ABSTRACT
Hydration heat can be a serious problem in massive concrete such as bridge abutments and piers. High temperature generated by chemical reactions in the very early age concrete mix can result in cracking and other problems. Therefore, there is need to reduce the temperature gradient between interior and exterior of the large concrete blocks. This problem does not only occurs in mass concrete constructions but also in bridges. Improper curing of concrete or badly composed mix, can cause thermal and shrinkage cracking in cast elements of bridge constructions.
The objective of this study is to propose an approach that can reduce the temperature gradient by considering the reinforcement bars as heat conductors. In practical cases, bridge abutments and piers require a considerable amount of steel reinforcement. Concrete is placed in stages, one layer after another. The rebar are then projecting from the completed layer, before the next layer is placed. The heat transfer is intense during the critical early hours, and this is when the projecting rebar dissipate the heat carried from the central part of the concrete block. To quantify the heat transfer, a series of tests was per-formed on specially prepared concrete blocks of 50 cm × 50 cm × 50 cm. These blocks were made using self-consolidating concrete with three different cements and for each cement, there are two blocks, one with reinforcement and the other one without it. The temperature was measured using special sensors in three points: in the center, close to the outside surface and in between. Figure 2 shows comparison of temperature in the middle point of concrete sample of reinforced (R) and non-reinforced (C) concrete samples. Samples after test. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig174_1.jpg"/> Temperature inside concrete samples. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig174_2.tif"/>
The tests showed that the heat that is conducted by reinforcement can reduce the temperature gradient by about 13°C. This observation will help in the design of protective systems that are needed to control cracking in massive concrete. The presented results are considered as a pilot study for further research.
