Eco-Friendly Optimum Structural Concrete Mix Design

Abstract

Concrete, the most consumed man-made material worldwide, has shaped the environment and the modern world. Even though concrete is a major contributor to the carbon footprint, it is indispensable for building the sustainable world of tomorrow. Researchers have been exploring ways to reduce the carbon footprint and to implement strategical waste management plans in which wastes are repurposed. Pollution has been a challenge for almost all countries, especially with the increase in the release of greenhouse gases in the atmosphere and the emissions resulting from wastes in unmanaged landfills. Additionally, the areas available for landfills have become scarce. Daily all around the world, generated are wastes such as wood ash, waste glass, used tires, construction debris, and demolition wastes. These wastes usually accumulate in landfills for years, as they are mostly nondecomposable. This research explores a solution to this twofold problem in which concrete components are replaced by wastes and by-products, which in return reduces the need for raw materials that have a significant carbon footprint and repurposes wastes as part of a circular economy. In this research, wood ash is used as a partial replacement of cement and sand, fine crushed glass and crumb rubber as partial replacements of sand, and crushed glass and recycled concrete aggregates as partial replacements of gravel. The optimum eco-friendly structural concrete mix was determined to be the combined mix consisting of 5% wood ash as a partial replacement of cement; 20% wood ash, 20% fine crushed glass, and 2% crumb rubber as partial replacements of sand; and 5% crushed glass and 50% recycled concrete aggregates as partial replacements of coarse aggregates. By mass, the recycled waste materials constituted 32% of the mix, translating into 34% of its volume. Additionally, identified were mixes that may be used for structural applications.

Alteration of Structure and Characteristics of Concrete with Coconut Shell as a Substitution of a Part of Coarse Aggregate

“…In our study, the increase in the obtained characteristics was 4.1% for compressive strength, the density decreased to 9.1% and the CCQ increased by 6.1% compared with the control sample. In [ 19 , 20 , 42 ], the compressive strength decreased to 25% and the density decreased to 7%; the indicator of CCQ also decreased. In [ 65 ], the values of the CCQ varies from 0.00989 to 0.01950 for fine-grained concrete depending on the cement type and the amount of microsilica added, which is comparable with the CCQ values in the current study.…”

“…It is becoming promising to develop technologies that can reduce the rate of depletion of natural non-renewable components of concrete [ 4 , 17 , 18 ]. One of the most promising methods to solve this problem is the complete or partial substitution of the mineral components of concrete with natural renewable plant analogues that are industrial and agricultural waste; this solves a number of problems for these industries [ 14 , 15 , 19 , 20 ]. However, new renewable materials should not reduce the strength characteristics of concrete or adversely affect its durability [ 21 ].…”

Property Improvement of Recycled Coarse Aggregate by Accelerated Carbonation Treatment under Different Curing Conditions

“…(1) On the basis of the carbonation curing conditions CC-1 to CC-4, as provided in Table 2, three parallel RCA samples with completely drying state were weighed, with the initial weight of each sample as 500 g. Subsequently, these samples were placed in a custom-made stainless-steel container with holes and then placed within the carbonation chamber, as shown in Figure 3b. (2) The carbonation chamber was turned on and the accelerated carbonation treatment experiment for RCA samples was carried out under the carbonation curing conditions listed in Table 2. During this process, the mass variations of each RCA sample were tested after certain intervals of carbonation time, and these intervals occurred more frequently at the beginning of carbonation until the masses of RCA samples remained essentially constant, at which point the carbonation was stopped During the accelerated carbonation treatment experiment for RCA, the environmental temperature inside the carbonation chamber remained constant.…”

“…where m 0 is the mass of the coarse aggregate samples before drying (g) and m 1 is the same as in Equations ( 1) and (2). During this paper's experiment, the water content for the RCA was ω = 0.…”

“…High demand for natural resources and a continuous increase in engineering projects are driving the construction industry to search for new and more environmentally friendly building materials [1,2]. In China, approximately 0.14-0.24 billion tons of construction waste per year are generated, and the amount of waste concrete accounts for is approximately 50-60% of that total, which makes the country one of the world's largest producers of construction waste [3,4].…”