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The correlation between the void structure, as a representative of bleeding behaviour, and the strength of concrete is investigated in the current article. Early age cracking, due to dry shrinkage, can negatively influence the durability of pavement structures. Also, dry shrinkage of concrete is directly proportional to the bleeding rate. Thus, modifying the bleeding rate reduces the early cracking that happens in hardened concrete. Geopolymer concrete is presented as a suitable material for the replacement of Ordinary Portland Cement (OPC). Geopolymers have shown superior bleeding behaviour to that of OPC concrete and can be substituted for paving by means of increasing the durability. This research has used section image analysis and rebound hammer techniques to create a relationship between the void structure and the strength of concrete. Mixtures are prepared by 10% substitution of the iron-making slag to study the effects of slag on the bleeding rate. Also, the influence of water-to-binder ratio on the void structure and strength development is studied. The results indicate that the void volume has an indirect correlation to the strength development of normal concrete, while the addition of slag makes it reverse. Geopolymer concrete shows less bleeding than OPC concrete, making it a suitable alternative for pavement. It is also concluded that the replacement of slag in concrete enhances the bleeding rate and durability. [ABSTRACT FROM AUTHOR]

This paper attempted to isolate variables that govern concrete spalling when exposed to a hydrocarbon fire. The influence of specimen size was investigated by studying 4 specimen sizes consisting of cylinders, columns, and panels. Three aggregate sizes, 7 mm, 14 mm, and 20 mm were used in the concrete mixes to determine their effect on concrete spalling. Influence of aggregate type on concrete spalling was also investigated. Forty-two different specimens were considered in this investigation. Concrete spalling was quantified as nominal spalling depth, which has been presented as a new way of quantifying the degree of concrete spalling. The results indicated that specimen size did have an effect on the spalling of concrete under hydrocarbon fire exposure and that nominal spalling depth of concrete increases as the specimen size increases. Aggregate size effect was evident when the maximum aggregate size increased from 7 mm to 20 mm, and explosive spalling was more severe for specimens with small size aggregates. Specimens with 14-mm aggregate size showed inconsistent results and the spalling behavior witnessed was more random and sporadic. The type of aggregate used has no clear bearing on concrete spalling given both aggregates had similar linear expansion profiles. [ABSTRACT FROM AUTHOR]

Additive manufacturing is a common technique used to produce 3D printed structures. These techniques have been used as precise application geometry in different fields such as architecture and medicine, and the food, mechanics and chemical industries. However, in most cases only a limited amount of powder has been used to fabricate scaffold (structure). In this study, a unique mix of cements (calcium aluminate cement passed through a 150 μm sieve and ordinary Portland cement) was developed for Z-Corporation’s three-dimensional printing (3DP) process. This cement mix was blended and the resulting composite powders were printed with a water-based binder using a Z-Corporation 3D printer. Moreover, some samples were added lithium carbonate to reduce the setting time for the cement mixture. The aims of the study were to firstly, find the proper cementitious powder close to the targeted powder (Z-powder); and secondly, evaluate the mechanical properties of this material. Cubic specimens of two different batches with varying saturation levels were cast and cured in various scenarios to enhance the best mechanical properties. The samples were characterised by porosity analyses, compression tests, Olympus BX61 Microscope imaging, 3D profiling Veeco (Dektak) and the Scanning Electronic Microscope (SEM). The maximum compressive strength of the cubic specimens for cementitious 3DP was 8.26 MPa at the saturation level of 170% for both the shell and core. The minimum porosity obtained was 49.28% at the saturation level of 170% and 340% for the shell and the core, respectively. [ABSTRACT FROM AUTHOR]

