This research aims to develop sustainable high-strength concrete (SHSC) by replacing 100% fine and/or coarse aggregates with fine recycled aggregate (RA) and/or coarse RA. Due to the high surface water absorption of coarse RA, a surface treatment method was adopted, consisting of immersing it in a cement and silica fume slurry. Moreover, to improve the performance of the produced SHSC, steel fibers were employed at a relatively low volume fraction (0.5%). Eleven blends were cast and tested in this experimental study. A control SHSC mix (without RA) and ten other mixtures, including fine natural and RA, treated and untreated coarse RA, with and without steel fibers, were prepared. Compressive, splitting, and flexural strengths, water absorption, density, and ultrasonic pulse velocity (UPV) of the resulting SHSC were conducted. The results indicated that the use of RA in SHSC resulted in an average drop of 25% in its mechanical properties and an increase of about 30% in water absorption. However, using treated RA compensated the compressive and tensile strength reductions in SHSC by 9% and 7%, respectively, compared to mixes containing untreated RA. On the other hand, adding fibers helped improve compressive, flexural, and splitting tensile strengths by about 8%, 23%, and 31%, respectively, compared to the corresponding control mix. Consequently, the results showed that it is possible to produce durable SHSC made from 100% RA and 0.5% steel fibers with a reduced density and improved mechanical performance to a comparable level or even superior to high-strength concrete (HSC) with only natural aggregates (NAs).
Reactive powder concrete (RPC) is one of the distinctive kinds of concrete whose benefits are high mechanical performance and durability. It contains a high content of cement, which means a high amount of carbon dioxide emitted during manufacturing. Scientists have tended to search for a way to reduce environmental damage, and one solution is to partially replace cement with mineral admixtures, waste from other industries, or by-products. There are restricted studies involving the use of high content of compounding mineral admixtures in the making of RPC. Therefore, this research aims to produce sustainable RPC with a low cement content (50%). The main objective of this research is to study the impact of substituting cement with 50% of silica fume (SF) + fly ash (FA) on the mechanical characteristics of RPC. Three mixtures containing various percentages of SF + FA were poured, in addition to the reference mixture. Flowability, flexural and compressive strengths, ultrasonic pulse velocity (UPV), and density were examined. The results showed that a sustainable RPC can be produced by substituting the cement with 10% SF and 40% FA with an improvement in workability and compressive strength and an insignificant reduction in other properties.
The rapid growth of population and consequent urgent need for building units have led to an increase in demand for the production of construction materials, including concrete. Traditionally, cement is the prime-type binder in concrete, and therefore, its production...
This study examines how incorporating ultrafine cerium dioxide particles (UFCe) into recycled coarse aggregate concrete affects its physical, mechanical, and long-term properties. No analogous research exists about the impact of ultrafine cerium dioxide particles on various characteristics of concrete containing recycled aggregates (RCA). UFCe was employed, and its mean particle size was 350 nm in different doses (0.0, 0.5, 1.0, and 1.5 % by cement weight) to explore its effect on the properties of concrete containing 25 % coarse aggregates (RCA) prepared from ceramic wall waste. The setting time, slump flow, porosity, water absorption, compressive and tensile strengths, electrical resistance, chloride penetration resistance, corrosion resistance, and microstructure analysis were investigated. The findings indicated that UFCe significantly enhanced the compressive and tensile strength while decreasing water absorption and pore ratio comparison to the control mixture after 90 days of curing. Moreover, all mixtures displayed significantly lower chloride penetration depth and corrosion rate than the reference mixture. The inclusion of UFCe additionally improved the microstructure due to the enhancement of the ultrafine particle hydration process. On the other hand, the optimum improvement of mechanical strength, durability properties, and microstructure was recorded at a UFCe replacement rate of 0.5 %. For example, the compressive and tensile strengths increased by 33 % and 9 %, respectively, while the total water absorption and migration coefficient were reduced by 42 % and 67 % at 90 days, respectively, compared with the reference sample.
