Editorial: Magnesia-based cementitious materials

Lightweight and low thermal conducted face-centered-cubic cementitious lattice materials (FCLMs)

The botryoid hybrid nano-carbon materials were incorporated into cementitious materials to develop a new type of self-sensing cementitious composites, and then the mechanical, electrically conductive, and piezoresistive behaviors of the developed self-sensing cementitious composites with botryoid hybrid nano-carbon materials were comprehensively investigated. Moreover, the modification mechanisms of botryoid hybrid nano-carbon materials to cementitious materials were also explored. The experimental results show that the compressive strength and the elasticity modulus of the self-sensing cementitious composites botryoid hybrid nano-carbon materials decrease with the increase in the botryoid hybrid nano-carbon material content, while the Poisson’s ratio does the opposite. The percolation threshold zone of the self-sensing cementitious composites botryoid hybrid nano-carbon materials is from 2.28 to 3.85 vol.%. The optimal content of botryoid hybrid nano-carbon materials is 3.38 vol.% for piezoresistivity of the self-sensing cementitious composites botryoid hybrid nano-carbon materials. The amplitude of fractional change in resistivity goes up to 70.4% and 28.9%, respectively, under the monotonic compressive loading to failure and under the repeated compressive loading within elastic regime. The piezoresistive stress/strain sensitivity reaches (3.04%/MPa)/354.28 within elastic regime. The effective modification of botryoid hybrid nano-carbon materials to electrically conductive and piezoresistive properties of cementitious materials at such low content is attributed to their botryoid structures, which are beneficial for the dispersion of botryoid hybrid nano-carbon materials and the formation of conductive network in cementitious materials. The use of botryoid hybrid nano-carbon materials provides a new bottom–up design and fabrication approach for nano-engineering multifunctional cementitious composites.

Experimental study on the properties of a polymer-modified superfine cementitious composite material for waterproofing and plugging

Influence of PZT volume fraction, composite thickness and cement matrix on the performance of d15 shear mode 1–3 connectivity cement-based piezoelectric composites

Previous studies have shown that coal-based solid waste can be utilized in combination with cement, silica fume, and other modified materials to create a cemented backfill material. However, traditional cemented backfill materials have poor mechanical properties, which may induce the emergence of mining pressure and trigger dynamic disaster under complex mining conditions. In this study, the nanocomposite fiber was used to modify the traditional cemented backfill materials and a new cemented backfill material was developed using coal-based solid waste, nanocomposite fiber and other materials. Specifically, coal gangue, fly ash, cement, and glass fibers were used as the basic materials, different mass fractions of nano-SiO2 were used to prepare cemented backfill materials, and the mechanical enhancement effect of the compressive strength, tensile strength, and shear strength of the modified materials was analyzed. The results show that when the nano-SiO2 dosage is 1%, the optimal compressive strength of the specimens at the curing age of 7 d can be obtained compared with cemented materials without nano-SiO2, and the compressive strength of the modified specimens raises by 84%; when the nano-SiO2 dosage is 1%, the optimal tensile strength and shear strengths of the modified specimens can be obtained at the curing age of 28 d, increasing by 82% and 142%. The results reveal that nanocomposite fibers can be used as additives to change the mechanical properties of cemented backfill materials made using coal-based solid waste. This study provides a reference for the disposal of coal-based solid waste and the enhancement of the mechanical properties of cemented backfill materials.

