Replacement Of Ordinary Portland Cement Research Articles

Numerical Study of Potential Delayed Ettringite Formation in Cemented Nuclear Wasteforms

This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and hydration phases in a wide range of blended cements. In particular, the influence of nuclear waste loading, waste package size, and the addition of supplementary cementitious materials (SCMs) on DEF is systematically and numerically investigated. The analyses show that higher amounts of ordinary Portland cement (OPC) and waste loadings result in higher hydration temperatures and consequently increased DEF potential by enhancing sulfoaluminate dissolution and hydrogarnet precipitation. Partial replacement of OPC with SCMs reduced hydration heat and mitigated DEF risks. The analysis indicated that the DEF evolution may be different for waste packages of different sizes due to a shift from sulfate-controlling to aluminate-controlling reactions at high temperatures. Interestingly, higher temperatures did not necessarily induce higher DEF potential due to the excessive precipitation of aluminates in the form of hydrogarnet. This research enriches our understanding of DEF’s complex behavior, providing valuable insights for engineering applications beyond civil engineering, such as nuclear waste conditioning.

Assessment of the viability of pozzolanic activity of copper slag for use as supplementary cementitious material in ordinary Portland cement

The production of ferrous as well as non-ferrous metals generates slag as a byproduct material. Ferrous slags are extensively used in the construction sector as supplementary cementitious material (SCM) and aggregates. In this regard, the investigation of potential applications in similar areas for slags derived from the production of non-ferrous metals can help to address issues associated with their disposal, dumping, environmental concerns, etc. The primary aim of this research is to assess the pozzolanic activity of copper slag (CS), a type of non-ferrous slag. This investigation is conducted to replace a portion of ordinary Portland cement (OPC) incorporating CS as an SCM for sustainable construction. To assess the reactivity of the CS, comparisons were drawn with a known pozzolanic material fly ash (FA), and an inert material quartz powder (QP). The processing of raw CS (granular material) was carried out using a laboratory scale ball mill to achieve varying fineness to evaluate the effect of specific surface area (SSA) on reactivity. Initially, the investigations were conducted on paste samples of OPC-CS and suspensions of CS-calcium hydroxide (CH) and were later extended to mortar studies. Mechanical characteristics such as compressive strength and open porosity of mortar specimens were determined to correlate with the paste studies results. The findings suggest that CS does exhibit pozzolanic characteristics although its reactivity is comparatively lower than that of FA. An increase in the fineness of the CS resulted in enhanced pozzolanic activity. Analysis of the hydrated suspension samples showed the formation of Fe-siliceous hydrogarnet phase indicating “Fe” from CS was involved in the reaction with CH. Although OPC-CS mortar samples exhibited similar open porosity compared to OPC-QP mortar samples, the interfacial transition zone (ITZ) porosity in mortar samples of OPC-CS was observed to be reduced indicating the densification of the region due to the pozzolanic reaction of CS. The permissible replacement of OPC with CS as a substitute for FA can be adjusted according to the material's fineness and the desired compressive strength.

Effect of harsh environment on cement mortar containing natural pozzolans

This investigation aims to study the effect of the harsh environment on cement mortar containing pumice powder (natural pozzolana) as a partial substitute for ordinary Portland cement (OPC). The harsh environmental conditions applied in this study consisted of seawater supplemented with 5% of sodium sulfate (Na2SO4). Mortar mixtures were produced by replacing 0%, 5%, 10%, and 20% of the OPC mass with natural pozzolana (NP). Mortar samples were treated under two conditions. First, the mortar samples were immersed in tap water. Second, mortar samples are immersed in harsh environmental conditions. In the harsh environment, mortar samples were subjected to 90 cycles of dry-wet, 48-hour drying, and 48-hour wetting over a period of 360 days. Compressive strength, flexural strength, strength loss, change in length, water absorption, and initial surface absorption tests were performed on specimens aged 7, 28, 90, 180, and 360 days. Besides thermogravimetric and microstructure analysis of cement samples that were conducted at a test age of 180 days. The inclusion of NP as a partial replacement of OPC at a rate of 10% improved the results of compressive and flexural strength and achieved the lowest rates of porosity and water absorption of the mortar samples. The inclusion of NP as a partial replacement for OPC reduced the damage caused by the harsh environment.

