International Concrete Abstracts Portal

Self-consolidating concrete (SCC) is a highly flowable, yet stable concrete that can spread readily into place, fill the formwork, and encapsulate the reinforcement without any mechanical consolidation and without undergoing any significant separation of material constituents. SCC has many advantages over conventional concrete, such as: eliminating the need for vibration; decreasing the construction time and labor cost; reducing noise pollution; improving the filling capacity of highly congested structural members; improving the interfacial transitional zone between cement paste and aggregate or reinforcement; decreasing the permeability and improving durability of concrete; and facilitating constructibility and ensuring good structural performance. SCC has been attracting more and more attention worldwide since its introduction in the late 1980s. New applications for SCC are being explored.

An experimental investigation was performed to determine the hydraulic pressure variation of cementitious based materials (cement paste, limestone paste,concrete, Self compacting concrete (SCC), etc.) during the plastic phase. A method based on measurements of both total lateral pressure and hydraulic pressure, using a noveldevice, has been investigated. Just after mixing, a simultaneous drop of both thehydraulic and the total lateral pressures was recorded, followed by a cancellation of totallateral pressure and a negative value of hydraulic pressure. Compared to other standard methods (Vicat, calorimetry, ultrasonic pulse-echo, etc …), the device was able to givesimple and direct information about the mechanical state of the material, in situ. Thekinetic variation of the hydraulic pressure occurring during the plastic phase of cement pastes using two portland cement fractions and a limestone filler was investigated. Torelate the hydraulic pressure measurements with workability, a study on the evolution of the rheology of the cement paste was conducted. The experiments on standard concretes,which had the same free water content as an equivalent cement paste, show a similar hydraulic pressure variation as long as the pressure is positive. This is not the case for SCC where the observed hydraulic pressure variation is slower and the time of zero pressure is delayed compared to the equivalent cement paste. The presence of limestoneand the HRWRA is the main reason for this retardation effect. In addition, as soon as the pressure becomes negative, due to the presence of aggregates, a delaying effect on the pressure variation was observed. In the end, field test show that the hydraulic pressure device could be used to monitor the field schedule of successive pouring, setting and demolding.

Self-Compacting Concrete (SCC) was developed in the later 1980’s and has attracted a wide interest in the world due to its unique properties. This study investigatesthe workability and earthquake resistance of SCC. Several chemical admixtures are added to the concrete to adjust its workability. The workability of fresh concrete is tested using different methods including slump cone, inversion slump cone, L-box and Orimet apparatus. Then the best SCC mixture ratio is selected for microstructural and earthquakeresistance investigations. The earthquake resistance of SCC is investigated on concrete frame. Two frames with the same size are designed and but one cast with SCC and theother one with ordinary concrete. The two frames are tested under low-cyclic loadingusing MTS loading system. ANSYS software is used to simulate and analyze the statictest. The test results give indication how the materials characteristics and constructability of SCC affect earthquake resistance behavior of the frame.

Fresh concrete is a complex fluid consisting of a suspension in water of a high volume percentage of particulate solid having a very wide particle size distribution. The rheological properties of fresh concrete control the flow behavior of the material in mixing, placement, consolidation and finishing. Test methods that measure flow using a single parameter (e.g. slump) cannot properly evaluate the rheological properties of concrete in all uses. ACI committee 236A with the support of the Concrete Research Council and industry has tested four concrete rheometers specifically designed to evaluate rheological properties of concrete materials. The second test series expands the data from the first test series using the same approach of bringing the rheometers together at a common test site and testing the same concrete mixtures simultaneously. All of the rheometers can measure a flow curve for fresh concretes with slumps in the range from 100 mm to 250 mm or non-segregating concretes with slump flows in the range from 300 mm to 800 mm. Each rheometer evaluates yield stress and plastic viscosity by fitting a Bingham model flow curve to measurements of rotation rate and torque for each mix. All of the rheometers gave different absolute values for the Bingham constants of yield stress and plastic viscosity for each mix. But all of the rheometers ranked the mixes in the same order for both yield stress and plastic viscosity.

This research examines the effect of aggregate content and gradation on self-consolidating concrete (SCC) passing ability. Passing ability is defined as an SCC mixture’s ability to flow through narrow spaces (e.g. closely spaced reinforcement) without segregating or blocking. The mixtures tested ranged over two uniform aggregate sizes, two aggregate contents, two different mixture design philosophies, and a gradated aggregate mixture. Passing ability tests, slump flow tests, horizontal flow tests, and stereology tests were performed on these mixtures. Stereology is a statistical counting technique used primarily by natural scientists. Concrete researchers have used this to describe bubble size and distribution in concrete. A vertical flow box was developed by McBride to determine the passing ability of the various mixtures. Various bar spacings are tested. From the results of this study, it seems that two stereology parameters can be correlated to the minimum bar spacing that will allow SCC to pass. These parameters are the ratio of maximum aggregate size to mean aggregate free distance and the ratio of maximum aggregate size to mean aggregate random spacing.