Performance Of Cement-based Materials Research Articles

The impact of environmental humidity on the mechanical property and microstructure of magnesium silicate hydrate cement

Environmental factors have a significant impact on the performance of cement-based materials. As a new type of low-carbon cementitious material, the performance of magnesium silicate hydrate cement (MSHC) under different environmental humidity conditions is crucial for its application. This study aimed to investigate the effects of environmental humidity on the hardening properties of MSHC. Compressive strength tests of MSHC were conducted under four different relative humidity (RH) conditions (RH of 33%, 58%, 75%, and 97%) and water curing (RH-w) condition. Microanalysis techniques were employed to reveal the strength mechanisms of MSHC under different environmental humidity conditions. The results showed that MSHC exhibited the optimal mechanical performance when RH was 75%, reaching 42.29 MPa. When RH was 58%, the compressive strength of MSHC was close to the optimal level, which was 41.02 MPa. However, under other humidity conditions (RH33, RH97, and RH-w), the compressive strength of MSHC was much lower than the optimal level, decreasing by 30.93%, 41.90%, and 63.66%, respectively. Pore structure analysis showed that the volume of detrimental pores (>100 nm) in the sample was the lowest when RH was 75%. Compared with RH75, the volume of detrimental pores in RH33, RH58, RH97, and RH-w increased by 20.47%, 9.83%, 36.77%, and 156.92%, respectively. In addition, the variation of environmental humidity resulted in different polymerization levels in the M-S-H gel, and higher degrees of polymerization were observed when RH was 58% and 75%.

Rheological properties and workability of PVA fiber and nano-SiO2 modified cement-based materials

Nanoparticles and fibers are frequently applied to improve the mechanical properties and durability of cement-based materials (CBM). In this study, rheology, workability and compressive strength tests were carried out to investigate the effect of PVA fiber (PF) and nano-SiO2 (NS) on rheological properties, workability and mechanical properties of CBM. Also, the function relationships of PF/NS content with rheological and workability parameters, rheological parameters with compressive strength were established separately. In addition, the effect mechanism of PF and NS was explained in depth. Finally, the fuzzy matrix method was employed to make a comprehensive evaluation on CBM performance. The results indicated that PF had negative influence on both rheological properties and workability of CBM. Whereas, NS only exhibited an increase in rheological properties of CBM at 0.5% content and a slight improvement in workability at 1.0% content. The comprehensive performance of CBM reached the optimum with PF content of 0.6%.

Effect of salty water on performance of cement-based materials

Effect of salty water on performance of cement-based materials

Seismic behavior of shear walls partially strengthened with UHPC in boundary element

Inspired by studies on shear walls reinforced with high performance cement-based materials, this paper explores the applicability of ultra-high performance concrete (UHPC) for improving the seismic behavior of shear walls. In this study, a novel shear wall partially strengthened with UHPC in the boundary element was developed, in which the UHPC was cast into the potential plastic hinge region of the boundary element. Partial application of UHPC can reduce construction costs and promote its use in building structures. To study the influence of distribution height and width of UHPC and axial load ratio on the seismic performance, six shear walls with a shear span ratio of 2.1 were tested under axial load and cyclic lateral load. The failure modes, lateral load-lateral displacement hysteretic behavior and ductility of the shear walls were also investigated. The experimental results indicated that the partial application of UHPC in boundary elements could effectively improve the performance of shear walls. Moreover, even if the volume ratio of UHPC was only 0.12, the shear wall partially strengthened with UHPC still showed good seismic performance under a high axial load ratio, indicating that this type of shear wall can be applied to the high seismic intensity and high axial load ratio regions.

