This paper examines some properties of concrete, such as strength, oxygen permeability and sorptivity using starch [cassava (CA) and maize (MS)] as admixtures. Concrete cubes containing different percentages of the CA and MS by weight of cement (0, 0.5, 1.0, 1.5 and 2.0 %) were cast. Compressive strength tests were carried out after 3, 7, 14, 21, 28, 56, 90, 180, 270 and 365 days of curing. Oxygen permeability and sorptivity tests were carried out on another set of concrete specimens with the same percentages of starch at 7, 28, 90, 180, 270 and 365 days. Oxygen permeability and sorptivity tests data obtained were subjected to Kruskal-Wallis one-way analysis of variance by ranks. The strength increase after 1 year over the control for CA 0.5 and CA 1.0 are 2.7 and 3.8 % respectively, while MS 0.5 and MS 1.0 gave 1.5 % increase over control. These results showed a decrease in oxygen permeability and rates of sorptivity, with concretes containing starch as admixtures giving better performance than the control concretes.

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Single story masonry buildings with light weight steel roof were designed and constructed on a specially designed shaking table at the Spoornet Laboratory in Johannesburg. The test structures were instrumented with LVDTs and accelerometers to measure the structural responses and behaviours of the structures at the bottom, middle and top of the in-plane and the out-of-plane walls. Accelerometers were also mounted on top of the steel roof to measure the roof responses. Displacements of the structures relative to the shaking table was measured from a rigid octagonal reference frame located inside the structure. The responses of two types of structures are reported. The first is a conventional block masonry structure. The second test was carried out on dry-stack interlocking block masonry structure which relies mainly on the interlocking features for structural resistance. The conventional masonry structure was subjected to 52 test runs ranging from minor peak ground acceleration (PGA = 0.05 g) to severe (PGA = 0.7 g). A similar test pattern was also used for loading the dry-stack system until failure was attained. Results obtained from the conventional structure show that test runs 1-10 caused no visible damage. Test run 11 produced cracks along the base of the in-plane wall due to racking, and surface or hairline cracks on the plastered surface of out-of-plane walls. Vertical cracks above the lintel level of the inplane wall was noticed after the test run 19. The progress of the above cracks was seen more clearly during the subsequent test runs. During test run 33 an inclined shear crack was developed. Widening of this shear crack was seen during subsequent tests leading ultimately to the collapse of parts of the walls during test run 52 and the test was concluded. The PGA at last run for the conventional masonry structure was 0.7 g which is equivalent to a magnitude of between 7.4 and 8.1 on the Richter scale or XI on the Modified Mercalli Intensity, MMI scale. This paper reports the structural responses of the test structures to simulated earthquake loading.

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A series of sisal fibre reinforced concrete roofing tiles were produced and tested using both standard methods and non-standard methods of testing corrugated Roman II tiles. The concrete was blended with ground granulated blast-furnace slag to various degrees to determine the optimum blend. The effectiveness of solar chamber curing was studied. The curing method was based on the utilization of solar energy to produce moisture movement in a sealed system with a chamber temperature that is significantly higher than the normal level in the surroundings. The failure modes and strengths of the tiles under bending load were presented and discussed. The effect of admixtures was also investigated on some of the samples. The viability of the techniques studied for commercial production of concrete roofing tiles was discussed.