In this thesis, improved approaches to the laboratory characterisation of cemented materials are developed and verified enabling a more informed understanding of the load-carrying capacity of cemented materials used in road pavements. The increasing use of high productivity road freight vehicles and the application of mechanistic-empirical pavement analysis has led to the need for improved knowledge of the performance of pavement materials. In Australia, standard methods are not available for the elastic characterisation of cemented materials. As a result, presumptive values or correlations with parameters such as unconfined compressive strength (UCS) are used. In this study pavement design methods, failure mechanisms and approaches to cemented materials characterisation are investigated. Theoretical modelling and prediction of crack growth in cemented materials under repetitive loading is reviewed. The use of initial modulus and the reduction in modulus under repetitive loading is proposed as a pragmatic indicator of fatigue crack growth. Improved laboratory protocols for the characterisation of strength, breaking strain, modulus and fatigue are developed using a four-point bending, dynamic flexural beam test. The protocols were applied to two typical cemented materials, a hornfels with 3% cement and a siltstone with 4% cement at a range of curing ages. Breaking strain was identified as an indicator of initial micro-cracking. A stress controlled fatigue test was used to establish relationships between initial strain (S) and fatigue life (N) (load cycles to half initial modulus). The verification of the improved laboratory protocols involved a comparison of the labboratory test results with the results of full-scale accelerated pavement testing (APT). For the siltstone, the laboratory and field performance results aligned well. Differences between the laboratory and field materials properties resulted in a lesser alignment of the performance results for the hornfels. The relative performance ranking between the two cemented materials from the improved laboratory protocols matched that from the APT. The ranking from the traditional UCS did not align with the APT results. Further verification was sought using the Australian long term pavement performance study and anecdotal evidence of cemented materials performance to enable consideration of combined environmental and traffic effects over an extended timeframe. In the final stage of the study, the applicability of the improved laboratory protocols to a wide range of cemented materials was confirmed and a limited study into the extent of initial micro-cracking and the fatigue load-damage exponent was undertaken for two cemented materials. It was concluded that the four-point bending flexural beam test developed and verified in the study provided a significantly improved method of assessing the performance of cemented materials compared to the UCS test. The improved laboratory protocols were found to be suitable for testing a wide range of cemented materials. It was also found that, where consistent micro-cracking was present, the load-damage exponent was not dependent on the extent of initial micro-cracking.

Nanomaterials have garnered significant attention in recent years for their potential to enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. This review aims to explore the effects of various types of nanomaterials on the mechanical properties of concrete materials. Current developments in the synthesis, characterization, and use of nanomaterials in the field of cementitious materials are thoroughly examined in this review. The incorporation of various nanomaterials such as nano-silica, nano-titania, carbon nanotubes, nano-clay, and nano-alumina can significantly enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. These nanomaterials contribute to denser microstructures, improved hydration products, and enhanced interfacial bonding within the cement matrix, ultimately leading to superior mechanical performance. However, proper dispersion, dosage, and compatibility considerations are essential to realize the full potential of nanomaterials in cementitious materials. The optimum % of NS in cement was reported to be between 1 and 8%, whereas the optimum % of graphene oxide (GO) in cement was reported to be only between 0.05 and 0.5%, imparting high strength characteristics to concrete. The findings of the study promote the use of nanoparticles in cement concrete to enhance the strength of high-rise concrete buildings. The results of various studies are compared, and some significant recommendations are also made. Furthermore, this research underscores the practical applications of nanocomposite-based concrete materials while acknowledging their limitations and opportunities.

Aiming to remedy the deficiency of research related to water-to-cement (w/c) ratio (near 1·0) grouting materials, particularly calcium-sulfo-aluminate (CSA)-type cementitious grouting materials, we discuss the influence of w/c ratio on CSA-type cementitious grouting materials. Various experimental data sets reveal that the cube strength, hydration exothermic rate, total energy released and in situ non-destructive resistivity all decrease with increasing w/c ratio. It is observed that pompom spherulites of ettringite differ from most cementitious materials. A lower solution concentration resulted in thicker ettringite crystal prisms. The results also show that these spherulites form because of excessive dehydrate gypsum, which also causes unexpected X-ray diffraction results in the induction period; the content of ettringite of the 1·0-w/c hardened material was highest, whereas that of the 0·8-w/c material was the lowest, indicating that the contact probability among the Al3+, SO42−, and ye'elimite (C4A3S̄) crystals that act as nucleation sites becomes low, the ion-dissolution rate of the C4A3S̄ framework and the precipitation rate of ettringite both decrease, the Al–O octahedral nucleation barrier increases and the crystal nucleation critical size increases.