Concrete is a constantly evolving building material whose demand is increasing due to population growth and urban development. This calls for more research on this composite material to improve its performance. However, concrete has some disadvantages, including that it is a brittle material and...
This study investigates the effectiveness of replacing the cement with 0, 5, 10, 15, and 20 wt.% of ceramic waste powder (HCCP) to improve the performance of recycled aggregate concrete (RCA) prepared using 25 wt.% wall tile ceramic coarse aggregates. The slump, initial and final setting time, compressive strength, splitting tensile strength, flexural strength, electrical resistivity, bulk density, porosity, total and surface water absorption, pH level, ultrasonic pulse velocity, dynamic elastic modulus, chloride ion diffusion coefficient, chloride penetration depth, microstructure analysis, and environmental assessment properties were investigated. The results showed that replacing cement with HCCP by 5 to 20 wt.% prolonged the setting time and improved all hardened properties. The highest improvements in mechanical properties were observed at 5 wt.% HCCP, with increasing rates of 26.5%, 22%, and 22.4% at 90 days for compressive strength, tensile strength, and flexural strength, respectively. On the other hand, the optimum enhancement for the durability, microstructural, and environmental efficiency properties was recorded at a 20 wt.% HCCP replacement rate. However, the strength at this ratio tended to decrease but remained higher than that of the control RAC. For instance, the total water absorption, surface water absorption, void ratio, chloride penetration depth, and migration coefficient were reduced by 47%, 45%, 38%, 62.3%, and 55.52%, respectively, compared to the reference sample.
Building materials such as sand, cement, bricks, and steel are usually the main components of the construction sector. All these materials are produced from existing natural resources and they will cause substantial damage to the environment as a result of their continuous depletion. Moreover, during the manufacture of various building materials, especially cement, a high concentration of carbon dioxide is constantly emitted into the atmosphere. Therefore, to reduce this environmental damage as well as to save natural resources, this study was performed to recycle the wastes of some of building materials such as marble, granite and porcelain tiles and clay brick through using them as cement and aggregate replacement materials in cement mortar. Sixteen mixtures were cast for this study. In addition to the control, the mortar mixes were divided into five groups, three mixes in each group. In four of the five groups, cement was replaced in three proportions (5%, 10%, 15% by weight) with each of marble, granite, porcelain and clay brick waste powders (passing through 150-μm sieve). The fifth group included 100% replacing (by weight) of the natural sand with the marble, granite and porcelain tiles wastes (with a comparable gradation). The influence of these wastes on flow rate, compressive strength, flexural strength, bulk density, ultrasonic pulse velocity (UPV) and water absorption tests were observed. Results showed that it is possible to produce an eco-friendly mortar made with 100% recycled marble or porcelain aggregate with a significant improvement in the mechanical and durability properties in comparison with natural aggregate mortar.
The exposure of concrete or cement mortars to fire or other elevated temperatures negatively affects the mechanical properties, and a change may also occur in the pore structures, leading to cracking and spalling. In order to hinder or reduce the negative impact of elevated temperature on cement mortar, as well as to promote reuse of waste in the concrete industry to improve the environment, this study aims to investigate the effect of elevated temperature on the mechanical properties of cement mortar reinforced with rope waste fibres (RWF). The fibres were obtained by cutting a used polymeric rope (0.034 mm in diameter) into small fibres with average lengths of 12 mm. Four mortar mixtures, including one reference mixture (without fibres) and three mixtures containing RWF in proportions of 0.25%, 0.5% and 0.75% (by mortar weight), were cast. After 28 days of curing, the hardened specimens were air dried for at least two weeks, and some specimens were exposed to a controlled temperatures of 300 and 600 °C for two hours, while the others were placed at ambient temperature. All specimens were then examined via compressive strength, flexural strength, mass loss, ultrasonic pulse velocity and visual inspection tests. The results indicated that RWF can prevent cracks appearing at 600 °C; however, the RWF had a negative impact on the compressive strength of the mortar under elevated temperatures, despite the flexural strength and UPV properties being improved significantly.
