The feasibility of using kimberlite tailings as aggregates in concrete was assessed. Compressive strength and selected durability tests were carried out on concretes made using various replacement levels (0, 40, 60 and 100%) fine and/or coarse blended crushed andesite and kimberlite tailings as aggregates. A w/b ratio of 0.50 and a CEM I 52.5R were used. The results show that the kimberlite tailings as aggregates have a relatively high water demand which was manifested as a reduction in workability of the fresh concretes with kimberlite tailings as a proportion of either fine and/or coarse aggregates. The results also showed that the use of the kimberlite tailings as a proportion of either fine or coarse aggregates in concrete resulted in a decrease in both compressive strength and durability properties viz water sorptivity and oxygen permeability. This was partly attributed to the low workability of the concretes which is known to limit the degree of compaction of fresh concrete. It is envisaged that careful concrete mix proportioning including the use of admixtures and pre-wetting of the aggregates can be used to offset the negative effects of high water demand of the kimberlite aggregates.

The influence of low curing temperatures (5, 10 and 15 ± 2 °C) on the strength and durability properties of ground granulated blastfurnace slag (GGBS) and ground granulated Corex slag (GGCS) concretes was studied. A standard curing temperature of 23 ± 2 °C) was also used for comparative purposes. Test specimens were cast using 100% CEM I 52.5N (PC), and three PC/Slag (GGBS or GGCS) replacement ratios of 50/50, 65/35 and 80/20, and a w/b ratio of 0.40. The specimens were cured for 28 days by submersion in water at the respective curing temperatures and then tested for durability. Durability was assessed using oxygen permeability, water sorptivity and chloride conductivity tests. The results showed that durability of the concretes decreased as the curing temperature decreased – gas permeability and water sorptivity increased while chloride resistance decreased. It was also observed that at a given curing temperature, the slag blended concretes showed superior durability performance than the plain PC concretes.

This study investigated the effect of production and curing parameters on the mechanical performance of compressed earth blocks (CEBs) stabilized with 0-20 wt % CCR (calcium carbide residue). Kaolinite (K) and quartz (Q)-rich earthen materials were mixed with the CCR and used to mould CEBs at optimum moisture content (OMC) and OMC+2 % of the dry mixtures, cured at 20 °C, ambient temperature in the lab (30±5 °C) and 40 °C for 0-90 days. After curing, the reactivity of the materials and compressive strength of dry CEBs were tested. Increasing the moulding moisture from OMC to OMC+2 decreased the compressive strength 0.3 times (4.4 to 3.3 MPa) for the CEBs stabilized with 20 % CCR cured at 30±5 °C for 45 days. Similarly, the compressive strength (4.4 MPa) was reached by CEBs stabilized with 10 and 20 % CCR after 28 and 45 days of curing, respectively. At 40 °C, the compressive strength increased 3.3 times (1.1 to 4.7 MPa with 0 to 20 % CCR) for K-rich and 2.5 times (2 to 7.1 MPa) for Q˗rich materials. At 20 °C, the compressive strength increased only 1.3 times (1.1 to 2.5 MPa) for K˗rich and barely 0.7 times (2 to 3.4 MPa) for Q-rich materials. These suggest that CCR is useful for stabilization and improving the performances of CEBs in hot regions.

Stabilized earth is a very ancient material that has been used in many countries as a low cost, environment friendly construction material. However, its durability under humid environments is low. Stabilization using cement, lime and natural fibres could enhance its durability and lowers the risk of cracking. This paper presents an experimental investigation into the performance of stabilised local soil by either, cement mixed with a proportion of granulated blast furnace slag (GBFS) /or straw naturel fibres. Unconfined compressive strength (UCS), shrinkage, wetting and drying, capillary absorption and thermal conductivity tests were performed on both untreated soil samples and stabilised soil samples. The results show that stabilising the soil with cement and GBFS increased both compressive strength, durability, thermal conductivity and decreased the capillary absorption and the shrinkage. The addition of natural wheat fibres increased the capillary absorption but leads to a decrease in the thermal conductivity and to a further reduction in the shrinkage and hence a better insulating less prone to cracking material.

