The Influence of the Water–Cement Ratio on the Mechanical Properties of Cement Mortars with the Addition of Sewage Sludge Biochar

Effect of waste plastic fibers on the printability and mechanical properties of 3D-printed cement mortar

This study has established the impact of a nano-ТіО 2 P25 modifier and a nanocomposite based on titanium dioxide, doped with sulfur and carbon dioxide (ТіО 2 /S,C), on the photocatalytic, mechanical properties and the structural formation of cement mortars. The paper reports the results of the particle size distribution of the Portland composite cement and the ТіО 2 nano additives; a comprehensive assessment of the particle size distribution has been performed both in terms of volume and specific surface. It has been proven that the ТіО 2 /S,C nanocomposite is characterized by the extremely high surface activity, which determines the photocatalytic properties of the surface of cement mortars. The comparison of the mechanical properties of cement mortars modified by titanium dioxide nano additives has been carried out. An experimental study has confirmed the improved photocatalytic properties of the cement mortar surface in the visible spectrum through the doping of the nano-sized titanium dioxide with carbon and sulfur. A combination of the ТіО 2 nano additives and the superplasticizers of polycarboxylate type leads to the increased strength of the modified samples in proportion to a hardening age. Given the high surface activity of the ТіО 2 /S,C nanocomposite's particles, the cement paste hydration products deposit at their surface, thereby forming such conglomerates with them that seal the microstructure of the cement matrix. It has been shown that using a nanocomposite based on the modified titanium dioxide decreases the indicators of free energy while the surface of the cement mortar acquires hydrophobic properties, which contributes to the processes of self-cleaning. Thus, there is a reason to argue about the feasibility of using the ТіО 2 /S,C nanocomposite to improve the photocatalytic, self-cleaning, mechanical, and hydrophobic properties of cement mortars

The mortar loses strength under acid rain conditions, causing cracking, weight loss and damage to the structure. This paper studies the effects of graphenene nanoplatelets(GNP) mortar under simulated acid rain conditions. A control sample without GNP and the addition of GNP were ranging from 0.2% to 0.6% by weight of ordinary Portland cement were prepared. In different corrosion days, the mechanical properties of the GNP cement mortar were measured, scanning electron microscopy also applied. Results showed that the mechanical properties of cement mortar added with graphene are improved. Compared with the control sample, the compressive strength and flexural strength of specimens containing 0.2wt% GNP are increased by 10% and 8%, respectively. Adding GNP can improve the acid resistance and durability of cement mortar.

Using recycled materials as renewable source of materials is the trend of researches all over the world. The aim of this work is study the possibility of using steel wires which extracted from tires recycling for reinforcing cement mortar. Extracted steel wires had been cleaned and chopped to (10) mm length before using for reinforcing cement mortar. different volume fractions, (0%, 0.8%, 1.7%, 2.5%, 3.4%), of chopped steel wires had been used to perform the study. Some physical and mechanical properties of prepared specimens had been tested to evaluate reinforcing efficiency after (28) days curing times. The results show improvement physical and mechanical properties of cement mortar, and the best improvement obtained when adding (0.8%) volume fraction of chopped wires. also experimental observations show corroded the chopped steel wires after curing treatment.

Effects of artificial geopolymer sand as an alternative to natural sand on dynamic mechanical properties of cement mortar

In this study, the modification of three types of fibers (basalt fiber, carbon fiber, high-silica fiber) on the structure and mechanical properties of cement mortar was investigated. Firstly, the basic mix proportion of the mortar was determined based on different contents of fly ash. The results revealed that the morphology effect of fly ash contributed to the improvement of mortar workability, reduction of water-binder ratio, and enhancement of mechanical properties of specimens. However, excessive fly ash led to severe carbonation in the cement mortar, damaging the structural compactness and adversely affecting the strength. The optimum content of fly ash was determined to be 4.45 wt%. Based on this, the optimal addition amounts of basalt fiber, carbon fiber, and high-silica fiber were determined to be 0.3 wt%, 0.6 wt%, and 0.3 wt% respectively. The main reinforcing mechanisms of each fiber in the mortar matrix were fiber fracture and fiber pull-out. Among them, the dispersion uniformity of basalt fiber was relatively poor, while the interface bond strength between carbon fiber and mortar matrix was optimal. The reinforced mortar incorporating carbon fiber exhibited a 28-day flexural strength, compressive strength, and elastic modulus of 18.0 MPa, 109.8 MPa, and 47.5 GPa respectively.

