Portland Cement Mixes Research Articles

Sustainable Concrete Production: Utilizing Cow Dung Ash and Corn Stalk Ash as Eco-Friendly Alternatives

This study aims to determine whether it is feasible to replace conventional materials used in manufacturing concrete with waste materials, namely cow dung ash and corn stalk ash. This study proposes to assess the possibility of using these agricultural by-products to improve the sustainability of concrete while simultaneously tackling the environmental issues related to the manufacture of conventional concrete. The research aims to assess the mechanical qualities, optimize the mix proportions, and examine the ecological implications of using these substitute materials. This research aims to mitigate environmental challenges like carbon dioxide emissions, resource depletion, and the accumulation of agricultural waste by combining agricultural waste and lowering dependency on traditional cement. The study investigates the use of cow dung ash (CDA) and corn stalk ash (CSA) as alternatives for conventional Portland cement (OPC) in mortar mixes at varying quantities, ranging from 5% to 25% CDA and 2.5% to 10% CSA. Chemical composition reveals that CDA and CSA predominantly comprise O, Mg, Al, Si, P, K, and Ca. The workability, hardened characteristics, and microstructure of CDA and CSA were assessed. Increasing CDA and CSA percentages reduced mortar workability; nevertheless, replacing 8% to 10% CDA and 7.5% CSA maintained compressive, tensile, and flexural strengths comparable to control mixes. However, more significant CDA and CSA proportions resulted in lower mortar strength. For example, 10% CDA-enriched mortar had a compressive strength of 31.77 N/mm2, a tensile strength of 3.42 N/mm2, and a flexural strength of 3.61 N/mm2, whereas 7.5% CSA-enriched mortar had a compressive strength of 28.4 N/mm2, a tensile strength of 3.04 N/mm2, and a flexural strength of 3.7 N/mm2. According to the findings, CDA and CSA can replace OPC by up to 10% and 7.5% in mortar manufacturing, making cementitious material alternatives viable. Doi: 10.28991/CEJ-SP2024-010-02 Full Text: PDF

Enhancing hydration and internal curing in cementitious mixes: The impact of pre-treated milkweed fibres

This study investigates the internal curing effects of milkweed fibres (MW) in Portland cement mixes, exploring various dosage levels and pre-treatment methods. The study first assessed the impact of MW fibres on the effective water-to-cement (w/c) ratio through rheological measurements, enabling accurate comparisons of samples with identical effective w/c ratios. Both MW fibre pre-treatments and dosages were found to impact the effective w/c ratio in the mixes, leading to the categorization of MW fibre-incorporated samples into three groups based on their effective w/c ratio. In the subsequent phase, the internal curing effect and hydration characteristics of cementitious mixes were evaluated with varying dosages of MW fibres. Optimal internal curing performance was achieved with 0.1% pre-treated MW fibres compared to 0.2%, resulting in up to a 17% improvement in the degree of hydration compared to the reference sample with the same effective w/c ratio. This showed the adverse effect of higher percentage due to the reduction in the free water availability and higher leaching of extractives, which further intensified the hindrance of the hydration process. Furthermore, microstructure analyses, including TGA/DTG, XRD, and SEM-EDS, of cementitious mixes incorporating MW fibres confirmed that the inclusion of 0.1% hybrid and hydrothermally-treated MW fibres resulted in a higher formation of hydration products. This is achieved by providing an adequate amount of free water for the initial reaction of cement hydration and entrained water in the lumen for the subsequent internal curing. These findings show the effectiveness and suitability of using pre-treated MW fibres for internal curing applications, as validated by the comprehensive analyses conducted in this study.

