Initial Setting Time Research Articles

Parametric optimization of Cement-based solidification combined with vacuum-assisted filtration

This study delves into the parametric optimalization of cement-based stabilized soft clays (CBSC) combined vacuum-assisted filtration (VAF) technique on for engineering applications, focusing on the influence of the retarder, calcium source and intermittent time etc. Key findings include VAF benefiting CBSC’s strength for water discharge from the paste, where the UCS of CBSC treated with VAF can increase more than ten times higher than the untreated samples (e.g., 767 kPa versus 60 kPa). The added retarders extend the initial setting time, thus facilitating the removal of excessive water, that the 0.2 % addition of calcium lignosulfonate causes 6.5 % increment of dewatering mass. Especially, calcium lignosulfonate, working as a versatile agent of imparting significant improvements in the rheological properties of cement mixtures and augmenting the structural integrity of clayey soils, was found to significantly enhance the VAF efficiency and the UCS, of which 28-day’s UCS further increases comparing to referential group after VAF. The study also reveals that calcium sources, such as desulfurized ash and lime, are also vital in replenishing calcium ions lost during VAF and maintaining a strong alkaline environment, significantly contributing to the strength enhancement. Additionally, the intermittent timing is also critical to the filtration efficiency, where the intermittent time was recommended within two hours post-mixing. These findings offer valuable insights for the practical application of CBSC by the VAF assistance, particularly involving soft clays with high water content.

Application study of seashell powder calcined sludge cement: Effects of different superplasticizer on working properties, mechanical properties and microstructure of materials

Seashell powder calcined sludge cement (SCSC) is a low carbon ternary cement prepared from waste seashells and waste sludge. However, the addition of seashell powder and calcined sludge reduces the working performance of the material and restricts the engineering application of SCSC. To enhance the adoption of SCSC in construction projects, this investigation evaluates the influence of three distinct superplasticizers—Polycarboxylate Ether (PCE), Sulfonated Naphthalene Formaldehyde (SNF), and Sulfonated Melamine Formaldehyde (SMF)—on the workability, mechanical strength, and microstructural properties of SCSC. The effects of superplasticizers on SCSC slurries were analyzed by mechanical property tests and macro-micro property characterization means such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), hydration thermal analysis and nuclear magnetic resonance (NMR). The results showed that the fluidity of SCSC slurries was increased by 73.3 %, 32 %, and 23.5 %, the initial setting time was extended by 29.6 %, 21.3 %, and 16.6 %, and the compressive strength was increased by 22.7 %, 19.6 %, and 5.7 % for the additions of PCE, SNF, and SMF at an amount of 0.25 %, respectively. The addition of superplasticizers prolonged the hydration induction period of SCSC, optimized the pore size distribution of the material, and reduced the structural porosity. The study shows that PCE has the best suitability for SCSC slurries, and should be preferred in the practical application of SCSC slurries. The results of the study can provide a reference for the application of SCSC slurries in engineering.

New geopolymer preparation methods and its application by recycle of double-waste: ground granulated blast furnace slag and fly ash

ABSTRACT This article mainly studies new geopolymer preparation methods by recycle of double waste:ground granulated blast furnace slag (GGBFS) and fly ash as geopolymer precursor, through different mass ratio of GGBFS and fly ash, to prepare geopolymers by alkali activation, the samples is cured at ambient temperature and the mechanical test is carried out together with the analysis of XRD, SEM and EDS to research the mechanism of strengthening and geopolymerisation. After analysis we find that the sample prepared by 30% mass ratio of GGBFS have good initial strength and short setting time, as well as best mechanical performance, which is attributed to moderate Ca2+ introduction accelerates the speed of geopolymerisation and the reactants of N-A-S-H gel, C-A-S-H gel and hydrated C-S-H help to bridge the gaps between the different hydrated phases, unreacted particles and matrix, result in a homogeneous and compacted geopolymeric sample. When GGBFS mass ratio above 50%, the mechanical of samples is deteriorated due to too much hydrated calcium containing compounds are formed and covered on the unreacted GGBFS particles surface to block further geopolymerisation. The acid attack test and water resistance test are carried out to analysis the durability between 30% GGBFS introduced geopolymer and ordinary Portland cement (OPC). In additional, a field application in case of 30% GGBFS introduced geopolymer grouting repair material indicated desirable construction based on visual observation and ground-penetration radar scanning.