Photoinduced processes governed by light activated TiO2 have been studied in many ways. One of the most active areas is the development of TiO2 photocatalysis technologies on their application for reducing environmental impacts. The immobilization of TiO2 on solid support, such as cementitious materials, greatly enhances its use in practical applications. In this review, a wide range of applications for achieving eco-efficient building using cementitious composite materials containing TiO2 photocatalyst was presented. The basic mechanism of photocatalysis, such as electron excitation, charge transfer process, reactive oxygen species (ROS) generation, and its role to oxidize the pollutant and microorganisms were extensively discussed. Unlike self-cleaning and air purification systems, the study on the antibacterial function of a cement-based surface containing TiO2 is very limited. In photocatalytic cementitious materials, the key element affecting the photocatalytic performance is the accessible active surface area. However, microstructure of cementitious materials changes with age due to hydration and surface carbonation. Hence, surface area reduction and mass transfer limitation become the main drawbacks of incorporating TiO2 in cementitious materials. This review, therefore, provides the state of the art in photocatalytic cement-based composite materials and identifies the areas in which future improvement is needed.

This report describes work performed by the Savannah River National Laboratory (SRNL) in fiscal year 2014 to develop a new Cementitious Barriers Project (CBP) software module designated as FLOExcel. FLOExcel incorporates a uniform database to capture material characterization data and a GoldSim model to define flow properties for both intact and fractured cementitious materials and estimate Darcy velocity based on specified hydraulic head gradient and matric tension. The software module includes hydraulic parameters for intact cementitious and granular materials in the database and a standalone GoldSim framework to manipulate the data. The database will be updated with new data as it comes available. The software module will later be integrated into the next release of the CBP Toolbox, Version 3.0. This report documents the development efforts for this software module. The FY14 activities described in this report focused on the following two items that form the FLOExcel package; 1) Development of a uniform database to capture CBP data for cementitious materials. In particular, the inclusion and use of hydraulic properties of the materials are emphasized; and 2) Development of algorithms and a GoldSim User Interface to calculate hydraulic flow properties of degraded and fractured cementitious materials. Hydraulic properties are requiredmore » in a simulation of flow through cementitious materials such as Saltstone, waste tank fill grout, and concrete barriers. At SRNL these simulations have been performed using the PORFLOW code as part of Performance Assessments for salt waste disposal and waste tank closure.« less

Measurement of benzene, toluene, ethylbenzene and o-xylene gas phase photodegradation by titanium dioxide dispersed in cementitious materials using a mixed flow reactor

Evaluation of accelerated degradation test methods for cementitious composites subject to sulfuric acid attack; application to conventional and alkali-activated concretes

The preparation and axial compressive properties of 3D-printed polymer lattice-reinforced cementitious composite columns

In this experimental study, two different cementitious materials, including (i) a class of expansive cement currently used for plug and abandonment (P&A) operations and (ii) a non-cement-based naturally occurring rock, known as geopolymer, are selected to examine the hydraulic bond strength and shear bond strength. Clean machined steel and rusty corroded steel were selected to represent the casing. The test samples were cured at 90 °C considered as bottom-hole static temperature (BHST) and under elevated pressure of 17.2 MPa for 1 week. The hydraulic sealability of the barrier materials tested up to 3.4 MPa of differential pressure. The results indicated that additives used in slurry preparation impact the hydraulic sealability of the material. Additionally, the rusty corroded steel provided a better hydraulic sealability comparing to the clean machined steel for the same cementitious material. The shear bond strength test was performed by running the push-out test. According to the present test observations, no correlation was found between the shear bond and hydraulic bond strength of different barrier materials. The geopolymer showed the lowest shear bond strength, while it provided the highest hydraulic sealability.

Cement-based ductile rapid repair material modified with self-emulsifying waterborne epoxy