Calcined Clay Research Articles

Influence of curing methods on properties of mine overburden-based geopolymer aggregate

Many earlier studies have focused on using calcined clay rather than raw clay for conventional geopolymerization methods to manufacture coarse aggregate. This paper deals with utilizing overburden soil, having low silica and alumina content, which is available in large quantities from the mining industry, as coarse aggregate, through pelletization. This study adopted geopolymerization for the effect of sodium-silicate-hydroxide activators and geopolymer precursors such as fly ash and ground granulated blast furnace slag by varying the alkaline concentration. Unlike the conventional sintering-based hardening method, the present study used oven-curing and short-duration microwave sintering as hardening methods. We assessed the effect of mix and hardening methods on the relative performance of aggregates through density, strength, water absorption, and strength-to-density relationship of geopolymer aggregates. Increased alkaline concentration improved the pelletization efficiency and fineness modulus of aggregates. The aggregate's density and water absorption primarily depend on the alkaline activator concentration and the curing parameters for both oven and microwave curing methods. Short-duration microwave curing led to aggregates of similar density and strength compared to longer oven curing. Volumetric heating during microwave curing caused densification, development of additional fused surface coating, strength gain, and reduced water absorption of the aggregate.

Influence of PCE superplasticizers on the fresh properties of low carbon cements containing calcined clays: A comparative study of calcined clays from three different sources

The performance of low carbon cements prepared using calcined clay can be very inconsistent due to variations of the composition of the calcined clay samples. To gain a better understanding and further promote the practical application of this kind of “Green” cement, the influence of calcined clays from different sources on the behavior of the blended cement was investigated. First, cement blends holding 30 wt% of calcined clays sourced from Germany, India and China were prepared and admixed with PCE superplasticizers. Their properties in mortar regarding workability, time-dependent fluidity and strength development were evaluated and compared with that of OPC. Two commonly used individual PCEs, one for precast and one for ready-mix concrete, were employed. It was found that the performance of the blended cement significantly depends on the kind and property of calcined clay. High pozzolanic reactivity promotes early strength development (up to 7 days), but reduces fluidity and slump retention. To elucidate the mechanism behind this, surface charge (zeta potential) and PCE adsorption on the calcined clays were determined, and hence, a correlation between highly negatively charged calcined clay samples and high PCE adsorption was found.

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.

Ductility response of RC beams composed of limestone calcined clay cement (LC3) and polypropylene (PP) fibre

Ordinary Portland Cement (OPC) is distinguished by considerable pollutant emissions and excessive energy and resource consumption. The development of low-clinker blended Portland cement with mineral additives is the most practical and recognisable method of resolving these issues in the cement industry. The traditional OPC consists of 95% clinker. Supplementary Cementitious Materials (SCMs) enhance the OPC by lowering clinker production. To reduce CO2 emissions, an innovative low-carbon cement called Limestone Calcined Clay Cement (LC3) replaces clinker with additional cementitious ingredients (SCMs). Clinker (50): calcined clay, limestone, and gypsum are the primary sources of LC3 cement. Adding Polypropylene (PP) Fibre endorses ductility and reduces the shrinkage cracks. PP Fibre generates a three-dimensional random distribution network structure when mixed with concrete, significantly preventing the creation and growth of micro cracks. PP Fibre can keep water and other potentially hazardous ions out of concrete. The beam specimens were incorporated with a 1.5% volume fraction of PP Fibre randomly distributed through the section. This study focused on LC3 and PP Fibre on the ductility response of RC beams. RC beams tested for the study consisted of Reference RC Beam, Reference RC beam with 1.5% PP Fibre, RC Beam with LC3 cement, and RC Beam with LC3 cement & 1.5% PP Fibre. The size of RC beams is 100 × 150 × 1000 mm, and they underwent four-point bending testing until failure, and the maximum load were recorded. First crack load and first deflection, yield load and yield deflection, ultimate load and ultimate deflection, as well as ductility and failure mechanisms, are all studied parameters. The findings revealed that LC3 and Portland Pozzolana Cement have almost identical compressive strengths (PPC). The addition of 1.5% PP exhibited better performance appreciably. RC beam with 1.5% PP Fibre shows an ultimate strength of 8.0% compared to the Reference RC Beam.