Performance of recycled concrete aggregates based self-compacting concrete containing coal combustion ashes and silica fume

The objective of the current study is to evaluate the performance of Recycled Concrete Aggregates (RCA) based Self-compacting Concrete (RCA-SCC) comprising coal ashes and Silica Fume (SF). Coal ashes [Fly Ash (FA) and Coal Bottom Ash (CBA)] were incorporated as partial replacement for Ordinary Portland Cement (OPC) and Fine Natural Aggregates (FNA), respectively, while RCA were incorporated in place of Coarse Natural Aggregates (CNA). In order to compensate for the anticipated performance loss caused by the incorporation of RCA, a fixed percentage (10%) of SF was used as filler. The performance of aforesaid SCC was evaluated through various laboratory tests in fresh and hardened state. Five different substitution levels of CNA with RCA (0–100%), parallel with constant substitution level of FNA with CBA (10%) and OPC with SF + FA (10% + 20%) have been used throughout the investigation. Overall, the experimental outcomes along with regression results confirmed the potential of RCA-SCC prepared with CBA. RCA-SCC mix (25%) with coal ashes (FA + CBA) resulted in nearly equivalent performance to that of the reference SCC mix. Finally, the outcomes imply the successful contribution of SF, coal ashes (CBA + FA), and RCA leading towards the sustainable development of non-conventional SCC with identical performance.

Durability of clayey soil stabilized with calcium sulfoaluminate cement and polypropylene fiber under extreme environment

Calcium Sulfo-Aluminate Cement (CSAC) is gaining interest among researchers, consultants, engineers, and environmentalists as a prospective replacement of Ordinary Portland Cement (OPC) across many construction industries. The main reason is that the production of CSAC generates a lower carbon footprint as compared to OPC cement production. Other benefits of CSAC include quick bonding & strength development, and less shrinkage. Many studies are available and ongoing on the advantages and limitations of CSAC in concrete. However, only a few studies are available on its application in soil stabilization. Therefore, the efficiency of CSAC for soil stabilization is a topic of discussion in geotechnical engineering. In this research, a locally sourced highly compressible clayey soil was stabilized with different combinations of CSAC and polypropylene fiber (e.g., 5.0%, 7.5% & 10.0% of CSAC and 0.5% & 1.0% polypropylene fiber), and its effectiveness was observed and evaluated in terms of durability (Wetting-Drying and Freezing-Thawing tests) against extreme environments and also checked Unconfined Compressive Strength (UCS) as per American Society of Testing and Materials (ASTM) guidelines. The findings of this research are evaluated in terms of percentage of soil loss, change in moisture content and volume, and loss of strength after durability exposure. Moisture content and bulk unit weight were determined after each stage in the Freezing-Thawing durability cycles. Samples prepared with 10.0% of CSAC and 1.0% of fiber were able to survive all durability cycles of Wetting-Drying with PCA (Portland Cement Association) soil-loss percentage criteria. On the other hand, samples prepared with 10.0% cement with 0.5% as well as 1.0% fiber were able to survive all durability cycles of Freezing-Thawing with PCA soil-loss percentage criteria. These survived samples showed a significant amount of unconfined compressive strength even after being subjected to these durability cycles.

Stabilization/solidification of heavy metal-contaminated marl soil using a binary system of cement and fuel fly ash.

The stabilization/solidification (S/S) method is one of the most effective remediation techniques for treating contaminated soils. Several stabilizers, mostly the cementitious materials, have been used for the S/S treatment. In this paper, the feasibility of utilizing fuel fly ash (FFA) as a partial replacement of ordinary Portland cement (OPC) for the S/S treatment of marl soil contaminated with heavy metals was investigated. Two industrial waste materials, namely steel and electroplating wastes, were used to synthetically contaminate the marl soil. The stabilizers comprising of OPC and FFA were mixed with the contaminated soil at different dosages ranging from 10 to 40%, by mass, and a total of 48 S/S-treated soil mixtures were prepared. A series of experiments, including density, porosity, permeability, unconfined compressive strength (UCS), and toxicity characteristics leaching procedure (TCLP), were carried out on the soil mixtures to evaluate the efficiency of the proposed S/S treatment. Test results showed that the incorporation of FFA at higher volumes reduced the density and increased the porosity and permeability of the treated mixtures. Although FFA addition resulted in reducing the UCS values by an average of 46%, and this reduction was more significant at higher FFA percentages, the UCS values of all mixtures were more than 0.35 MPa (350 kPa), which passed the minimum requirements set by USEPA. In addition, the metal immobilization ability of the proposed treatment was confirmed by the TCLP analysis. As compared to the negative effect of the contamination of the soil by the electroplating waste, the contamination of the soil by steel waste had a higher negative effect. The results of this study would contribute in selecting an environment-friendly treatment of the contaminated soils using industrial waste materials, such as FFA, as a partial replacement of OPC. Nevertheless, the present study is an initial attempt to explore the possibility of utilizing FFA as a partial replacement of OPC in S/S treatment of marl soil contaminated with heavy metals. It is recommended to conduct another study in future including analysis of the treated soil mixtures using XRD, SEM, and FTIR techniques to better understand the stabilization/solidification mechanism and its implications on the test results.