Stabilisation of estuarine sediments with an alkali-activated cement for deep soil mixing applications

In this work, an alternative alkali-activated cement (AAC) made of ladle slag precursor mixed with sodium hydroxide and sodium silicate has been developed to enhance the bearing capacity of estuarine soils in coastal conditions via deep soil mixing (DSM). The AAC was optimized to use a low reactivity precursor (ladle slag) and to deal with a contaminated high-water content natural sediment cured under water. The material performance was analysed by comparison to a mixture made with Portland cement and cured in the same conditions. Flexural and unconfined compressive strength tests as well as seismic waves measurements after 3-, 7-, 14- and 28-d curing were performed to obtain a relationship between elastic stiffness and strength with curing time for both mixtures. Remarkably, the AAC mix demonstrated superior strength results, exhibiting almost double flexural and compressive strengths after 28 d compared to the Portland cement mix. The AAC mix also showed a higher rate of stiffness increase than the Portland cement mix, which has a higher initial stiffness at young ages but lower stiffness evolution. Leachate analysis confirmed that the proposed AAC could effectively immobilise any contaminants from soil or precursors. The effect of curing under stress was analysed in triaxial compression tests and found to be insignificant, indicating that laboratory data obtained without stress curing can represent the material's behaviour in a DSM column, which will cure under the weight of the column.

Improved ettringite stabilization by calcium carbonate and calcium nitrate additions in ternary PC-CSA-C$ systems

Mixing Portland cement (PC) and calcium sulfoaluminate (CSA) cement can provide several advantages for specific applications. However, the stability of ettringite has a significant impact on ettringite-rich cements properties. This study aims to investigate the impact of calcium nitrate (Ca(NO3)2 = CN) and calcium carbonate (CaCO3 = CC) on the performance evolution and stabilization mechanism of PC-CSA-C$ systems. The experimental results demonstrate that the incorporation of CC and CN has a significant impact on the early hydration kinetics. A second exothermic peak appears indicates the depletion of the calcium sulfate, and its appearance time is related to the amount of CC and CN added. The blended system containing CN exhibited the highest early and late compressive strength, as well as excellent volume stability. Compared with CC, CN was confirmed to be more effective in stabilizing ettringite in the PC-CSA-C$ system and preventing its conversion into monosulfate. Furthermore, the analysis of the pore structure reveals a significant increase in the proportion of pores with diameters ≤50 nm in the systems containing CN. In particular, CN displays a stronger ability to stabilize ettringite to reduce chemical shrinkage and increase the content of C-(A-)S-H gel, and the 28-day compressive strength was approximately 10 MPa higher compared to the control group.

Passivation of reinforcing steel in reactive MgO cement blended with Portland cement

Reactive MgO cement (RMC) has an ability to gain strength by carbonation. One of the main concerns in RMC systems is the potential corrosion of reinforcing steel in structural applications. This study evaluated the feasibility of replacing small proportions of RMC with Portland cement (PC) to promote the passivation of reinforcing steel. Reinforcing steels embedded in RMC with different proportions of PC were investigated by electrochemical measurements and microstructural analysis. Pore solutions extracted from these pastes were evaluated for their chemical compositions. Inclusion of ≥2% PC enabled the passivation of steel. Passive film forming in RMC-PC blends consisted of Fe3O4 and Mg(OH)2, which was thicker than those in pure PC mixes. The formation of passive film was mainly attributed to the increased pH of the pore solution, which reached over 12 in RMC mixes containing only 2% PC. These findings highlighted the potential of using RMC mixes in reinforced concrete applications.

The Compressive Strength and Microstructure of Alkali-Activated Mortars Utilizing By-Product-Based Binary-Blended Precursors

