Solubility of concrete in acid solution as a determinant factor in the assessment of concrete strength

Abstract

The need exists for early assessment of strength of concrete in modem reinforced concrete construction to minimise losses. Possibility of using solubility of concrete in acid solutions to carry out its strength assessment
was investigated. Standard concrete cubes were cast and cured for different days. At each curing day, a set of concrete cubes of the same water-cement ratio was tested for strength using a conventional method. Another set of the same concrete cubes was also soaked for 48 hours in HCl at different acid concentrations. Dissolved solids concentration was later determined using Standard method. The results showed that dissolved solids increased with increase in HCl concentration, likewise, compressive strength increased with increase in curing days. Relationship between compressive strength and dissolved solids concentration of concrete in HCl solutions indicated that there was perfect correlation between them with correlation coefficient of 1.0. For 3, 7 and 28 days
uncrushed concrete at 0.55 water-cement ratio in 75 mg/l of HCl the dissolved solids were 29637, 27288 and 26148 mg/l respectively while compressive strength were 20.36, 22.41 and 26.20 N/mm² respectively. Similarly, for 3, 7 and 28 days uncrushed concrete at 0.65 water-cement ratio in 75 mg/l HCl concentration, the dissolved solids were 35062, 32286, and 33032 mg/l respectively while compressive strength were 8.40, 11.23 and 12.66 N/mm² respectively. It was concluded that solubility of concrete in HCl solution could be used as an alternative method in the assessment of strength of hardened concrete.

Keywords: Solubility, concrete, acid solutions, concentration, dissolved solids, compressive strength, correlation coefficient, water-cement ratio.