Efficient utilization of coral waste for internal curing material to prepare eco-friendly marine geopolymer concrete

To address shortages in construction materials for island engineering, tackle the accumulation of solid waste, and inhibit the shrinkage of geopolymers, coral waste was utilized as the internal curing material to prepare high-performance marine geopolymer concrete (MGC) with seawater, sea-sand, and normal limestone aggregate (LsA). The coral coarse aggregate (CorA) used in this investigation has a total porosity ranging from 50% to 58.3% with internal pore diameters spanning 50–400 μm. The water desorption of CorA followed a two-stage pattern within a relative humidity (RH) range of 75%–85%, becoming nonlinear above 90% RH, which released about 85% of its moisture within 200 h at 97% RH, demonstrating potential for internal curing. Adding a small amount of CorA to MGC increased slump and setting time by providing internal curing water. However, as CorA content exceeded 30%, the slump significantly decreased due to reduced mixing water and elevated activator concentration, while the initial setting time slightly decreased. Furthermore, the inclusion of saturated CorA in MGC significantly reduced autogenous shrinkage, with higher CorA contents (exceeding 30%) leading to slight expansion in the early stages and nearly eliminating shrinkage at contents above 40%. The greater drying shrinkage in geopolymer systems compared to ordinary Portland cement is due to capillary pressure compressing the product framework, converting larger gel pores into smaller ones. Additionally, the layered calcium aluminosilicate hydrate (C-A-S-H) gel exhibits more pronounced creep characteristics under low internal humidity conditions. The higher CorA content in MGC promoted the formation of hybrid C, N-A-S-H gel and hydrotalcite-like phases, and reduced carbonation issues. The interfacial transition zone (ITZ) between CorA and the geopolymer matrix formed a robust mechanical interlock, enhancing tensile strength and minimizing shrinkage-induced cracks. Based on overall performance and marine material utilization, an optimal substitution rate of CorA between 40% and 50% is recommended.

Resource utilization of sulfidic copper tailings in calcium aluminate cement: Mechanical property, hydration process and environmental impact

Sulfidic copper tailings (STs) is a byproduct generated from mineral processing activities. To address this environmental burden, calcium aluminate cement (CAC) was used to utilize STs as cementitious materials. The influence of STs on the hydration process, mechanical properties and life-cycle assessment of STs blended CAC were investigated. Results show that the initial setting time of the samples is significantly shortened with the presence of STs. Moreover, the addition of STs greatly accelerates cement hydration and promotes the formation of ettringite, which is caused by the dissolution of sulfidic-rich STs. Hence, the hardened cement paste containing 5 wt.% STs with dense microstructure and high elastic modulus is achieved, which enhances the compressive strength for STs blended CAC. From an environmental point of view, the utilization of STs can save energy and reduce CO2 emissions. Such work may provide new insights into the application of sulfidic copper tailings in low-carbon cementitious materials.

Design and evaluation of alkali-activated slag-calcined coal gangue cement and the shrinkage control by calcium carbonate whisker

The rapid solidification and significant shrinkage of alkali-activated slag cement are key issues that restrict its practical engineering application. This paper explores the composition design of alkali-activated cements (AAC) with slow coagulation and shrinkage reduction. This paper adjusts the proportion of slag (SG) and calcined coal gangue powder (CCGP), regulates the content of Na2O·2.4SiO2-NaOH-Na2CO3 ternary activator components, and uses calcium carbonate whiskers (CW) instead of SG to prepare AAC with slow coagulation and shrinkage reduction. When the activator is composed of (66 %) Na2O·2.4 SiO2-(2 %) NaOH-(32 %) Na2CO3 mixed composition, the CO32- and Ca2+ in the system react preferentially to produce CaCO3. The decrease of Ca2+ concentration delays the formation of C-(A)-S-H, resulting in the initial and final setting time of AAC reaching 334 min and 346 min, respectively. When the CW substitution rate is 3 %, the 28d compressive strength of AAC reaches 102.2 MPa. The 49d drying shrinkage of the AAC is 7020μm/m and the 49d autogenous shrinkage is 2387μm/m. This is attributed to the combined effect of enhancement mechanisms such as whisker bridging, crack deflection, whisker pullout, whisker–matrix coalition pullout and whisker breakage. This study establishes the relationship between the composition and performance of high performance AAC, which is significance for the resource utilization of coal gangue and the practical engineering application of AAC.