Researchers have investigated the feasibility of using ultrafine palm oil fuel ash (u-POFA) as a cement replacement material because of its potential to reduce the environmental impact of concrete production. u-POFA, a by-product of palm oil fuel combustion, is a suitable replacement for Portland cement in concrete mixes because of its sustainability and cost-effectiveness. This study investigated the microstructural and compressive strengths of alkali-activated mortars (AAMs) based on fly ash (FA) and granulated blast-furnace slag (GBFS) being added with varying percentages of u-POFA. The mixture samples were prepared in eighteen mortars using sodium metasilicate (Na2SiO3) as the source material and sodium hydroxide (NaOH) as the alkaline activator. This study used field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, X-ray diffraction, X-ray fluorescence, and Fourier-transform infrared spectroscopy to characterize the binary-blended mortars after 28 days of curing and determined the strength of the FA+GBFS (87.80 MPa), u-POFA+GBFS (88.87 MPa), and u-POFA+FA mortars (54.82 MPa). The mortars’ compressive strength was influenced by the CaO/SiO2 and SiO2/Al2O3 ratios in the mixture, which was directly due to the formation rate of geopolymer products of the calcium–alumina–silicate–hydrate (C–(A)–S–H), aluminosilicate (N–A–S–H), and calcium–silicate–hydrate (C–S–H) phases. Based on the contents of FA and GBFS, u-POFA significantly enhanced concrete strength; therefore, u-POFA used in a suitable proportion could enhance binary-blended AAMs’ microstructure.

Relationship between electrical Conductivity, Half cell Potential, Linear polarization resistance and Macrocell current of cementitious repair materials

Corrosion degradation of RC could lead to instability and eventually the collapse of structures if not detected early. Electrochemical methods like Half Cell Potential (HCP), Linear Polarization Resistance (LPR), Macrocell Current and Electrical Conductivity were used in this research to evaluate the relationship between these four non-destructive methods. These four Non-Destructive Test (NDT) methods were used to assess the resistance against chloride attack on three different types of cement-based materials and Ordinary Portland Cement mix (control). Experimental research conducted in this study reveals that there is a linear relationship between electrical conductivity and corrosion current. There is also a fairly good relationship between corrosion current and half cell potential when measuring the degree of corrosion potential and corrosion current for all three repair materials and the control, showing a R2 = 0.72. However, there is an insignificant relationship between corrosion current and macrocell current showing a value of R2 = 0.66.

Use of finely ground basalt as a mineral admixture in blended Portland cement production

Basalt powder is an active mineral admixture used commonly in the production of mixed Portland cement in Vietnam. Addition of basalt powder may improve many important properties of cement and cement concrete: increasing compressive and flexural strength at late age, increasing sulphate sulfate resistance, increasing freeze-thaw resistance, reducing water absorption, and reducing heat of hydration. However, the use of basalt powder with the same fineness as cement currently has the disadvantage of reducing the compressive strength of cement from the initial stage up to 90 days or 180 days. The magnitude of the decrease was greater at earlier ages than at later ages. This disadvantage of basalt power limits its amount that can be added in blended Portland cement production. In theory, increasing the fineness can increase the activity of basalt powder. Therefore, the objective of this study was to evaluate the possibility of using finely ground basalt powder as a mineral admixture in the production of blended Portland cement, by determining the influence of basalt powder of different fineness (Blaine 3600 cm2/g, 4800 cm2/g and 6000 cm2/g) on some properties of Portland cement. The investigated properties of cement included water of consistency, setting time, compressive strength at 1, 3, 7, and 28 days, and soundness. The results show that, increasing the fineness of basalt increased slightly the water demand and setting time of cement. Increasing the fineness of basalt powder increased significantly the strength of cement at early ages and increased less significantly at late ages. Therefore, the use of finely ground basalt can minimize the disadvantage of basalt powder, then allow to increase its content that can be added in the production of blended Portland cement.

Diatomites from the Iberian Peninsula as Pozzolans.

