Analysis of Timing Results during Continuous Concreting of a Massive Foundation Slab

Introduction. Risk assessment of early cracking during hardening of massive monolithic reinforced concrete foundation slabs due to temperature gradients enhances the relevance of studies of a host of factors related to a concreting technology given the technical capabilities of workers and suppliers of concrete mixtures, as well as weather conditions. While developing technological regulations for concreting with a calculation of the thermal stress state in the early period in order to reduce and control heat dissipation, studies in the field of assignment and regulation of time parameters of the process of forming the body of the foundation slab taking into account the prescription features of concrete mixtures and weather conditions are relevant. The aim of the study is to obtain new data for calculating the time parameters of concreting massive structures using concrete pumps with technical characteristics that are not available in the regulatory framework. Materials and Methods. The paper presents the results of timing the process parameters of continuous concreting of a massive foundation slab with a volume of 1642 m 3 in 13.6 h. The numerical values of the concrete mixture pumping speed, maneuvering time of concrete mixer trucks as well as the coefficients of transition from technical to operational performance of concrete pump trucks with a technical capacity of 170 and 180 m 3 /h are obtained. The use of concrete pumps with such a capacity at an actual unloading speed of concrete mixer trucks of up to 2.3 m 3 /min ensures an actual pumping performance coefficient of up to 0.81, which basically corresponds to normal operation. Research Results. The values of the concrete pump utilization coefficient over a time period ranging from 0.478 to 0.841 with an average value of ≈ 0.66 were obtained. The actual average productivity of one concrete pump during the concreting period was ≈ 61 m 3 /h. Discussion and Conclusion. With a distance from the concrete pump truck to the concrete mixer truck waiting area within 25–50 m, the maneuvering time does not depend greatly on the distance, according to 69 measurements, it is no more than 5.76 min with a reliability of 0.95 and is identified by the convenience of an area for maneuvering concrete mixer and access roads. The results can be used in developing process regulations for continuous concreting of similar massive structures.