This research presents the use of flexural performance criteria for determining the required spliced length of tensile plain bar embedded in unconfined high strength-high volume fly ash-self compacting concrete (HS-HVFA-SCC) beam. Subsequently, the obtained splice length is compared with the splice length database of other concrete types. For the purpose of the investigation, five beams are designed with various spliced bars within the pure bending area. In addition, a beam with continuous bar is prepared as a reference beam. The beams are tested by a four-point loading scheme. The results show that splice lengths within a 342–570 mm (34.2db–57db) range provide sufficient development of strength in the reinforcements to sustain a higher flexural load than the reference beam. However, in term of stiffness and ductility, only beams with a splice length of at least 380 mm (38db) are superior compared to the reference beam. Based on the above consideration, the minimum splice length of tensile plain reinforcement for the investigated beams is 380 mm (38db). Comparison of the result with other concrete types suggests that the required splice length of tensile plain bar embedded in HS-HVFA-SCC follows the equations for estimating splice length of general concrete and self-compacting concrete (SCC) even though the equations are derived for deformed bars. This finding implies that an efficient splice length in HS-HVFA-SCC beam can be expected. Article Highlights HS-HVFA-SCC beam with a lap-spliced plain bar of 38db gives an equal flexural performance to the beam with continuous bar. The required splice length of plain bar in HS-HVFA-SCC beam is comparable to that of deformed bar in other concrete types. An expected efficiency of splice length can encourage the use of HS-HVFA-SCC for a variety of structural applications.