Sustainable Cementitious Materials Research Articles

Effects of Biochar as a Green Additive on the Self-Healing and Properties of Sustainable Cementitious Materials

Effects of Biochar as a Green Additive on the Self-Healing and Properties of Sustainable Cementitious Materials

Sustainable development of pavement base stabilization using future road base material (FROBM)

Sustainable road construction has emerged as a critical issue in assessing natural resources and urban development. With the rapid expansion of pavement networks to meet growing traffic demands, road base construction relies heavily on the consumption of natural aggregates and Ordinary Portland Cement (OPC) through the cement-treated base (CTB) technique. This practice contributes to the global warming and greenhouse gas (GHG) emissions associated with road construction. This study investigated a novel road base material, Future Road Base Material (FROBM), which emphasizes both eco-friendliness and economic advantages. Fine crushed rock (FCR) served as the parent aggregate and was modified with a chemical binder comprising 4% of the FCR weight. The proposed sustainable cementitious material, functioning as a non-OPC binder, incorporated fly ash and hydrated limestone as pozzolanic materials, along with sodium hydroxide (NaOH) as an alkali additive. An asphalt emulsion (AE) was employed as a special additive to enhance crucial pavement engineering properties. Through life cycle analysis (LCA), the construction activities and material acquisition of each stabilized base technique were evaluated in terms of project costs and carbon footprints. The non-OPC binder offered sufficient compressive strength for a stabilized base course. Furthermore, the addition of AE improved the elastic modulus and modulus of rupture of the non-OPC binder-stabilized mixture. Utilizing a non-OPC binder and AE in the base layer provides advantages in terms of construction cost and environmental impact. Although the costs increased slightly, the GHG emissions were reduced by approximately 30% compared to conventional base materials, with equivalent functionality and service life for road construction. The proposed stabilizing agent reduced the operational processes and demand for natural aggregates compared with the unbound FCR base course. Road-base stabilization using a non-OPC binder and AE represents an innovative approach to mitigate waste in coal mining and power plant industries by transitioning to a cleaner product. The concept of the FROBM serves as a valuable guideline for the development of future sustainable pavement materials.

Efficiency of self-compacting concrete made with variable sustainable cementitious materials: A TOPSIS algorithm approach

The use of supplementary cementitious materials as a partial replacement for cement is taking the lead in the concrete production industry. Being known as by-products from various manufacturing properties, concrete produced with such materials is considered a sustainable alternative to normal concrete. Three different by-product materials have been investigated in this study for the production of sustainable self-compacting concrete (SCC), namely, ground granulated blast furnace slag (GGBS), fly ash (FA), and silica fume (SF). Compressive strength, production cost, and global warming potential (GWP) were the main testing parameters for the mixes' performances. Multi-criteria decision-making algorithm was implemented using the TOPSIS model to investigate the ultimate performance of those SCC mixes considering all tested parameters simultaneously. Results showed the best SCC performance can be attained when using about 60 % of GGBS as a partial replacement for cement.

Sustainable MgO-calcined clay cementitious material: Reaction mechanism, strength development and performance enhancement via initial CO2 stirring

With the massive utilization of concrete and other cement-based materials worldwide, the high carbon emissions and energy consumption have become severe issues. This study proposes a sustainable cementitious material based on MgO and calcined clay and investigates its reaction mechanism and strength development by combining experimental characterizations and thermodynamic modelling. Furthermore, the performance of the MgO-calcined clay cementitious material is enhanced by CO2 stirring. The results indicated that the introduction of CO2 during stirring generates massive high reactive magnesium carbonate nano/micro-particles. It provides the nucleation sites for promoting the formation of hydration products and reacts with calcined clay to form carbonate-type hydrotalcite. Due to the unique advantages of CO2 stirring in the MgO-calcined clay system, the performance of sustainable cementitious material is remarkably enhanced, providing a new routine for developing high-performance low-carbon building materials.

