A nondestructive technique was used as an alternative method to monitor the hardening of cement-treated clay as a function of time. This monitoring technique makes use of bender elements to measure the small-strain shear modulus (G₀) at various time intervals. The strength increase was evaluated by conventional unconfined compression testing. Experimental work was carried out on kaolin clay treated with Portland cement and blast furnace slag cement at different dosages. The results showed that G₀, as well as strength, of cement-treated samples increases logarithmically with time. However, blast furnace slag cement produces a slower hardening rate early after mixing. It was found that for each binder type, the G₀ increase and the strength increase, when normalized, follow a common trend. Such hardening trend may be used as the basis of a strength prediction rule. The functions obtained are in good agreement with data on other cement-treated inorganic clays published in the literature.