This report presents the results of an experimental investigation that was carried out to evaluate the performance characteristics of modified basalt rebar reinforced concrete beams. The modified basalt rebars were supplied by Research and Technology Corporation, Madison.
The primary objective of this investigation was to determine the strength of the bond between the modified basalt rebars and concrete, and to compare the experimentally determined ultimate moment capacity of basalt rebar reinforced concrete beams, and their calculated ultimate moment capacities according to ACI-3I8 Building Code recommended design procedures.
Bond tests according to ASTM C 234 procedure were performed on modified basalt rebars (4 slot and 8 slot) and plain basalt rebars. Bond tests were also done on single, double and triple cables. The double and triple cables were obtained by twisting together two and three single cables respectively. The results indicated that all the modified basalt rebars and cables, had considerably higher bond strength than the plain basalt rebars. The plain basalt rebars without slots failed due to the pUll-out of the basalt rebars. The basalt rebars with slots, and the
cables were not pulled out, they failed due to the fracture of basalt rebars in tension.
A total of seven beams reinforced with modified basalt rebars were tested. All the seven beams were designed and cast in the Rama Materials Laboratory of South Dakota School of Mines & Technology. Deflections were measured with the help of LVDT’s. Strains in the concrete and basalt rods were measured using electrical resistant strain gauges, and the readings were recorded using MEGADAC data acquisition system. The ultimate moments were much higher than the first crack moments, indicating good bond between the rebar and concrete. The beams had considerable cracking and large deflections before ultimate failure. Most of the beams failed primarily in flexure followed in shear failure.
Some beams had typical flexural failure. Beams with modified basalt rebars (with slots, corrugations, and smart alloy anchors) had adequate load carrying capacity and their actual ultimate moment capacities exceeded the calculated moment values. All the modified basalt rebars tested had adequate bonding capacity with concrete and therefore they could be effectively used as reinforcement in concrete structures.
Vladimir B. Brik,
Research & Technology Corp., Madison, WI