This study presents an investigation of the effect of hydrocarbon fire exposure on the residual compressive strength properties of geopolymer concrete panels and cylinders. Gladstone flyash was utilized as the binder whilst the alkaline solution/fly-ash ratio and sodium silicate to sodium hydroxide (Na 2 SiO 3 /NaOH) ratio was 0.4 and 2.5 respectively. The compressive strength at the test date was 64 MPa. Two different cylindrical specimens’ sizes (150 and 100 mm diameter × 300 and 200 mm high) were exposed on all sides to the hydrocarbon fire scenario for 120 min whilst panels of 1075 × 1075 × 200 mm were exposed on one side for the same time duration. Results showed that no significant spalling occurred in any of the specimens and the mass loss during heating was between 2.70 and 4.65% respectively which was attributed due to moisture loss. Low differential gradients and thermal incompatibility between the geopolymer paste and aggregates provides geopolymer concrete with superior spalling resistance than Ordinary Portland cement concrete. Residual compressive strength testing showed that the panels maintained approximately 60% of their initial compressive strength indicating that geopolymer concrete specimens can maintain sufficient load bearing capacity in the event of fire exposure. The residual strength profiles indicated that specimen size effect was also exhibited with the remaining strength of the cylinders being approximately 10 and 20% for the 100 mm and 150 mm dimeter specimens respectively. The dull red color exhibited in all specimens after fire testing indicated the presence of high iron content in the geopolymer matrix. Insitu temperature analysis showed that the geopolymer concrete had excellent heat resistance capabilities with temperatures at a depth of 100 mm from the exposed surface ranging between 39 °C and 45 °C after 30 min of fire exposure even though the temperature at exposed surface exceeds 1000 °C. This is reinforced by the fact that the geopolymer has a high heat storage capacity as indicated by the geopolymers lower thermal diffusivity than OPC concrete. [ABSTRACT FROM AUTHOR]

Geopolymer composite research is aimed to make sustainable alternatives to Portland cement-based composites. However, the two main obstacles for commercialization are the use of large quantities of user-hostile liquid activators and heat curing. This study is aimed to overcome these obstacles by developing an ambient temperature cured “one-part” strain hardening geopolymer composite (SHGC). The developed composite as a “dry mix” uses a small amount of solid activator and eliminates the necessity for heat curing. The quantitative influences of curing condition and type of slag on the composite tensile performance were evaluated. The developed composite demonstrated strong strain hardening behavior comparable to typical strain hardening cementitious composite (SHCC) with high tensile strength of 4.6 MPa and very high tensile strain capacity of 4.2%. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high tensile ductility of the developed composite. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The crack-bridging relation of the developed composite, computed via a micromechanics-based model, satisfied the necessary strength and energy-based conditions of steady-state flat crack propagation, which result in sequential development of multiple cracking. The material sustainability evaluation verified that the developed ambient temperature cured one-part SHGC is a promising sustainable alternative to typical SHCC offering 76% less carbon emissions and 36% less energy consumption. This research presents the rational basis for design of such cement-less composites with both high tensile ductility and high material sustainability. [ABSTRACT FROM AUTHOR]

A hybrid adaptive neuro-fuzzy interfacial systems-imperialist competitive algorithm (ANFIS-ICA) was presented to determine the effect of concentration of alkali solution, alkali binder to alkali solution weight ratio, alkali activator to ordinary portland cement (OPC) weight ratio, oven curing temperature, and age of curing on the compressive strength of OPC-based geopolymers. Optimization of the type and number of membership functions was carried out by ICA while the training, testing and validating of the collected data sets was conducted by ANFIS. The obtained results indicated that the proposed ANFIS-ICA model is capable to predict the compressive strength of geopolymeric specimens well and suitably determine the effect of each parameter on this property. A parametric study is presented to show the effect of each parameter predicted by the model on compressive strength of the specimens. [ABSTRACT FROM AUTHOR]