Effect of manufactured sand, micro silica, and GGBS on properties of high-performance concrete

The most often used building material for engineering constructions is concrete. The rapid urbanization has necessitated the need for High Strength (HS) and High -Performance Concrete (HPC) for specialized constructions, such as high rise/tall structure and other important structures. Greater cement content may be required for concrete with higher performance like strength and durability, but code does not permit it, because higher cement content increases the heat of hydration, which leads to the development of thermal cracks in concrete, reduces its structural performance and damage environment by producing CO2 during production of Ordinary Portland Cement (OPC). This study tries to replace OPC by Micro Silica (MS) and Ground Granulated Blast Furnace Slag (GGBS) by some percentage to find our effect of these materials on properties of concrete HPC.In this work, the influence of Manufactured Sand (M-Sand), Micro Silica (MS) and Ground Granulated Blast Furnace Slag (GGBS) on the mechanical and durability qualities of High - Performance Concrete (HPC) is examined experimentally. Ordinary Portland cement (OPC) is used to create the HPC mixtures and then 40%,45%, 50% by weight of OPC is replaced with GGBS and 2.5% and 5% by weight of OPC is replaced with MS respectively. Additionally, OPC is replaced by 40%GGBS+ 2.5% MS, 40% GGBS+5% MS, 45%GGBS+ 2.5% MS, 45% GGBS+5% MS, and 50%GGBS+ 2.5%MS, 50%GGBS+5% MS. For each percentage replacement workability test, compressive test at the age of 28,56 and 90 days, water permeability test at 28 days and 90 days, Scanning Elector Microscope (SEM) test after 90 days are carried out. The investigative study’s findings showed that partial replacement of OPC with GGBS, MS, and combinations of GGBS and MS produces more consistent outcomes for strength and durability when compared to control mix.

Effect of Rice Husk Ash on the Properties of Concrete

Abstract: As a binder for infrastructure development, conventional Portland cement is currently the primary material that is used. However, cement production has a substantial impact on the environment, and many pozzolanic materials can reduce their carbon footprint with conventional Portland cement. In this experimental study, replacement of OPC (ordinary portland cement) is replaced with the ash produced from rice husk (An agricultural waste) and analyzed for durability and strength performance in concrete samples and mortar as well as chemical composition analysis and microstructure observation of rice hull ash according to X-ray differential test data were also conducted in the research analysis. it is produced by burning of husk (produced by rice barley waste) of oxygen for the production of rice husk ash. Its chemical composition is rich in silicates and aluminates which promotes the binding property of ordinary Portland cement and does not affect the IST(Initial setting time), FST(Final setting time) and does not increase the fineness of the cement particles hence it gives significant results with cement replacement. It was determined that 10% rice husk ash replacement was the optimum value for rice husk ash replacement based on the strength and workability criteria of the concrete quality assurance system.

Mechanical performance and shrinkage of compressed earth blocks stabilised with thermoactivated recycled cement

This paper explores the production and mechanical characterisation of compressed earth blocks (CEB) stabilised with thermoactivated recycled cement (RC) as a more sustainable alternative to ordinary Portland cement (OPC). CEB with 5–10% stabiliser, considering different OPC replacement percentages with RC, were characterised in terms of their main physical and mechanical properties in different moisture conditions.RC revealed high rehydration and stabilisation capacity, significantly improving the mechanical strength of CEB. The mechanical strength improved as much as twice after RC stabilisation and new eco-efficient blocks met the normative requirements. The mechanical strength was little affected up to 50%OPC replacement. RC showed high potential as an eco-efficient alternative to OPC in earth stabilisation.