Kajian Setting Time dan Permeabilitas pada Beton Variasi Limbah Granit Sebagai Subtitusi Parsial Agregat Kasar

Currently, infrastructure development is a priority of the Indonesian government which aims to improve the quality of life of the community and equitable distribution of infrastructure development. The need for concrete material as a construction material also increases in line with the increase in infrastructure development. The use of recycled aggregate materials, especially granite waste, is a promising option in sustainable infrastructure development. This study was conducted with the aim of knowing the effect of partial substitution of coarse aggregates using granite waste variations on the binding time and permeability of concrete. Experimental method was chosen in this research. The levels of granite waste used were 0%; 15%; 30%; and 45% by weight of coarse aggregate or gravel. The test specimens used for the concrete bond time study were fresh concrete poured into cube molds measuring 20 cm x 20 cm x 20 cm with a minimum height of 15 cm. Testing concrete bond time using a penetrometer tool. The test specimen for concrete permeability is a cube measuring 15 cm x 15 cm x 15 cm, totaling 12 pieces and tested with a Permeability Test Apparatus (Water Permeabilty Apparatus).The results showed that partial substitution of coarse aggregate with granite waste variation did not affect the setting time of concrete up to a certain level. Based on the results of the research conducted, the initial setting time and final setting time values of 0%, 15%, 30%, and 45% granite content variations fluctuate and the coefficient of determination (R2) value in linear regression is only 0.5 and 0.3. Partial replacement of coarse aggregate with granite waste has an effect on the impermeability of concrete which meets the requirements for medium aggressive impermeable concrete. Water pressure of 5 kg/cm2 for 72 hours applied to the concrete partial replacement of coarse aggregate with granite waste variation resulted in permeability coefficient values of 4.11 x 10-12 cm/s; 3.48 x 10-12 cm/s; 2.17 x 10-12 cm/s; and 3.25 x 10-12 cm/s. The minimum coefficient value of concrete with partial substitution of coarse aggregate with granite waste is obtained at 30% by weight of coarse aggregate. Granite, whose specific gravity is greater than gravel, produces denser and more water-resistant concrete.

Properties of self-curing and self-cooling eco-friendly novel green cement-based mortar

In this study, mullein plant (MP) (Verbascum Thapsus) was replaced with cement at a dosage of 300 (the amount of cement in mortar for producing 1 m3 mortar) in cement-based mortars at different weight ratios (0%, 1.5%, 3%, 4.5% and 6%). To investigate the impact of MP on the hydration (internal) temperature and the formation time of hydration products in mortars, the mortars' interior temperature and moisture ratios were measured and recorded every minute for one day. It was concluded that the MP had a high-water absorption capacity and delayed the initial and final setting times. The optimum ratio of MP as a replacement for cement was found to be 1.5%. The study also investigated the effects of direct current (DC) application on fresh mortars (both with and without MP). The results showed that the 7-day mechanical strength of the reference mortars exhibited a significant increase with the application of DC. Previous studies have not explored the use of MP in cementitious composite materials. This study concluded that adding a specific amount of MP to cement-based materials can provide self-curing and self-cooling properties. This research is critical for water conservation as it develops a novel self-curing method.

Wood ash-based binders for lightweight building materials: Evaluating the influence of hydraulic lime and cement on the setting and mechanical properties of wood ash pastes