An experimental study on high strength self-compacting concrete inclusion of zeolite and silica fume as a potential alternative sustainable cementitious materials

One of the major sources of carbon dioxide and other greenhouse gases around the world is the cement industry. They make up 6–8 % of global warming. Therefore, by conducting this experiment, we may examine the possibility of replacing cement with different cementitious materials which include zeolite,silica fume and fly ash. These mineral additives will lessen the need for cement while enhancing the properties of the concrete that has just been hardened and also in fresh state. The objective of this experiment is to explore the impact of zeolite and silica fume on the physical and durability qualitiesof high strength, self-compacting concrete utilising nano silica that has been optimised. In the course of this study, various concrete mixtures were cast with zeolite and silica fume substituted for cement in varying amounts, and there was also a control mix for reference. These additives arereplacedcement in multiples of 5 up to 20 %. The preferred dosage as 2 % Nano silica is substituted as a regular mineral additive in all mixtures. Workability tests on the fresh qualities of concrete mixtures are conducted and the EFNARC stipulations are met by these experimental findings. All the concrete mixes' parameters, including strengths like splitting tensile and compressive were identified. Tests such as the Rapid chloride permeability test, the abrasion test, water absorption and desorption test were used to evaluate the concrete's durability.

Energy-saving calcination of hydromagnesite for sustainable magnesia-based cement: A new route towards MgO production

The MgO production worldwide is mainly achieved through the calcination of magnesite in the wake of higher energy requirements. This study proposes an energy-saving calcination strategy through low-temperature partially calcining hydromagnesite (4MgCO3·Mg(OH)2·4H2O). Furthermore, the feasibility of using the partially calcined hydromagnesite and slag to produce a sustainable cementitious material was investigated by various techniques. This approach requires relatively low temperature and short processing time with a potential energy saving of production and CO2 emission of fuel combustion. Moreover, it accelerates the hydration rate due to amorphous magnesium carbonate. Results indicated that the amorphous magnesium carbonate is formed during the partial calcination of hydromagnesite. It tends to transform to nesquehonite (MgCO3·3H2O) in the initial stage of hydration, which is responsible for promoting early hydration and excellent early compressive strength. Finally, the reaction mechanism of the partially calcined hydromagnesite-based cementitious materials has been established, demonstrating its enormous potential for preparing low-carbon cementitious materials.

Effect of PVA fiber on properties of geopolymer composites: A comprehensive review

Geopolymer composites (GC) have drawn much attention regarding sustainable cementitious materials in recent years. Polyvinyl alcohol (PVA) fiber is often added into GC to improve properties of the composite. In order to better understand the effect of PVA fiber on properties of GC and its mechanism, this paper sums up the advance in properties of PVA fiber-reinforced geopolymer composites (PVA-FRGC). Viscosity of GC increases with the increase of PVA fiber, so a reduced setting time and poor flowability of GC occurs. This paper expounds that PVA fiber with moderately high content and short length has significant effects on mechanical properties of GC. Most mechanical performances of GC can be tremendously improved thanks to fiber-bridge effect. Besides, it's worth noting that 0.2%–0.3% content of PVA fiber has optimal enhancement in compressive strength of GC. The details also contain the enhancement of PVA fiber incorporation on durability of GC, and related models used in predicting performance of PVA-FRGC are expounded. In addition, the strengthening mechanism from scanning electron microscope (SEM) images showed that PVA fibers had strong chemical bond strength and friction bond strength with geopolymer matrix, and future work need to be done is recommended. In general, PVA-FRGC has an excellent performance on mechanical properties and durability compared with plain GC. The paper is designed to make contributions for development of green building materials. This paper aims to provide guidance for the application of PVA fiber in GC and serve as support for practical application of PVA-FRGC in construction engineering.

Transforming construction and demolition waste concrete as a precursor in sustainable cementitious materials: An innovative recycling approach

Construction and demolition wastes amount to 10,000 Mt/year worldwide, a large fraction of these is concrete, along with other potentially useful constituents, like bricks, ceramics, glass, etc. This study investigates the potential of harnessing this environmental passive into cementitious precursors in novel one-part alkaline cements, in which pulverized hardened concrete was blended with 0–80 % of Portland cement and activated with 15 % Type G sodium silicate. Paste specimens underwent curing at 20 or 60 °C for 24 h and then completed 28-days at 20 °C under dry and underwater conditions to test the hydraulicity. The pastes cured at 20 °C having 45 and 25 % recycled concrete reached 45 and 50 MPa, respectively; further characterization suggested the formation of cementitious gels like C-S-H and silica gel. An evaluation of the environmental footprint as CO2 emissions, energy requirements and cost suggest that these novel cements offer a promising and sustainable alternative for the construction industry.