Influence of Brick Powder with Different Replacement Ratio on Concrete Performance and its Microscopic Mechanism

Due to the shortcomings of waste bricks, they cannot be used repeatedly. The brick powder can partially replace cement for construction production, which can solve the problem of cement energy consumption. This paper studies the influence of brick powder on the performance of cement-based materials. The research shows that the water absorption effect of brick powder and the friction force are the two main factors affecting concrete. Energy dispersive spectrometer, inductively coupled plasma mass spectrometry and compressive strength tests show that the addition of brick powder leads to the increase of silicon/calcium. inductively coupled plasma mass spectrometry shows that although brick powder dissolves in the early stage, the volcanic ash effect is weak. The results of mercury intrusion porosimetry and ultrasonic pulse velocity are consistent with the compressive strength. When 5 % is added, it shows excellent durability. In addition, with the increase of age, the durability will not decrease significantly. Since the brick powder only needs to be ground to avoid the related process of cement, good economic and environmental benefits can be obtained with the increase of substitution rate.

A composite phase change material for improving the freeze–thaw resistance performance of cement mortars

Over 50% of engineering structures on earth seasonally suffer from long-term freeze–thaw cycles, which significantly decreases their durability. Cement-based materials (CBMs) are most widely used in civil engineering and often damaged by cyclic freeze–thaw action, so their service lives fall below design expectations. To improve the freeze–thaw resistance performance of CBMs, we chose n-tetradecane encapsulated in expanded graphite as a phase change material (PCM) to produce a new composite phase change cement mortar (PCCM). Four mass ratios of the PCM to cement were selected to mix with cement and fine aggregates. The key physical and chemical properties of the components in the new PCCM are tested to prove their material functions. Then, the physical and mechanical performance of the new PCCMs were also tested under different numbers of freeze–thaw cycles. The monitoring results show that the new composite PCCMs designed in this study all have excellent freeze–thaw resistance performance, according to which an optimal content of the PCM for the PCCMs was pointed out. The PCCMs’ ability to reduce freeze–thaw cycles was sufficiently analyzed by a numerical simulation of the heat transfer. The composite method and experimental results of the new PCCMs proposed in this study provide an important reference for industrial production and are also helpful for understanding the freeze–thaw mechanism of cement mortars.

Effects of ground coal bottom ash on the properties of cement-based materials under various curing temperatures

Steam curing is usually used in the production of precast concrete for modern industrial buildings. To promote the recycling of industrial waste and further reduce the amount of cement used in prefabricated construction materials, this study aims to investigate the effects of coal bottom ash (CBA) on the performance of cement-based materials under various curing temperatures. The microstructures and mineral phases of hydrated cement pastes were analyzed. The hydration reactivity of CBA was improved via grinding and elevating the curing temperature. Results showed that under the curing condition of 20 °C, the compressive strength of cement mortar added with 30 wt% of CBA-40 (the ash after 40min's grinding) was increased by 12.59% compared with the one made with 30 wt% of CBA-10 (the ash after 10 min's grinding). With the same addition of 30 wt% CBA-40, the compressive strength of cement mortar cured under 192 °C was increased by 12.66% compared with that cured under 20 °C. In general, finer CBA particles and higher curing temperature exhibited positive effects on improving the properties of cement materials. This study provides a novel approach to utilize the CBA to prepare high quality mineral admixtures for being used as a replacement of cement. It was concluded that the combination of suitable steam curing regime and proper fineness of CBA could produce low cost steam-cured concrete with excellent performance which possesses significant environmental benefits.

Assessment of low-cost organic phase change materials for improving infrastructure thermal performance