The shift from fossil fuels to bioenergy has led to increased wood ash output. Since a large proportion of this waste ends up in landfills, recycling wood ash in construction materials is one of sustainable approaches of managing this by-product. However, the amount of biomass ashes currently recycled in building materials is still limited. This study therefore explored the feasibility of valorising four different types of wood ashes in large quantities in the production of lightweight building materials. Thirty pastes with different levels (80, 90, 95 and 100 wt%) of wood ash and (0, 5, 10 and 20 wt%) of natural hydraulic lime (NHL) or ordinary Portland cement (PC) were developed. Partial replacement of wood ash (WA) by NHL or PC accelerated the setting and improved the mechanical properties of blended pastes. The initial and final setting times decreased with increasing NHL or PC content in the mixes. The strength of the pastes increased with increasing NHL or PC levels and curing time. However, wood bottom ash (WBA) mixes were controversial because their mechanical properties gradually weakened over time. For WA-NHL blends, the 28-day flexural and compressive strength ranged from 0.02 to 1.12 MPa and from 0.05 to 2.59 MPa, respectively. On the other hand, for WA-PC pastes, the flexural and compressive strengths at 28 days varied from 0.07 to 2.72 MPa and from 0.13 to 5.49 MPa, simultaneously. These results prove that wood ash can be used effectively as a main component of binding matrices for lightweight building materials.

Feasibility of adding calcium hydroxide to FETNS–OPC: working performance, mechanical properties and reaction mechanism

To solve the problem of low early-phase reactivity of ferrous extraction tailings of nickel slag (FETNS), the effects of calcium hydroxide (Ca(OH)2) as an alkali activator on the working performance, mechanical properties and hydration products of FETNS–ordinary Portland cement (OPC) composite cementitious systems were studied. The addition of calcium hydroxide was found to shorten the initial setting time by about 40% and the final setting time by about 20%. The compressive strength at 3, 7, 28 and 60 days was increased by 51.95%, 45.27%, 8.53% and 8.9%, respectively, with the addition of calcium hydroxide. Microstructural assessment (by scanning electron microscopy, X-ray diffraction, simultaneous thermal analysis, nitrogen adsorption test and low-field nuclear magnetic resonance analysis) showed that the incorporation of calcium hydroxide increased the reaction degree of the FETNS–OPC system, and more calcium silicate hydrate gel and ettringite were generated to fill internal pores, thus improving the compactness of the matrix. In summary, the incorporation of calcium hydroxide stimulated the early-phase reactivity of the composite system, promoted the formation of reaction products and optimised the internal pore structure.

Optimisation of the performance of alkali-activated mortars using CDW binders from different sources

This study investigates the fresh-state properties and the hardened-state physical and mechanical properties of a total of 64 alkali-activated mortars incorporating different wastes as binders, such as fly ash (FA), recycled concrete (RC), recycled brick (RB), and recycled tile (RT). These waste materials were activated using sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Linear regression analysis was employed to evaluate the impact and significance of Na2O concentration (9 % or 15 %), modulus of silica (0.5 or 1), curing time in the oven (24 or 48 h), and temperature (50 °C or 70 °C) on the properties of the mortars. The results, analysed using ANOVA, indicate that all properties were affected by these parameters, except for the initial curing time in the oven for mortars made with construction and demolition waste (CDW), which showed no significant differences between periods of 24 and 48 h. Compared to mortars produced with RC, the contribution of these parameters to mechanical properties was more prominent in the mixes with RT and RB. The highest compressive strength at 28 days, for the mortars with CDW binders, was obtained by incorporating RT with 12 % of Na2O, modulus of silica of 1 and 70 °C for 48 h of initial curing, reaching 12.5 MPa. This value is 2.1 times higher than the strength obtained in mixes with RB or RC. The results also show that the performance of the mortars is highly related to the reactivity of the waste material (mortars with RT performed better) and prove that each raw material has its own optimum criterion.

Environmental-Friendly, Long-Lastingly Moist Phase Change Gel with Tunable Cross-Linking Time for Effective Borehole Sealing.

Flexible environmental phase change gel (EPCG) is a promising and attractive material for borehole sealing due to its relatively lower usage, tunable cross-linking time, and potential degradable properties. However, conventional borehole sealing materials lack a lower manufacturing cost, lower reaction temperature, remarkable antimold function, and admirable hole sealing performance for long-term high-performance borehole sealing. Hence, it remains a critical challenge to realize a flexible phase-change gel featuring tunable cross-linking time, antimold ability and degradability, and long-lasting moist performance for high-performance borehole sealing. Herein, we illustrate a facile approach to fabricate the borehole sealing materials based on environmentally friendly, antimold, long-lasting moist composite phase-change gel fabricated from a modified cellulose gel polymer network. The prepared phase change gel presents adjustable cross-linking time with the initial setting time of 30-60 min, which could be used to seal holes with different drilling parameters. Furthermore, the fabricated gel illustrates reliable water retentiveness performance and antimold ability, assuring the long-period borehole sealing effect. Furthermore, EPCG has been applied for borehole sealing and shows great sealing ability and gas extraction performance. Therefore, this work paves the way to fabricate a flexible phase-change gel featuring tunable cross-linking time, antimold ability, and long-lasting moist performance for high performance borehole sealing.

