1 Introduction
Few and very limited papers found in the literature use the olive’s seed ash and corncob ash (CCA) in conventional concrete industry. The following section summarizes the up-to-date literature focusing on the behavior of concrete incorporating such recycled post-consumer environmental wastes.
The main goal and challenge for the coming century, is to design a smaller and shallower reinforced concrete sections and for taking into consideration the economic aspects. Nowadays, the material engineers are investigating new concrete mixtures with different admixtures to reach the outmost performance and durability for severe environmental conditions. The waste-by-products and recycled materials are under a big push to be added to the conventional concrete ingredients and to replace cement content, keeping the strength and durability close to the desired specifications. The workability is considered an important factor when concrete mixtures are designed; especially in some applications where members are heavily reinforced. Thus, to lessen any difficulties associated with concrete placement in congested reinforced concrete members, concrete mixtures should be designed to workable. The sustainability of concrete members also is strongly related to global warming, which is a major problem for today’s infrastructures. One of the most sustainable tools is the supplementary cementitious and recycled materials (SCMs) to be buried in concrete mixtures as attractive options to achieve green concrete.
The mechanical properties of kenaf fiber reinforced concrete (KFRC) are studied by Elsaid et al. (
2011). The study showed the findings of an experimental research program that was conducted to study the mechanical properties of a natural fiber reinforced concrete (FRC), which is produced using the bast fibers of the kenaf plant. The fiber volume contents were taken 1.2 and 2.4 %. The compressive strength, modulus of elasticity, splitting tensile strength and modulus of rupture of KFRC specimens are measured and compared to the properties of plain concrete control specimens. The experimental results indicate that the mechanical properties of KFRC are comparable to those of plain concrete control specimens, particularly when accounting for the effect of the increased w/c ratio required producing workable KFRC. Further, more distributed cracking was found and higher toughness than plain concrete. In general KFRC specimens exhibited more ductile behavior with greater energy absorption and more well distributed cracking patterns, which is typical for KFRC.
Coconut fibers are one of the highest toughness natural fibers. The mechanical and dynamic properties of coconut fiber reinforced concrete (CFRC) members are performed by Ali et al. (
2012). The damping ratio and fundamental frequency of simply supported CFRC beams are determined experimentally as well. The influence of 1, 2, 3 and 5 % fiber contents by mass of cement and fiber lengths of 2.5, 5 and 7.5 cm is investigated and all the results were compared to plain normal concrete. Damping of CFRC beams increases while their fundamental frequency decreases with structural damage, Ali et al. (
2012). CFRC with higher fiber content has a higher damping but lower dynamic and static modulus of elasticity. It is found that CFRC with a fiber length of 5 cm and a fiber content of 5 % has the best properties to be used in normal low cost concrete structures.
The mechanical properties of four types of date palm surface fibers on reinforced concrete were investigated by Kriker et al. (
2005). The volume fraction and the length of fibers reinforcement were 2–3 % and 15–60 mm respectively. Increasing the length and percentage of fiber-reinforcement in both water and hot dry curing, was found to improve the post-crack flexural strength and the toughness coefficients, but decreased the first crack and the compressive strengths. In hot-dry climate a decrease of first crack strength with ageing was observed for each concrete type. Water curing decreased the global degree of the voids and cracks with time for each concrete type, but increased it in hot-dry climate.
Corncob is the waste-by-product obtained from corn, which is considered one of the most important cereal crops in Egypt. According to food and agriculture organization (FAO) data, 589 million tons of maize was produced worldwide in the year 2000. The United States was the largest maize producer having 43 % of world production. The effect of using CCA (pozzolanic waste-by-product of corncobs) as a cost-effective additive in blended cement is conducted by Adesanya (
1996). The effects of the blended cement in various concrete mixtures were analyzed. The results show that replacing 20 through 50 % respectively of ordinary portland cement by weight with CCA produces stabilized clay and laterite exhibiting greater strength. The results also indicate that replacing 20 % of cement with CCA in conventional concrete mixtures improves water absorption and durability. It is also found that there is no significant difference between the strength of concrete produced with 0.0 and 20 % CCA as a partial cement replacement.
Adesanya and Raheem (
2009a) attempted to convert waste-by-product into useful material for the construction industry, the study considered the use of CCA as a pozzolan in cement production. The chemical composition of CCA was investigated and used for replacing 0, 2, 4, 6, 8, 10, 15, 20 and 25 % by weight of ordinary portland cement clinker with CCA. The 0 % cement replacement was used as a control mixture. The results showed that CCA is a suitable material for use as a pozzolan as it satisfied the minimum requirement of combined SiO
2 and Al
2O
3 of more than 70 %, which means a good pozzolan to manufacturer blended cement. The blended cements produced also satisfied both NIS 439 (
2000) and ASTM C 150 requirements especially at lower levels (<15 %) of CCA percentage replacement. Based on the test results, it was concluded that CCA could be suitably used in blended cement production. Adesanya and Raheem (
2009b,
2010), performed an investigation on the workability, Durability, and compressive strength characteristics of CCA blended cement concrete. The study showed that only up to 8 % CCA substitution is adequate where the blended cement is to be used for structural concrete. The resistance of the mortar cubes to chemical attack was improved as the addition of CCA up to 15 % replacement level, and caused a decrease in permeability and reduction in weight loss due to reaction of the specimens with HCL and H
2SO
4 acid water. The improvement was up to about 50 % for HCL and 40 % for H
2SO
4 acid water (Jorge et al.
2012).