Preparation of Nano Calcite by the Carbon Capture Technology to Improve the Performance of Ultrahigh-Performance Concrete Containing Calcined Clay

Preparation of Nano Calcite by the Carbon Capture Technology to Improve the Performance of Ultrahigh-Performance Concrete Containing Calcined Clay

Mechanical Performance and Physico-Chemical Properties of Limestone Calcined Clay Cement (LC3) in Malawi

Malawi is one of the least-developed countries in Sub-Saharan Africa with disaster-prone housing infrastructure characterized by poor construction materials. Therefore, there is a need to provide resilient and cost-effective materials, such as limestone calcined clay cement (LC3). However, the exploitation of LC3 in Malawi is limited due to a lack of mineralogical information about the clays and limestone and related strength and durability when used as a cementitious material. In this study, the strength and physico-chemical properties of LC3 systems with 50% and 40% clinker contents (LC3-50 and LC3-40) were investigated. Cement mortar specimens were prepared at water to cement (w/c) ratios of 0.45, 0.5, and 0.6 with varying calcined clay (CC) to limestone (CC/LS) ratios (1:1, 2:1, and 3:1). The effects of CC/LS ratio on the fresh properties, strength, and durability were investigated. The results showed that specimens with 40% Portland cement replacement levels (LC3-40) exhibited higher standard consistency (up to 45%) than LC3-50, porosity in the range of 8.3–13.3%, and maximum water uptake in the range of 3.8–10.9%. On the other hand, LC3-50 samples offered the highest strength of approximately 40 MPa, complying with requirements for pozzolanic cementitious materials, whereas LC3-40 conforms to the strength requirements for masonry cements. This work shows that LC3 systems can be manufactured with local clays and limestone available in Malawi, and used as a sustainable construction material to mitigate carbon emissions as well as boost the local economy.

Chloride Penetration Resistance, Electrical Resistivity, and Compressive Strength of Concrete with Calcined Kaolinite Clay, Fly Ash, and Limestone Powder

This study aims to examine the chloride penetration resistance, chloride binding capacity, electrical resistivity, and compressive strength of multibinder systems, including ordinary portland cement (OPC), calcined kaolinite clay (C), fly ash (F), and limestone powder (L). At all tested ages, the results revealed that calcined kaolinite clay concrete had better chloride penetration resistance and chloride binding ability compared with the control OPC concrete. Moreover, at all tested ages, calcined kaolinite clay concrete had greater compressive strength compared with the control OPC concrete and fly ash concrete. At the curing age of 91 days, improved performance of fly ash concrete was observed. The overall performance of the ternary binder system of cement-fly ash-calcined kaolinite clay surpassed that of the binary binder systems. Among the tested combinations of binders, the ternary binder C30F15 (55% OPC+30% C+15% F) demonstrated the best overall performance. The test results also indicate that fly ash can be beneficially integrated into the cement-calcined kaolinite clay binder system to obtain a ternary binder system, which is better than the ternary binder system of cement, calcined kaolinite clay, and limestone powder, at both tested early and later ages.

Physical and Chemical Effects in Blended Cement Pastes Elaborated with Calcined Clay and Nanosilica

Supplementary cementitious materials (SCMs) are commonly used in the manufacture of commercial cements with lower clinker content and carbon footprints, enabling environmental and performance improvements. The present article evaluated a ternary cement combining 23% calcined clay (CC) and 2% nanosilica (NS) to replace 25% of the Ordinary Portland Cement (OPC) content. For this purpose, a series of tests were performed, such as compressive strength, isothermal calorimetry, thermogravimetry (TG/DTG), X-ray diffraction (XDR), and mercury intrusion porosimetry (MIP). The ternary cement studied, 23CC2NS, presents a very high surface area, which influences hydration kinetics by accelerating silicate formation and causes an undersulfated condition. The pozzolanic reaction is potentialized by the synergy between the CC and NS, resulting in a lower portlandite content at 28 days in the 23CC2NS paste (6%) compared with the 25CC paste (12%) and 2NS paste (13%). A significant reduction in total porosity and conversion of macropores in mesopores was observed. For example, 70% of pores in OPC paste were macropores that were converted in the 23CC2NS paste into mesopores and gel pores.