This study seeks to identify an environmentally sustainable method for utilizing the synergetic effects of window glass (WG), ceramic powder (CP), and ultrafine cerium oxide (UFC) in developing concrete containing 25% coarse ceramic aggregate. Four different mixtures were formulated. The first represents control, consisting of 100% ordinary Portland cement (OPC), two other mixtures were composed of 10% WG, 10% CP and 80% OPC, and the fourth mixture consisted of four compositions of 79.5% OPC, 10% WG, 10% CP, and 0.5% UFC. The effect of these additives on recycled ceramic concrete (RA) properties, including workability and setting time, compressive strength, total water absorption, permeable pore ratio, electrical resistivity, and corrosion resistance, was studied. The results showed that when 10% WG and 0.5% UFC were combined, the components' synergistic effect was more noticeable. It had a compressive strength of 44.53, 48.83, and 56.17MPa after 28, 90, and 180 days, which is higher than the ternary mixtures of Portland cement, ultrafine cerium oxide, and ceramic powder, as well as the quaternary mixtures of Portland cement, WG powder, CP, and UFC. Moreover, it recorded a lower corrosion rate than the reference mix (RA-C), ternary mix (RA-CP10UFC0.5), and quaternary mixes (RA-CP10WG10UFC0.5) mixes. Meanwhile, the quaternary mix (RA-CP10WG10UFC0.5) showed 40% and 45% lower porosity and water absorption than the control mixture and 54% higher electrical resistivity values compared to the control mixture and ternary mixtures (RA-WG10UFC0.5 and RA-CP10UFC0.5) at 180 days.
Sustainability and reducing environmental damage caused by CO2 emissions have become issues of interest to researchers in the construction sector around the world. Reducing the cement content in concrete by partially substituting it with by-products or waste falls within this field as the cement industry is responsible for 7% of global CO2 emissions. On the other hand, self-compacting concrete (SCC) is one of the special types of concrete that contains a large amount of powder (most of which is cement) to ensure its flow under the influence of its weight without separating its components. Therefore, to produce eco-friendly SCC, many researchers have replaced part of the cement with clay brick waste powder (CBWP) since brick units are among the most widely used building materials after concrete. Accordingly, this study aims to review previous research that included using CBWP in SCC. The effect of these wastes on the fresh, mechanical, durability and microstructural properties of cement was reviewed. Additionally, a comparison between the environmental impacts of SCCs with different CBWP contents has been conducted using the life cycle assessment (LCA) approach. It was found that the highest value of CBWP that can be used without negatively affecting the different properties of concrete is 10% by weight of cement. Moreover, regarding environmental impact, using CBWP as a substitute for cement reduces environmental damage, and the lowest environmental impact that can be achieved per strength unit (MPa) is 37.5%.
Pavement deterioration is mainly caused by high traffic loading and by increased levels of runoff water resulting from storms, floods, or other reasons. Consequently, this issue can be efficiently solved by employing permeable pavement, such as permeable interlocking concrete pavement (PICP) to control water runoff and endure increased traffic loads. This study investigates the performance of PICP, in both 45° and 90° herringboned surface patterns, in terms of the infiltration of volumes of water, runoff water volumes, and the ability of pavement to withstand static loading. All the related tests in this study were implemented using a lab apparatus that was fabricated as a simulator for rainfall. Various conditions were adopted during the performance tests, including the application of longitudinal slopes (0, 2.5, 5, and 7.5%), side slopes (0, 2.5, and 5%), and different rainfall intensities (25, 50, 75, and 100 L/min). The results indicated that at high rainfall intensities (75 and 100 L/min), PICP with the 45° herringboned surface pattern had the highest volume of infiltrated water and the lowest runoff water at all the adopted longitudinal and side slopes. In addition, PICP with the 45° herringboned surface pattern showed higher resistance to deflection under a static loading test than the 90° herringboned pattern under the same conditions. Therefore, PICP with a 45° herringboned surface pattern showed supremacy in terms of runoff reduction and load resistance in comparison to PICP with a 90° herringboned pattern. Even though there are differences between the two types of PICP, they are both strongly recommended as alternatives to regular pavement.