Recent studies in the literature have investigated the use of different phase change material (PCM) types and their incorporation techniques into cement-based materials (CBMs). The outcomes of such analysis have demonstrated similar negative and positive impacts on the overall performance of CBMs. So, it is challenging for the researchers to select one specific PCM type or incorporate a technique over the other. But, if appropriate PCMs and means of integration are employed, the undesirable properties of PCMs on the CBMs can be minimized. This study investigates the application of mixtures of 50 wt% ratios of coconut oil and soybean oil (COSO) and paraffin wax and soybean oil (PWSO) as blended organic-organic PCMs. These PCMs and paraffin wax (PW) were vacuum impregnated into expanded clay lightweight aggregate (LWA) to produce thermal energy storage aggregates (TESA). The results from differential scanning calorimetry (DSC) analysis of the as-received PW or prepared PWSO, and COSO or after multiple thermal cycles, showed high latent heat of fusions necessary to store a large quantity of heat. A wide range of melting points could be suitable for different degrees of phase transitions. Vacuum-impregnated TESA showed PCMs absorption capacity of 30.20% for PW, 28.00% for PWSO, and 27.42% for COSO. Moreover, to prevent leakage, the TESA was coated with latex. The application of low-cost/widely available PCMs/TESA, developed in this study, can be beneficial for improving the thermal infrastructure performance in developed/developing countries in different weather conditions.

Insight of key parameters in freeze-thaw damage on the performance of cement-based materials: A comparative study with rapid-freeze method

The degree of saturation (DOS) and water transport have significant influences on the F-T damage in cement-based materials. However, as a traditional test method, the regime of the rapid-freeze method restricts sealing conditions and the DOS before the F-T process (named initial degree of saturation: IDOS) of the specimen. In this study, the effects of IDOS and sealing conditions on the F-T damage were investigated by modifying these two conditions of the rapid-freeze method. The dynamic elastic modulus and compressive strength test results demonstrated that the unsealed specimens were more sensitive to IDOS in the water environment compared to the sealed specimens. For the unsealed specimens, a negative correlation relationship between the IDOS and the loss of the mechanical indicators for the unsealed specimens was originally disclosed in this work, which is opposite to the regularity for the sealed specimens reported in previous studies. Furthermore, the unsealed specimens with low IDOS exhibit greater F-T damage, implying that in the water environment, reducing the IDOS required by the rapid-freeze method will create harsher F-T conditions. In addition, decreasing the IDOS of the specimen results in a changed pattern of development of the compressive strength loss rate of the specimen. As supplement examinations, microstructure analysis (including TG, SEM, and MIP tests) was performed. Furthermore, a new mechanism of IDOS and sealing conditions on F-T damage was presented.

Effect of industrial waste molecular sieves on internally cured cement-based materials

Using waste molecular sieves (MS) instead of sand as water-absorbing fine aggregates in cement-based materials can effectively deal with factory adsorption waste and reduce sand consumption. In this article, the industrial waste molecular sieve is recycled and incorporated into cement-based materials. The effect of the molecular sieve as a hydration internal curing agent on the performance of cement-based materials is studied. A series of experiments are designed to find out the appropriate ratio and to evaluate and analyze the internal curing effect of waste molecular sieves. Compressive strength, flexural strength, and dry shrinkage properties of mortar with different dosages of the molecular sieve are tested. The water release behavior of the molecular sieve in mortar is comprehensively analyzed combined with the desorption test of the molecular sieve. Results show that the compressive and flexural strength increase by 5% and 10%, respectively, and the drying shrinkage decrease by 6% when 10% of sand is replaced by a molecular sieve under the same total water content. The hydration behavior of the sample is characterized by a microcosmic test of paste. Thermogravimetric analysis is used to calculate the content of corresponding hydration products and quantitatively describe the hydration degree of the internal curing paste mixed with MS. Results show that the content of hydration products is improved by the addition of the molecular sieve, which provides a theoretical basis for the enhancement of mortar to a certain extent.

Performance of Building Solid Waste Powder in Cement Cementitious Material: A Review.

Recycled powder (RP) is a by-product of preparing recycled aggregates from construction waste through debris removal, step-by-step crushing, screening, and mechanical strengthening. It is a fine powder with a particle size of less than 75 μm. Reasonable use of RP can increase the utilization rate of construction waste and reduce dust pollution. This study introduces the current research status of RP. It describes the source of RP; the activation mode of activity; the effect on several aspects, such as early performance and mechanical properties of cement-based materials; and its mechanism of action in light of the research and development. Moreover, the linear regression analysis method was used to obtain the mathematical model between the content of RP and the performance of cement-based materials. The correlation degree between the content of RP and the performance of cement-based materials was obtained based on the gray relation analysis method. It was concluded that the change of the content of RP had the most significant influence on the compressive strength of foamed concrete over 28 d. Finally, some feasible suggestions and prospects for RP are provided.

