Calcined Clay-Cement Stabilisation - Physicochemical Attributes and Stabilised Strengths of a-1-a and a-2-6 Soils

This work extends the investigations on calcined clay-cement blends to soil stabilisation works as obtained for other pozzolans. Samples of calcined clay (CC) were prepared from a natural kaolinite clay source from south-west Nigeria and were blended with Portland cement (PC) in CC:PC ratios of 0:1 (control), 1:3, 1:1, 3:1 and 1:0 to stabilise samples of lateritic soils from two sources. For each blend, combined stabilisers' percentages of 0, 2.5, 5, 7.5 and 10 of the soils' dry weight were adopted. The physical properties of the soils placed them in the A-1-a and A-2-6 AASHTO classes with fineness moduli (FM) of 4.33 and 2.18 respectively, indicating that the A-2-6 soil is finer, while the corresponding exchangeable cations (ECs) were 1.678 meq/100 gms and 1.738 meq/100 gms; these indicating that the A-2-6 soil has higher capacity for pozzolanic reactions. The 28-day unconfined compressive strength (UCS) tests on the stabilised soils samples show that the 1:1 and 1:3 blends were better stabilisers; this translating to environmental friendly alternatives to cement. The effects of these blends were more pronounced for the A-2-6 soil being the finer and with higher EC of the two soils. The two blends showed enhanced performance on the A-2-6 soil up to 10% binder content with UCS being 120% and 160% of control for 1:1 and 1:3 blends respectively. For the A-1-a soil, the edge over control was limited to 5% and 7% binder contents for the 1:1 and 1:3 blends respectively. The FM and ECs of the parent soil were raised as factors with potentials of affecting the performance of CC:PC blends as soil stabilisers. The paper calls for further work on lateritic soils from other sources to clearly establish the impact of these factors on their strengths when stabilised with CC:PC blends.