The object of this work is to study and characterize diatomites from the southeast of the Iberian Peninsula to establish their character and quality as natural pozzolans. This research carried out a morphological and chemical characterization study of the samples using SEM and XRF. Subsequently, the physical properties of the samples were determined, including thermic treatment, Blaine particle finesse, real density and apparent density, porosity, volume stability, and the initial and final setting times. Finally, a detailed study was conducted to establish the technical properties of the samples through chemical analysis of technological quality, chemical analysis of pozzolanicity, mechanical compressive strength tests at 7, 28, and 90 days, and a non-destructive ultrasonic pulse test. The results using SEM and XRF show that the samples are composed entirely of colonies of diatoms whose bodies are formed by silica between 83.8 and 89.99% and CaO between 5.2 and 5.8%. Likewise, this indicates a remarkable reactivity of the SiO2 present in both natural diatomite (~99.4%) and calcined diatomite (~99.2%), respectively. Sulfates and chlorides are absent, while the insoluble residue portion for natural diatomite is 1.54% and 1.92% for calcined diatomite, values comparatively lower than the standardized 3%. On the other hand, the results of the chemical analysis of pozzolanicity show that the samples studied behave efficiently as natural pozzolans, both in a natural and calcined state. The mechanical tests establish that the mechanical strength of the mixed Portland cement and natural diatomite specimens (52.5 MPa) with 10% PC substitution exceeds the reference specimen (51.9 MPa) after 28 days of curing. In the case of the specimens made with Portland cement and calcined diatomite (10%), the compressive strength values increase even more and exceed the reference specimen at both 28 days (54 MPa) and 90 days (64.5 MPa) of curing. The results obtained in this research confirm that the diatomites studied are pozzolanic, which is of vital importance because they could be used to improve cements, mortars, and concrete, which translates to a positive advantage in the care of the environment.

Testing The Compressive Strength Of Concrete With The Utilization Of Rice Husk Ash And Palm Fiber

Development in the field of structure is currently progressing very rapidly in various field so that concrete is one of the choices as a structural material in building construction, basically concrete is made by mixing portland cement, coarse aggregate, fine aggregate, and water as a binder for these materials. Due to the development of the issue of current resource limitations, the prevention is by innovating the manufacture of concrete using palm fiber waste as an added ingredient from sand and rice husk ash waste as an added ingredient from cement. The purpose of study was to (1) analyze the compressive strength of concrete with variations ini rice husk ash and palm fiber (2) analyze the addition of rice husk ash and palm fiber with different mixture variations that could affect the compressive strength of concrete. The result showed that normal concrete with an average compressive strength of 24.20 MPa and an increase in compressive strength with a mixture of 0.5% palm fiber and 5% rice husk ash with an average strength of 25.90 MPa without using superplasticizer, if the variation mixture exceeding the mixed variation of 0.5% palm fiber and 5% rice husk ash will deacrease

Effect of calcined clay and marble dust powder as cementitious material on the mechanical properties and embodied carbon of high strength concrete by using RSM-based modelling

In the last decade, there has been an increase in research on ecologically benign, cost-effective, and socially useful cement alternative materials for concrete. Alternatives involve industrial and agriculture waste, the potential advantages of which may be recognized by recycling, repurposing, and recreating techniques. Important energy reserves and a decrease in Portland cement (PC) consumption may be attained by using these wastes as supplementary and substitute ingredients, contributing to a reduction in carbon dioxide (CO2) production. Consequently, the incorporation of marble dust powder (MDP) and calcined clay (CC) as supplementary cementitious material (SCM) in high strength concrete may lower the environmental effect and reduce the amount of PC in mixes. This study is conducted on concrete containing 0%, 5%, 10%, 15%, and 20% of MDP and CC as cementitious materials alone and in combination. The main objectives of this investigations are to examine the effect of MDP and CC as cementitious materials on the flowability and mechanical characteristics of high strength concrete. In order to examine the ecological effect of CC and MDP, the eco-strength efficiency and embodied carbon were considered. In this context, there are so many trial mixes were performed on cubical specimens for achieving targeted compressive strength about 60 MPa after 28 days. After getting it, a total of 273 concrete specimens (cubes, cylinders, and prisms) were used to test the compressive, splitting tensile, and flexural strength of high strength concrete correspondingly. Moreover, when the amount of MDP and CC as SCM in the mixture grows, the workability of green concrete decreases. In addition, the compressive strength, flexural strength, and splitting tensile strength are increased by 6.38 MPa, 67.66 MPa, and 4.88 MPa, respectively, at 10% SCM (5% MDP and 5% CC) over a period of 28 days. In addition, using ANOVA, response prediction models were generated and confirmed at a 95% level of significance. The R2 values of the models varied from 96 to 99%. Furthermore, increasing the amount of CC and MDP as SCM in concrete also reduces the amount of carbon embedded in the material. It is recommended that the utilization of 10% SCM (5% MDP and 5% CC) in high strength concrete is providing optimum outcomes for construction industry in the field of Civil Engineering.

