Assessment of cover to reinforcement in slabs using different spacer and tying distances

Abstract

Given that the durability of structures is directly related to the thickness of the cover to reinforcement, it is essential to ensure minimum cover is achieved when building a structure. However, studies show that this is not always the case. One of the reasons for the this problem is the lack of indication, in structural projects, of the positioning of spacers. This situation is compounded by the lack of standards and regulations on the use of spacers (i.e. minimum quantities and required layout). This study assesses three different spacer distances and two different tying distances in order to examine the influence of these factors in the cover to reinforcement. To achieve so, three slabs were prepared in situ using different arrangements. After demoulding, cover thickness was determined using a digital covermeter. It was observed that the factors investigated have a significant influence in the final cover.

Computational and experimental simulation to analyze loss in concrete cover by reinforcement deformation in solid slabs

“…This diameter is not typically used in solid slabs, however it was considered in this laboratory investigation because it is allowed by the standard [12]. The other diameters are frequently used in solid slabs [27], [34], [37]- [39] and were chosen for verification in structural design.…”

“…Some aspects should be considered when choosing the spacer type to be used, such as the product performance [11], the structural element to be concreted, the reinforcement characteristics [10]. Also, the spacer correct quantity and position are essential because the distance between them has a significant influence on the final cover in slabs [27]. Their distribution should consider that an excessive spacing between spacers could cause bars to flex, especially during concreting process.…”

“…Many researchers report the failure to obtain the cover thickness specified in the current reinforced concrete structure constructions [27], [30], [31], [33], [34], where the probability of inefficient cover varies between 38.7% and 88.8% in solid slabs [30]. In general, the design reinforcement position is not achieved even before construction [35].…”

“…In general, the design reinforcement position is not achieved even before construction [35]. Among the structural elements, the slabs are one of the most damaged elements as a result of insufficient cover thickness [27]. Unsatisfactory covers could be a consequence of uneven placement or insufficient quantity of spacers, lack of formwork leveling [35], [36], spacers with a poor performance [11], wrong choice of spacers, or workers walking through the reinforcement meshes [34].…”

Evaluation of the ultrasound test for estimating the depth of cracks in concrete

“…However, there are several non-destructive tests (NDTs) that allow for important information about concrete properties to be extracted (Rehman et al, 2016), and are usually used to locate and evaluate defects in hardened concrete (Lorenzi et al, 2016). Lee, Chai, and Lim (2016) (Aggelis et al, 2010), thermography (Bagathiappan et al, 2013, pachymetry (Maran et al, 2015), radar (Dabous et al, 2017), and sclerometry (Tomazali and Helene, 2017). The ultrasound test can determine the modulus of elasticity and specific mass of the concrete (Pacheco et al, 2014), estimate the compressive strength with a reasonably good approximation (Bungey, Millarde Grantham, 2006), and locate and determine the size of discontinuities in the structure (Menezes et al, 2016).…”