Investigation and experience of using concrete-pump transport at the construction of the Shul'binsk Hydroelectric Station

Abstract

The current state of construction of concrete structures as the most labor-intensive necessitates an improvement of existing and development of new highly effective cyclic and continuous technologies of conducting works with the creation of an interrelated complex of highly productive machines and equipment completely mechanizing all elements of the works.A highly efficient technology based on the use of especially stiff, low-cement concrete mixes with the use for their placement and compaction of simple highly productive operating methods similar to the methods of constructing earth dams is presently gaining popularity for massive lightly reinforced concrete structures. The new technology has a high rate of placing the mixes (200-500 m3/h), which in many respects predetermined continuous methods of its preparation and conveyor delivery.For concrete-encased steel members and structures, especially heavily reinforced and thin-walled ones and those with a complex configuration, a progressive technology, in our opinion, is that with the use of modern concrete-pumping plants [1], which provides: combining horizontal and vertical delivery of mixes by one mechanism; the possibility of laying the concrete-delivery pipeline under the most complex and confined conditions of the construction site; movement of the concrete mix under pressure and its protection from unfavorable environmental effects; high mobility of the concrete-pumping equipment providing continuous delivery of the concrete mix; possibility of pumping the mixes through stationary piplines to considerable distances.The impetus to the creation of new economical designs and technologies of conducting concreting operations by means of concrete pumps was the intense development of superplasticizing and complex additives to concrete. Additive made it possible to obtain nonsegregating cast concrete mixes (CCMs) with a fluidity of 20-26 cm with respect to the slump of a standard cone (SSC) with prescribed physical and mechanical properties and workable in concreting blocks by nonvibration methods. Some progressive scheme of constructing hydraulic structures and members with the use of concrete-pumping techniques and CCMs are given in [2, 3, 4].Concrete-pump transport of cast concrete mixes has been studied little [5]. Rather extensive investigations of this problem as applied to the technology of constructing reinforced-concrete hydraulic structures are being carried out at the M. I. Kalinin Leningrad Polytechnic Institute (LPI) [6]. The following main technological problems have been established in the general problem of concreting technology: calculation of the maximum distance of transporting the mixes through stationary concrete-delivery pipelines; selection of the type of concrete pumps and their number; selection of the composition of the concrete mix meeting the given conditions of the delivery distance.These problems can be solved with consideration of the main characteristic of a concrete pump --the magnitude of the maximum pressure of the piston on the c...

Effect of Air-Entraining Agent LHD on the Technological Properties of Concrete Mix Containing Superplasticizer S-3

“…The use of air-entraining additives together with superplasticizers is a promising way to improve the technological properties of the concrete mix, in particular its pumpability using Concretepumping systems [12], which is especially important in the case of of highly reinforced constructions [13].…”