The Effect of Construction Wastes in Concrete Bricks for Load Bearing Wall

Natural disasters, demolition projects, and construction projects generate massive waste. Materials from demolition, roadwork, and excavation were included in the “construction wastes” category, and more complicated wastes, including cardboard, plastic, metal, and ceramic. The objective of this study focused on the possibility of utilizing construction wastes such as plastic wastes such as reinforcing steel bars, tiles, tie wires, and nails in making effective concrete bricks for the load-bearing wall. Construction wastes such as 10%, 15%, and 20% were used to replace aggregates in concrete. Laboratory tests, such as compressive strength and water absorption tests, were carried out to evaluate replacements on the properties of ordinary Portland cement mixes. Results showed that as the amount of construction waste increases, the compressive strength of brick significantly increases. Also, as the percentage of construction wastes increases, with decreasing sand percentage, the water absorption decreases. Thus, this study on creating sand bricks from construction wastes as a replacement for aggregate is an excellent possibility for utilizing as building and construction material and a workable solution in combating the waste problem.

Ultrasound Non-Destructive Characterization of Early Hydration of Cement Pastes: The Effects of Water-Cement Ratio and Curing Temperature

A newly developed ultrasound method that acquires at the same time both reflected and transmitted P-waves, at different angles, using two immersion transducers of 0.5 MHz central frequency, is described in this present study. This non-destructive method allows calculating the longitudinal and transverse velocities, and thus, the Young modulus, so that its evolutions is followed in time domain. The closely correlation between the evolution in time domain of those calculated parameters and hydration properties of cement based materials was used to characterize the effects of different water-cement ratio and curing temperatures on early age hydration behaviour of cement pastes. To do so, cement samples were prepared by mixing Portland cement and freshwater. Results indicates that lower water to cement ratio reduces the workability and increases the Young modulus of resulted cement medium. Also, both ultrasound velocities and Young modulus values increases linearly with increasing curing temperature.

Mechanical and durability performance of alkali-activated slag cement concretes with carbonate and silicate activators

In the race for decarbonization, the construction industry is increasingly turning its interest to alkali-activated cements (AAC) as an alternative to Portland cement (PC). This paper studies sodium carbonate (Na2CO3) as a potentially environmentally-friendlier and cheaper activator of ground granulated blastfurnace slag (GGBS) in comparison to Na2SiO3 or combined Na2SiO3-Na2CO3 activators. The laboratory study started with an investigation of suitable mixing procedures, after which mechanical and durability testing was performed under four curing conditions. Ambient temperature with high-moisture curing gave better strength gain in time, whereas thermal curing gave the highest early strengths and lowest absorption and porosities but strengths stopped evolving at later times. The strengths of all tested AAC mixes were suitable for structural concrete although those containing Na2SiO3 had the highest strengths at all curing conditions and ages. For the mix with Na2CO3 only (suitable for C30/40 grade concrete vs C50/60 concrete for the mixes containing Na2SiO3) strengths were evolving considerably with curing time despite the lower early strengths. All mixes with AAC performed better in terms of chloride attack (accelerated corrosion test) compared to the PC mix, despite their higher water absorption and, in most cases, porosity. AAC mixes with Na2CO3 only (as activator) were the least affected in terms of strength after exposure to sulphates. Overall, the study gives promise that Na2CO3-activated slag can be a good AAC system as alternative to PC towards an increased sustainability in the construction sector.