Effects of a novel hydrophobic admixture on the sulfate attack resistance of the mortar in the wet-dry cycling environment

The sulfate attack tends to cause deterioration in the performance of cement-based materials. An innovative hydrophobic agent named Yellow River Engineering Consulting (YREC) was developed to improve the resistance of the mortar to sulfate attack in wet-dry cycling environment. In this study, an investigation was conducted to investigate the effects of the acid, alkali and salt solutions on the durability of the YREC. Meanwhile, a series of hydrophobic mortars with varying YREC mass fractions were prepared to explore the sulfate resistance in the wet-dry cycling environment. The water migration in wet and dry process was compared by conducting the water absorption and desorption tests. In addition, the XRD, FTIR, ESEM and MIP were applied to further analyze the properties of the YREC. According to the analytical results, the microstructure and hydrophobic functional group of the YREC remained unchanged under the erosion of the acid, alkali and salt solutions. The YREC could significantly reduce the surface cracking, strength loss and structural loosening of the mortar under the wet-dry cycling sulfate attack. In addition, the YREC played a role in reducing the rate of the water absorption and desorption, resulting in a decrease in the sulfate concentration and penetration depth. Finally, the mechanism analysis showed that the YREC could enhance the inhibitory effect on bi-directional water migration through hydrophobization and refining the pore structure of the mortar.

Performance of cement-based materials containing calcined coal gangue with different calcination regimes

The storage of coal gangue (CG) takes up a lot of lands and pollutes the environment. Calcined CG has the potential to be used as supplementary cementitious material. In this paper, the CG from Yibin, Sichuan province of China were treated with different calcined temperature, holding times and cooling modes, and the microtopography, phase composition and pozzolanic reactivity of calcined CG were studied. Meanwhile, the fluidity, mechanical properties, hydration products, and pore structure of cement paste and mortar with different calcined CG were analyzed. The apparent color of coal gangue under different treatment methods has also been studied to promote its better application for a wider range in cement-based materials. Results showed that there exists an optimal calcination condition of calcined CG at 800 °C and holding time of 2 h. Rapid cooling and slow cooling reduced the activity of calcined CG. Calcined CG powder would reduce the fluidity of cement mortar. However, proper calcination temperature and sufficient holding time could eliminate it to some extent. It was also found that calcination temperature has a greater impact on the early age reactivity of CG when compared to different temperature treated CG powder, C8T2 sample has the best early activity. Compared to rapid cooling, slow cooling and water-cooling mode, room temperature cooling would result in higher reactive CG. CG powder after proper thermal treatment could refine the pore structure of the hardened cement paste in the later age (28 days), reduce the harmful pores content (>100 nm), and increase harmless pores content (<100 nm) in hardened cement paste. It was found that the CG powder of calcined at 800 °C for 2 h, cooling in water and room temperature might be more suitable as the supplementary cementing material combined the apparent color, pozzolanic reactivity, and preparation process.

Numerical and theoretical analysis of beam-to-column connections with ECC ring beams subjected to local compression loading

Engineered cementitious composite (ECC) is a kind of high performance cement-based composite materials with strain hardening and multiple cracking behaviour. Replacing concrete with ECC in the beam-to-column connection with ring beam may effectively improve the load-carrying capacity and ductility, as well as prevent cracks and solve durability problems caused by the brittleness of concrete. In this paper, the failure mechanism of beam-to-column connection with ECC ring beam subjected to local compression loading was investigated with the nonlinear finite element (FE) method. The results indicated that continuous lateral pressure was provided by the ECC ring beam, which improved the local compression performance of the ring beam connection. Extensive parametric studies on the local compression behavior of connections with ECC ring beams were also conducted. According to the simulation results, the peak strength of ECC connections was 13.0%–24.2% higher than that of concrete specimens. Increasing the ECC compression strength or ring beam width can effectively increase the load-carrying capacity of the connection, but the ECC tensile strain can only affect the ductility of the connection when the ultimate tensile strain was lower than 1.5%. Based on the FE analysis, an effective restraint width of the ECC ring beam was proposed, and theoretical models were established to predict the axial compressive bearing capacity of the beam-to-column connection with ECC ring beam.

