Introduction
Concrete is considered as a major material that is the second most consumed material on Earth after water. The world is unbelievable without concrete!
One of the most important concrete property that it is a sustainable building materials once each the energy consumed throughout its manufacture and its inherent properties in-use are taken into consideration. The cement and concrete sectors work along to repeatedly cut back their impact on the surroundings environment through improved producing manufacturing techniques, product innovation and improved specification.
• Materials aspects and Eco-Friendly alternative materials
A life cycle approach is the standardized method for identifying and evaluating the environmental effects of building products over their life cycle (extraction, processing, transport, use and maintenance and disposal). There are many ways of optimizing the eco-efficiency and life-cycle economy of concrete projects, such as recycling or the use of industrial by-products during production or using design strategies that use the thermal properties of concrete. Buildings can also be designed so that they can be easily serviced and altered.
The significant environmental impact of concrete is caused by CO2 emissions from the production of cement. Especially for concretes with normal strength, there is great potential for reducing impact. The use of superplasticizers and highly reactive cements, as well as optimizing the distribution of particulate matter and reducing the water content, allows for a significant reduction in the Portland cement clinker in concrete. The addition of mineral fillers (e.g. limestone powder) to provide an optimal paste volume is essential. Furthermore, The already feasible substitution for the cement clinker of secondary raw materials such as fly-ash or furnace-slag is an appropriate option, but limited by the availability of these resources. In several test series, the fresh and hardened concrete properties of concrete with reduced water and cement content, in particular its workability, strength development, mechanical properties relevant to design and durability aspects such as carbonation, have been investigated.
Concretes with a cement clinker and slag content of up to 150 kg / m3 have been shown to meet the usual requirements of workability, compressive strength (approx. 40 N / mm2) and mechanical characteristics. The carbonation depth of concrete with a clinker and a slag of 150-175 kg / m3 was equal to or below the depth of conventional reference concrete for external structures. The ecological advantages of environmental performance assessments were identified. It was calculated that the environmental impact was reduced by up to 35 percent compared to conventional concrete and by over 60 percent with granulated blast - furnace slag. Practical application was verified in a precast and ready-mix concrete plant by means of full - scale tests.
• Optimized design in terms of section size and geometry
The minimum embodied energy section has a smaller concrete volume and a greater reinforcement than the minimum cost section. These findings confirmed those of Villalba et al. (2010). In order to ensure that ductility is adequate for design purposes despite the increase in the amount of steel, the restrictions in the optimization process include a stress in the reinforcement bars.
• Construction aspects to minimize cost and repair
The initial cost of reinforced concrete structures can be reduced through advanced planning and detailing to minimize the expenses related to the materials and the construction activities associated with formwork, reinforcement and concrete.
These cost - cutting techniques are often not obvious to the designer. For example, the cost of shaping is generally between 40 and 60% of the completed reinforced concrete structure. The material costs of concrete and reinforcement are between 10 and 30%. The percentage of labor costs for the concrete and the reinforcement is the remainder.
Corrosion in chloride-contaminated concrete leads to the destruction of the protective oxide film that is normally developed in alkaline environments on surfaces steel. If the chlorides could be removed from both concrete and steel and the PH is sufficiently high to restore the protective film, the problem would be resolved. This has traditionally been done by removing the concrete layer with a chloride concentration of more than 0.3 percent to 0.4 percent of the cement content and replacing it with a new material (usually referred to as \" patching \" in the literature). This technique of repair is not only labor intensive, but can also have negative structural consequences. Alternatively, electrochemical methods that normally allow rehabilitation without extensive structural breakdown appear to be particularly suitable for the repair of high architectural or historical value structures.
• Recycling and waste management
RECYCLED-AGGREGATE CONCRETE
Recycled-aggregate concrete (RAC) for structural use can be produced by completely replacing natural aggregates to achieve the same strength class as the reference concrete produced using only natural aggregates [Corinaldesi et al. 1999]. This is obviously a provocation, as a large stream of recycled aggregates is not available to fully substitute natural aggregates. However, it is useful to prove that it is indeed feasible to manufacture structural concrete by partially replacing natural with recycled aggregates by up to 50%. In any case, if the adoption of a very low water to cement ratio means that the amount of cement in the concrete mixture is unsustainable, Recycled-aggregate concrete can also be produced using a water-reducing mixture to reduce both the dosage of water and cement, or by adding fly ash as a partial substitute for the fine aggregate and using a superplasticizer to achieve the required workability [Corinaldesi & Moriconi 2001]. In addition, high volume ash recycled aggregate concrete (HVFA-RAC) can be produced with a water to cement ratio of 0.60, recycled aggregate, is used [Corinaldesi & Moriconi 2004]. Moreover, this behavior appears to be enhanced by the reuse of concrete-rubble powder, which is the fine fraction produced during the process of recycling concrete-rubble to make aggregates. The segregation resistance is so high in this condition that the coarse recycled aggregate can float on highly viscous cement paste, And an adjustment could be attempted by adding fly ash, which gives reduced flow-segregation resistance and increased flow ability to concrete when used alone as a filler.
REUSE OF GRP INDUSTRIAL WASTE IN CEMENTITIOUS PRODUCTS
Glass Reinforced Plastic (GRP) is a composite material made of resin-dispersed fibers of glass, usually polyester, widely used in several fields from buildings to boat furniture. Every year, GRP processing in Western Europe produces 40000 tons of industrial waste. Due to the difficulty of separating the glassy part from the polymer matrix, this waste is disposed of in the landfill.
The finest GRP residues were physically and chemically characterized to identify compatibility problems with cement, if any. Taking into account the distribution of its particulate size, it was considered that this waste could be used as a partial cement replacement to produce new GRP blended cements. By replacing up to 15 percent of cement with GRP, the mechanical strength threshold acceptable to actual cement standards could be confirmed.
The “GRP cements”, Even if they show less mechanical strength, the cement products manufactured with them could confer lightness and some deformability. Due to the higher water to cement ratio and the absence of any binding capacity of GRP, the mortars produced by using these cements were more porous with regard to the reference mortar without GRP. However, their capillary water absorption and drying shrinkage was lower than without GRP in the reference moratorium. These results showed the potential to reuse an abundant industrial by-product to produce durable prefabricated concrete elements, which is currently filled with land.
Conclusion
The built environment is prime to a sustainable society as construction, by definition, involves the utilization of natural resources. Awareness throughout the construction phase and effective management of energy throughout the lifetime of the building will deliver important energy savings and CO2 reductions, whereas maintaining the standard of the building and also the safety and luxury of its occupants. The aim of sustainable construction is for “the creation and accountable management of a healthy designed surroundings supported resource economical and ecological principles”.