Solid waste produced from construction and demolition activities amount to several million tons globally, and one of the prominent wastes is brick waste. In recent years, there have been increasing ...number of researches carried out on recycling brick wastes to produce a more eco-friendly concrete. This review summarizes the usage of brick waste as potential partial cement and aggregate replacement materials whereby the performance in terms of the mechanical strengths and some durability-related properties of the concrete were discussed. It was found that the most feasible usage of recycled brick is in the form of brick dust, whereby up to 20% cement replacement could enhance the strength and some durability properties of the concrete due to the potential pozzolanic reactivity of the brick dust particles. On the other hand, the inclusion of recycled brick as aggregate does not give profound improvement of the properties of concrete as it is governed by the inherent porous nature of the aggregate. Hence, the use of recycled brick as partial aggregate substitute should be confined to low volume replacement levels and when environmental consideration necessitates its usage.
•The utilization of brick waste as cement and aggregate substitute is summarized.•Effects on the properties of concrete and mortar are discussed.•It is recommended to use waste brick dust as up to 20% cement replacement material.
The utilization of recycled coarse aggregates (RCA) from construction and demolition wastes to produce green concrete serves as a sustainable solution with manifold environmental benefits. This study ...aims to widen the potential uses of RCA to fabricate pervious concrete for non-structural applications. The mechanical and surface properties, permeability, and greenhouse gases assessment of pervious concrete made with blended normal granite aggregates and RCA were investigated in this work. RCA replacement levels of 20%, 40%, 60%, 80% and 100% were used. Experimental results show that the RCA mixes have lower mechanical properties. Microscopic analyses show that the lower strength of RCA mixes was attributed to the failure path of RCA specimens which occurred at the weaker adhered mortar on RCA. Despite the drop in strength, all RCA-mixes attained the minimum BS EN 1338 requirements in terms of skid and abrasion resistance. In the mix with 100% RCA, the waste content in the pervious concrete mix was 87% by weight and 73% by volume. The greenhouse gases assessment also shows that the CO2 emission of this 100% RCA mix is 24% lower than the control mix.
•RCA can be fully used in pavement lower layers and concrete pavement surfacing.•There is disparity in reported replacement levels of RCA for asphalt mixtures.•RCA mixes can be improved by chemical, ...thermal, and biological treatments.•RCA is a sustainable alternative to natural aggregates for highway pavements.
Highway pavements are very expensive infrastructures that consume very high amounts of natural resources. Utilisation of recycled concrete aggregates (RCA) for highway pavement construction can bring a number of benefits towards environmental, economic and societal sustainability. This would reduce the carbon footprint of the construction industry, result in natural resource conservation, reduction in harmful emissions, and minimisation of cost of pavement construction. This paper reviews available literatures on the use of RCA for highway pavements. Both flexible and rigid pavements were covered. The studies revealed that RCA can be applied in all pavement layers; subgrade, capping, subbase, roadbase, and surfacing. The physical and mechanical properties of the RCA and how they affect its performance were studied and compared with those of natural aggregates (NA). Available techniques for improving the performance of RCA in concrete and asphalt mixes were also discussed. The benefits and sustainability gains of RCA utilisation were summarised from available life cycle assessments conducted in the literatures. RCA has been considered as a feasible sustainable alternative to NA in highway pavement applications, but there still exists a large disparity in the recommendations of the replacement levels for asphalt mixes. To ensure that the pavements are sustainable without compromising their quality and functionality, the utilisation of RCA should be encouraged after further indebt studies that would lead to a more consensus standard specifications and guidelines.
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•Palm oil clinker is a potential by-product for replacement of sand in geopolymer.•Comparable mechanical properties were achieved with POC sand geopolymer mortar.•POC geopolymer ...mortar showed a great resistance to HCl and MgSO4 solutions.•Density reduction of about 17% was achieved using POC as sand in geopolymer mortar.•The strength development of mixes was increased with higher GGBS content.
As a result of excessive exploitation and the growing need for conventional sand, a potential replacement for sand has never been this vital to preserve the environmental ecology. This paper investigated the performance of palm oil clinker sand (POCS), a local industrial by-product and waste as a whole sand replacement in geopolymer mortar; a total number of 16 mixes were cast by varying the molarity of NaOH and binder. Mechanical properties, durability, and microstructural characteristics were investigated. The novelty of this research lies on the use of sustainable POCS as sand replacement for conventional mining sand; the mix design was carried out using a volume-based approach by employing the specific gravity of the fine aggregates. In addition, with partial replacement of the fly ash (FA) with ground granulated blast furnace slag (GGBS) as the binder, the need for oven-curing was avoided. Based on the test results, the 28-day compressive strength of 53 MPa was achieved for ambient-cured mix with FA-GGBS (50:50) as binder and replacement of conventional sand with POCS. Geopolymer mortars showed higher resistance to the HCl and magnesium sulfate compared to cement mortar. XRD and EDX analyses showed enhanced formations of Si-O-Si and C-A-S-H bonds in GGBS incorporated mixes, and the presence of calcite mostly in the ambient-cured mixes resulted in stronger mechanical properties.