The use of solid activators in the manufacture of geopolymer enhances its commercial viability as it aids the development of a one-part “just add water” geopolymer mixture, similar to the conventional Portland cement-based materials. This study is aimed to synthesize heat and ambient cured one-part geopolymer mixes. Appropriate combinations of low calcium (Class F) fly ash, slag and hydrated lime as the aluminosilicate source materials were activated by three different grades of sodium silicate and a combination of sodium silicate and sodium hydroxide powders. A conventional two-part geopolymer mix with the commonly used sodium hydroxide and sodium silicate solutions was also made for comparison. Effects of the type and amount of the solid activator, the amount of fly ash replacement with slag and hydrated lime and water content on short term mechanical properties of the heat cured one-part geopolymer mixtures including workability of the fresh mix, hardened density and compressive strength were evaluated. Subsequently, effects of ambient curing on the properties of the developed one-part geopolymer mixes were also investigated. Moderate to high compressive strength of over 37 MPa developed for the heat and ambient cured one-part geopolymer mixes. The 28-days compressive strengths of the ambient cured one-part geopolymer mixtures, regardless of the type of activator and geopolymer source materials, were comparable to those of the counterpart heat cured one-part geopolymer mixes. Such one-part geopolymer mixes could enhance the commercial viability and large-scale applications of the geopolymer in the construction industry. [ABSTRACT FROM AUTHOR]

Mix design in production cementitious materials is of importance where selection value of each parameter has a critical effect on final properties of material. In the present work, a new method has been developed to determine the effect of each considered mix design factor on output properties. A specific property can be related linearly to factors of mix design through normalized nonlinear weight functions. The proposed procedure was applied on two different mix designs available in the literature. The first analysis was conducted on ordinary Portland cement based concrete specimens to analyze the importance of each factor on their compressive strength. The second one was conducted on a geopolymeric system to analyze compressive strength. For both systems, the factors were divided into sensitive and non-sensitive where sensitive factors were suggested to be considered with more attention in mix design procedure. [ABSTRACT FROM AUTHOR]

The strength and transient creep of geopolymer and ordinary Portland cement (OPC)-based material (paste and concrete) were compared at elevated temperatures up to 550°C. The strength properties were determined using an unstressed hot strength test and unstressed residual strength test for paste and concrete, respectively. At 550°C, compared with the original strength, the strength of geopolymer was increased by 192% while the strength of OPC paste showed little change. However, after exposure to 550°C, the residual strength percentage of both geopolymer and OPC concretes was similar. Transient creep data show that geopolymer had little change in transitional thermal creep (TTc) between 250 and 550°C while OPC paste developed significant TTc in this temperature range. In comparison with OPC concrete, a higher strength loss of geopolymer concrete is thus believed to be due to the absence of TTc to accommodate nonuniform deformation during thermal exposure. [ABSTRACT FROM AUTHOR]

As environmentally-friendly materials, geopolymers have the potential to replace ordinary Portland cement (OPC) for the construction of railway sleepers and multi-flue chimneys, where the vibration control capabilities of the material must be considered. The critical damping value ( ξ) is the main parameter in relation to vibration reduction. In this study, the traditional logarithmic decrement technique was used to measure the ξ of geopolymers. Geopolymers were prepared by activating fly ash using alkali solutions with different SiO/NaO ratios. The results show that the ξ of the geopolymers is similar to that of the OPC counterpart. Finite element analysis (FEM) based on the Rayleigh damping model was conducted to replicate the test results, and scanning electron microscopy and mercury-intrusion porosimetry were used to study the microstructure of the geopolymers. A discussion of the possible damping mechanisms based on the microstructural investigation and the FEM analysis is presented. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study on the effect of aggregate size on spalling of concrete in fire. Three concretes with completely different chemical compositions and strengths were investigated, namely, geopolymer concrete and high strength and normal strength Portland cement concretes. The effect of aggregate size was found to be the same regardless of the type of concrete. The concretes containing 10mm aggregates spalled while the ones with 14mm did not spall. Since this effect is the same in geopolymer and Portland cement concretes, it is independent of binders’ chemical compositions. This paper shows that the degree of spalling has a good correlation to the fracture process zone length, which increases with increasing aggregate size; this in turn reduces the flux of kinetic energy from pore pressure and thermal stress that is released into the fracture front and thereby improves the spalling resistance. [Copyright &y& Elsevier]

