Problems experiences with the construction of cement and lime stabilized layers and working solutions for these problems

Abstract

Stabilized layers are used extensively in South-Africa in the construction of roads. The layers are usually stabilized with hydrated road lime, cement, slag, fly-ash, bitumen emulsion, foamed asphalt or a combination of several of these agents. In recent times, major problems were experienced with chemical stabilization in the Southern African Region, particularly when CEM I 42,5 cement was used. The standard laboratory design procedure worked in the laboratory but did not perform in the field. This was left contractually to the so called experienced Contractors to identify the cause of the problem and to present the Client/Consultant with working solutions. The paper deals with the cause of these problems, showing that they are generally material and not construction related, and how working solutions were found to overcome these problems. The main reason why these problems were generally not identified before during the design phase was because testing techniques presently used in soils laboratories do not simulate the conditions on site during and after construction. Furthermore, most of these tests only deal with the short term reactions, whilst in many cases these detrimental reactions continue well past the construction phase. This paper discusses the new testing protocol to identify the type of reaction that is taking place in the stabilized material and the experience gained.