Investigating the ternary cement containing Portland cement, ceramic waste powder, and limestone

The cement production process produces enormous amounts of carbon dioxide (CO2). Hence, using new types of cement, like ternary cement, which contains calcined clay, limestone, and cement clinker, can significantly reduce the CO2 emissions of the cement industry and even increase the mechanical properties and durability of samples. This paper investigates the cement mortar's mechanical and durability characteristics, containing ceramic waste powder (CWP) and limestone powder (LSP) as partial cement substitution. Samples with 5, 10, and 15 % LSP and 10, 20, and 30 % (by weight of cement) CWP as cement substitutes were produced. The mortar specimen tests were performed after 7, 28, and 90 days of curing in the water pool, then compressive strength and alkali-silica reaction (ASR) tests were evaluated. Furthermore, setting time test, thermogravimetric analyses, X-ray diffraction analyses, and scanning electron microscopy (SEM) of cement paste were carried out. The ternary cement mortar containing 10 % CWP and 15 % LSP has the highest compressive strength. Also, the ternary cement mortar containing 30 % CWP and 15 % LSP shows the lowest compressive strength (decreased by 8.5 % compared to the reference sample). In addition, the mix containing 20 % CWP and 15 % LSP has a lower ASR value than the control sample (52 % less). Eventually, SEM images showed the reference sample and the specimen containing 30 % CWP and 15 % LSP have the lowest and highest pores and cavities, respectively.

Sustainable and rapid pillared clay synthesis with applications in removal of anionic and cationic dyes

Adsorbents that remove both anionic and cationic dyes in aqueous solutions are essential in wastewater treatment. To address this need, chromium metal polycations are intercalated in bentonite clay and the efficacy of the resulting adsorbent for anionic as well as cationic dyes removal are explored in this study. The problems to be addressed are ensuring permanent porosity in the raw clay which tends to swell upon contact with water, and identifying optimal conditions for high capacity of the adsorbent. Further the time-consuming steps involved in preparation of the pillaring solution and its intercalation in the clay need to be expedited. Pillared clays with different chromium contents were synthesized using an economical and sustainable method. Ultrasonication at 35 kHz frequency intensified chromium polycations synthesis and their intercalation into the clay by reducing the time from 24 h to 40 min. Cr pillared clays with high basal spacing, surface area, total pore volume, and micropore volume were synthesized. The residual Cr polycations solution after intercalation could be reused in two additional stages, minimizing the disposal of spent Cr solution into the environment. The pillared clay's point of zero charge was reduced considerably with increasing Cr content while the basal spacing increased. Cr was stable in calcined pillared clay matrix and was non leaching. Cationic Basic Orange 2 dye and anionic Acid Blue 74 dye was used for adsorption studies with Cr pillared clays. Effects of dosage, pH, initial concentration of the dyes, and temperature on the adsorbent loading were analyzed. The maximum adsorbent loading for Acid Blue 74 and Basic Orange 2 dyes were 81 mg/g and 170.9 mg/g respectively. Gibbs free energy, enthalpy and entropy changes were estimated. Cr pillared clay adsorbents could successfully adsorb both cationic and anionic dyes. Ultrasound accelerated the Basic Orange 2 dye desorption time from the clay by 48 times and enabled its reuse over four more cycles without an appreciable drop in capacity. Basic Orange 2 dye could still adsorb on pillared clay which was permanently saturated with Acid Blue 74 dye. The ultrasound aided rapid chromium pillared clay adsorbent synthesis process proposed in this study enables the reuse of the intercalating solution over three cycles without discharge into the environment and led to a non-leachable as well as reusable adsorbent. This adsorbent had adjustable point of zero charge depending on its chromium content and revealed a high capacity for anionic as well as cationic dyes.

