Progress in developing self-consolidating concrete(SCC)constituting recycled concrete aggregates:A review

Recycled concrete aggregate(RCA)derived from demolition waste has been widely explored for use in civil engineering applications.One of the promising strategies globally is to incorporate RCA into concrete products.However,the use of RCA in high-performance concrete,such as self-consolidating concrete(SCC),has only been studied in the past decade.This paper summarizes recent publications on the use of coarse and/or fine RCA in SCC.As expected,the high-water absorption and porous structure of RCA have posed challenges in producing a high-fluidity mixture.According to an analysis of published data,a lower strength reduction(within 23%regardless of coarse RCA content)is observed in SCC compared with vibrated concrete,possibly due to the higher paste content in the SCC matrix,which enhances the weak surface layer of RCA and interfacial transition zone.Similarly,SCC tends to become less durable with RCA substitution although the deterioration can be minimized by using treated RCA through removing or strengthening the adhered mortar.To date,the information reported on the role of RCA in the long-term performance of SCC is still limited;thus,a wide range of research is needed to demonstrate the feasibility of RCA–SCC in field applications.

Combined Recycling of White Rice Husk Ash as Cement Replacement and Metal Furnace Slag as Coarse-Aggregate Replacement to Produce Self-Consolidating Concrete

According to empirical evidence,high levels of energy and considerable amounts of natural resources are used in the production of concrete.Given the context,this study explores self-consolidating concrete(SCC)that includes rice husk ash(RHA)and metal furnace slag(MFS)as an alternative to cement and the natural aggregates in standard SCC mixes.In this study,mixture designs are investigated with 20 wt.%of RHA,10–30 wt.%of MFS and water-to-powder material ratios of 0.30 and 0.40.Based on the findings regarding the fresh-state,hardened-state,and durability properties of the resulting SCC mixes,it is evident that the use of RHA and MFS can significantly improve the properties of concrete.The highest compressive strength was achieved for SCC with 20 wt.%RHA and 10 wt.%MFS.This outcome should be used as a basis for further investigations into the production of concrete materials that are both high-performance and sustainable.

Cracking behaviors and crack control of self-consolidating concrete: a review of literature

Cracking in concrete occurs from volumetric instability, mechanical loading, and/or environmental attack. Compared to conventional vibrated concrete, self-consolidating concrete often has a higher susceptibility to crack due to different mixture design, material properties and construction practices. To obtain a better understanding of self-consolidating concrete cracking behaviors for designing and constructing crack-controlled structural elements, reported current research and practices are reviewed and analyzed in this paper. It has been believed that when well designed and welt constructed, high quality self- consolidating concrete can be successfully used in various structures with cracks properly controlled.

Influence of Hydrostatic Pressure on Compressive Strength of Self-consolidating Concrete

The design of unique chamber, in which the SCUWC （self-consolidating underwater concrete） can be tested under the impact of the hydrostatic pressure from 0.1 MPa to 0.5 MPa, is presented in the paper. The results of the preliminary tests of the effect of the hydrostatic pressure on the compressive strength of SCUWC were shown. The impact of the hydrostatic pressure on the compressive strength values of test specimens has been confirmed. There has been an increase in the strength of the specimens taken from the upper parts of the concrete samples. As it can be seen from the preliminary research, the differences in compressive strength are related to the differences that occur in the size and distribution of air voids in the samples taken from upper and lower parts of the test specimens. On the basis of the carried out investigations of the compressive strength, it can be concluded that the hydrostatic pressure has a favorable effect on the compressive strength of the tested specimens of SCUWC. Increase of the compressive strength is observed mostly in the upper layers of the samples. Preliminary analysis of the quantity and distribution of air pores in the samples of concrete subjected to pressure 0.5 MPa confirms the positive impact of the hydrostatic pressure on the layers close to the surface indicated by the absence of large air voids above 1,500μm and by reducing the quantity of air pores of size above 300μm.

Carbon steel slag as cementitious material for self-consolidating concrete

This study deals with the recycling of carbon steel slag (CSS) to produce self-consolidating concrete (SCC). Since the chemical composition of CSS is similar to that of Portland cement or blast furnace slag (BFS), it is expected to behave similarly. In the current study, the pozzolanic activity index of CSS is examined. Furthermore, the use of CSS as a pozzolanic material to partially replace Portland cement in the production of SCC is tested. We designed concrete mixtures with different water-tocementitious material ratios (w/cm) keeping water and superplasticizer (SP) contents constant. Results showed that the design and performance of all the concrete mixtures used in this investigation were comparable to those of SCC and high performance concrete (HPC). However, compared to ordinary plain concrete (OPC), the additional CSS content increases the setting time. In the CSS mixtures set for 90 d, compressive strengths of 86%, 134% and 121% were attained as compared to the control concrete; the corresponding w/cm ratios were 0.28, 0.32 and 0.40, respectively. Verifying the soundness of the SCC for meeting the criteria for HPC, the ultrasonic pulse velocity (UPV) of CSS was found to be comparable to that of ordinary concrete. In conclusion, the recycling of CSS can be advantageously employed in the production of SCC.

Compressive strength and stability of sustainable self-consolidating concrete containing fly ash, silica fume, and GGBS

This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete （SCC） mixes where up to 80% of Portland cement was replaced with fly ash, silica fume, or ground granulated blast furnace slag. Compressive strength of SCC mixes was measured after 3, 7, and 28 days of moist curing. It was concluded in this study that increasing the dosage of fly ash increases concrete flow but also decreases segregation resistance. In addition, for the water-to-cement ratio of 0.36 used in this study, it was observed that the compressive strength decreases compared to control mix after 28 days of curing when cement was partially replaced by 10%, 30%, and 40% of fly ash. However, a fly ash replacement ratio of 20% increased the compressive strength by a small margin compared to the control mix. Replacing cement with silica fume at 5%, 10%, 15%, and 20% was found to increase compressive strength of SCC mixes compared to the control mix. However, the highest 28 day compressive strength of 95.3 MPa occurred with SCC mixes in which 15% of the cement was replaced with silica fume.

Effect of microlimestone on properties of self-consolidating concrete with manufactured sand and mineral admixture

Self-consolidating concrete(SCC)with manufactured sand(MSCC)is crucial to guarantee the quality of concrete construction technology and the associated property.The properties of MSCC with different microlimestone powder(MLS)replacements of retreated manufactured sand(TMsand)are investigated in this study.The result indicates that high-performance SCC,made using TMsand(TMSCC),achieved high workability,good mechanical properties,and durability by optimizing MLS content and adding fy ash and silica fume.In particular,the TMSCC with 12%MLS content exhibits the best workability,and the TMSCC with 4%MLS content has the highest strength in the late age,which is even better than that of SCC made with the river sand(R sand).Though MLS content slightly affects the hydration reaction of cement and mainly plays a role in the nucleation process in concrete structures compared to silica fume and fly ash,increasing MLS content can evidently have a significant impact on the early age hydration progress.TMsand with MLS content ranging from 8%to 12%may be a suitable alternative for the Rsand used in the SCC as fine aggregate.The obtained results can be used to promote the application of SCC made with manufactured sand and mineral admixtures for concrete-based infrastructure.