Reduction In Compressive Strength Research Articles

Zonal Isolation Material for Low-Temperature Shallow-Depth Application: Evaluation of Early Properties Development

Summary Shallow-depth cementing presents unique challenges due to its low temperature and low pore pressure characteristic. The curing process of the cementitious material is typically prolonged at low temperatures resulting in a delayed curing process. The use of a low-density slurry to mitigate low pore pressure introduces another challenge, as it leads to a reduction in the final compressive strength. On the other hand, the operation requires the material to develop enough strength swiftly to be able to efficiently continue the next drilling operation. In addition, the presence of flow zones such as shallow gas and shallow water flow increases the complexity of the cementing process. There have been many developments in cementitious materials for shallow-depth cementing such as rapid-hardening cement and gas tight cement. However, there is little research focusing on the performance evaluation of each material at low-temperature conditions. This paper aims to present a thorough material evaluation for low-temperature shallow-depth cementing. The incorporated materials are American Petroleum Institute (API) Class G cement, rapid-hardening cement, gas tight cement, and geopolymer. Geopolymer is included to evaluate its potential as the green alternative to Portland-based cement. The sets of characterization were conducted during the liquid, gel, and solid phases. The samples were prepared under wide-ranging low temperatures and typical bottomhole pressures for shallow sections. The result shows different performances of each material and its behavior under low temperatures such as prolonged strength development and low reactivity, which necessitates further development of these materials.

Effect of variegated biosolids incorporation on the technological properties of fired clay bricks using Taguchi method

Green routes to effectively mitigate the extensive generation of variegated biosolids (VB) from the artisanal basketry sector has been specially constrained with traditional waste management practices. In this investigation, VB is used as a pore forming material in the development of fired clay bricks. Three compositional different bricks formulated with different dosages of VB (i.e., 0, 6 and 12 wt%) inclusion in brickmaking clay (BC) were fired at 900, 1000 and 1100 °C temperatures, and assessed for their physico-mechanical and thermal properties. Weight loss (WL) results showed the bricks WL increased with elevated firing and high addition VB admixed proportion. The highest 12.8% WL was observed among the BS12–1100 bricks. Fired shrinkage (FS) values were within recommended limits of 2.4–7.6%. Apparent Porosity (AP) results ranged from 19.3% to 38.6%. AP increased by 52.3% with VB addition but decreased up to 23.83% due to improved firing. Water absorption (WA) results were mostly found within the quality standards of 9.1 – 19.8%. Bulk density (BD) variations were observed between 1.3 g/cm3 and 2.2 g/cm3. Compressive strength (CS) reductions were in the acceptable range of 25.0 – 9.1 MPa. The thermal conductivity (TC) test results of the bricks showed a 28.59% improvement in the thermal insulation properties of the bricks. The Taguchi method revealed BS12–900 brick series as best optimized products due to its acceptable 9.1 MPa CS and least TC (0.452 W/mK). Thus, the usage of VB for brick production has an important contributory role to the economy and ecology of Ghana.

Waste Glass “An Alternative of Cement and Fine Aggregate in Concreteˮ

The major aim of this study is to use Waste Glass Powder (WGP) which is obtained from grinding glass waste using an abrasion apparatus, as cement and a fine aggregate substitute in concrete. The physical and mechanical characteristics, workability, and compressive strength of concrete were studied by using WGP as cement and fine aggregate replacement simultaneously. In order to perform correctly, the glass has to be sieved to particle sizes of less than 150 µm sieve for cement replacement and 4.75 mm for fine aggregate replacement. WGP was used to replace the cement and fine aggregate in concrete, yielding products with respective cement contents of 10.0% and 15% and fine aggregate contents of 15.0% and 20%, and the properties of this concrete have been compared with reference specimens with zero replacement. Cube specimens were cast, cured, and tested for compressive strength and workability at 7, 14, 28, and 56 days of age, and the results were then compared to those of traditional concrete. The use of WGP as a cement and fine aggregate substitute resulted in a reduction in concrete's compressive strength and workability. However, the findings revealed that WGP could be used as a partial substitute for cement and fine aggregates, with 10 to 15% of cement and fine aggregate substitution by WGP being the optimum in terms of strength and economy. As a result, we can utilize it in structures that are moderately heavy.