Cementitious binders consisting of ground granulated iron slag and an alkaline activator (alkali activated slag) have considerable environmental benefits when used as an alternative to conventional 100% ordinary portland cement binders. The objective of this paper is to demonstrate the effect of pore cross section shape on unsaturated flow and to contrast the laboratory and numerical predictions of alkali activated slag binders and 100% portland cement binders. Convection-based uptake of water within capillary pores is modeled using pore size distribution data; however, most existing predictive models are based on the assumption of a circular cross section. This model allows for changeable capillary cross-sectional shape by employing ellipses ranging in shape from circular to slit. By applying a shape factor that accounts for departure from circularity of the pore cross section, the prediction model shows reasonable agreement with water sorptivity test data. As well as different binder types, the predictive model is assessed over a range of concrete ages and curing conditions. [ABSTRACT FROM AUTHOR]

Alkali activated slag concrete (AASC), based on a binder that consists of 100% blast furnace slag that is activated by an alternative alkali to conventional Portland cement, has considerable environmental benefits. Nevertheless, the durability of the exposed surface zone of AASC needs consideration. The ingress of harmful agents is highly influenced by convection-induced effects; e.g., moisture gradients caused by exposure to rainfall or the wetting and drying effects in the splash zone of a marine environment that can lead to high surface concentration of chloride. The convective effects also propagate steel reinforcement corrosion, once initiated, by making available moisture and oxygen for the cathodic reaction at the steel reinforcement, as well as changing the conductivity of the concrete surface zone. This paper reports the behavior of convection-induced uptake of water into AASC and ordinary Portland cement concrete. The sensitivity to “exposed,” “sealed,” and “bath” curing and the resultant pore structure for concrete made with different water/binder is contrasted. [ABSTRACT FROM AUTHOR]

Since the initial introduction of geopolymers, these materials have been characterised as environmentally-friendly sustainable substitutes for ordinary Portland cement (OPC). There is a routine increase in the application of geopolymers, especially in advanced technologies. Because of its better rheological characteristics compared to OPC, geopolymers are appropriate materials for extrusion-based 3D printing technologies. This paper focuses on the optimisation of an ambient temperature cured geopolymer for 3D printing construction applications. The effects of mixture parameters, including the type of hydroxide solution (HS), the type of silicate solution (SS) and the mass ratio of SS to HS on the workability, extrudability, shape retention ability and mechanical performance of different geopolymer mixtures were investigated. Accordingly, an optimum mixture was identified for geopolymers cured at ambient temperatures. Mechanical properties of the optimised mixture, including flexural and compressive strengths, were measured in different directions with respect to the printed layers. Further, uniaxial tension tests were also conducted on the optimised mixture to measure its interlayer bond strength. The results showed that among the activators investigated, the sodium-based activator composed of sodium hydroxide and sodium silicate solutions, with a SiO2/Na2O ratio of 3.22, was the most effective activator, providing appropriate workability and extrudability, along with reasonable strength and a high shape retention ability. The acquired mechanical properties exhibited anisotropic behaviour in different testing direction. The strength of the interlayer bond was found to be adequate to avoid interfacial shear failure. [ABSTRACT FROM AUTHOR]

• Geopolymer concrete (GPC) tends to have higher shrinkage strains compared to conventional concrete. • Shrinkage of GPC is extremely sensitive to initial moisture conditions. • Sealed curing reduces the shrinkage of GPC. • Existing standard prediction models significantly underestimate the shrinkage of GPC. • The newly developed model can estimate the shrinkage of GPC with conventional precursors and clay-based binders. This study investigated the shrinkage behaviour of geopolymer concrete (GPC) under various curing environments. One-part GPC was prepared by using waste clay bricks (WCB), fly ash and slag as precursors and anhydrous sodium silicate as the sole activator. The samples were subjected to initial curing in three different environments: standard curing in lime-saturated water, unsealed ambient curing, and sealed ambient curing. Irrespective of the curing environment, GPC showed a higher shrinkage than conventional concrete with ordinary Portland cement. Compared to sealed and unsealed curing, standard curing was able to reduce the shrinkage in GPC by more than 22%, considering the 28-day shrinkage strain. However, this curing environment was not suitable in terms of strength development. For WCB-based GPC, the sealed curing improved the strength gain, and also reduced the shrinkage compared to unsealed curing by more than 50%. The existing standard prediction models for Portland cement concrete significantly underestimated the shrinkage of GPC. This study proposed a new model with higher accuracy to predict the shrinkage of GPC. The model used a 28-day shrinkage value to estimate the long-term behaviour, and has the flexibility to adjust its coefficient based on the exposure environment. [ABSTRACT FROM AUTHOR]