Data-driven models to predict the water-to-cement ratio and initial setting time of cement grouts

ABSTRACT As a common defect, the water–cement ratio of grout can currently be monitored only during the maintenance phase, which limits the repair methods and misses the optimal opportunity for repairs. To overcome this limitation, this study integrated ultrasonic parameters previously used to characterise cement-based materials and developed a new Initial Setting Time and Water–Cement Ratio (IST_WCR) risk model to predict the setting time and water–cement ratio grout using machine learning (ML) algorithms. Experiments on grout involved four different water–cement ratios, ranging from 0.11 to 0.18. A data-driven method based on ML was used to extract predictive factors from eight ultrasonic parameters, including the speed, energy, main frequency, and main frequency amplitude of P-waves and S-waves, and to evaluate multiple ML classifiers to establish the IST_WCR risk prediction model. This model underwent internal and external cross-validations and demonstrated very strong performance with a Brier score of under 0.01. The dataset for ML classifiers contained a total of 956 signals and 7648 features. Compared with traditional methods, this method can automatically characterise the setting process of grout and identify defective water–cement ratios at a very early stage of curing.

Experimental investigation on physical properties and early-stage strength of ultrafine fly ash-based geopolymer grouting material

The conventional cement grouting materials possess certain drawbacks that hinder their environmental compatibility. The utilization of geopolymer grouting materials with the raw material of fly ash is anticipated to serve as a proficient approach in mitigating the environmental problem caused by solid wastes. Consequently, this study employed ultrafine fly ash (UFA) and granulated blast furnace slag (GBFS) as composite base materials to fabricate a kind of novel geopolymer grouting material. The addition of 0.05 % − 0.2 wt% graphene oxide (GO) facilitated the preparation of this material, and the physical properties and early-stage strength were experimentally investigated. The micro-analysis was conducted using micro-analysis techniques, including Fourier transform infrared and energy dispersive X-ray spectroscopy, etc. The findings indicated that as the contents of GO and GBFS increased, the flowability slightly decreased; the addition of GBFS and GO can contribute to the elevation of viscosity; the initial and final setting times were decreased. The bleeding rate decreased and increased with increasing GO and GBFS contents. It was also found that the GO and GBFS were beneficial to increase the water retention rate. Furthermore, the inclusion of GO and GBFS significantly enhanced the early-stage compressive strength of the grouting material. The GO and GBFS contents of 0.1 % and 60 % resulted in the attainment of maximum compressive strength of samples, with the value of 15.89 MPa at the first day. The simultaneous utilization of GO and GBFS facilitates the generation of a greater quantity of calcium-alumina-silicate-hydrate gel, thereby substantially enhancing the initial compressive strength of grouting materials. The results of this study could provide valuable perceptions into the production of sustainable grouting materials with low carbon emissions and the recycling utilization of solid wastes.

Study on the basic properties of iron tailings powder-desulfurization ash mine filling cementitious material

Abstract To realize the recycling of iron tailings powder (IP) and desulfurization ash (DA) and reduce the high preparation cost of mine filling cementitious materials (MCs), this article adopts sodium carbonate (SC) as an activator to prepare iron tailings powder-desulfurization ash mine filling cementitious materials (IDMC). The effects of IP content, DA content, SC content, and mirabilite content on the mechanical properties and setting time are experimentally investigated. The micromorphology and phase compositions of the hydration products of IDMC are analyzed and characterized by scanning electron microscopy and X-ray diffraction. The results show that the initial setting time of the IDMC is reduced by 0.87 and 21.83% when the mirabilite content is increased from 0 to 1% and 2%, respectively, and the compressive and flexural strengths of the IDMC are increased by 24.01 and 86.25% when the IP content is increased from 0 to 20%, respectively. The IP not only participates in the hydration reaction but also plays an aggregate filling effect, significantly improving the mechanical properties of the IDMC. The pozzolanic effect is gradually enhanced with the increase of the DA content, and the hydration degree of the IDMC increases. The SC as an activator can moderately reduce the shrinkage rate of the IDMC. Based on the multi-index optimization analysis, the optimal mix proportion of the IDMC is obtained, which provides an effective reference for the preparation of the novel MC.