Effect of Phaeodactylum Tricornutum in Seawater on the Hydration of Blended Cement Pastes

Seawater can be used as mixing water for concrete with no steel reinforcement in some areas with difficult access to fresh water. Diatoms such as Phaeodactylum tricornutum are among the most abundant micro-organisms living in seawater, and they could be unavoidable when collecting seawater. In fact, diatoms can provide bio-SiO2 and bio-CaCO3 sources, namely amorphous nano-SiO2 and crystallised nano-CaCO3, which could be beneficial to cement hydration. Thus, the effects of different Phaeodactylum tricornutum concentrations (0%, 2.5% and 5% by weight of suspension of seawater and diatoms) in seawater on cement hydration in ordinary Portland cement (OPC) mixes (100% OPC) and ground granulated blast-furnace slag (GGBS) mixes (70% OPC + 30% GGBS) were investigated through tests of compressive strength, XRD, DTG–DTA and SEM. The results show that diatoms accelerated cement hydration by providing the nucleus for C-S-H structure and contributed pozzolanic reactions by amorphous nano-SiO2 and nano-CaCO3. The accelerated cement hydration was also confirmed by the fact that more Ca(OH)2 was formed in cement pastes with diatoms. However, it has also been found that diatoms decreased the compressive strength of cement pastes by leaving more weak bonds between the C-S-H structure, which was considered to be caused by the organic parts and the micron gap formed in diatoms. When comparing an OPC paste mix with 5% diatoms to a blank OPC paste, the reduction in compressive strength at 28 days can reach a maximum of 50.1%. The ability to provide bridging effects between C-S-H particles in GGBS paste was discovered to depend on the development of additional ettringite. This resulted in a 7.6% loss in compressive strength after 28 days in a GGBS paste with 5% diatoms.

Comparative analysis of the geopolymer and Portland cement application as plugging material under conditions of incomplete displacement of drilling mud from the annulus

Portland cement is traditionally used in cementing of oil and gas wells. However, Portland cement has a number of shortcomings. The most important of these are the formation of microannuli between the cement plug and the rock or casing, as well as the formation of cracks and permeable channels in the cement matrix. Recent research shows that geopolymer can be a perspective alternate to portlandcement by overcoming beforementioned issues. The article comparatively analyzes the changes in the parameters of plugging materials containing geopolymer and Portland cement while contamination with water-based drilling mud. The results show that geopolymerbased solutions are more resistant to contamination with water-based drilling mud than Portland cement-based solutions. Thus, mixing Portland cement slurry with water-based drilling mud increases its viscosity and fluid loss, and sharply reduces its compressive strength. However, when a geopolymer solution is mixed with a water-based drilling fluid, its viscosity is almost unchanged, its fluid loss is reduced, and reduction in its compressive strength is less than in Portlandcement based material. Keywords: portland cement; geopolymer; fly ash; cementing; water based mud; mud contamination.

Early-age hydration characteristics and kinetics model of blended cement containing waste clay brick and slag

Low-carbon blended cement was prepared by mixing Portland cement, clay brick powder (CBP) and slag. The early-age hydration mechanism was studied by analyzing the hydration characteristics and kinetics parameters of blended cement with different admixture replacement rate, CBP to slag ratio and temperature. The results indicate that increasing admixture replacement rate accelerates cement hydration and leads to the displacement of exothermic peaks. However, the reduced C3S content in blended cement reduces the peak intensity and reaction rates of NG-I-D (nucleation and crystal growth - phase boundary reaction - diffusion) processes. Slag promotes the nucleation and growth of C–S–H gel slightly more than CBP before the third exothermic peak. Then, the slag reaction in the deceleration period consumes a lot of sulfate ions, resulting in the high third exothermic peak. High temperature provides nucleation driving force to accelerate the cement dissolution and ions migration, thus, the reaction rates of NG-I-D processes are increased as the temperature rises.