Long-Term Durability of Cement-Treated Soil Used in Offshore Airport Island Construction

In port and harbour areas, soft soils such as dredged soil can be solidified by mixing them with cement and other solidifiers in a pumping pipe. This method is known as pneumatic flow mixing. In this method, the soil and solidifiers are stirred and mixed using the turbulence effect of the plug flow generated in the pipe. The authors investigate the long-term durability of the treated soil on the artificial island where this method was first fully introduced. This paper summarises the results of five investigations on the island immediately after construction and 4, 10, 15, and 20 years after construction. No reduction in the unconfined compressive strength or needle penetration gradient was observed in the treated soil. Some degradation was observed at the top and bottom exposed surfaces of the treated soil, similar to that of soil subjected to other treatments. In addition to needle penetration and chemical tests, elemental mapping using an electron beam microanalysis was performed to determine the degree of degradation. The depth of degradation 20 years after construction was 18–25 mm. Although the amount of cement added in the pneumatic flow mixing method was relatively small, this value was within the range of degradation depths over time investigated in previous studies and did not represent a significant degradation.

Mechanical Properties of Rubberized Concrete at Elevated Temperatures

The use of rubberized concrete has become increasingly popular as a means of disposing of waste materials, such as used and end-of-life tires, while also providing an effective solution for construction applications. The strength and durability of rubberized concrete can be negatively affected by temperature fluctuations, but little is known about the performance of this material. Hence, the work presented herein aims to evaluate the performance of rubberized concrete when it is exposed to different temperature levels. In this study, rubberized concrete specimens were prepared by replacing 5–20% of crumb rubber by volume of fine aggregate. The specimens underwent a curing process for 28 days, followed by exposure to temperatures of 200 °C, 400 °C, and 600 °C for a period of 2 h. The residual test and normal cooling method were adapted. Surface characteristics by visual inspection, the residual weight, compressive strength, splitting tensile strength, ultrasonic pulse velocity, and dynamic modulus of elasticity were assessed and compared to unheated specimens. The study’s findings revealed that, when exposed to temperatures between 200 °C and 400 °C, rubberized concrete containing a 5% to 15% rubber content experienced less reduction in compressive strength than conventional concrete, which showed a reduction of 43% to 48.5%. Also, it was observed that the splitting tensile strength was more sensitive to elevated temperatures than the compressive strength.

Predictive modelling for the acid resistance of cement-based composites modified with eggshell and glass waste for sustainable and resilient building materials

The increasing demand for cement-based composites (CBCs) due to the advancement of infrastructure causes the exhaustion of natural materials and environmental pollution. Also, dumping industrial and agro-derived waste materials in landfills has negative impacts. Therefore, producing waste-derived CBCs by partially replacing cement and sand will be a favourable approach. Since CBCs' performance degrades when exposed to hazardous substances, their efficacy in a hostile environment is the key concern. This work utilised new computing methods to estimate the reduction in compressive strength (CS) of eggshell and glass powder-modified cement mortar (EG-CM) exposed to acidic conditions. Machine learning-based methods, including gene expression programming (GEP), decision tree (DT), multilayer perceptron neural network (MLPNN), and support vector machine (SVM), were employed. In addition, to examine the effectiveness of eggshell and glass powder for acid resistance, the SHapley Additive exPlanations (SHAP) approach was used. The built models exhibited good prediction performance for evaluating the loss in CS of EG-CM after the acid attack. SVM was noted to be the most accurate predictor with the highest R2 and least errors. SVM, DT, MLPNN, and GEP yielded results with R2 values of 0.88, 0.87, 0.85, and 0.85, respectively. The mean absolute percentage error for MLPNN was 17.9%, GEP was 15.5%, DT was 15.0%, and SVM was 10.6%. These error evaluations further confirmed the SVM's greater accuracy compared to other models. The SHAP study showed that glass powder was the most important element for EG-CM's resistance to CS loss after an acid attack, followed by 90-day CS, eggshell powder, cement, sand, silica fume water, and superplasticiser.