Fresh And Microstructural Properties Of Saw Dust Ash (SDA) Admixed With Millet Husk Ash (MHA) In Self Compacting Concrete (SCC)

The quest to mitigate the high cost and the environmental hazard associated with cement production has increased globally. Saw dust ash (SDA) and Millet husk ash (MHA)were obtained by burning at temperatures between 600ºC-650ºC and used at a varied mix proportion of 0%, 5%, 10%, 15%, 20%, 25%, and 30%. SDA and MHA were employed to partially replace Ordinary Portland cement (OPC) in the production of grade 40 self-compacting concrete (SCC). To enhance the strength properties of SDA-SCC, an optimum dose of MHA was incorporated to produce SDA-MHA-SCC. Several trial mixes per standard specifications were conducted to obtain grade 40 SCC with a suitable proportion of plasticiser at 7.49 kg/m3 and a water-to-binder ratio of 0.37. They revealed the study that SDA-SCC's slump flow and passing ability reduces with an increase in SDA content in SCC and improvement in the resistance against segregation of MHA-SDA-SCC. Also, MHA has satisfied the requirement of ASTM C618 for good pozzolana.
 Keywords: Cement, millet husk ash, saw dust ash, fresh properties, self-compacting concrete

TEMPERATURE IMPACT ON THE HYDRATION AND SETTING MECHANISM OF C-S-H BONDING ON NANO-BIOMASS SILICA WITH POLY-CARBOXYLATE ETHER

<p>Pozzolanic material and a chemical admixture have been used in the current investigation; Nano Biomass Silica (NBS) and Poly-Carboxylate Ether (PCE). NBS produces 20% of the 590 million tonnes of paddy produced globally. Amorphous silica, a mineral component used in concrete, is present in sizable levels in these by-products (NBS). A binary and ternary of NBS with partial replacement of Ordinary Portland Cement (OPC) and the addition of PCE with varying dosage by weight of cement were used. This study's goal is to determine how they affect paste Setting time (ST) and Standard consistency (SC), and hydration temperature evaluation conducted in hot weather with various percentage at NBS from 6, 12 and 18% and PCE with varying dosage from 0.8, 0.9 and 1%. The chemical bond & structure of pozzolanic and chemical admixture in the FTIR were analysed. While PCE showed very little impact on consistency, higher w/b ratios with higher NBS levels were required for the maintenance of OPC-NBS paste consistency standards. The Initial setting time (IST) & Final setting time (FST) for binary OPC-NBS pastes significantly raise to 6% NBS, followed by a decrease at 12% and 18% NBS. However, for OPC-PCE pastes, the IST increased to 0.8%PCE followed by decrease at 0.9% and 1% PCE. In cement paste, PCE can be added as an additive, but the FST increases with an increase in the PCE percentage. At the same time, the mineral admixtures NBS can be used as a cement paste to decrease the FST and also reduce agricultural waste. NBS will effectively use silica ash as a microstructure filler as an additive in manufacturing to produce a certain form of cement with specific IST and FST, in particular for the sustainability of building materials and in hot weather.</p>

Investigation on the impact of elevated temperature on sustainable geopolymer composite

Geopolymer concrete (GPC) is an eco-friendly, sustainable, cementless and green concrete. It could be an alternative to the conventional concrete. In alkaline circumstances, the alumina and silica concentration in geopolymer concrete creates the geopolymer bond, while regular concrete creates C-S-H (calcium silicate hydrate bond). The final result of the geopolymer bond does not include any water. At elevated temperatures, geopolymer concrete would thus be more stable. Due to its greater strength and durability quality, geopolymer concrete may be the ideal replacement for ordinary portland cement (OPC) concrete. This research intends to examine how specimens of geopolymer concrete and regular concrete respond to exposure to increased temperatures between 100°C and 800°C. Mass loss, ultrasonic pulse velocity, compressive strength, X-ray diffraction, thermogravimetric analysis and derivative thermogravimetric analysis were all examined throughout the experimental examination. Both concrete specimens lose mass or weight as the exposure temperature rises; OPC concrete samples spalls at 600°C, while GPC sample fail at 800°C. GPC specimens lose around 12% of their original mass after being exposed to temperatures of 800°C, while OPC specimens lose about 7%. The GPC specimens maintained 60% of their initial compressive strength after being exposed to a temperature of 700°C, but the OPC concrete specimens only kept 52%. With each increase in exposure to extreme temperatures, the peaks of quartz and cristobalite are lowered. Only the form or structure of the mineral oxide would change; the chemical linkages would remain. The GPC samples subjected to temperatures of 100°C exhibit effective thermal stability than all other specimens exposed to extreme temperatures. As the exposure temperature rises, the GPC specimens become more thermally stable. According to the experimental findings, the GPC specimens’ bonding structure makes them more resistant to high temperatures than regular concrete specimens. Micropores are present in the voids of the geopolymer matrix, while mesopores and micropores are present in the voids of the OPC matrix. While OPC bonding is C-S-H formed by the hydration of lime and silica contained in the cement, the geopolymer bonding did not include the water content in the final or end result of geopolymerisation for strengthening.

