Civil Engineering April 2022 | Vol 30 No 3

Civil Engineering April 2022 35 of cement or lime have been provided by Netterberg (1984). NOTES 1. Clean, washed sand can be substituted for the actual material if it is only desired to compare stabilisers, other- wise use the actual percentage of the stabiliser and the material to be used on the project. 2. Preparation of one litre each of the phenolphthalein and dilute hydro- chloric acid solutions: 0.5 % phenolphthalein solution Dissolve 5 g of the powder in 500 mℓ of approximately 70% to 95% ethanol and add 500 mℓ of distilled water with con- stant stirring. Filter if a precipitate forms. Approximately 1.2 N dilute hydrochloric acid Add the following amount of concen- trated HCl according to its concentra- tion to at least 500 mℓ of water and make up to 1 000 mℓ: Q Q 36% (about 12 N): 100 mℓ Q Q 35% (about 11 N): 110 mℓ Q Q 32% (about 10 N): 120 mlℓ The exact concentration of the diluted acid is not important within the range 1.0 N to 1.5 N and a commercial grade of concentrated HCl can be used. This more dilute acid is more sensitive than the 5 N HCl previously recommended and with care and a little practice allows the detection of carbon- ated stabiliser even in calcretes.  REFERENCES De Wet, L.F. and Taute, A. 1985. Durability of stabilized materials. Proc. Ann. Transport Convention Pretoria, FB, 1-15. Netterberg, F. 1984. Rapid field test for carbonation of lime or cement treated materials. Nat. Inst. Transp. Road Res. Rep. RS/2/84, CSIR, Pretoria, 14 pp. Netterberg, F. 1987. Durability of lime and cement stabilization. Nat. Inst. Transp. Road Res. Rep. TS/9/87, Revision of July 1987, CSIR, Pretoria, 35 pp. Netterberg, F. 1991. Durability of lime and cement stabilization. In: Concrete in pavement engineering, Portland Cement Inst., Halfway House, 27 pp. Netterberg, F. and Paige-Green, P. 1984. Carbonation of lime and cement stabilized layers in road construction. Nat. Inst. Transp. Road Res. Rep. RS/3/84, CSIR, Pretoria, 10 pp. Netterberg, F., Paige-Green, P., Mehring, K. & Von Solms, C.L. 1987. Prevention of surface carbonation of lime and cement stabilized pavement layers by more appropriate curing techniques. Proc. Ann. Transp. Convention, Pretoria, 4A, Paper 4A/X, 45 pp. Netterberg, F. and De Beer, M. 2012. Weak interlayers in flexible and semi-flexible road pavements: Part 1. J. S. Afr. Instn Civil Engng, 54, (1), 32-42. Discussion by CJ Semmelink and response from authors: 55, (1), 114-116. Paige-Green, P. 1984. A laboratory investigation into the influence of carbonation on the strength of lime-stabilized materials. Proc. 8 th Reg. Conf. Africa Soil Mech. Fndn Engng, Harare, 1, 403-406. Paige-Green, P. 1991. The long-term durability of lime-treated soils. Proc. 10 th Reg. Conf. Africa Soil Mech. Fndn Engng, Maseru, 1,193-196. 13 12 8 5 3 7 18 21 6 4 24 1 23 10 26 16 2 7 17 2 22 9 20 19 11