EFFECT OF CAUSTIC SODA FROM DETERGENTS ON THE COMPRESSIVE STRENGTH OF CONCRETE

ABSTRACT This research work was on the effect of caustic soda from detergent on the compressive strength of concrete. The aim of the study was to determine if caustic soda from detergent will have effect on the compressive strength of concrete over a period of time. The concrete cubes of size (150x150x150) mm were prepared in four samples of 9 cubes per batch with a nominal mix of 1:2:4 (grade 15) and a water-cement ratio of 0.5. Crushed gravel of size 9mm and sand of fineness modulus of 2.32 were used for both coarse and fine aggregates respectively. The curing condition comprised of two tanks of which one was clean water suitable of drinking (Tank A) and the other was clean water suitable for drinking but mixed with 4kg of powdered detergent (Tank B). Sample A was cured for 24hours per day in tank A, Sample B was cured in both tank A and B at 12hours intervals per day, Sample C was cured in both tank A and tank B at 6hours intervals per day and Sample D was cured in tank B for 24hours per day. Compressive strength test was carried out on 3 concrete cubes from each batch after 7,14 and 28 days of curing respectively. At 7 days, Sample C exhibited the highest compressive strength (8.29 N/mm²), while Sample B showed the lowest (7.7N/mm2). By 14 days, Sample A (control) led with (13.11 N/mm²), followed by C and B, with Sample D trailing at 11.41 N/mm². At 28 days, Samples A, B, and C converged at 14.81 N/mm², while Sample D remained slightly lower at 14.52 N/mm². These results indicate that intermittent exposure to detergent mixed water had minimal effects, whereas continuous exposure mildly reduced strength. Overall, hydration in clean water consistently produced the best strength outcomes across all stages.