Impact of Calcined Natural Clinoptilolite Zeolite on Hydration Kinetics and Shrinkage of Cementitious Materials

Abstract Previous literature has provided contradictory results, so we present the current investigation to provide additional information to assess the suitability of using soak calcination as a pretreatment method to increase the performance of calcined zeolite when used as the supplementary cementitious material. In this study, natural clinoptilolite zeolite was calcined for three hours at 200°C, 400°C, 600°C, 800°C, and 1,000°C, and the effects of calcination on different physical and chemical properties were observed using a range of experimental tests. The impacts of calcined zeolite were investigated in the hydrated system with the replacement of portland cement up to 20 % by mass on hydration kinetics (i.e., heat of hydration, setting time, chemical shrinkage, degree of hydration), drying shrinkage, and compressive strength. Results revealed that calcination minorly decreased the crystallinity, particle size, and peak pore size of the zeolite, leading to a slightly increased external specific surface area, whereas it increased the rate of moisture absorption and pH of zeolite particles. In the hydrated cementitious system, calcined zeolite reduced the workability and heat of hydration and retarded the initial setting time. The calcined zeolite particles absorbed a part of the water from the fresh mixture and expanded volumetrically, which led to a negative volume of chemical shrinkage up to the final setting time and increased the drying shrinkage. As the dosages of calcined zeolite increased, the compressive strength substantially decreased because of the lower degree of hydration. Overall, soak calcination pretreatment decreased the reactivity of clinoptilolite zeolite particles and impacted the performance of calcined zeolite in the blended system.

Influence of SiO2@CaAl-LDH core-shell nanocomposite on rheology and hydration of cement

Nano-SiO2@ Layered double hydroxide (LDH) core-shell nanocomposite shows a promising application as high-efficiency chloride adsorbent in cement-based materials. However, its effect on rheology and hydration of cement is not yet known. In this study, the SiO2@CaAl- LDH core-shell nanocomposite by growing the LDH on nano-SiO2 surface was firstly created using in-situ co-precipitation method. The influence of as-synthesized nanocomposite on the rheology and hydration of cement was systematacially researched through contrasting experiments. Besides, microstructures of SiO2@LDH and its cement paste were characterized. The results show that the LDH with petal-like shape on the nano-SiO2 surface exhibits a higher specific area than pure nano-SiO2 and LDH alone. The addition of SiO2@CaAl-LDH core-shell material significantly shortens the initial and final setting time of cement and increases cement hydration heat generation rate and the total exothermic amount for 72 h. Contrary to the mixture of LDH, the additions of nano-SiO2 and SiO2@LDH increases the yield stress and plastic viscosity of cement paste. Compared to the additions of LDH and SiO2, the addition of SiO2@LDH more significantly enhances the strength of cement, of which the highest increasing level reaches 66 % at the early age of 1 d. In addition, SiO2@LDH exhibits the best refinement effect on the pore structure of cement because of the synergetic effect between the LDH and nano-SiO2.

Effect of Superabsorbent Polymers and Presoaked Coarse Recycled Shale Lightweight Aggregates on Relative Humidity Development in Early-Age Concrete