Comparative Study on LC3-50 with OPC Concrete Using Raw Materials from Pakistan

The cement industry is expanding rapidly around the globe, despite its significant contribution to global carbon dioxide emissions. Likewise, in Pakistan, the cement industry produces million tons of cement and has a history of contributing as high as 10% of the country’s carbon dioxide emissions annually. The most effective technique for reducing carbon dioxide emissions is to use supplementary cementitious materials (SCMs). Limestone Calcined Clay Cement (LC3-50) is a recently developed cement blend comprised of 50% clinker, 30% calcined clay, 15% raw limestone, and 5% gypsum by weight. The focus of this research is to assess the mechanical properties and durability performance of LC3-50 cement composition formulated using raw materials from Pakistan. The comprehensive case study would help advance the research and commercialization activities in the country. In this study, compressive strength, split tensile, flexural, and pull-out tests were performed for evaluating the mechanical properties. For the assessment of durability, water permeability, sorptivity, carbonation, and rapid chloride penetration test (RCPT) tests were performed as per the available standards. It is concluded that the use of LC3-50 instead of ordinary Portland cement (OPC) improved the strength and durability of the end concrete.

Reactivity Assessment of Supplementary Cementitious Materials and Their Binary Blends Using R3 Test

The suitability of the rapid, relevant, and reliable (R3) heat of hydration and bound water tests for measuring the reactivity of various supplementary cementitious materials (SCMs) and their blends with calcium hydroxide (CH) was investigated in this study. These tests have been recently standardized in current standards. The test was carried out on pastes of fly ash (FA), slag (S), kaolinitic calcined clay (K), limestone (LS), and their blends. A detailed analysis of the heat of hydration and bound water measurements specified according to the R3 test was carried out. A good correlation was found between the two types of test results and also between the reactivity test results versus strength activity index measured using cement mortar compressive strength. The formation of hydration products in the R3 test paste specimens was also studied using X-ray diffraction (XRD). The hydration products for SCMs formed in the test were similar to those reported in cement systems. It was seen that the interactions in the blended SCMs with CH were also similar to those reported in cement pastes. Further, the microstructure of the specimen was studied using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis, and the overall hydration of various SCMs was studied. The influence of the proportions of the SCMs in the blended SCMs and that of fineness were also investigated. The applicability and limitations of this test method for SCMs and their blends were discussed.

Workability and strengths of ternary cementitious concrete incorporating calcined clay and limestone powder

Problems associated with the production and utilization of Portland cement have necessitated the use of alternative or supplementary binders in concrete production. This study investigated the use of two supplementary binders; calcined clay (CC) and limestone powder (LP) as substitutes for cement in the production of concrete. Both the calcined clay and limestone powder were characterized using X-ray diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM). Blended concrete mix proportions containing calcined clay and limestone powder were prepared and tested for fresh and hardened concrete properties including workability, compressive and splitting tensile strengths. The outcomes of this research showed that calcined clay is majorly amorphous with traces of crystal particles while limestone is all crystal particles. Based on oxides composition, calcined clay can be used as pozzolan while limestone powder can be best utilized as pore fillers. The addition of both calcined clay and limestone powder resulted in the loss of slump, although the effect is more pronounced in concrete blends containing calcined clay. While the inclusion of limestone powder caused a slight loss of strength in the blended concrete, it can still be utilized to achieve reasonably high strengths. Only concrete mix incorporating 10% of calcined clay gives a slight increase in strength, hence calcined clay can be utilized to a limited volume in concrete production.

Potential of Local Clay for the Development of Limestone Calcined Clay Cement in East Java

Limestone Calcined Clay Cement (LC3) offers an innovative and sustainable alternative to traditional binders, utilizing calcined clay and limestone as partial substitutes for Ordinary Portland Cement (OPC) clinker. This study investigated the potential of local clays found in East Java, Indonesia, for LC3 production. Clay samples from three sites in East Java, with pure kaolin as a benchmark, were assessed. A formulation with 50% OPC clinker substitution was employed, integrating limestone powder, calcined clay, and gypsum. The clays underwent drying, grinding, sieving, and calcination at both 700°C and 800°C. For comparison, a sample of local Trass, typically used in Portland Composite Cement, was also evaluated. Compared to OPC, the LC3 samples exhibited reduced workability and a faster initial setting time. However, the LC3 mortar displayed commendable compressive strength, achieving a Strength Activity Index exceeding 75% at 28 days. The calcination temperature influenced the ultimate strength, especially in specimens with a higher kaolin concentration. One of the local clays, sourced from Trenggalek, with a kaolinite content of 49%, achieved a compressive strength of 43 MPa at 28 days. This value closely parallels the strengths of both OPC (49 MPa) and the metakaolin (42 MPa) mixtures.