Investigating the governing factors influencing the pozzolanic activity through a database approach for the development of sustainable cementitious materials

Pozzolans, known to possess high pozzolanic activity, enhances the long-term engineering properties of concrete due to the consumption of calcium hydroxide and the consequent formation of the calcium-silicate-hydrate gels within the cementitious matrix. Although the key factors that affect the pozzolanic activity such as the chemical composition, amorphousness, and fineness are commonly addressed in literature, there is a growing need to further gain an insight into the factors that govern this activity in a more comprehensive approach. The aim of this empirical study is to develop concrete models comprising optimal replacement of pozzolans based on the governing factors affecting the activity through the database approach. The database, consisting of 631 number of data points harvested from the literature, is established to determine the optimum replacement levels of the designated pozzolans in concrete. The governing factors therefore played a key role in establishing the boundary conditions that enabled the potential concrete models to be generated particularly for the sustainability assessment of concrete incorporating pozzolans. The study shows that the optimum replacement levels in concrete mixtures are 15–50% for GGBS, 10–35% for fly ash, and 5–15% for silica fume. The study furthermore demonstrated that the utilisation of these substitutions leaded a considerable reduction in carbon emissions that ranged from 13% to 43% for GGBS, 9–31% for fly ash, and 4–13% for silica fume. The study significantly contributes to the generation of greener construction materials, and offers a cleaner disposal route for the pozzolans principally compared to the traditional waste management alternatives.

Reduce the cost and embodied carbon of ultrahigh performance concrete using waste clay

Recent research has recognized limestone calcined clay cement (LC3) a promising sustainable cementitious material. While LC3 could be used in a wide range of applications, it is important to explore its feasibility in developing (ultra-)high performance concrete. In this paper we attempt to produce ultrahigh performance LC3 concrete (UHP-LC3). With 20%, 30%, and 40% OPC replaced by coal gangue waste calcined clay and limestone (LC2), the mechanical, hydration, and microstructural properties were extensively studied. The mechanical properties were investigated by compressive and flexural tensile tests. The hydration behavior of UHP-LC3 was evaluated by thermogravimetric analysis (TGA), quantitative X-ray powder diffraction (QXRD) analysis, 29Si nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscope (SEM). Finally, the microstructure of UHP-LC3 was studied by mercury intrusion porosimetry (MIP). Results show that the substitution of LC2 improve the early strength by quickly pozzolanic reaction to form denser hydration products as well as the synergistic interaction between silica fume and limestone/calcined clay in the system. However, the long-term strength would drop as LC3 caused insufficient hydration reaction due to the high water-demand of calcined clay that reduced the amount of free water. Also, there are abundant unreacted calcined clay particles in the hydrated system. Meanwhile, LC3 substitution of OPC seems to improve the polymerization of C-A-S-H gel and densify the pore structure, thus display excellent carbonation resistance. This paper explores new options to prepare more sustainable and cost-effective UHPC.

Tailoring self-pulverized low-calcium clinker for CO2 sequestration

To reduce energy consumption and greenhouse gas emissions in the cement industry, this study develops a novel low-calcium clinker with self-pulverization properties. The clinker is synthesized from limestone and sandstone raw materials and comprises dicalcium silicate (2CaO·SiO2 (C2S)) as the primary mineral and rankinite (3CaO·2SiO2 (C3S2)) as the auxiliary mineral. The influence of calcination temperature, cooling rate, and holding time on clinker pulverization and mineral formation is investigated through a series of experiments. The optimal calcination condition involves heating at 1240 °C for 1 h, followed by natural cooling, resulting in a self-pulverized low-calcium clinker (SPLCC) with main mineral is γ-C2S and contains β-C2S, C3S2, and C2AS (Calcium alumina feldspar (2CaO·Al2O3·SiO2)). The self-pulverized clinker exhibits a pulverization ratio of 93.0 %, a specific surface area of 666.4 m2/kg, and an average particle size of 8.2 μm. Additionally, the clinker displays excellent carbonation reactivity, with the compressive strength reaching 69.3 MPa and 82.2 MPa after 4 h and 24 h of CO2 curing, respectively. The carbonation products are identified as calcite and silica gel. SPLCC can reduce and sequester approximately 277.3 kg of CO2 emissions compared to the hydration of Portland cement clinker when considering the preparation and curing stages. The results highlight the potential of SPLCC as a sustainable cementitious material.

