Investigating the extent of the effect of sulphuric acid attack on compressive strength of laterised concrete.

Abstract

The research investigated the extent of the effect of acid attack on Laterised concrete in order to determine whether this concrete would be suitable for acidic environments. Laterised concrete is concrete whose fine aggregate has been replaced with laterite fine aggregate. The specific objectives were to collect and characterize fine aggregate laterite to be used in the laterised concrete; to assess variation of the compressive strength of laterised concrete before and after exposure to acidic conditions with laterite aggregate percentage replacement at 0%, 25%, 50%, 75% and 100% and to identify and recommend suitable mix design for laterised concrete based on acid resistance performance.

Laterite soil samples were collected from Lukwanzi Hill, Bunamwaya, crushed from the Directorate of Geological Survey and Mines lab and then characterized for their particle size distribution. A comprehensive experimental program was then designed and conducted to evaluate the compressive strength of laterised concrete samples subjected to sulphuric acid attack conditions. Concrete cubes were manufactured with respect to the mix ratio 0.6:1:1.35:1.65 (water-cement ratio: cement: fine aggregate: coarse aggregate), cured in fresh water for 28 days and then transferred to 5% concentration sulphuric acid and cured for more 14 days and 28 days. The mix ratio was obtained from literature, and it gave a compressive strength of 30.66 MPa. Compressive strengths were carried out at after 28 days in fresh water, 14 days in acid and 28 days in acid.

After carrying out compressive strength at 28 days of maturity, it was observed that all the mixes gave a strength greater than that in literature, 30.66 MPa. The mix with 25% replacement gave a peak strength of 34.4 MPa. There was a decrease with increase of laterite content but still higher than the strength of the conventional concrete (0% replacement).

The cubes were then immersed in acid. After 14 days in acid, the cubes were subjected to compressive strength tests. There was definitely a reduction in strength but the conventional concrete gave the least reduction, from 32 MPa to 30 MPa. The conventional concrete also gave the peak strength in acidic conditions for 14 days.