Cracks in concrete structures can significantly decrease their lifespan by exposing reinforcement to outside environment, leading to concrete degradation. To address this issue, self-healing ...techniques have been developed, including biomineralization-based-self healing, where bacteria are employed to initiate microbially induced calcium precipitate (MICP), promoting the healing of cracks. This article explores the extreme environmental conditions including pH and temperature which can reduce sustainability and self-healing potential of bacteria. Furthermore, it explores the implementation techniques of using bacteria in concrete aimed at mitigating the adverse effects of the concrete environment on bacteria, thereby enhancing their self-healing capabilities. Notably, studies have found that the mechanical strength of concrete can be increased at cell concentrations of 105 to 108 cells/ml. Based on this review, it is found that the self-healing of concrete depends on factors such as environmental conditions of pH and temperature, as well as the implementation methods of bacteria in concrete. Moreover, there exists a direct correlation between bacterial cell concentration and alterations in the mechanical properties of concrete. The incorporation of bacteria in concrete leads to increment in strength properties, with strength enhancement of up to 42.8 %. Understanding the interplay between environmental factors and bacterial sustainability is crucial in optimizing biomineralization-based self-healing and enhancing the durability of concrete infrastructure.
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•Bacterial concrete offers a novel approach to sustainable advancements in concrete technology, reducing carbon emissions and minimizing cracks, thereby enhancing durability and lowering maintenance costs.•pH and temperature can impact bacterial viability and effectiveness in healing cracks.•Implementation methods influences crack-repair abilities of bacteria.•Bacterial cell concentration affects concrete's hardened properties.•Microbial self-healing concrete's successful application in tunnels, water channels, retaining wall panels, and highways.
Transforming phosphogypsum (PG) to β-hemihydrate PG with cementitious properties at low calcination temperature is an effective method for large-scale utilization of by-product PG. Nevertheless, due ...to the poor water resistance of PG, its application and recycling rate is limited. This study aims to produce water-resistant β-hemihydrate synthetic gypsum (SG) with minimum cost and energy consumption, using calcined PG as the raw material. The effect of PG calcination temperature (100 °C, 140 °C, 180 °C, and 220 °C) on the properties of SG was evaluated, and it was found that 180 ºC calcination temperature was able to fully convert the PG to β-hemihydrate SG. Additionally, SG prepared using 180 ºC calcined PG exhibited the highest compressive strength (9.15 MPa). On the other hand, various contents of the mineral admixture, namely, GGBS (5 %, 10 %, 15 %, 20 %, and 25 %), were incorporated in SG to evaluate the viability of GGBS to improve the compressive strength and water resistance of SG. However, the results revealed that adding GGBS has little effect on the performance of SG. Especially, when 25 % GGBS was added, the compressive strength of SG was reduced by 66.3 %. Consequently, further investigation into how to enhance the effect of GGBS is required.
Palm oil clinker (POC) aggregates is a viable alternative to the naturally occurring sand and gravel in the manufacturing of concrete. The usage of POC aggregates assists in the reduction of solid ...waste and preserves the consumption of natural resources. Although researchers investigated the mechanical response of POC-containing concrete, limited research is available for its torsional behavior. In general, the torsional strength depends on the tensile strength of concrete. This research investigates the compressive, tensile, and torsional response of concrete with various ratios of POC-aggregates. Five batches of concrete were casted with POC-aggregate replacing granite at ratios of 0, 20, 40, 60, and 100%. The selection for the mixture proportions for the various batches was based on the design of experiments (DOE) methodology. The hard density, compressive strength, splitting tensile strength, and flexural strength of concrete with a 100% replacement of granite with POC-aggregates reduced by 8.80, 37.25, 30.94, and 14.31%, respectively. Furthermore, a reduction in initial and ultimate torque was observed. While cracks increased with the increase in POC-aggregates. Finally, the cracking of concrete subjected to torsional loads was monitored and characterized by acoustic emissions (AE). The results illustrate a sudden rise in AE activities during the initiation of cracks and as the ultimate cracks were developed. This was accompanied by a sudden drop in the torque/twist curve.