Characterization of net-zero pozzolanic potential of thermally-derived metakaolin samples for sustainable carbon neutrality construction

Metakaolin (MK) is one of the most sustainable cementitious construction materials, which is derived through a direct heating procedure known as calcination. Calcination process takes place substantially lower temperatures than that required for Portland cement, making it a more environmentally sustainable alternative to traditional cement. This procedure causes the removal of hydroxyl water from the naturally occurring kaolin clay (Al2Si2O5(OH)4 with MK (Al2O3·2SiO2) as its product. Kaolin naturally exists in large amount within 5°29′N–5°35′N and 7°21′E–7°3′E geographical coordinates surrounding Umuoke, Obowo, Nigeria. Alumina and silica are the predominant compounds in MK, which provide it with the pozzolanic ability, known as the 3-chemical pozzolanic potential (3CPP), with high potential as a cementitious material in concrete production and soil stabilization. Over the years, researchers have suggested the best temperature at which MK is derived to have the highest pozzolanic ability. Prominent among these temperature suggestions were 800 °C (3CPP of 94.45%) and 750 °C (3CPP of 94.76%) for 2 h and 5 h’ calcination periods, respectively. In this research paper, 11 different specimens of Kaolin clay obtained from Umuoke, Nigeria, were subjected to a calcination process at oven temperatures from 350 to 850 °C in an increment of 50 °C for 1 h each to derive 11 samples of MK. The MK samples and Kaolin were further subjected to X-ray fluorescence), scanning electron microscopy (SEM) and X-ray diffraction (XRD) Brunauer–Emmett–Teller (BET) tests to determine the microstructural behaviour and the pozzolanic properties via the 3CPP as to exploit the best MK with the highest cementing potential as a construction material. The results show that the MK heated at 550 °C and 800 °C produced the highest pozzolanic potentials of 96.26% and 96.28%, respectively. The enhancement in pozzolanic potential at optimum calcination temperature is attributed to an increase in the specific surface area upon calcination of kaolinite confirmed by BET results. The SEM and XRD results further supported the above result with the strengthened crystal structure of the MK at these preferred temperatures. Generally, 550 °C is more preferred due to the less heat energy needed for its formulation during 1 h of calcination, which outperforms the previous results, that suggested 750 °C and 800 °C in addition to longer hours of heat exposure.

Crack Binding and Filling Properties of Modified Proteins in Sustainable Cementitious Materials

Crack Binding and Filling Properties of Modified Proteins in Sustainable Cementitious Materials

Shallow Coastal Carbonate Sediment Mapping for Biomimetics MICP, Case Study of Indonesia Beachrock, Yogyakarta

The nomenclature for beachrock sedimentary has been in scientific discussions prior to the notable methodology of sustainable cementitious binding material based on microbially induced calcium carbonate (MICP). Typically, coastal erosion mitigation involves modifying surface conditions using materials like concrete, among other materials. This study aims to challenge the conventional practice by evaluating the feasibility of expeditiously constructing artificial beachrock utilizing natural components (e.g., microbes, sand, shells, coral fragments, seaweed, etc.) and propose it as an innovative coastal protection strategy. The primary focus of this research is to characterize the Java South coast, specifically Parangtritis Beach and Krakal-Sadranan Beach, where beachrock formations are present. Subsequent investigations were conducted to (i) identify occurrences of beachrock deposits in Krakal-Sadranan, Yogyakarta, and (ii) develop cementation method based on ureolytic bacteria derived from naturally formed beachrock as an alternative technique for stabilizing sandy coastal environments. The experiment employed bacteria isolated from the Yogyakarta coast (Pseudoalteromonas tetradonis). The outcomes revealed that the sample treated with a gradually injected cementation solution achieved an approximate strength of 10 MPa after a 14-day treatment.