Production of eco-friendly UHPC with high durability and resistance to harsh environmental conditions using copper mine tailings

In recent years, constructing environmentally friendly buildings, also known as green buildings, has become a crucial aspect of sustainable development principles. This experimental study investigates the partial replacement of Portland cement with Sungun copper mine tailings (SCMT) for the production of eco-friendly UHPC. The research includes resistance testing against sulfate attack at a 5% Na2SO4 concentration at 30, 90, and 180 days, with SCMT replacement ratios ranging from 5% to 30%. Furthermore, the mechanical properties of eco-friendly UHPC are examined. The study also assesses the mass loss and compressive resistance of UHPC after exposure to an HCl acid solution for 30 and 90 days. The resistance of UHPC to chloride penetration is evaluated using the rapid chloride migration test (RCMT). Additionally, capillary water absorption and microstructural properties of eco-friendly UHPC are studied through SEM analysis. The results indicate that UHPC with partial cement replacement by SCMT had improved mechanical properties, durability, and microstructure. The compressive strength reduction in eco-friendly UHPC mixtures due to acid attack was minimal when 10% SCMT was used as a replacement for cement after being immersed in HCl acid for 90 days. Furthermore, the mixture that contained 10% SCMT demonstrated lower penetration for chloride ions, Which referred to an improvement of 17.6%, compared to the control mixture. In addition, the results of the tests demonstrated that the incorporation of SCMT in UHPC at a rate of 5%–15% had a beneficial impact on the resistance of UHPC to sulfate attack when exposed to a 5% Na2SO4 concentration. This study demonstrates the potential of sustainable UHPC production with SCMT as a suitable alternative to cement in aggressive environments containing acids, sulfates, chlorides, and similar compounds.

Cyclic freezing-thawing induced rock strength degradation, crack evolution, heave and settlement accounted for by a DEM model

A general discrete element method-based model is proposed to investigate the cyclic freezing-thawing induced damage of fractured rocks. A set of cracks is defined as an assembly of interparticle pores that are interconnected due to self-definition (pre-existing) or contact breaking (external force induced). During the freezing-thawing simulation, only the rock grains surrounding the cracks are subjected to frost heave pressure, which are expected to cause contact breaking and crack propagation. In this sense, most of the pores that do not form cracks in the numerical model will not participate in the calculation, so the computational cost and time are substantially reduced. The cracks connected to the atmosphere, i.e. the model boundaries, are classified as inactive cracks and their frost heave pressures are removed accordingly. Therefore, model convergence is recognized when all cracks are converted to inactive. Parametric analysis is further performed to show the influence of some important input parameters, including the unfrozen water content, calibration factor of frost heave pressure, crack density and dip. Finally, the freezing-thawing damage of rocks is quantified by the reduction in uniaxial compressive strength after a prescribed number of freezing-thawing cycles. The results are validated with an analytical solution. It is shown that the rock strength degradation, crack evolution, heave and settlement can be well simulated by the proposed model. This methodology can be extended to large-scale problems such as glacier slope instability or landslides.

A comparative experimental investigation of high-temperature effect on fibre concrete and high strength concrete using UT and CM methods

In this paper, a 28-day compressive strength test has been performed on samples including normal fibre concrete and high-strength concrete. The ultrasonic test (UT) as a non-destructive and compression machine (CM) as a destructive test were applied, and the results were compared. To investigate the effect of temperature, the samples were subjected to 200, 400, 600, 800, 1000, and 1200 degrees Celsius and the exposure time was equal to 30, 45, 60, 90, 120, and 180 minutes. Based on the results, it was observed that the minimum error observed between the UT and CM tests was 2.9 % and the maximum error between the two methods was 10.9 %, which shows the high accuracy of the ultrasonic testing method in determining the specimen’s strength. The average probable error of the method is determined to be around 6.8 %.Based on the results of the average decrease in compressive strength versus the heat exposure time, it is observed that the trend of changes and decrease in resistance over time for both types of tests is almost the same and has a negligible difference. At the end of 180 minutes of exposure, the resistance ratio for the ultrasonic test is 69.8 %, and 71.1 % for the compression machine. Furthermore, according to the average reduction in compressive strength due to heat exposure time, it has been observed that the results of the UT and UM tests have slight numerical differences, however, the trend of changes and reduction in resistance over time for both types of tests is almost the same. Finally, the accuracy of the UT in determining the compressive strength of specimens at high temperatures is fully confirmed.

