Sustainable Concrete

This investigation includes the use of glass wastes after recycling to produce High Strength Eco-Friendly Concrete. The glass waste was collected, crushed, and grinded for 10 minutes to produce a powder with fineness higher than that for cement of about 7340 cm2/gm. Many tests were conducted on this powder including, chemical analysis, pozzolanic activity index tests, and the remaining content on sieve of 45 microns. The results show that the glass waste powder considered as a natural Pozzolan class (N) according to ASTMC618. Many concrete mixes with different percentages of glass waste powder as a partial replacement to cement (10%, 15%, 20%, 25%, and 30%) were prepared. The properties of concrete (fresh density, compressive strength at 7, 28, 60, and 90 days age, and water absorption at 60 days age)were studied and compared with the results of the reference concrete mix (without glass powder). The compressive strength for concrete specimens with 10%, 15% glass powder content at 28, and 60 days age is increased. When the content of glass powder is increased to 20%, 25%, and 30%, the compressive strength is decreased compared with the reference concrete specimens. The highest percentages increase in compressive strength are 1.17%, 13.3%, 19.34% for specimens with 15% glass powder at 28, 60 and 90 days age respectively, while the water absorption is decreased.

Construction industry is connected either logically or collaterally with the cement industry. In concrete mix, it plays the role of most significant, versatile and energy consuming material. Hence, the substitute of the cement with some secondary cementitious or cheaper material SCM can directly impact the cost of concrete. So, among SCM, the flyash, which is the burnt residue, has been replaced with cement in various percentages. Utilization of Fly ash by replacing with the cement will definitely solve the problem of its dumping and on the other way it will decrease the costing of concrete. It impart strength to the concrete as well as it makes the concrete more compact, durable and sustainable. In this study, replacement of cement was made by weight at different intervals in making of specimens to test the compressive, flexural and tensile strength of Flyash blended Steel fiber concrete (FASFRC).Different percentages of Steel Fibers were added, to observe the effect of it on the mechanical properties flyash blended steel fibers. The proportions of flyash used by replacing cement has been taken as, 20%, 30%, 40% 50% and steel fibers as an additive material at interval of 0.5%, 1%, 1.5%, 2% and 2.5 % respectively. Slump test was also performed to determine the workability of FASFRC and consistency of flyash cement paste.

This article discusses the utilization of palm oil fuel ash (POFA) in normal and geopolymer concrete. Malaysia, one of the world's largest producers of palm oil, produces more than 10 Mt/year of palm waste as ash, which is called POFA. Since 1989, extensive research has been conducted on its utilization in concrete. Several published studies have noted POFA's enormous potential as a partial replacement of cement in concrete. This paper describes the effects of using POFA on different fresh and hardened properties of concrete. The latest studies on the use of ground POFA revealed that concrete made from this material possesses better fresh properties and medium to higher strength than ordinary Portland cement (OPC) concrete. One of the major findings is that concrete that incorporates 20% fine POFA by weight of cement showed better durability properties than OPC concrete. Because limiting CO 2 emissions has become a matter of increasing importance in the construction industry, concrete that uses less cement in its production and utilizes an increased amount of waste, such as POFA, offers an environmentally viable solution. Moreover, 100% cement-free geopolymer concrete can be produced using blended ash, such as POFA and fly ash.

Cementitious composites are the most used man-made materials in the world with a global annual production quantum of 25 billion tonnes worldwide, contributing approximately 5% to the global greenhouse gas emissions. In the initiative to reduce the carbon footprint of cementitious composite production, are growing interests in the large volume reuse of industrial by products such as ground granulated blast-furnace slag (GGBS), pulverized fuel ash (PFA) and granite quarry dust (GQD) in cementitious composites production. Such an approach offers a two-fold solution towards addressing the waste management problem related to those industry by-products. At the same time however; reduction of carbon footprints of cementitious composite materials exists. However, in order to enable scalable applications of such a recycling approach, a comprehensive body of knowledge on the mechanical strength and durability performance of the cementitious composite products containing a large volume of the materials needs to be established. Hence, it is the primary aim of the study to report a comprehensive assessment on the mechanical strength and durability properties of high strength cementitious composites. These materials are produced with a large volume of the aforementioned materials as the primary binder and aggregate phase. Throughout the investigation, high strength cementitious composites mixes were produced with a large volume of PFA and GGBS binder. Then phase coupled with ordinary Portland cement (OPC). GQD was used as the fine aggregate phase in substitution of natural river sand at various level of substitution ranging between 0 - 100 % by volume. The cementitious composites were characterized in terms of its fresh cementitious composites. Its flowability and hardened cementitious composites properties mainly bulk density, compressive strength, flexural strength, and Ultrasonic Pulse Velocity were also assessed. In addition, the durability properties such as water absorptivity and porosity were also covered in this experimental program. Pore continuity was assessed in terms of air permeability and capillary absorption of the hardened specimens according to the testing age. This paper has also covered the dimensional stability assessment in terms of drying shrinkage. Besides, a comprehensive microstructural assessment was also performed to examine the microstructure morphology. From the results, we found full incorporation of GQD as NRS without significant impairment to the mechanical, durability and length change performance. Thus, the production of sustainable high strength cementitious composites with large volume recycling of GQD is feasible which in turn reduces the depletion on the natural river sand resources.