Highlights • Totally different responses of OPC and geopolymer that subjected to the elevated temperatures. • Post-thermal shocked geopolymer exhibited superior compressive strength. • Geopolymer concrete holds an advantage in water and air-cooling based thermal shock situations. • Geopolymers are suitable for higher risk of fire that requires immediate quenching with water. Abstract Thermal shock resistivity is one of the most important characteristics of the concrete. There are numerous research papers, which investigate the reduction of fundamental engineering properties after Ordinary Portland cement (OPC) is subjected to thermal shock. In consequence to this functional disadvantage of OPC, this study explores the post thermal shock behaviour of geopolymer concrete constructed from Gladstone fly ash compared to Ordinary Portland cement-based concrete by means of rapid water to air-cooling after being heated to temperatures of 400 °C, 600 °C, 800 °C and 1000 °C. Specimens were analysed via the use of the universal testing machine, scanning electron microscopy, X-ray powder diffraction and energy dispersive spectroscopy to assess their compressive strengths and microstructure. The results show that after thermal shock via air-cooling, geopolymer concrete exhibited superior compressive strength and microstructure than conventional concrete. Concurrently, after thermal shock via water-cooling geopolymer concrete retained more of its compressive strength and microstructure than OPC. The findings demonstrate that geopolymer concrete holds an advantage in water and air-cooling based thermal shock situations and thus can be applied in conditions where there is a higher risk of fire that would require immediate quenching with water. [ABSTRACT FROM AUTHOR]

This study reports the investigation of the durability of a low-calcium fly ash based geopolymer concrete (GPC) mix in a saline lake environment. Core specimens from the GPC and Ordinary Portland Cement (OPC) concrete structures underwent durability assessment including in-situ carbonation, chloride and sulphate ingress, microstructural characterization and porosity analysis. It was found that the particular GPC mix design studied was more vulnerable to carbonation and the deterioration effects due to chloride and sulphate ingress in GPC were higher than OPC concrete after 6 years of exposure. According to FT-IR and XRD analysis, there was no evidence of carbonation reaction products remaining in GPC. This indicates that the carbonation products dissolved when in contact with water, which caused high porosity of the concrete surface thereby facilitating more diffusion into the concrete. This study revealed that the development of a durable geopolymer concrete mix design for aggressive environments requires appropriate consideration of binder chemistry and preliminarily durability property testing to avoid premature deterioration. [ABSTRACT FROM AUTHOR]

Hybrid alkali cement (HAC) is regarded as a sustainable alternative to cementitious materials due to the use of more than 70 % of supplementary cementitious materials while the issues associated with geopolymers are avoided to a great extent. This paper proposes a new method of delivering HAC-based mixtures by a two-part printhead mixing process suited for 3D concrete printing (3DCP). The two-part mixing process addresses the conflicting rheological requirements in 3DCP by facilitating the rapid early-age strength development after placement while showing excellent pumpability prior to the extrusion. The proposed approach is based on introducing the Portland cement in a secondary mixing process to partially replace the fly ash or slag in the printable geopolymer mix. A series of experiments assessing the printability of fresh concrete following the two-part mixing process and the properties of hardened concrete were assessed. The results demonstrate that the replacement of FA with Portland cement (HAC-FA) yielded a more pronounced enhancement than slag-replaced mixes (HAC-S) with the increase in static yield stress (SYS) and modulus of elasticity by 17 times and 3.5 times respectively at 30 min, compared to the control mix. The hardened properties of printable mixes, namely compressive strength and interlayer bond strength at 28 days, revealed an enhancement for the HAC-25FA mix by 20 % and 64 %, respectively, again in comparison to the control mix. The apparent volume of permeable voids (AVPV) and microstructural analysis validated the hardened concrete properties, where the HAC-FA mixes showed the densest microstructure with a reduced apparent porosity, compared to other mixes. • HAC is studied as a sustainable alternative to Portland cement in concrete 3D printing. • A two-part print head mixing technology is proposed to meet the conflicting rheological requirements for 3D printing. • The static yield stress and elastic modulus of fresh printed concrete increased by 17 times and 3.5 times respectively. • HAC mixes showed dense and compacted microstructure. [ABSTRACT FROM AUTHOR]