Effect of the waste ornamental rocks on the hydration and life cycle of Portland cement composites

The production (extraction, cutting and polishing) of ornamental rocks generates a high volume of waste (abrasive slurry) which, when dry, generates a fine powder. The main impacts generated by the inadequate disposal of these residues are the contamination of the soil and the water table, alteration of the biological chain of living beings and siltation of rivers. Few studies analyze the influence of mud heterogeneity on the hydration of cementitious composites. In this context, this work aimed to evaluate the effect of the characteristics (chemical, physical and mineral) of waste from wet processing in ornamental rock plants (marble, granite, slate, among others) of different origins on the hydration process, performance and life cycle of composite with 20% replacement of Portland cement. Heterogeneity was evaluated by chemical composition, mineralogical and physical characteristics of the waste. The reactivity of the residue was determined in the Chapelle Modified test, Thermogravimetric analysis, and expansion test by Le Chatelier needles. The evolution of hydration was studied in pastes by evaluating the setting time and using the differential scanning calorimetry test. The mortars were characterized for consistency, porosity, and compressive strength. The results indicated that the residues show considerable heterogeneity. However, this does not influence the analyzed properties of the cementitious compounds. The high reduction in axial compressive strength indicates the use of these residues in lower contents or indication of this cement with this residue for non-structural purposes. It was concluded that the filer feat accelerated the hydration reactions in a similar way to the cement removed from the mixture.

Long-term deformation and mechanical properties evolution of cement paste with ultra-low water-to-cement ratio driven by water migration

Degradation of cement-based materials with ultra-low water-to-cement ratio may occur under water and drying conditions. However, the mechanisms remain unclear. In this study, we compared the mechanical properties, deformation, and mass change of cement pastes with a water-to-cement ratio of 0.17, which had been cured in saturated calcium hydroxide solution, sealed, and drying conditions for one year. The results show that the compressive strength of the cement pastes enhances and afterwards degrades under the three curing conditions. In both self-desiccating and drying conditions, the non-uniform shrinkage induced by water consumption dominates the evolution of the mechanical properties. Hydration affected by water adsorption/desorption has a stronger influence on compressive strength development compared to the weakening effect induced by water adsorption/desorption itself. When there is enough additional space in cement paste, extra hydration products formed with the external water supply can repair defects and fill pores, increasing compressive strength. In contrast, in dense structures, further hydration can cause swelling, cracking, and reduction in compressive strength. This study also confirms the contribution of the swelling of the calcium-silicate-hydrates gel on the expansion of cement paste in saturated conditions.

Age influence on compressive strength for concrete made with different types of aggregates after exposed to high temperatures

This study investigates the influence of concrete age and the type of coarse aggregate on compressive strength after exposure to high temperatures. Three coarse aggregates were used: crushed clay bricks as recycled aggregates, expanded glass as lightweight aggregates, and normal quartz aggregates. Specimens were initially cured in water for seven days, and then kept in laboratory conditions for different durations (28 days, 120 days, and 240 days). On the age of 120 and 240 days, specimens were exposed to high temperatures ranging from 200 °C to 1000 °C, and their residual compressive strength was determined.Results indicate that the compressive strength tests for the unheated specimens revealed an increase in strength with age, which can be attributed to the hydration of cement and the formation of a denser microstructure. The results of the residual compressive strength tests for concrete with quartz aggregates (M1-QZ) at 120 and 240 days showed a decline with increasing temperature and age. At 120 days, the strength ranged from 74.3% to 16.9%, and at 240 days, it ranged from 83.5% to 23.8%. Similarly, concrete with expanded glass aggregates (M2-EG) demonstrated decreased compressive strength with increasing temperature and age. The strength ranged from 94.3% to 8.6%, and 88.9% to 10.3% at 120 and 240 days, respectively. In contrast, concrete with crushed clay bricks (M3-CB) exhibited more favourable resistance to high temperatures, with a lower compressive strength reduction. The values ranged from 97.9% to 23.1% at 120 days and from 98.7% to 22.2% at 240 days. The reduced compressive strength after exposure to high temperatures can be attributed to the differences in thermal expansion and aggregates and the moisture loss.These findings demonstrate that the coarse aggregate type significantly influences the concrete's residual compressive strength after exposure to high temperatures.