Introduction The vast increase in CO 2 and waste generation in recent decades has been a major obstacle to sustainable development and sustainability. In construction industry, the production of ordinary Portland cement is a major greenhouse gas emitter with almost 8% of total CO 2 production in the world. To address this, Alkali-activated materials and geopolymer have more recently been introduced as a green and sustainable alternative of ordinary Portland cement with significantly lowered environmental footprints. Their use to replace Portland cement products generally leads to vast energy and virgin materials savings resulting in a sustainable concrete production. In doing so, it reuses the solid waste generated in industrial and manufacturing sectors, which is aligned with circular economy. In turn, it reduces the need for ordinary Portland cement consumption and its subsequent CO 2 generation. Objective To provide further insight and address the challenges facing the substitution of ordinary Portland cement, this article reviews different types, mechanisms, and result of mechanical and durability properties of alkali-activated materials and geopolymer reported in literature. Finally, it discusses future projections of waste materials that have cementitious properties and can replace ordinary Portland cement and be used in alkaliactivated materials and geopolymer.

Today, with the increasing rate of construction, concrete is being manufactured in the world on a large scale. It is important for the growth of infrastructure for many decades. But concrete consumes a lot of natural resources due to which it is not considered as an environment-friendly material. Portland cement is a major constituent of concrete which generates carbon dioxide gas during its production which in turn adversely affects the environment. Also, the other ingredients such as sand and coarse aggregates are depleting at a faster rate thereby increasing the cost of construction. Due to this, there is a need to identify alternate materials for cement, sand and coarse aggregates. In this study, GGBS, fly ash and recycled aggregates addresses this issue. The main objective of this research is to analyse and identify the effects of recycled waste materials in different proportions on Compressive and Split tensile strength of concrete. Ground Granulated Blast Furnace Slag (GGBS) (as a partial replacement of cement), Fly Ash (as a partial replacement of sand) and Recycled Aggregates (as a partial replacement of coarse aggregates) were the different recycled materials used. Taguchi's Approach is being used in this study to obtain different combinations of percentage replacement. It was observed that when cement, sand, and coarse aggregates are being replaced by 30% GGBS, 30% Fly ash and 20% Recycled Aggregates respectively, the compressive strength and split tensile strength test values show better results than conventional mix concrete.

Supplementary cementitious materials (SCM) are a key ingredient of today’s concrete and can vastly improve the durability (e.g., ASR mitigation) and sustainability of concrete mixtures. While the demand for fly ash (the highest used SCM) and other suitable pozzolans continues to grow, the supply of high-quality and specification-compliant fly ash has been shrinking. To maintain and expand the market share and ensure the durability of concrete products and structures, it is critical that a stable supply of high-quality and economical fly ash and other SCMs is available for foreseeable future. This study evaluates the feasibility, performance, and beneficiation of two alternative and abundant sources of fly ash: recovered landfilled fly ash and fluidized bed combustion (FBC) fly ash. Samples of both fly ashes were collected from an ash landfill in Pennsylvania and two FBC power utilities in Pennsylvania. These fly ashes were characterized against the composition, physical properties, and performance requirements of ASTM C618. A statistical sampling plan was also developed for characterizing the heterogeneity of fly ash in landfills.
The results show that the ash from the Pennsylvania landfill can be classified as ASTM C618 Class F ash and used in concrete after drying and particle size reduction (e.g., via sieving). Other ash landfilled should be evaluated on a case-by-case basis to determine (a) their heterogeneity, (b) their viability for use as concrete pozzolan, and (c) beneficiation measures that may be needed such as carbon reduction and separation of deleterious substances where possible.
The results also show that FBC fly ashes from the two Pennsylvania powder plants generally meet the chemical and physical requirements of ASTM C618, with exception of elevated SO3 in one fly ash. Regardless, paving-grade concrete with good fresh and hardened performance could be prepared incorporation 20% of these fly ashes as a cement replacement. Further research is recommended to evaluate other coal-based FBC fly ashes in the United States in terms of their properties, uniformity in time, and performance in concrete mixtures. Overall, it is determined that some FBC fly ashes have a very good potential for use as pozzolan. Specifications (prescriptive or performance) need to be developed to identify good quality FBC fly ashes and enable their use as concrete pozzolan.

This study has been conducted to explore the possibility of utilization of steel slag in concrete as coarse aggregate. After collection of steel slag aggregate from a local steel manufacturing company, the steel slag aggregate was separated into lightweight (SL), heavyweight (SH), and mixed (SM) slag aggregates. The aggregates were tested for different physical properties as well as mechanical properties by preparing cylindrical concrete specimens (100 mm by 200 mm) with different W/C ratios, cement contents, and sand to aggregate volume ratios. Total eleven cases for slag aggregates and five cases for brick aggregates were investigated. The concrete specimens were tested at 7, 28, 60 and 90 days. Also, ultrasonic pulse velocity (UPV) test was conducted prior to crushing of the specimens for evaluation of compressive and tensile strengths. For comparison, similar investigations were also carried out on brick aggregate commonly used in Bangladesh. Experimental results show that slag aggregates absorb less water compared to the brick aggregates. The compressive strength of concrete made with mixed slag aggregate is similar or better than that of concrete made with brick aggregate. Concrete made with heavyweight slag aggregate gives more compressive strength than other aggregates. Relationships between compressive strength and modulus of elasticity of concrete, compressive strength and tensile strength of concrete are proposed for different slag aggregates.