Self-desiccation-induced shrinkage may result in cracking at an early age, which is averse to the durability of concrete. Internal curing (IC) agents, such as superabsorbent polymers (SAP), are normally used for moisture regulation and shrinkage reduction. In addition, the make-up of recycled shale lightweight aggregate (RSLA) results in a good absorbing capacity, which makes it a potential candidate for IC. In this paper, the synergistic effect of SAP and RSLA on the relative humidity (RH) variation in early-age concrete under sealed conditions is investigated experimentally in terms of the setting time, relative humidity, and autogenous shrinkage. The results indicate that adding SAP and presoaked RSLA can significantly postpone the initial and final setting times. The initial setting time of RSLA30 and SAP06 is delayed by 127 and 171 min, respectively, compared to the benchmark mixture. In addition, increasing the amounts of SAP and presoaked RSLA can effectively extend the duration of the vapour-saturated stage, reducing the decrease in RH and autogenous shrinkage at 28 days. When the RSLA dosage increases from 0 to 10%, 20%, and 30%, the duration of the vapour-saturated stage is extended by 2, 9.4, and 26 days, respectively. Moreover, due to different water desorption behaviours, more IC water released by RSLA during the initial stage can slow the water release of SAP and lead to a higher RH level at 28 days.

REVIEW: AN EXPERIMENTAL STUDY ON EFFECT OF NANO MATERIALS ON STRENGTH OF CONCRETE AND PLANE STRESS ANALYSIS USING ANSYS SOFTWARE

These days, making efficient and cost-effective use of resources has taken precedence. The main ingredient in concrete, cement has been under criticism in recent years for the quantity of CO2 released during production. Although cement has better mechanical properties, it hasn't been able to live up to the expectations in terms of durability. Owing to cement's shortcomings, scientists started looking into additives that would enhance concrete's qualities while also making it stronger and lighter. Fly ash, silica fume, and other micro particles were added to cementitious materials to improve their compactness, strength, and durability. These additives were also selected because they are eco-friendly by products of industrial waste that may be handled ethically. Fly ash has significant disadvantages because it is not good for initial strength increase and setting time. Because silica fume affects cementitious material performance, researchers have recently become interested in combining it with ceramic waste and rice husk ash. A more effective way to utilize rice husk ash, a by-product of rice cultivation, would be to replace 10% to 15% of cement. Studies have shown improvements in the durability performance of recycled ceramic waste concrete and rice husk ash concrete. There are issues since the RHA production process is quite time-consuming. With the discovery of nano-particles (NP) smaller than 100 nm, researchers have advanced the field of nanotechnology to new levels. The mechanical properties of many materials, including polymers and cementitious materials, can be enhanced by NP. NP is also helpful in the fields of food, engineering, and medicine. This led researchers to investigate the effects of nano-silica (NS) on concrete in further detail. Nano materials can improve the compressive strength and ductility of concrete. In this project an effort will be made to increase the compressive strength of concrete using Nano materials and waste product like GGBS. Also plane stress analysis of concrete cubes and cylinders is to be done using Ansys Software to find deformation, principal stresses and shear stresses. Keywords: Nano –Silica, Nano Titanium dioxide, Ansys, GGBS, Compressive strength

Synergetic impact of volcanic ash and calcium carbide residue on the properties and microstructure of cementitious composites

The synergetic impact of using volcanic ash (VA) and calcium carbide residue (CCR) on the engineering properties of cementitious mortar was assessed. Cement was replaced with VA at 0–40 % by mass and/or CCR at 0–20 % by mass. Blended mortars were tested for flow, setting time, compressive strength, and ultrasonic pulse velocity (UPV). The flow increased when using VA but decreased with the inclusion of CCR. Compared to the cement-based control mix, ternary mixes had a lesser flow. The impact of VA replacement on the initial and final setting times was marginal until a substitution rate of 40 %, after which the setting times were prolonged. Similarly, the setting time was extended with CCR replacement. The compressive strength and UPV improved with the use of 10–20 % VA and/or 5 % CCR for binary and ternary mortar mixes, with the highest strength of 55.4 MPa and UPV of 4490 m/s being recorded for the mix comprising 20 % VA and 5 % CCR. Mixes were further analyzed through isothermal calorimetry, X-ray diffraction, and scanning electron microscopy. The cumulative heat generation was reduced for binary and ternary mixes except for those containing 20 % VA only. The microstructure analysis highlighted the formation of C-S-H and C-A-S-H as reaction products and the consumption of Ca(OH)2. This study provides novel insights into optimal combinations of VA and CCR for superior mortar performance, offering practical approaches to reducing cement content and lowering carbon emissions without compromising performance.