Workability and Compressive Strength of Recycled Aggregate Concrete with Different Water-Cement Ratios

Use of demolishing waste in new concrete to develop green concrete has proved the need of the day with respect to the preservation of the environment from negative effects and natural sources of the aggregates. This research work presents laboratory investigations on the effect of different water-cement ratios on the workability and compressive strength of concrete made with 50% replacement of natural coarse aggregates with coarse aggregates from demolishing waste. Basic properties: water absorption, specific gravity, and abrasion resistance of both types of aggregates were assessed. A total of eight mixes were designed with water-cement ratios from 0.45 to 0.75 with an increment of 0.05. One mix with 100% conventional aggregates was designed and considered as a control mix to equate the results. A slump test was done to check the workability of all blends. Followed by casting, curing for 28 days, and testing of specimens for compressive strength were done. Test results show that a higher water-cement ratio increases the workability of the concrete but the compressive strength reduces. Assessment of the obtained results with those of the control mix shows a 70% improvement in slump values and 6.7% reduction in compressive strength with water cement ratio equal to 0.55 in comparison to the control mix made with water cement ratio equal to 0.45.

Crack healing in cement mortar using enzyme induced calcium carbonate precipitation

The current study highlights a breakthrough approach to crack healing by harnessing the potential of plant-based urease enzymes derived from urease-rich seeds. In this investigation, pulverized watermelon seeds (Citrullus lanatus) served as a valuable source of urease, which facilitated the production of calcium carbonate for crack repair in cement mortar. The healing process involved introducing a specialized suspension, consisting of urea, watermelon seeds’ urease, and calcium hydroxide, into the existing cracks of the specimens. Prior to treatment, the cracked mortar specimens exhibited a substantial 35% reduction in compressive strength as compared to the control specimens. The application of the biocementing suspension led to complete repair of the cracks, resulting in an impressive recovery of approximately 90% of the compressive strength on 7th day, comparable to the control specimens. The UPV results clearly indicated that the crack was healed on the 7th day thus confirming that the proposed biocementing suspension was able to repair the crack completely within 7 days of application. Moreover, the treated i.e experimental specimens demonstrated significant improvements in water tightness, indicating remarkable effectiveness of this crack healing methodology.

Investigation on the influential mechanism of FA and GGBS on the properties of CO2-cured cement paste

In the present work, the synergetic effect of fly ash (FA) and ground granulated blast furnace slag (GGBS) on the early compressive strength and microstructure development of CO2-cured mortars was investigated. A rim of several micrometers was found around carbonated cement particles, which contained not only silica-rich gel but also crystal calcium carbonate. The calcium carbonate formed around the cement particles were surrounded by an amorphous layer of around 3 nm, while no layers were observed around the calcite formed on FA or GGBS particles. The calcite formed on FA particles were hexagonal plate shaped, while the one on GGBS particles were rhombohedral shaped. The use of FA resulted in the increase of crystal size and crystallinity of calcite, while GGBS decreased the crystal size of calcite. The incorporation of FA and GGBS increased the calcite content and polymerization of silica-rich gel. However, this didn't result in a higher compressive strength. This was due to the looser microstructure and nanopores within the carbonation products compared to the pure ordinary Portland cement sample. The compressive strength of the ternary binder system showed linear relationship with capillary pores and the crystal size of calcite. Moreover, the effect of GGBS on the compressive strength reduction was more obvious than that of FA.

Experimental Study on Compressive and Flexural Performance of Lightweight Cement-Based Composites Reinforced with Hybrid Short Fibers.

This paper aims to experimentally study the compressive and flexural characteristics of cement-based composites developed for fabricating thin, lightweight, and high-performance components of buildings. Expanded hollow glass particles with a 0.25-0.5 mm particle size were used as lightweight fillers. Hybrid fibers made of amorphous metallic (AM) and nylon fibers were used to reinforce the matrix with a total volume fraction of 1.5%. The primary test parameters included the expanded glass-to-binder (EG/B) ratio, the fiber volume content ratio, and the length of the nylon fibers in the hybrid system. The experimental results demonstrate that the EG/B ratio and the volume dosage of the nylon fibers exhibited insignificant effects on the compressive strength of the composites. Additionally, the utilization of nylon fibers with a longer length of 12 mm resulted in a slight compressive strength reduction of approximately 13% compared to that of the 6 mm nylon fibers. Further, the EG/G ratio exhibited an insignificant effect on the flexural behavior of lightweight cement-based composites in terms of their initial stiffness, strength, and ductility. Meanwhile, the increasing AM fiber volume fraction in the hybrid system from 0.25% to 0.5% and 1.0% improved flexural toughness by 42.8% and 57.2%, respectively. In addition, the nylon fiber length significantly affected the deformation capacity at the peak load and the residual strength in the post-peak stage.