To study the influence of multi-wall carbon nanotubes (MWCNTs) on the mechanical and microstructural properties of cementitious composites, 0.00, 0.02, 0.08, 0.10, and 0.20 wt% of multi-wall carbon nanotubes were added into cement mortar, in which the cement-sand ratio was 1:1.5. The flexural and compressive strengths of cement mortar at the age of 3, 7, 28 and 90 d and the fracture performance at the age of 28 d were determined, its 2D micrograph was tested by means of SEM, and the 3D defects distribution was firstly determined with or without CNTs by means of XCT (X-ray computerized tomography). The results showed that 0.08 wt% of CNTs improved the compressive strength and flexural strength by 18% and 19%, respectively, and a significant improvement of its fracture property was observed. Moreover lower addition of carbon nanotubes to cement mortars can improve its microstructure and decrease the defects significantly compared to the cement mortar without CNTs. With the increase of the content of CNTs, the mechanical properties of cement mortars presented to be declined largely due to the agglomeration of CNTs.

Previous research indicates that the inclusion of nanosilica (NS) modifies the properties of the fresh and hardened state, compared to the traditional mineral additions. NS decreases the setting times of the cement mortar compared to silica fume (SF) and reduce of required water while improving the cohesion of the mixtures in the fresh state. Some authors estimate that the appropriate percentage of Nano-silica should be small (1 to 5% by weight) because of difficulties caused by agglomeration to particles during mixing, while others indicate that 10% by weight, if adjustments are made to the formulation to avoid an excess of self-drying and micro cracks that could impede strength. For this purpose, the present work aim to see the effect of the introduction mode of the nanosilica on the rheological and physic mechanical properties of cement mortars. In this study, NS was used either powdered with cement or in solution with the superplasticizer (Superplasticizer doped in nanosilica). Results show that the use of nanosilica powder (replacing cement on the one hand) has a negative influence on the rheological parameters and the rheological behavior of cementitious pastes. However, the introduction of nanosilica in solution in the superplasticizer (SP) was significantly improved the rheological parameters and the rheological behavior of cementitious pastes. Indeed, more the dosage of NS-doped SP increases more the shear stress and viscosities of the cementitious pastes become more fluid and manageable. A significant reduction of shear stress and plastic viscosity were observed that due to the increase in superplasticizer. A dosage of 1.5% NS-doped SP gave adequate fluidity and the shear rate was lower.

The g-C3N4/CoAl-LDH nanoflowers with a strong photocatalytic activity under UV–visible light irradiation was synthesized and applied with different dosages to prepare photocatalytic cement mortars (PCM). Besides the photocatalytic assessment by NOx degradation, the effect of g-C3N4/CoAl-LDH on the microstructural and mechanical properties of cement mortars were investigated by means of X-ray diffraction (XRD), X-ray computed tomography (X-CT), mercury intrusion porosimetry (MIP), capillary water absorption and strength tests. The results show that in addition to the unique air self-purification characteristics, g-C3N4/CoAl-LDH can promote cement hydration with filling effect and further improve the microstructural and mechanical properties of mortar. Moreover, the ability of g-C3N4/CoAl-LDH to capture CO32− can alleviate the influence of carbonation on photocatalytic performance. Therefore, g-C3N4/CoAl-LDH exhibits lasting photocatalytic performance in cement-based materials. This work is expected to contribute to the effort of searching for new multifunctional nano-additives for improved sustainability of building materials.

With the increasing need for sustainable construction materials and to cope with plastic waste management, a lot of research has been undertaken on the recycling of plastics in cementitious composites. An experimental investigation was performed in the current study to study the effect of adding ground polyvinyl chloride (PVC) waste particles on physical, mechanical and thermal properties of cement mortars. Fifteen series of mortar mixtures were made with four plastic contents (5%, 10%, 15% and 20% by cement weight) and three water-to-cement (w/c) ratios (0,35, 0,40 and 0.45). Workability, density, thermal conductivity and flexural and compressive strength were investigated by comprehensive tests in compliance with the applicable ASTM standards. The results obtained showed that plastic admixture induced a significant reduction in mortar density (up to 4.5%) and thermal conductivity (11%), representing its applicability as an artificial lightweight material. It was shown that workability was more affected by plastic dosage amount and w/c ratio according to the flow table test results, whereas moderate amounts of plasticizer enhanced workability. It was also found that the mechanical performance followed nonlinear behavior, where the flexural strength increased by approximately 43% and compressive strength up to 59% with a 5% plastic content achieved; thereafter, both performances decreased at higher concentrations due to the lack of strong interfacial bonding with particles and higher porosity. The findings demonstrate that the controlled incorporation of plastic waste at low dosages is mechanically feasible and effective, identifying 5-10% addition as the optimal range for improving mortar performance without compromising strength.