Separation of calcined coal gangue and its influence on the performance of cement-based materials

Coal gangue (CG) is a kind of solid waste which discharged from the process of coal mining and washing. It has complex and volatile composites is not conducive to control its quality. If the high content minerals in CG could be separated relatively and applied properly according to its characteristics, the utilization of CG resources could be much more efficient. In this paper, granular CG was calcined and activated. According to the difference of color and texture, calcined coal gangue (CCG) was divided into yellow-white CCG (YW-C), red-brown CCG (RB-C) and light-red CCG (LR-S). The composition and properties of separated CCG were studied, and the feasibility of separating granular CCG based on its color, apparent density and composition difference was analyzed. The difference in reactivity of separated CCG and its causes were analyzed based on 29Si and 27Al NMR. The influences of separated CCG on the properties of cement-based materials were investigated. Results showed that, the three kinds of separated CCG all contained quartz, among those CCGs, LR-S has the highest content of quartz. YW-C contained a large amount of metakaolin, and its apparent density was only 2550 kg/m3. RB-C contained more colored iron phase, while LR-S contained a small amount of feldspar. The apparent density of RB-C and LR-S were significantly higher than that of YW-C. The reactivity of separated CCG was quite different. The relative contents of Q3(-101.86 ppm) structure and Al [5] in YW-C were 81.31% and 81.19% respectively, which were much higher than those in LR-S. Comparing with LR-S, YW-C with higher pozzlanic reactivity was mixed into cementitious materials could react with cement hydration products to produce C-(A)-S-H gel which will enhance the interface bonding between CCG particles and matrix, refine the pore size of matrix. The addition of YW-C is more conducive in improving the mechanical properties of cement-base materials.

Particle Distribution Characteristics and Hydration Mechanism of Cement-Based Paste Subjected to Mechanical Vibrations

AbstractMechanical vibrations have a significant impact on the performance of cement-based materials in engineering. In this study, the particle distribution characteristics and hydration mechanism...

Effect of Nano-Magnesium Oxide on the Expansion Performance and Hydration Process of Cement-Based Materials.

Many scholars are concerned about the effect of nano-MgO as an expansion agent on the performance of cement-based materials at an early age, but over a long period less attention is paid to expansion stability and mechanical properties. This article examines the influence of nano-MgO on the long-term consistency, fluidity, expansion stability, hydration, and mechanical properties of 30% fly ash cement-based materials and improves research into nano-MgO as an expansion agent. Expansion performance, flexural and compressive strength, and stability after boiling and autoclave treatment were tested for specimens mixed with a 2, 4, 6, 8 and 10% cementitious material mass of nano-MgO. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were employed to study their hydration process and microstructure. The results showed that nano-MgO had an obvious effect on the consistency, fluidity and expansion performance of cement paste. After curing in water for 365 days and autoclaving thereafter, the hydration of nano-MgO was relatively complete. The volumetric expansion pressure of the magnesium hydroxide (Mg(OH)2) crystals and the crystallization pressure generated after their continuous precipitation were the main reasons for the expansion of the slurry. Nano-MgO improved the microstructure of cement paste and significantly enhanced its long-term flexural strength and compressive strength. When the content of nano-MgO was less than 10%, the cement with 30% fly ash had good long-term stability with the potential to compensate for the shrinkage of large-volume concrete.

