considerably reduced yield stress and viscosity when compared with single-sized CA. In addition, a multiple-parameter linear regression analysis was conducted to evaluate how different CA characteristics (fineness, uncompacted void and friction angle) and mix design parameters (mortar composition, and CA volume fraction) affect concrete rheological behavior.

Experimental Characterization of Recycled Aggregate Concrete

MATEC Web of Conferences

The field of construction is evolving rapidly over the last decade. This is justified by the evolution of human activity in various fields mainly tourism, industry … and the aging of several buildings which implies a renovation or a demolition/re-construction. These construction activities involve a large need for aggregates for new construction and a large tonnage of waste from demolitions. In order to remedy this, various stakeholders in the field (suppliers, cement works, research centers, etc.) have valued recycled aggregate concrete (RAC). Recycled aggregates concrete is considered a new type of concrete based on the use of aggregates retrieved from the demolished structures instead of natural aggregates. This replacement affects, for sure, the characteristics of the concrete produced specially the mechanical properties. Developed countries have made a great progress in normalizing the use of recycled aggregates (RA) in concrete implementation as a result of many studies done s...