Lithium slag(LS) is industrial solid waste during the production of lithium carbonate. LS has pozzolanic effect and replace cement to achieve the purpose of protecting the environment and saving resources. In order to clarify the influence of fineness and content of LS on the performance of cement mortar. The effects of different fineness and content of LS powder on the workability, mechanical properties and microscopic properties of cement mortar were studied. The results shown that the grinding time refined the particle size of LS and increased the particle content in the range of 0.95μm~5.68μm. Fineness of LS had little effect on the workability and mechanical properties of cement mortar. Excessive LS had significant negative impact on workability and mechanical properties of cement mortar. When the content of LS was 10 %, the heat release, the production of Ca(OH)2 and ettringite of cement paste increased. Early mechanical property of cement mortar was unreduced and effectively improved later mechanical properties under this content. The research can provide data support for the application of LS in practical engineering.

Study on the effect of plant extracts as low carbon green admixtures on the performance of cement mortar

Despite many of the research studies on the effect of the silica fume content on the mechanical properties of the cement mortar, there has not been a comprehensive study investigating the effect of silica fume content, curing time and water to cement ratio on the compressive, tensile and flexural strengths of cement mortar. In this study investigates the subject which could be beneficial for building and construction field. More than 1000 data on the mechanical properties of the cement mortar modified with different percentages of silica fume varied from 5% to 55% (by dry weight of the cement) collected from the literature. The statistical analysis, modelling and non-linear regression analysis were performed on the collected data. The water to cement ratio (w/c) ranged between 0.20% and 1% and the compressive strength, tensile strength and flexural strength of cement mortar modified with silica fume up to 90 days of curing were ranged between 2.5MPa and 87 MPa; 2 MPa and 6.8 MPa; and 1.2 MPa and 9.2 MPa, respectively. Vipulanandan correlation model was used and compared with the Hoek-Brown model to correlate the mechanical properties of cement mortar modified with silica fume. The Vipulanandan correlation model has a lower root mean square error (RMSE) compared to the Hoek-Brown model. The results of the present study showed that there is a good relationship between the compressive strength with flexural strength and tensile strength for cement mortar modified with silica fume. Based on the data analysis the per cent of silica fume up to 55% had the lowest effect on increasing the compressive strength compared with w/c and curing time.

Despite many of the research studies on the effect of the particle size distribution of the sand and fly ash content on the mechanical behavior of the cement mortar, there has not been a comprehensive study investigating the effect of particle size distribution curve corresponding to 10% of finer (d10), fly ash content, curing time, sand particle size distribution properties (d10), and water to cement ratio (w/c) on the compressive (σc), tensile (σt), and flexural (σf) strengths of cement mortar. Therefore, this study investigates the subject which could be beneficial for the geotechnical and building and construction field. In this study, more than 1000 data on the mechanical properties of the cement mortar modified with different percentages of fly ash varied from 5 to 75% (by dry weight of the cement) collected from the literature. Statistical analysis and modeling were performed on the collected data. Vipulanandan p-q model was used and compared to the Logistic Growth model to predict the particle size distribution of sands used in the cement mortar. The water to cement ratio (w/c) of the cement mortar ranged between 0.20–0.80 percent and the compressive strength (σc), tensile strength (σt) and flexural strength (σf) of cement mortar modified with fly ash up to 90 days of curing were ranged between 15–88 MPa, 0.4–5 MPa, and 1–10 MPa, respectively. Vipulanandan correlation model was also used and compared with the Hoek–Brown model to correlate the mechanical properties of cement mortar modified with fly ash. The analysis and modeling results of the present study showed that there is a good relationship between the compressive strength (σc) with w/c, curing time, fly ash content and d10. Based on the coefficient of determination (R2) and root mean square error (RMSE) the compressive strength (σc), flexural strength (σf) and tensile strength (σt) of cement mortar quantified well as a function of w/c, the percentage of fly ash, curing time, and d10 using nonlinear relationship.

Effect of nano clay particles on mechanical, thermal and physical behaviours of waste-glass cement mortars