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Many researchers have studied the use of agro-waste ashes as constituents in concrete. These agro-waste ashes are siliceous or aluminosiliceous materials that, in finely divided form and in the presence of moisture, chemically react with the calcium hydroxide released by the hydration of Portland cement to form calcium silicate hydrate and other cementitious compounds. Palm kernel shell ash (PKSA) is a by-product in palm oil mills. This ash has pozzolanic properties that enables it as a partial replacement for cement but also plays an important role in the strength and durability of concrete. The use of palm kernel shell ash (PKSA) as a partial replacement for cement in concrete is investigated. The objective of this paper is to alleviate the increasing challenges of scarcity and high cost of construction materials used by the construction industry in Nigeria and Africa in general, by reducing the volume of cement usage in concrete works. Collected PKSA was dried and sieved through a 45um sieve. The fineness of the PKSA was checked by sieving through 45um sieve. The chemical properties of the ash are examined whereas physical and mechanical properties of varying percentage of PKSA cement concrete and 100% cement concrete of mix 1:2:4 and 0.5 water-cement ratios are examined and compared. A total of 72 concrete cubes of size 150 × 150 × 150 mm³ with different volume percentages of PKSA to Portland cement in the order 0:100, 10:90 and 30:70 and mix ratio of 1:2:4 were cast and their physical and mechanical properties were tested at 7, 14, 21 and 28 days time. Although the compressive strength of PKSA concrete did not exceed that of OPC, compressive strength tests showed that 10% of the PKSA in replacement for cement was 22.8 N/mm2 at 28 days; which was quite satisfactory with no compromise in compressive strength requirements for concrete mix ratios 1:2:4. This research showed that the use of PKSA as a partial replacement for cement in concrete, at lower volume of replacement, will enhance the reduction of cement usage in concretes, thereby reducing the production cost. This research was carried out at the University of Ibadan, Ibadan, Nigeria.

This study comparatively evaluated the flexural performance and deformation characteristics of concrete elements reinforced with bamboo (Bambusa vulgaris), rattan (Calamuc deerratus) and the twisted steel rebars. The yield strength (YS), ultimate tensile strength (UTS) and the elongation of 50 specimens of the three materials were determined using a universal testing machine. Three beams of concrete strength 20 N/mm 2 at age 28 days were separately reinforced with bamboo, rattan and steel bars of same percentage, while the stirrups were essentially mild steel bars. The beams were subjected to centre-point flexural loading according to BS 1881 to evaluate the flexural behaviour. The YS of bamboo and rattan bars were 13% and 45% of that of steel respectively, while their UTS were 16% and 62% of that of steel in the same order. The elongation of bamboo, rattan and steel were 7.42%, 10% and 14.7% respectively. The natural rebars were less than the 12% minimum requirement of BS 4449. The load-deflection plots of bamboo and steel RC beams were quadratic, while rattan RC beams had curvilinear trend. The stiffness of bamboo RC beams (BB) and rattan RC beams (RB) were 32% and 13.5% of the stiffness of steel RC beams (SB). The post-first crack residual flexural strength was 41% for BB and SB, while RB was 25%. Moreover, the moment capacities of BB and RB corresponded to 51% and 21% respectively of the capacity of steel RC beams. The remarkable gap between the flexural capacities of the natural rebars and that of steel can be traced not only to the tensile strength but also the weak bonding at the bar-concrete interface. It can be concluded that the bamboo bars are suitable rebars for non-load bearing and lightweight RC flexural structures, while more pre-strengthening treatment is required more importantly for rattan for improved interfacial bonding and load-carrying capacity. * Corresponding author.A. P. Adewuyi et al. 229

The increasing research endeavors on nanotechnology encompasses a number of disciplines including the aspects of sustainable construction in civil and environmental engineering. Tremendous achievements have been reported on nanotechnology adoption on sustainable construction, but there are so much more to explore than has been achieved. Some of the advancements on the adoption of nanotechnology on sustainable construction, includes the enhancement of the rheology, strength and durability properties of concrete; which has been proved to be hinged on the nanoscopic characteristics of its constituent. Any modification at the nanoscopic level of concrete and its constituent influences its behavior, including its strength and durability characteristics. Hence, it is projected that the performance of concrete and sustainable construction materials in the future would be greatly enhanced by the application of nanotechnology to manipulate the atoms and molecules of these materials and their constituents at the nanoscale.