Utilization of Coir Fibre Ash (CFA) in Cement Stabilized Peat

Peat is a soil that has a high compressibility property beside having a low bearing capacity. Due to these problems, the peat soil is not suitable for construction purposes. Coconut waste is an example of agricultural waste. In the context of environmental sustainability, the use of coir in geotechnical applications is desirable. This research was conducted to study peat stabilization by using Coir Fibre Ash (CFA) in partially replacing Ordinary Portland Cement (OPC) to improve the physical and geotechnical characteristics. Geotechnical laboratory experiments involved in this study are moisture contents, organic contents, fiber content, Atterberg limits, specific gravity, Unconfined Compression Strength Test (UCS), Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX). In this study, the use of CFA as a stabilizer were used at mixture ratio of 5, 10, 15 and 20% of OPC replacement. Based on the UCS test carried out, it is found that the optimum strength for each ratio of CFA in the mixture showed a decrement pattern if compared to cement stabilized peat (PC). The results of SEM test shows that the structure of untreated peat becomes denser after stabilized. This is due to the cementing process. EDX test shows that the carbon content in the soil decreases while calcium content increases after the stabilization process is executed. Therefore, CFA is suitable to be used as pozzolan material in stabilized peat and can reach up 200kPa of UCS at 20% OPC replacement.

Effect of processed sugarcane bagasse ash on compressive strength of blended mortar and assessments using statistical modelling

There is much agriculture and non-agricultural waste that contains pozzolanic material, which can be recommended to use as a partial replacement for Ordinary Portland Cement (OPC). One of the waste products from sugar industries, which possess pozzolanic properties, is Sugar Cane Bagasse Ash (SCBA). Because of the negative impact associated with cement production, OPC is being replaced by several supplementary cementitious materials / pozzolanic materials. In the current study, an effort has been made to use the SCBA by partially replacing the OPC for mortar studies. SCBA has been processed to enhance the chemical and physical properties. OPC is partially replaced by Processed Sugar Cane Bagasse Ash (PSCBA) up to 30% by a 5% increment. PSCBA blended cement mortar contains different proportions of PSCBA blended cement: river sand as 1:3, 1:4, and 1:5 with different water-to-binder (W/B) ratios based on the flow studies. Experimental research was done to determine the effects of the W/B ratio, river sand, and PSCBA on the formation of the cube compressive strength of PSCBA blended cement mortar for curing times of 7, 14, 28, 56, and 112 days. An increase in compressive strength about 6.4%, 9.3%, and 8.2% for 1:3, 1:4 and 1:5 with different W/B ratios for 28 days is reported. Based on the investigational results, the coefficients of strength for various relationships proposed by different researchers have been calculated for the binder: sand ratio as 1:3 and 28 days curing period. Various relationships, including Abraham, Feret, Singh, and Bolomey law are used to validate the mixes of the PSCBA blended cement for different water-to-binder ratios and different curing periods. A novel relation has been developed through the extension of studies to forecast the compressive strength of PSCBA blended mortar mixes with various W/B ratios for various curing times.