Geopolymers possess comparable properties to ordinary Portland cement (OPC) with less consumption of natural resources and lower carbon emissions. This paper investigated microstructural characteristics of geopolymer concrete (GPC) and OPC concrete (OPCC) and their correlation to strength and durability. The effects of the liquid to binder ratio and addition of silica fume/slag blend to mixtures were studied through compressive strength, ultrasonic pulse velocity (UPV), apparent volume of permeable voids (AVPV), pore detection image analysis (PDIA), and liquid nitrogen porosimetry (LNP). From the results, the strength development of geopolymers and OPC was strongly correlated to the void distribution and the pore structure. Like UPV and AVPV, PDIA showed that the void volume of OPC varying from 7% to 14% was significantly lower than geopolymers with 8%–32% of void volume. Additionally, LNP indicated the specific surface area of OPC distributed over 4.1 m2/g to 20.8 m2/g was 50%–66% lower than that of geopolymers. The tolerance of these parameters could control the mechanical and durability characteristics. The variations in the void and pore distribution of GPC illustrated a layer-based transition from the top to the bottom of sections. The UPV and PDIA results stated that the pore volume decreased gradually in the middle and bottom layers of GPC, and the LNP illustrated a shift and increase in nanometric gel pores in the pore size distribution of lower layers. • Strength development is a function of the void distribution and the pore structure. • Geopolymers have a sectional void and pore distribution. • Additional amorphous constituents are required for strength development of geopolymer. • OPC-based binders possess less porous structure than geopolymers. [ABSTRACT FROM AUTHOR]

• The long-term durability of fly ash-based geopolymer concrete in the buried environment was assessed in 10 years. • GPC exhibits higher chloride diffusion coefficients and a lower binding capacity than conventional OPC concrete. • The sulphate penetration of GPC was greater than OPC concrete. • The deterioration of microstructure in salt lake environment was studied using SEM and FT-IR analyses. Durability of geopolymer concrete is an important property for its application in construction sector; however, it is less explored. In this study, the long-term durability of fly ash-based geopolymer concrete (GPC), exposed in a severe salt lake environment with the buried and fully saturated condition for 10 years, is investigated. The outcome of chloride and sulphate attack on the durability behaviour of GPC was compared to ordinary Portland cement (OPC) concrete at the same exposure conditions. The results of this study reveal that the GPC has an adverse effect of chloride transportation with higher chloride diffusion coefficient and the lower binding capacity, compared to OPC concrete. The sulphate penetration of GPC was also greater than OPC concrete, however, its detrimental effect has been found more pronounced in OPC concrete due to the gypsum formation resulting in the softening of its matrix. The pH measurement indicated that the GPC has the neutral to mild alkalinity with the pH range of 7.0–8.0, whereas OPC concrete showed between 12.0 and 12.5. The mineralogical and morphological changes within the microstructure as a result of long term exposure in the buried saline environment were also studied by FT-IR and SEM/EDX analysis. [ABSTRACT FROM AUTHOR]

