Effect of alkali-silica reaction on the flexural behavior of beams with tensile lap splices

Abstract

A series of 19 beam specimens, with varying stirrup spacing and tensile lap splice lengths, were tested at the National Institute of Standards and Technology (NIST) under four-point loading to investigate the impact of alkali silica reaction (ASR) on the flexural strength and bond behavior of reinforced concrete members. The beams contained highly reactive aggregates, were cured in an environmental chamber at high relative humidity and temperature, and were tested in batches at regular intervals in time. The development of strains in the deformed bar reinforcement was monitored in five beam specimens to provide an assessment of the level of ASR expansion achieved prior to testing. The strain development in the tensile reinforcement bars and stirrups was generally similar between the specimens, despite differences in stirrup spacing and lap splice length. Strains in the transverse stirrups due to ASR-induced expansion at the time of testing were roughly twice the strains recorded in the longitudinal tensile reinforcement, reaching a maximum value of approximately 0.002 mm/mm prior to testing. The concrete mixture studied exhibited expansions in the range of 0.2% and the tested beams exhibited randomly oriented surface cracking with no localized spalling or general loss of section at the time of testing. The effects of ASR included reductions in the compressive strength and modulus of companion cylinders of up to 15% and 50%, respectively. A rigorous statistical analysis of the measured data was performed to quantify the influence of ASR-induced expansion, splice length, and stirrup spacing on the beams’ flexural capacity and the maximum achieved average bond strength. Results indicated that in the range of expansions, stirrup spacings, and lap splice lengths studied, there was no evidence that the moment capacity or the maximum average bond strength was reduced by the effects of ASR. Tested beams constructed with ACI 318 code compliant splice lengths achieved or exceeded the nominal flexural strength of the section, regardless of the degree of ASR-induced expansion observed.