The influence of bleeding, extra water and superplasticizer on the SCC plastic shrinkage cracking: case of hot weather

Abstract

a laboratory of experimental and numerical Modelling of Materials and structures in civil engineering (laMoMs), university Mouloud Mammeri of Tizi ouzou, Tizi ouzou, algeria; b l2Mgc, cergy-Pontoise university, cergy-Pontoise, france; c laboratory of Materials and durability of constructions (lMdc), university Mentouri of constantine, constantine, algeria ABSTRACT Self-compacting concrete (SCC) is a new material able to be put in place without vibration. However, this advantage is offset by some drawbacks, such as plastic shrinkage, one of the causes of cracking in concrete. Furthermore, the presence of fines absorbs a large amount of water and therefore minimizes bleeding. This paper endeavours to provide a better understanding of the appearance of plastic shrinkage cracking, and to justify his relation with bleeding phenomena. Five SCC formulas with different W/C ratios were prepared and compared to the same range of ordinary concrete (OC) in terms of restrained shrinkage (cracking width). At the same time, a study of cracks' propagation over time (cracking length) was conducted on the equivalent mortars (mOCe, mSCCe). Mixtures were placed in different hot environmental conditions. The results showed that bleeding significantly reduces cracking length and has no effect on cracking width. In the second part, extra water and superplasticizer was proposed as a solution to prevent SCC cracking and findings show the addition of 10% of water reduces cracking length and a slightly lower addition of superplasticizer reduces SCC's crack width.

Plastic settlement and hardened state assessments of manufactured sand made concrete for varying microfine levels

“…In addition, two metal inserts were provided besides the stress riser to accommodate the internal restraints of concrete. Similar test setup was reported in the literature by Boshoff and Combrick, 16 Ghourchian et al, 20 Sirajuddin and Gettu, 28 Leemann et al, 53 Yakoubi et al 54 and in a few more studies. However, based on some investigations it was identified that the provision of these two metal inserts alone was not sufficient to restrain the concrete shrinking 55,56 .…”

“…In some concrete specimens both primary and secondary cracks were identified after the 24‐hour observation since the exposure to the PSC environment. However, the investigation carried out by Yakoubi et al 54 reports that the PSC development over the time was low. The early age cracking was observed after 1 h for ordinary concrete and after 2 h for self‐compacting concrete, while after half an hour of the time, the modest development of cracks was noticed in the mortars.…”

“…Yakoubi et al 54 used the crack length alone as the main parameter to investigate the PSC behavior of ordinary and self‐compacting concretes where the authors were arrived with satisfactory results as predicted. Sivakumar 32 showed some good correlations between the w/c ratio of concrete and the crack width, crack length and crack area.…”

“…Based on the study by Topcu and Elgun 57 and Yakoubi et al, 54 it was concluded that the evaporation rate at the fresh concrete surface is determined by the climatic conditions compared to the concrete compositions. However, to examine the influence of varying MFA replacement levels the climatic conditions provided in the PSC chamber were maintained constant throughout the study where all concrete specimens were exposed to same environmental conditions until the crack investigation.…”

“…These conditions were able to maintain an evaporation rate of 1.5 -2 kg/m 2 /h which was obtained from the evaporation nomograph according to Kosmatka et al 29 This satisfies with the minimum requirements for PSC of concrete suggested by ASTM C1579. 52 Based on the study by Topcu and Elgun 57 and Yakoubi et al, 54 it was concluded that the evaporation rate at the fresh concrete surface is determined by the climatic conditions compared to the concrete compositions. However, to examine the influence of varying MFA replacement levels the climatic conditions provided in the PSC chamber were maintained constant throughout the study where all concrete specimens were exposed to same environmental conditions until the crack investigation.…”