Concrete is the most used material in the world after water because of its good mechanical characteristics and its reasonable cost. However, reinforced concrete structures can be damaged by corrosion or other chemical attacks and require repair and maintenance. The repair materials need to satisfy some mechanical and physico-chemical characteristics. Ready-made repair mortars are widely used. However, they are quite expensive, generally imported and they frequently incorporate low volume of synthetic fibers. This paper reports an experimental investigation designing an environmental friendly repair mortar made of local mineral addition (natural pozzolan (PN) and slag (SL)) and local natural fibers. The natural fibers used are Alfa fibers and date palm tree fibers at a volume ratio of 0.75%. The physical and mechanical properties studied are compressive strength, bending strength, total shrinkage and bond strength by slant shear and pull-off tests. The durability of the mortar was assessed by water capillary absorption. The results are compared to those of a reference mortar. The results showed that the substitution of cement by slag and natural pozzolan lead to a decrease in shrinkage (at 28 days of age). The use of date palm and alfa fibers improves the bending strength but reduces compressive strength. According to the results of the pull-off tests, only mortars containing slag meet the minimum value (1.5 MPa) required by EN1504-3. The types of failures observed for most composites show that they can be successfully applied with 20 mm thick layers.

This paper presents a recent study on recycling poly-ethylene-tetraphylate (PET), known as plastic waste material in Ghana, to wealth. Composites were produced by heating aggregates together with shredded PET plastic waste material, while bitumen was added to the plastic-coated aggregates. The composites produced were reinforced with 4.5 wt%, 9.0 wt%, 13.6 wt%, and 18.0 wt% PET. Mechanical properties of the fabricated composite samples were studied with a Universal testing machine for optimization. The work demonstrated that shredded PET plastic waste material acts as a strong binding agent for bitumen that can improve on the shelf life of the asphalt. From the results, 13.6 wt% concentration of PET was shown to experience the maximum compressive strength and flexural strength. Besides, water resistance was shown to increase with PET concentrations/weight fraction. From the data characterized 13.6 wt% of PET plastic gives the optimum plastic concentration that enhances the rheological properties of bitumen. The implications of the result are therefore discussed for the use of 13.6 wt% PET in road construction.

This paper presents the characterization of laterite-cement-based matrix composites, reinforced with chemically modified bamboo fibers. Fiber extraction and chemical modification were first explored by soaking slabs of bamboos in NaOH solution (5 wt.% of NaOH in distilled water) for 14 days. Fiber characterization, as well as the flexural and compressive strength of reinforced composites, were carried out with MTS universal mechanical testing machine. Comparative results on the compressive and flexural strength were obtained at 80 wt.% laterite (L) to 20 wt.% cement (C) with fiber ratios from 5-25 wt%. The compressive strength of the composites varied from 7.2 MPa (at 5 wt.% bamboo fiber) to 17.67 MPa (at 25 wt% fiber blocks). The hardness of the composites was found to improve from 66.67-75.0 HD with bamboo fibers. Results were then discussed for possible structural applications such as enhancing low-cost building blocks for rural communities in Ghana.

There is a need to introduce modern sand binder systems in the South African foundry industry as a means of improving its competiveness through the reduction of scrap castings and compliance to environmental regulations. According to the Industrial Policy Action Plan (IPAP). The foundry industry will play an important role with regards to the economic infrastructure priority advocated in the National Development Plan (NDP) of South Africa. In this study, a new generation water glass binder is introduced in a local foundry for production of cores for export plumbing casting production. The new water glass introduced is unique in that it contains an inorganic breakdown agent. The core making operating parameters including binder content, temperature and cycle time are optimised through core making trials without any alterations on the coremaking machines. Production data was evaluated using an optimization feature of Microsoft excel software. The results provided a set of optimum operating variables to manufacture 80-100% good quality sand cores for casting applications with an environmentally friendly binder. The most favourable binder content is above 2.60%.The most favourable operating temperature range is 160-174 0C. Therefore temperature and related energy costs can be reduced. The shortfall is reduction in cycle time.