The Impact of the Time When Casting the Second Layer of Concrete on Its Mechanical Properties

Abstract

Cold joint is one of concreting problem due to delay of casting the second layer. This is due to glitch of one of mechanical machines such as the concrete mixer, concrete truck, concrete batching plants, concrete pumps, and concrete mobile; that cause the stopping of the casting process which produce forced separator. Forced separation is different from known separators like: construction joint, expansion joint and settlement joint, where its location event and shape cannot be determined moreover the design engineer cannot put that in mind during the design phase of building construction. Therefore, the target in this work is to study the effect of delay in time period when casting the second layer of concrete after 4, 9, and 16 hour for two types of concrete with compressive strength 250 kg/cm 2 and 300 kg/cm 2. Eexperimental work was performed at laboratory to investigate the mechanical properties of concrete (compressive strength, splitting tensile strength and flexural strength), first when sprinkle the first layer with water before casting and second when coated with a grout material.The results were investigated and it indicates that, in case of delaying in the time period for casting the second layer, there is a great effect on the mechanical properties of concrete and the use of grout coating material in forced separation has a positive impact on improving its mechanical properties.

An experimental and numerical study for investigating the promising stratified reinforced concrete slabs

“…The most important achievement conclusion is the success of the idea of casting different strengths concrete layers using a short time (60 min) interval to improve the flexural behavior of the slab. Mohamadien (2013) had studied the effect of delay in time period when casting the second layer of concrete after 4, 9, and 16 h for two types of concrete with compressive strength 250 and 300 kg/cm 2 . Experimental work was performed at laboratory to investigate the mechanical properties of concrete (compressive strength, splitting tensile strength, and flexural strength), first when sprinkle the first layer with water before casting and second when coated with a grout material.…”