Overview Studies of High Strength Self-Consolidating Concrete
: Self-Consolidating Concrete (SCC) is considered as a relatively new technology created as an effective solution to problems associated with low quality consolidation. A SCC mix is defined as successful if it flows freely and cohesively without the intervention of mechanical compaction. The construction industry is showing high tendency to use SCC in many contemporary projects to benefit from the various advantages offered by this technology. At this point, a main question is raised regarding the effect of enhanced fluidity of SCC on the structural behavior of high strength self-consolidating reinforced concrete. A three phase research program was conducted at the American University of Beirut (AUB) to address this concern. The first two phases consisted of comparative studies conducted on concrete and mortar mixes prepared with second generation Sulphonated Naphtalene-based superplasticizer (SNF) or third generation Polycarboxylate Ethers-based superplasticizer (PCE). The third phase of the research program investigates and compares the structural performance of high strength reinforced concrete beam specimens prepared with two different generations of superplasticizers that formed the unique variable between the concrete mixes. The beams were designed to test and exhibit flexure, shear, or bond splitting failure. The outcomes of the experimental work revealed comparable resistance of beam specimens cast using self-compacting concrete and conventional vibrated concrete. The dissimilarities in the experimental values between the SCC and the control VC beams were minimal, leading to a conclusion, that the high consistency of SCC has little effect on the flexural, shear and bond strengths of concrete members.
Self-consolidating concrete
As self-consolidating concretes (SCCs) are easily pumpable and require little workmanship to be poured, their use is gaining acceptance in casting columns, walls and floors for high-rise buildings. SCCs are also currently used in pre-cast plants because they facilitate and accelerate the pouring of concrete, prolong the life of the moulds and decrease the noise level in the plant. This noiseless aspect is a great advantage when casting concrete in buildings during working hours or in cities where there are noise restrictions after 5 pm. The formulation of SCC is flexible enough to accommodate the addition of fine materials or viscosity-modifying admixtures (VMAs) that are used to adjust SCC viscosity. The overall cost balance of using SCCs must be considered in a global sense. Using SCCs requires tighter quality control, but knowledge and practical experience are now available to handle this properly.
Mineral element analyses of various tropical forages in Guatemala and their relationship to soil concentrations
Determination de la composition minerale de differents fourrages dans 3 regions d'elevage du Guatemala et etude des relations entre la chimie des sols et la composition minerale des fourrages