ANALISIS PERBANDINGAN PASIR JAMBI DAN PASIR PONTIANAK TERHADAP KUAT TEKAN BETON

This study aims to analyze the comparison of Jambi sand and Pontianak sand to the compressive strength ofconcrete. Concrete is a mixture obtained by mixing Portland cement, water and aggregate, which is an additivethat varies greatly from chemical additives. For the construction of roads, bridges, buildings, etc. which are in theconcrete mix. Aggregate is the largest part in the formation of concrete, while cement and water will form a pastethat will bind the aggregate. Concrete is a function of its constituent materials consisting of cement, hydraulic,fine aggregate, water and admixture additives. In this study, there are two types of fine aggregate used, namelyJambi Sand and Pontianak Sand. The quality results of Jambi Sand met the organic standard and test by achievinga result of 3, while the quality of Pontianak Sand on the organic test reached 5, and in terms of specific gravity,Pontianak Sand was better than Jambi Sand. The results of the compressive strength of concrete with Jambi Sandand Pontianak Sand were found to be stronger with Pontianak Sand with an average of 63.60

Durability performance of geopolymer ferrocement panels prepared by different alkaline activators

Ferrocement is a composite material consisting of a steel mesh bonded mortar used to form thin sections in numerous applications. Corrosion of ferrocement is more critical than the conventional reinforced concrete because of the small diameter of wire mesh and small concrete cover. This study aims to investigate the durability of fly ash-based geopolymer ferrocement composites. The accelerated corrosion test was conducted on ferrocement panel specimens with various affecting parameters. Series of ferrocement panel specimens were cast. The studied parameters included; type of steel wire mesh (welded, woven and expanded), thickness of panel specimens (20, 25 and 30 mm), number of mesh layers (1, 2 and 3 layers) and type of mortar mixtures. Four geopolymer (GP) mortar mixes were prepared with four different alkaline solutions. The alkaline solutions were a mixture of sodium silicate (NS), sodium hydroxide (NH), potassium silicate (KS) and potassium hydroxide (KH) as NS + NH, NS + KH, KS + NH and KS + KH. Parallel with the investigated GP mixture, a Portland cement mix was prepared. All mortar mixes were exposed to different aggressive environments including 5% sulphuric acid (H2SO4) and sodium sulphate for 24 weeks as well as water absorption test was conducted. Test results indicated that using a thicker steel mesh such as woven mesh, a thicker mortar cover and more than one layer in ferrocement panel specimens provides more resistance against reinforcement corrosion. The investigated GP mortar mixes provide a good passivation protection than cement mortar. Moreover, the fly ash-based GP mortar activated by NS showed passivation protection of steel wire mesh greater than the fly ash-based GP mortar activated by KS and showed a higher resistance to sodium sulphate and sulphuric acid exposure.

Shrinkage, hydration, and strength development of limestone calcined clay cement (LC3) with different sulfation levels

This study investigated autogenous shrinkage of limestone calcined clay cement (LC3)-based mixes with various sulfation levels of hemihydrate. Physicochemical evolution and strength development were also monitored. Superior mechanical performance of the mixes was achieved at an optimal sulfation level, although the shrinkage was reduced with the sulfate content. Calorimetry data showed the hemihydrate delayed and broadened the second aluminate peak. Both gypsum and ettringite formed early during hydration, and carboaluminates were observed after 3 days of curing. Ettringite in the LC3 mixes was of smaller sizes in comparison to that in the ordinary Portland cement (OPC) mixes, attributable to the pore refinement in the LC3 matrices. The content of portlandite (Ca(OH)2) was reduced with the curing time due to pozzolanic reactions. The findings demonstrated a coupling effect of both the chemical and microstructural change on the observed autogenous shrinkage and the consequent performance of LC3-based concrete composites.