Study of Microstructure, Crystallographic Phases and Setting Time Evolution over Time of Portland Cement, Coarse Silica Fume, and Limestone (PC-SF-LS) Ternary Portland Cements

The use of silica fume as a partial replacement for Ordinary Portland Cement provides a wide variety of benefits, such as reduced pressure on natural resources, reduced CO2 footprint, and improved mechanical and durability properties. The formation of more stable crystallographic phases in the hardened cement paste can promote resistance to concrete attacks. However, using coarse silica fume may result in lower expenses and shorter workdays. In this work, coarse silica fume was used as a partial replacement of cement, by weight, at 3%, 5%, and 7%, and it was used as limestone filler at different particle sizes. The size of coarse silica fume used was 238 μm. The microstructural, compositional analysis, and crystalline phase content of mixed cements at different ages were evaluated. The addition of coarse silica fume and limestone promoted pore refinement of the composites and increased the calcium and silica content. The filling effect of fine limestone and coarse silica fume particles, as well as the formation of CSH gel, was found to be the main reason for the densified microstructure. The contributions of combined coarse silica fume and limestone improve the stability of CSH gels and pozzolanic reaction.

Hydration, mechanical and transfer properties of blended cement pastes and mortars prepared with recycled powder or limestone filler

The fine fraction (<80 μm) of recycled aggregates from construction and demolition wastes, currently considered as waste, is investigated as a candidate mineral additive for partial replacement of Ordinary Portland Cement (OPC) to reduce the environmental impact of cementitious materials. Although recycled powder could affect hydration reactions due to the presence of residual anhydrous cement particles and to its high specific surface area, very few studies are available in literature concerning these aspects. Cement pastes and mortars prepared with 0%, 10%, and 20% replacement by weight of OPC by either Recycled Powder (RP) or Limestone Filler (LF) are compared in terms of hydration degree, mechanical and transport properties using several techniques, including Isothermal Calorimetry (IC), Thermogravimetric Analysis (TGA), water porosity, mercury intrusion porosimetry and gas permeability. The results revealed that mixtures blended with RP or LF have a similar decrease in the overall hydration degree compared to the hydration degree of pure OPC mixture due to a dilution effect, although both additives have a small reactivity. A moderate increase in porosity and intrinsic permeability with the replacement rate is observed. Pastes and mortars blended with RP have a compressive strength and a Young modulus nearly identical to those with the same amount of LF, despite RP having worse properties than LF. A multiscale micromechanical model is established and reproduces faithfully these experimental results for the elastic moduli, based on the simplified assumptions that LF is nearly inert while RP reduces the effective water to binder ratio by both absorption of water and internal hydration reactions.

An Evaluation of the Performance of Lateritic Soil Stabilized with Cement and Biochars to be Used in Road Bases of Low-Volume Sealed Roads

The study investigated the effects of adding Saw Dust Ash (SDA) and Sugar Cane Bagasse Ash (SCBA) on the strength of cement with stabilized lateritic soil. The experiments carried out in both the lateritic soil and stabilized lateritic soil considered Atterberg limits, sieve/hydrometer analysis, compaction, soaked California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS) at various curing periods. Ordinary Portland Cement (OPC) was introduced into the soil with varying content (0%, 3%, 5%, 7%, and 9%) by weight of the soil sample. The results showed that CBR and UCS increased to 175.7% and 1.999 MPa, respectively, as the OPC content increased to 7%. The optimal OPC content to meet the 1.5MPa UCS requirement for road bases on low-volume sealed roads in Kenya was 7%. The next treatment involved partially replacing the OPC content with SDA and SCBA in different doses (7-0-0%, 5-1-1%, 3-2-2%, 1-3-3%, and 0-3.5-3.5%, respectively) for various curing periods. The results showed that CBR and UCS decreased as the OPC content decreased and SCBA and SDA increased. At a content of 5% OPC, 1% SDA, and 1% SCBA, UCS and CBR were 1.877 MPa and 149%, respectively, suggesting that it was the optimal dosage to meet the 1.5MPa UCS requirement for road bases on low-volume sealed roads in Kenya. The durability test indicated that the specimens treated with 5% OPC, 1% SDA, and 1% SCBA met the 80% durability index mark, as recommended for cement-stabilized soils. Previous studies used SDA and SCBA separately with cement or lime to stabilize the subgrade or subbase of roads, but this study focused on using these materials together as a partial OPC replacement to stabilize lateritic road bases for use in low-volume sealed roads. The goal was to use local agricultural and industrial waste materials in road construction and improve the strength characteristics of road bases while preserving the environment through waste utilization.