Development of Green Cementitious Materials by Using the Abrasive Waterjet Garnet Wastes: Preliminary Studies

The constant need for recycling, waste prevention and general environmental protection represent the new directive approaches imposed by the geo-political, industrial and environmental context, at the regional, European and global level. Ensuring the environmental protection and reducing the natural resources consumption represent general purposes of the sustainable development and also considerations to implement the Circular Economy Model [1]. The present study is developed with respect to the previously mentioned principles: the waterjet cutting operations by the use of abrasive GARNETs for quality, speed and accuracy gain, are in continuous expansion, generating proportionally increasing wastes, which could be valorized by innovatively integrating them in advanced cementitious materials for the construction industry. The international research regarding the use of abrasive waterjet Garnet wastes as raw material for construction industry are at incipient stage and quite limited, but preliminary results are promising. Further studies are presently developed, considering the potential benefits and also the reduced toxicity degree of abrasive Garnet wastes. This paper offers a general overview concerning the recent studies performed in the topic of efficient use of abrasive Garnet wastes in different building materials. Supplementary, further research, both theoretical and experimental is considered, for developing green, advanced, high performance cement-based materials by using the abrasive waterjet Garnet wastes, mainly as fine grain addition or replacement in the composites.

Effects of ligno– and delignified– cellulose nanofibrils on the performance of cement-based materials

Abstract This article presents an investigation into the effects of lignocellulose nanofibrils (LCNF) and delignified cellulose nanofibrils (DCNF) on the hydration, microstructure, and mechanical properties of cement paste. The effects of various fine contents and dosages of the cellulose nanofibrils (CNF) additions on the properties of cement paste are presented in this article. Nearly all the CNF containing batches were observed to have an accelerated cement hydration reaction within the first 30 h. However, after 80 h of hydration, the CNF additions no longer exhibited any significant effect on the degree of hydration. The cement paste batches with LCNF were observed to have improved workability compared to those with DCNF. It was further observed that the compressive and flexural strengths of the cement paste can be increased up to 20% and 111%, respectively, by the addition of CNF. Both LCNF and DCNF were found to reduce the amounts of ettringite and portlandite in the hydrated cement paste. The ideal fine content of CNF to achieve both microstructural and mechanical performance enhancement was observed to be around 75%. The experimental findings presented in this article indicate that LCNFs with low fine content (60–75%) would be a more desirable and potentially more economical additive for concrete production compared to the DCNFs with high fine contents.

Effect of nano-metakaolinite clay on the performance of cement-based materials at early curing age

The aim of this study is to improve the physical and mechanical properties of cement-based materials by adding nanometakaolinite clay (NKC). The results show the mechanism by which NKC modifies cement-based materials at the microscale level. A comparative experimental analysis of micromorphology and pore structure of cement specimens with NKC prepared using different NKC dispersion methods was performed to investigate the influence of the dispersion method and time on the dispersion of NKC in cement slurry. This showed that NKC can be efficiently dispersed in cement slurry by ultrasonic dispersion and stirring lasting 15 min, providing the most significant improvement to the cement pore structure. A large number of Ca(OH)2(CH) crystals in the early stage of hydration of cement are transformed into closely packed calcium silicate hydrate gel, thereby increasing the compactness of the cement matrix. After 28 days of standard curing, the CH crystal content in the hardened cements paste containing 5% of NKC by weight of cement was 12.72% lower than that of ordinary cement paste. The microscale analysis of the hardened cement paste showed that NKC can effectively fill the internal pores of cement-based materials, optimize the pore structure, and significantly improve the microscale compactness. NKC can also effectively improve the early mechanical properties of hardened cement paste. After curing for three days, the bending strength of cement paste prepared with 3% of NKC was 14.97% higher than that of ordinary cement paste. The compressive strength of hardened cement paste with 5% NKC addition was 15.13% higher than that of ordinary cement paste. During the ring test, the cracking time of cement mortar with NKC was earlier initiation and its surface stress–strain increased rapidly. Adding NKC increased the brittleness of hardened cement paste, which increased the risk of early age cracking.