The valorisation of waste tyre crumb rubber (CR) as a sustainable construction material can alleviate environmental pollution and save natural aggregate consumption. However, its use in cement ...composite can result in a significant loss of strength due to weak adhesion and the non-uniform dispersion of CR. To compensate this strength loss, this research aims to investigate the innovative incorporation of chemically treated CR via the preplaced aggregate mixing (PM) method in producing a lightweight cement composite. The CR was treated with different chemicals, namely soaking in potassium permanganate and sulphuric acid solutions. The findings reveal a significant improvement in compressive strength (up to 160%) and water absorption reduction (from 20% to 175%) using the chemically treated CR and PM mixing methods, producing a lightweight cement composite with a density of about 1535 kg/m3. The SEM observation demonstrates the improvement in the CR–paste interface due to the treatment of the CR and the PM mixing methods, and due to the chemical treatment, which improved the wettability of the CR. On the other hand, the sound absorption and noise reduction coefficient of the chemically treated CR lightweight cement composite was almost similar for both the normal mixing (NM) and the PM methods. Overall, the results demonstrate that the CR treatment with sulphuric acid is promising for the PM method to produce a lightweight cement composite.
•Lightweight cement composite prepared with chemically treated crumb rubber.•An innovative mixing named preplaced aggregate mixing (PM) method was adopted.•The composite's fresh, strength, water and sound absorption properties are reported.•Cement composite was produced with a density and strength of about 1535 kg/m3 and 9 MPa.
Geopolymer has attracted various interests all around the world since its introduction. It is known as a beneficial alternative to cement as it can be produced at room conditions, effectively cutting ...down CO2 emissions compared to the high temperature calcination process in cement production. Moreover, industrial waste or by-products can be upcycled by incorporating as the precursor in geopolymer production, reducing the environmental burden of waste disposal. High calcium fly ash is emerging as a viable option to produce geopolymer binder material. Recycled brick waste (RBW) on the other hand, may be a good source of aluminosilicate, which is vital to produce geopolymer binder material. However, the incorporation of both materials in the production of geopolymer binder materials has not been well-studied. Hence, this paper presents a study on the properties of geopolymer mortar made with high calcium fly ash incorporating 10 % RBW and borax additive at dosages of 3 % and 6 %. In the fresh state, the geopolymer with 10 % RBW and higher borax dosage had a lower temperature, but all mixes gradually exhibited a similar temperature range between 31.3 °C and 31.9 °C. The geopolymer containing RBW exhibited a 13 % higher compressive strength compared to the RBW-absent counterpart in both mixes with 3 % and 6 % borax while the inclusion of borax from 3 % to 6 % reduced the compressive strength by 22 %. The geopolymer had compressive strengths of about 11.8–15.9 MPa after prolonged exposure to an acidic solution, showing a decreasing trend due to the acid attack on the reaction products. The geopolymer mixes containing 6 % borax exhibited lower strength loss (30.2 % and 28.2 %) compared to those with 3 % borax (40.3 % and 42.3 %) on 800 °C heat resistance while the effect of RBW was negligible. On the other hand, the drying shrinkage of geopolymer did not benefit from the inclusion of either RBW or higher borax dosage. The study provided important insights into the incorporation of these materials in the properties of the geopolymer.
Silica aerogel (SA) has recently gained attention as an alternative to lightweight aggregate in lightweight cementitious composite (LCC). However, it is challenging to ensure homogenous mix of ...hydrophobicity SA and aqueous cementitious composite. This study investigates a novel chemical treatment of micro-sized SA using methanol solution for incorporation in LCC. Initially, characterization of treated SA was performed and afterwards, it was used as sand replacement up to 80% by volume to obtain the LCC. The proposed treatment method was found effective to overcome the hydrophobic nature of SA temporarily. The incorporation of 80% treated SA caused 45% reduction in density (from 1935 kg/m3 to 1060 kg/m3), 81% reduction in compressive strength (from 36 MPa to 7 MPa), and 31% reduction in water resistance (from 0.76 to 0.52) of LCC, whereas the porosity and water absorption of LCC were increased by 260% and 375%, respectively. However, SA-LCC with 80% treated SA has an acceptable range of properties for non-structural and insulating application, such as low density (1050 kg/m3), sufficient compressive strength (7 MPa), and adequate porosity (59%).
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•Methanol treatment can temporarily overcome the hydrophobicity of SA for mixing.•The oven-dry density of LCC can be as low as 1050 kg/m3 with 7 MPa strength.•Treated SA-LCC has high porosity of 59% with good potential as insulating material.•LCC with 80% treated SA has potential for non-structural and insulating application.
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