Evaluating Fresh Properties of Non-Dispersive Reactive Powder Concrete: A Novel Approach

Abstract

A novel testing methodology was developed in this study to efficiently evaluate the non-dispersibility of Reactive Powder Concrete (RPC) that does not disperse (Non-Dispersive RPC or NDRPC) -a concrete variant derived from the amalgamation of RPC and non-dispersive concrete. To study the fresh behavior of NDRPC, a series of fourteen mixes were prepared, each incorporating an Anti-Wash Admixture (AWA) concentration ranging between 0.5% and 2%. Fresh state properties were identified through a series of Slump Flow, V Funnel, L-box, and Setting Time tests, while washout resistance was determined through modified Stream Test, Turbidity, and pH tests. The findings constitute the first efficient evaluation of the non-dispersibility of fresh Self-Compacted Mortar (SCM) or concrete mixtures when placed underwater, as ascertained by V Funnel and L-box tests under similar conditions. Experimental results indicated a synergistic effect between AWA and High Range Water Reducer Admixture (HRWRA) concentrations on the properties, which could be counterbalanced by increasing the incorporation of silica fume to 30%. Notably, a significant reduction in washout loss was observed when silica fume replacement was increased to 30%.

Comparative Study of the Performance of Underwater Concrete between Anionic and Nonionic Anti-Washout Admixtures

“…In practical tests, when the dosage of nonionic AWAs reaches 0.9%, the cement mortar is too sticky to meet the fine workabil ity requirements of UWC; thus, the dosage of AWAs is limited to between 0.1 and 0.6% in UWC [35]. According to the fluidity test, the average fluidity decreases by 45.1% and 37.5% with the use of nonionic and anionic AWAs, respectively, which shows that anionic AWAs have a less negative impact on the flow properties of concrete [36,37].…”

Dynamic Characterization Assessment and Optimization of Reactive Powder Underwater Concrete

“…Concrete mixing involves the gradual addition of the liquid mixture, HRWRA, and hydrated AWA. The mixing sequence for RPUWC was conducted according to the procedure described by Alsaffar et al [17]. After achieving a better consistency in the mixture, the MS was gradually added to the mixture during continued mixing, ensuring proper dispersion and mixed for an additional approximately 2 minutes after all fibers had been added.…”

“…All specimens were taken out from those molds after 48 hr. after the initial pouring, followed by standard curing [17,[24][25].…”

“…Although there has been a significant increase in research efforts focused on improving underwater concrete (UWC) properties by introducing additional cementitious materials and nano-additives, the effect of adding fibers to its dynamic characteristics remains an area that hasn't been extensively investigated [13][14][15][16]. This study endeavors to bridge this knowledge gap by investigating the dynamic properties of advanced UWC, achieved by amalgamating the attributes of Reactive Powder Concrete (RPC) with those of underwater cast concrete [17].…”