Evaluation of the Flexural Performance and CO₂ Emissions of the Voided Slab

Abstract

Reinforced concrete is regarded as one of the ideal structural materials which comprises concrete with high compressive strength and reinforcing bars with high tensile strength. However, concrete has been pointed out that it consumes a large volume of energy and emits a lot of carbon dioxide during its manufacturing. In order to lower such environmental burdens of concrete structures, a number of studies and approaches have been carried out. The voided slab is also suggested as a new method to reduce the environmental burden since voided section of the slab would use less concrete compared with the normal reinforced concrete slab. However, no studies have evaluated the CO2 emissions and environmental performance of voided slabs. The purpose of this study was to evaluate the structural performance of voided slabs and empirically corroborate their environmental influence. The flexural performance test was carried out based on the variables of the depth of slab, types of the void former materials, and the hollowness ratio. In addition, comparison of the emission of CO2 was also performed by considering the hollowness ratio and types of void former materials over the normal reinforced concrete slab. The structural performance of the voided slab was similar or slightly higher than the normal reinforced concrete slab. The yield strength of specimens was increased approximately 10∼30% over the anticipated yield strength. Based on this result, it is considered that the voided slab would be sufficient to structural performance and beneficial to plane planning in buildings. In general, it is considered that the voided slab would be beneficial to both structural and environmental aspects. However, the test results in this research showed that the voided slab would emit more carbon dioxide emissions compared to the normal reinforced concrete slab. The main source of more CO2 emissions in the voided slab was the anchoring materials. In this research, wires were used to fix the void former materials to the reinforcing bars. In order for the voided slab to become a more eco-friendly and sustainable material, new anchoring methods such as use of recycled materials, new void former materials without anchoring, or other eco-friendly materials should be applied to reduce the emission of CO2.

Assessment of CO2 Emissions by Replacing an Ordinary Reinforced Concrete Slab with the Void Slab System in a High-Rise Commercial Residential Complex Building in South Korea

“…The purpose of this study was to compare the CO2 emissions of two different slab systems, The additional steel materials or devices employed in the void slab systems discussed in the previous section are the main sources of carbon dioxide emissions [27]. In this regard, it is expected that VDS will produce less carbon dioxide, since both the anchoring materials and the void formers are made up of a common material other than steel.…”

“…The previous studies employed additional steel materials or devices to anchor the void formers securely in the slabs [22][23][24][25][26]; however, as the method of installation of void formers was slightly complicated, the accuracy and speed of installation strongly depended on the skill of the construction workers. Furthermore, Cho and Na [27] indicated that the utilisation of steel materials for anchoring the void formers to the lower and upper parts of the main reinforcement would cause more environmental burdens (~28% more CO 2 emissions) compared to ordinary reinforced concrete slabs. The previous studies employed additional steel materials or devices to anchor the void formers securely in the slabs [22][23][24][25][26]; however, as the method of installation of void formers was slightly complicated, the accuracy and speed of installation strongly depended on the skill of the construction workers.…”

“…The previous studies employed additional steel materials or devices to anchor the void formers securely in the slabs [22][23][24][25][26]; however, as the method of installation of void formers was slightly complicated, the accuracy and speed of installation strongly depended on the skill of the construction workers. Furthermore, Cho and Na [27] indicated that the utilisation of steel materials for anchoring the void formers to the lower and upper parts of the main reinforcement would cause more environmental burdens (~28% more CO2 emissions) compared to ordinary reinforced concrete slabs.…”

Comparison of Carbon Dioxide Emissions of the Ordinary Reinforced Concrete Slab and the Voided Slab System During the Construction Phase: A Case Study of a Residential Building in South Korea

“…Structurally, the voided slab system is an effective method for extending the span of a building or structure as it reduces the weight of concrete. Several researchers have maintained that the voided slab system would be advantageous not only in terms of structural and economic aspects but also because of its environmental friendliness [35][36][37]. From the structural design perspective, there are several studies that have examined and confirmed the stability and reliability of the voided slab system.…”

Flexural Rigidity in Concrete Beam by using the Crimped Steel Fibers with Rapid Hardening Admixtures

“…The mechanical properties of the concrete as such as bending stress of fibre reinforced concrete which improves with an increase in the percentages of steel fibre. The steel fibres prevent the early deforming of the beams and increase the durability of the structure [9][10][11][12]. The NDT methods for measuring the strength of a structure are not accurate but can help in correlating the values which can help in estimating the strength of the structure and also useful for analyzing the concrete characteristics and its homogeneity.…”