Carbonation of concretes containing LC³ cements with different supplementary materials

Due to the clinkerization process during the Portland cement production, large amounts of CO2 are emitted, increasing the effects related to climate change (approximately 5-10% of global CO2 emissions come from cement production), consequently, the seek for alternatives to mitigate these high emissions are necessary. The use of supplementary cementitious materials (SCM) to partial replace of Portand clinker/cement has been the subject of different research, including the use of LC3 cements (Limestone Calcined Clay Cements), where up to 50% of Portland clinker can be replaced, however, cement industry has already used othersupplementary cementitious materials with pozzolanic activities in commercial cements. In this sense, this work evaluates the performance of concretes containing LC3 mixtures with the presence of different SCM (silica fume, fly ash, sugarcane bagasse ash and açaí stone ash) regarding durability issues by carbonation. The results showed that all concretes with LC3 presented higher carbonation fronts in relation to the reference concrete, with Portland cement, due to the lower availability of calcium to react with the CO2 that penetrates into the concrete pores, so the adoption of curing procedures and coatings are recommended.

Influence of mineralogy and calcination temperature on the behavior of palygorskite clay as a pozzolanic supplementary cementitious material

Aiming to limit carbon dioxide (CO2) emissions by cement production and widen the supplementary cementitious materials' (SCM) resource options, recent research has been focused on developing the pozzolanic properties of low-cost calcined clays containing a blend of clay minerals and impurities as an alternative to metakaolin. This study investigated the effects of mineralogical composition and calcination temperature on the use of calcined palygorskite clays as SCM. Rietveld quantitative X-ray diffraction (RQXRD), thermogravimetric analysis and Fourier-transform infrared proved useful in shedding light on the relation of mineralogical composition and thermal treatment temperature of clays, with the properties of pastes and mortars, in which the calcined palygorskite clays substitute cement, at 20 wt%. The results indicated that with increasing palygorskite content in raw clays, the pozzolanic reactivity of calcined clays also increases. Moreover, the calcination of Mg – rich clays between 600°C and 750°C, presented higher calcium hydroxide (CH) consumption and strengths after 28 and 90 days of hydration compared to Al – rich ones. The former displayed the highest pozzolanic reactivity when calcined at 750°C, whereas the latter at 700°C. The substitution of cement by clays calcined at 750°C, and by metakaolin, resulted in a similar reduction of CH content in pastes; up to 60%, relative to neat cement, at all hydration ages. Calcined palygorskite clay could be introduced as a reactive pozzolan in mortar with comparable or higher strengths than neat cement counterparts.

Effects of Alternate Wet and Dry Conditions on the Mechanical and Physical Performance of Limestone Calcined Clay Cement Mortars Immersed in Sodium Sulfate Media.

Sulfate attack in concrete structures significantly reduces their durability. This article reports the experimental findings on the effects of sodium sulfate on limestone calcined clay cement (LC3) in an alternate wet and dry media. The samples underwent wet-dry conditions of 28 cycles. Two types of LC3 were studied, one made from clay (LC3-CL) and the other made from fired rejected clay bricks (LC3-FR). The composition of each LC3 blend by weight was 50% clinker, 30% calcined clay, 15% limestone, and 5% gypsum. The reference compressive strength was evaluated at 2, 7, and 28 days of age. Then, ordinary Portland cement (OPC) and LC3-CL blends were subjected to alternate wet-dry cycle tests, immersion in a 5% sodium sulfate solution, or in water. For all exposed samples, sorptivity tests and compressive strength were done. The results showed that LC3 blends met the requirements for KS-EAS 18-1:2017 standard, which specifies the composition and conformity criteria for common cements in Kenya. The LC3 blend also had a lower rate of initial absorption compared to OPC. Additionally, LC3 blend also showed good resistance to sodium sulfate when exposed to alternating wetting and drying environment. OPC showed higher compressive strength than LC3 blends for testing ages of 2, 7, and 28 days. However, the LC3 samples utilized in the sodium sulfate attack experiment, which were later tested after 84 days, exhibited higher compressive strengths than OPC tested after the same period.