The very early-age behaviour of Ultra-High Performance Concrete containing ground granulated blast furnace slag

Ultra-High Performance Concrete (UHPC), despite being a relatively new kind of advanced cement-based material (featuring outstanding mechanical performance and excellent durability), has been deemed unsustainable due to its high cement content, thus increasing its carbon footprint. The large amounts of cement and silica fume (SF) can also raise both production costs and cracking risks due to the high early-age autogenous shrinkage. This paper addresses an innovative approach for developing a more sustainable UHPC involving an efficient application of ground granulated blast furnace slag (GGBS). Slags of two fineness levels are used, displaying a Blaine fineness of 420 m2/kg (SL1) and 700 m2/kg (SL2), respectively. These slags have been incorporated as volume replacements for 30% and 50% cement.The results analysis shows that it is indeed possible to produce SL2-based UHPC with a behavior similar to that of classical silica fume-based materials. The partial replacement of ordinary Portland cement (OPC) by 30% of GGBS (SL1 or SL2) improves workability, promotes the hydration reaction of cement and accelerates setting. In this case, the nucleation site effect of GGBS particles dominates; it seems to be directly correlated with the fineness of the slag used. Thus, the finer additions result in a significant acceleration of setting and hydration. The dilution effect is more sensitive at 50% of SL1 substitution. This prevailing effect delays the hydration reaction, prolongs setting times and decreases the peak of heat flow. In contrast however, this delay effect was not observed for the mixture containing 50% of SL2. Shrinkage measurements indicated that 30% of SL1 induces a slight reduction in early-age chemical and autogenous types of shrinkage. The most severe shrinkage is clearly found in mixtures incorporating 30% of SL2. This phenomenon may be due to the distribution of refined pores, which increases capillary tension. A more sustainable UHPC containing a high level of superfine slag (50%) with less autogenous shrinkage has been successfully produced.

Shrinkage behaviour of self-compacting concrete with a high volume of fly ash and slag experimental tests and analytical assessment

This study assesses the effectiveness of the high-volume replacement of Ordinary Portland cement (OPC) by non-clinker binders in terms of shrinkage behaviour. Fly ash (FA) or granulated blast furnace slag (GBFS) was used as a partial replacement for OPC at 60% by volume of the paste in self-compacting concrete (SCC). SCC having both FA (30%) and GBFS (30%), as well as SCC only with OPC, were also investigated. In all tested self-compacting concretes, the volume of the paste, which determines the shrinkage strains, was preserved. The shrinkage behaviour of SCCs was tested in shrinkage drains, bending drains and shrinkage rings. The total effect of autogenous and drying shrinkage under different drying conditions, also with the additional heating of the concrete samples was analysed. The strains were registered in the early stage of concrete curing, directly after mixing all concrete components, as well as in the later period, up to 28 days. The results indicate that the applied high volume of supplementary cementitious materials in self-compacting concrete (SCC) significantly reduces the shrinkage strains in comparison to SCC only made of OPC. Simultaneously, fly ash replacement is found as the most effective in reducing the free shrinkage of self-compacting concrete. The registered shrinkage development also shows the significant role and the level of very early shrinkage, which decided the values of 28-day strains. In the analytical part, the results from three used testing devices were compared with each other to confirm the effect of the non-clinker components on the shrinkage behaviour. Additionally, the results have been related to the Eurocode 2 and ACI shrinkage models, as well as the method for calculation of the differences in the shrinkage strains between the bottom and top surface of the sample based on measurements in the bending drain was presented.

Strength and Microstructure Assessment of Partially Replaced Ordinary Portland Cement and Calcium Sulfoaluminate Cement with Pozzolans and Spent Coffee Grounds.

Supplementary cementitious materials are considered a viable and affordable way to reduce CO2 emissions from the cement industry's perspective since they can partially or nearly entirely replace ordinary Portland cement (OPC). This study compared the impact of adding spent coffee grounds (SCGs), fly ash (FA), and volcanic ash (VA) to two types of cement: OPC and calcium sulfoaluminate cement (CSA). Cement samples were characterized using compressive strength measurements (up to 210 days of curing), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy, and hydration temperature measurements. In all the studied systems, the presence of SCGs reduced compressive strength and delayed the hydration process. CSA composite cement containing 3.5% SCGs, 30% FA, and 30% VA showed compressive strength values of 20.4 MPa and 20.3 MPa, respectively, meeting the minimum requirement for non-structural applications. Additionally, the results indicate a formation of cementitious gel, calcium silicate hydrate (C-S-H) in the OPC-based composite cements, and calcium alumino-silicate hydrate (C-A-S-H) as well as ettringite in the CSA-based composite cements.