Assessing the potential application of bacteria-based self-healing cementitious materials for enhancing durability of wastewater treatment infrastructure

Wastewater treatment plants (WWTPs) around the world are mainly built using concrete. The continuous exposure to wastewater affects the durability of concrete structures and requires costly maintenance or replacement. Concrete production and repair represents ∼8% of the global anthropogenic CO2 emissions due to the use of cement, thus contributing to climate change. Developing a more sustainable cementitious material is therefore required for this vital health infrastructure. In this study, the feasibility of using bacteria-based self-healing (BBSH) cementitious materials for WWTPs is assessed by exposing BBSH mortar prisms to a continuous municipal wastewater flow and comparing their self-healing capacity to equivalent mortar prisms exposed to tap water. Microscopy imaging, water-flow tests and micro-CT analyses were performed to evaluate the self-healing efficiency of the mortar prisms, while SEM-EDX and Raman spectroscopy were used to characterise the healing products. Our work represents the first systematic study of the healing potential of BBSH in mortar exposed to wastewater. The results indicate that the purposely added bacteria are able to induce calcium carbonate precipitation when exposed to wastewater conditions. Moreover, if additional sources of calcium and carbon are embedded within the cement matrix, the rich bacterial community inherently present in the wastewater is capable of inducing calcium carbonate precipitation, even if no bacteria are purposely added to the mortar. The results of this study offer promising avenues for the construction of more sustainable wastewater infrastructure, with the potential of significantly reducing costs and simplifying the production process of BBSH concretes for this specific application.

Insights from molecular dynamics into the chemistry-structure relationships of calcium aluminosilicate glasses

Calcium aluminosilicate (CAS) glasses are ubiquitous in nature and play an important role in diverse technological applications ranging from structural glasses to sustainable cementitious materials. Understanding the relationship between the chemical composition and the structure of CAS glasses is an essential step towards optimizing their properties for different uses in the future. Here, we use extensive molecular dynamics (MD) simulations to characterize the multiscale structure of CAS glasses over the full compositional range. Analysis of the short and medium range order of the glasses reveals that Lowenstein's rule is widely violated, that silica is more susceptible than alumina to the depolymerizing effects of calcium, and that high-silica glasses favor calcium in lower oxygen coordination states, while the opposite is true for high-alumina ones. We also find the presence of highly coordinated aluminum and tricluster oxygens in high-alumina glasses, which form as a charge compensation mechanism. We find that current theoretical models used to predict oxygen species, oxygen bridge types, or tetrahedral coordination, while overall qualitatively reasonable, simplify the complex interplay between the different oxides which results in inaccurate predictions, particularly for glasses in intermediate compositional regions. Our analysis of the cluster, chain, and ring topological structures in the aluminosilicate network reveals a sharp transition from a connected to a disconnected graph which depends not only on the calcium content of the glass, but also on the ratio of silica to alumina. Glasses in the compositional region corresponding to such transition display the largest ring and longest chain structures of any glass studied.

On the feasibility of using Polyester (PE) waste particles from metal coating industry as a secondary raw materials in concrete

Reduction of CO2 emissions and plastic waste are the main environmental problems that modern society is dealing with. Concrete industry is continuously investing in research and development aimed at producing sustainable cementitious materials. In the last decades, it has gained interest the possibility of reusing polymer waste (mainly PET or PP) in partial substitution of natural constituents (aggregates) or as fiber reinforcement. As a matter of fact, because of the poor mechanical characteristic of polymers compared to the one of natural aggregates, the final cementitious composite has reduced mechanical performance. In the aforesaid framework, the experimental research reported in this paper aims at verifying the feasibility of a pathway able to use fine polymer particles, in detail a Polyester resin (PE resin) which is a waste product of the coating industry, as a partial replacement of sand and, in case, of binder particles, upon a gamma irradiation process similar to the one used for the sanification of containers in food industry, also their effectiveness in performing as seeds of the cement hydration. Firstly, intrigued by a study performed by MIT researchers (in which exposure of PET waste particles to gamma irradiation has been investigated as a method to improve their mechanical performance), the influence of different gamma irradiation dosages (10 kGy or 100 kGy) on PE resin particles was investigated. However, results led to the conclusion that, even with a mere 5% by volume substitution of Portland Limestone Cement (PLC) in the mix, the process does not significantly improve the mechanical performance of cement-based composites. In a second stage, the non-irradiated particles have been employed as a replacement of the binder and/or of the sand at different volume replacement ratios (10% and 20% respectively) in mortar mix designs formulated from typical Self-Compacting Concrete (SCC) mixes. Finally, once identified the most suitable type and level of replacement as the best compromise between performance maintenance and volume of added particles, the scaling up to the concrete mix-design has been performed and the related performance thoroughly tested. The results have provided limited reduction in mechanical properties, with a 20% by volume level of substitution of cement by PE resin particles, highlighting the possibility of reusing economically viable quantities of PE resins into concrete while still being able to use the material for structural application.