Propriedades reológicas e hidratação de cimentos ternários contendo resíduos de mármore, porcelanato, bloco cerâmico e fosfogesso

Abstract No research demonstrates the effect of combined waste raw materials as an alternative to natural sources in Limestone Calcined Clay Cement (LC3). In this context, this study aimed to evaluate the influence of the composition of ternary cements (TCs) containing industrial waste on their rheological and hydration properties. As raw materials, Portland cement and clay brick (CBW), clay tile (CTW), marble (MW), and phosphogypsum (PG) wastes were used. The rheological behaviour of the pastes was analysed by the mini-slump evolution over time and rotational rheometry. Hydration was evaluated by isothermal calorimetry and XRD/Rietveld. An increase in the specific surface area enhances the yield stress and plastic viscosity of the paste. CBW and CTW have pozzolanic reactivity, presenting an increase in the content of non-crystalline phases, including calcium silicate hydrate (C-S-H). The TCs reached at least 70% of the compressive strength of theHigh Early Strength Portland cement paste.The results suggest that CBW, CTW, MW and PG can be used as an alternative to reduce the clinker factor and decrease the environmental and economic impacts associated with extracting natural raw materials for cement production.

Strength properties and hydration of ultra-high performance concrete incorporating calcined clay and limestone with steam curing regimes

UHPC blended with low-energy mineral admixture and cement supplementary material is beneficial to the environmental protection and energy conservation. This paper investigated the hydration, micro-structure and strength development of LC3 based UHPC matrix with steam curing at 55 and 90 ℃ for 1 d and 2 d. The compressive and flexure strengths of UHPC mixtures incorporating limestone and various replacement levels of metakaolin were measured. Hydration, pore structure and micro-morphology of LC3 based UHPC mixture were investigated by various modern analysis and testing technologies. The test results indicate that the 2 d or 3 d compressive strengths for 90 ℃ steam cured UHPC mixture containing 15 % MK are about 60 % greater than that of standard cured mixture. While its flexure strengths for steam cured UHPC matrix blended with LC3 are generally smaller than that of standard cured mixture. It is noted that the degrading effect of flexure strength can be relieved when the UHPC mixtures are steam cured at 55 ℃ for 1 d. For the hydration of UHPC matrix, steam curing temperature is a key factor for stimulating the MK pozzolanic reaction, which contributes to a 30 % and 50 % higher MK reaction degree than that of standard mixture at 28 d when the steam curing temperature are 55 and 90 ℃, respectively. In addition, the significant MK pozzolanic reaction does not obviously restrict the cement hydration of steam cured LC3 based UHPC matrix. The pore size distributions of LC3 based UHPC matrix with steam curing regime are similar with that of standard cured mixture at 28 d, among which the ratios of pores with sizes smaller than 20 nm are over 70 %. Therefore, satisfactory mechanical strengths and micro-structures of LC3 based UHPC matrix can be obtained with steam curing regimes.

Influence of Mixing Order on the Synthesis of Geopolymer Concrete.

Geopolymers are high-performance, cost-effective materials made from industrial waste that ideally fit the needs of 3D printing technology used in construction. The novelty of the present work lies in the investigation of methods to mix geopolymer concrete from fly ash (FA) class F, ground granulated blast furnace slag (GGBS), and raw calcined kaolin clay (RCKC) to determine the mixing procedure which provides the best mechanical strength and structural integrity. The experimental results show that aluminosilicates with different reaction parameters when mixed one after another provide the optimal results while the geopolymer concrete possesses the highest compressive strength and the denser structure. The results demonstrated that the reactivity of GGBS, FA, and RCKC increased for different depolymerization speeds of the selected aluminosilicates. This research will provide results on how to improve the mixing order for geopolymer synthesis for 3D printing demands. The highest compressive strength and denser structure of geopolymer concrete is achieved when each type of aluminosilicate is mixed with an alkaline medium separately.