• F25 had a strength of 82 MPa and a density of 1566 kg/m3. • A correlation is identified between the FAC content and the formation of N-A-S-H gel. • The co-existence of CASH/NASH phases is responsible for high strength of the matrix. • Developed composites exhibited a higher merit number than the traditional materials. In the current work, the mechanical and thermal characteristics of environmentally friendly lightweight composites with high specific strength (defined as the ratio of strength to density) and low thermal conductivity are examined. To increase the sustainability of composites, ordinary Portland cement (OPC) was completely replaced with alkali-activated alumino-silicate by-products, including ground granulated blast furnace slag (GGBFS) and silica fume (SF). The micro-sized hollow fly-ash cenospheres (FAC), together with alkali-activated binders (AAB), are used to produce lightweight composites under ambient conditions. The novel composites had 28-day compressive strength ranging from 29.7 to 82.3 MPa, and dry densities ranged from 953 to 1566 kg/m3. The thermal conductivity of the optimal mix was 0.223 W/(m⋅K), which is lower than that of cementitious materials reported in the literature at the same specific strength. Based on the results obtained from the microstructural analysis, the high compressive strength associated with low thermal conductivity of FAC-modified AAB is attributed to (i) the co-existence of C-A-S-H/N-A-S-H phases is beneficial for the formation of a high-strength matrix, (ii) the presence of a strong interface between matrix and FAC, and (iii) the void sizes introduced is controlled below 50,000 nm. [ABSTRACT FROM AUTHOR]

Cement mixture with the properties of early strength and low hydrating thermal dissipation is necessary to cementing the shallow natural gas hydrate formation in deep water area. The research objectives are designed to utilize the energy storage microsphere in cement mixture to achieve early strength and low hydrating thermal dissipation. Considering the strength and hydrating thermal dissipation, the mixture of Class G oil well cement and aluminate cement with the quality ratio of 1:1 is proposed. The polymethyl methacrylate microsphere is used to coat phase change materials to prepare the energy storage microsphere, which can be used in cement mixture directly and stably. The energy storage microsphere could reduce the hydrating thermal dissipation of cement mixture obviously. Because of converting the hydration heat of Aluminate cement to cure Portland cement and PMMA framework, energy storage microsphere has little negative effect on the early strength of cement mixture. [ABSTRACT FROM AUTHOR]

This paper investigates binary and ternary binders of ordinary Portland cement, metakaolin and limestone as a possible solution to reduce the amount of cement content in mortar mixes. Furthermore, the mortar mixtures were reinforced with steel fibres and their properties were investigated. The effectiveness of metakaolin and limestone on compressive and flexural strength of mortar samples as mechanical properties was analysed. Results indicated that partial substitution of metakaolin in mortar mixtures provides higher compressive strength values at early ages; combined mixtures of limestone and metakaolin enhanced compressive strength comparing with 100% ordinary Portland cement (OPC) as the binder. Flexural strength values improved by increasing the number of steel fibres in mixtures; variations in metakaolin and limestone on mixtures seemed not to affect on final flexural results significantly. Electrical resistivity results revealed substantial improvements on the likelihood corrosion and corrosion rate of mortar mixtures. The addition of steel fibres to the admixture significantly decreased the ER mainly due to the conductivity of the fibres. [ABSTRACT FROM AUTHOR]

Alternative low-carbon cements could contribute significantly to CO 2 reduction in the cement industry. However, the existing methods require the input of the actual production data, and thus cannot be used to calculate CO 2 emissions of alternative low-carbon cements that are not yet produced in cement plants. This study aims to develop a model to analyze the theoretical CO 2 emissions of alternative low-carbon cements. The novelty of this model is that it can be used to calculate the fuel consumed in the production of new low-carbon cements based on the theory of heat balance, and then predict their CO 2 emissions. The model is used to calculate CO 2 emissions of several low-carbon binders and ordinary Portland cement (OPC). The results show that the direct CO 2 emissions of OPC clinker calculated by this model approach the value derived from the cement plants and the Cement Sustainability and Initiative (CSI). Calcium sulfoaluminate (CSA) clinker has the direct CO 2 emissions of 0.540 kg/kg, 34% lower than OPC clinker, while its cost of raw materials is over four times that of OPC clinker. High-belite calcium sulfoaluminate (HB-CSA) clinker, with the direct CO 2 emissions comparable to CSA clinker, lowers its cost of raw materials by half as it requires less expensive bauxite. Moreover, CO 2 emissions from HB-CSA cement production can be further reduced by the use of high volume of supplementary cementitious materials (SCMs). The knowledge gained provides a valuable reference for the design of new low-carbon binders. [ABSTRACT FROM AUTHOR]