Sustainable cementitious materials: exploring alkali-activated binders with natural pozzolan

The present paper describes the potential use of NP from Algeria for the production of a new AAB. CEMII 42.5 cement is added to the NP as calcium resource. The mixtures are then activated by NaOH, Na2SO4 and Na2SiO3 at concentrations of 3, 7 and 11%. The chemical activators are both added in liquid and/or solid form to develop a one-part alkali-activated material. XRD, ATG/ATD and SEM/EDS are used to assess microstructure and elemental composition of the hydration products. Fresh properties, such as, consistency and setting time of various mixtures and compressive strengths of AABs specimens cured for 7, 28, 90 and 420 days are determined. The cement carbon footprint vs strength ratio (kg·CO2·eq/MPa) is suggested as an indicator to highlight the environmental contribution of the AABs. The results indicate that AABs show different strength levels depending on the activator type and its concentration. Maximum 28-day compressive strength of 25.2 MPa is achieved with 7 % Na2SiO3. A high early strength development is also noted since more than 50% of the strength could be achieved within 7 days. Finally, the environmental advantage is demonstrated as the global warning of the AABs can be 70% lower than that of OPC.

Optimization of biochar and fly ash to improve mechanical properties and CO2 sequestration in cement mortar

The novelty of this study is to find out the optimum amount of biochar and high calcium fly ash to improve mechanical performance and promote CO2 uptake in cement mortar. The potential of biochar-fly ash mixes was optimized using response surface methodology (RSM) considering the influence of different amounts of fly ash (FA), biochar (B), and their interactions to achieve the optimal mix design with improved performance and carbonate mineralization. Additionally, the effect on the mineralization of different polymorphs of calcium carbonate was also investigated. The experimental results indicate that the accelerated carbonation of high calcium fly ash mortar enriched with biochar enables the effective utilization of biochar up to 5% for enhancing both the mechanical properties and CO2 sequestration. However, under normal curing conditions, it was observed that the optimal amount of biochar that can be used is <1%. This is a promising approach in terms of utilizing waste material and reducing cement content in the mix design together with the additional benefit of storing 50% of ambient CO2 permanently in the cementitious matrix. Carbonation of biochar-fly ash cement composite substantially improves fracture strength, and modulus of elasticity compared to uncarbonated cement mortar at 7 and 28 days. The present study demonstrates the advantages of synergistically combining biochar and fly ash in the development of low-carbon, sustainable cementitious building materials that have the potential to transform building structures into carbon sinks in the future.

Molecular-scale insight into improved waterproofing of cement paste by protective epoxy resins nano-coating

The durability of cement binding paste is an important challenge in building sector that can be improved by increasing the resistance to water infiltration in the cement paste. The aim of the present work is mainly devoted to analyze at nanoscale level the interfacial interaction of epoxy resins coated on (001) surface of the nanogranular Calcium-Silicate-Hydrate (CSH) paste. By means of molecular dynamics simulations, a full nano-coated CSH surfaces show that m-phenylenediamine (MPD) would highly improve the coating efficiency. Results reveal that the coated (001) CSH surface models are more stable and the calculated surface free energy is roughly 95% loss compared with the non-coated surface, reducing therefore the hydrophilicity of the CSH surface. The related values are found in the range of 33.7 mJ/m2- 45.5 mJ/m2, in agreement with experimental findings. The obtained averaged contact angle between the equilibrated water-nanodroplet and the best coated CSH is in the range of 84.29°- 91.97°, which corresponds to the observed experimental measurements. Finally, the calculated work of adhesion is estimated to102.81 mJ/m2,which is close to the experimental findings of 102.79 and 90.17 mJ/m2, corresponding to 2 and 28 days hydration of cement. Consequently, our findings reveal that 16.46 wt% of epoxy coating including 2.61% of MDP reduces by 3.14–3.57 times the hydrophilicity of CSH (001) surface, leading to a promising future of sustainable cementitious materials.