Combined Use of Sewage Sludge Ash and Silica Fume in Concrete

The lack of adequate space for sewage sludge disposal has become a significant challenge in many countries. Landfilling and using sewage sludge as fertilizer in agricultural lands are the main methods for disposal. However, these methods can result in soil and groundwater contamination as well as heavy metal and microbial pollution in soil. An alternative disposal method is using sewage sludge ash (SSA) in concrete production. If the sludge ash is reactive, it can replace a portion of cement in concrete; otherwise, it can be used as a filler. In the present study, X-ray fluorescence (XRF) experiments were conducted to determine the elemental composition of sewage sludge. Then, the sewage sludge was incinerated, and XRF and X-ray diffraction (XRD) tests were performed on the resulting sewage sludge ash. The ash was utilized in different proportions in the mortar and concrete specimens, and compressive strength tests were conducted on the resulting specimens. The results indicate that using 20% SSA instead of cement resulted in a 25% reduction in compressive strength in concrete specimens. However, the combination of 10% silica fume and 10% SSA was the optimal combination to compensate for the reduction in compressive strength caused using SSA.

Thermal energy saving and physico-mechanical properties of foam concrete incorporating form-stabilized basalt powder/capric acid based composite phase change material

The incorporation of phase change materials (PCM) in construction materials for the purpose of thermal energy storage (TES) can prevent temperature fluctuations and enable the conservation of thermal energy in buildings. Accordingly, this study aims to create a novel, environmentally friendly foam concrete incorporating a composite PCM composed of capric acid saturated waste basalt powder. Basalt powder, a byproduct of the grinding or crushing of basalt volcanic rock, was selected as a carrier material due to its high porosity resulting from its lightweight and porous nature. This allowed for the creation of a leak-free composite PCM, which was then integrated with foam concrete made of CEM I 42.5R cement, water, quartz sand, and a foaming agent. Basalt-PCM was substituted into the mixture at 50% and 100% by weight of quartz aggregate. Comprehensive evaluations were conducted on the novel foam concretes with regard to their morphological, mechanical, physical, thermal, and TES properties. The results indicate that the incorporation of basalt-PCM causes a minor reduction in the dry unit weight of the mixtures and a reduction in compressive and flexural strength. However, the leak-proof basalt powder/capric acid composite displayed a phase transition behavior, melting at 28.5 °C with a latent heat of fusion (47.9 J/g), which retained 99.5% capacity after 500 melting-solidification cycles. The specimen with 100 wt% basalt-PCM exhibited a melting temperature and latent heat of 27.8 °C and 17.4 J/g, respectively. Additionally, the basalt powder/capric composite exhibited high thermal stability up to 156 °C, far above its normal operating temperature. The foam concretes incorporating the basalt-PCM demonstrated solar thermoregulation properties, maintaining a more stable and comfortable indoor temperature. These results suggest that the form-stable PCM-incorporating foam concretes developed in this study can be considered as environmentally friendly building materials for thermoregulation and energy conservation.

Laboratory investigation of microstructure, strength and durability of cemented soil with Nano-SiO2 and basalt fibers in freshwater and seawater environments

The marine environment exposes cemented soils to a variety of adverse environmental conditions, which could substantially compromise the reliability and durability of foundations constructed on these engineered soils. Some researchers have recently proposed using nanoparticles to effectively strengthen and enhance the structure of cemented soil; however, this may compromise the ductility of cemented soils. Alternatively, some researchers have utilized basalt fibers to promote a stable network within the cemented soil by adding adhesion to the soil matrix, but this frequently results in a reduction in compressive strength. To address these issues, the addition of nanoparticles and basalt fibers to cement-treated soils is proposed as an engineering solution for extending the service life of cemented soils with adequate strength and durability in both freshwater and saltwater environments. This investigation utilized six different Nano-SiO2 concentrations and four different basalt fiber concentrations in the specimens. The specimens were then cured for 28 days in both freshwater and saltwater environments, and unconfined compressive strength tests (UCS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) experiments were performed to evaluate their properties, i.e. the microstructure, strength, and durability of cemented soil. The research results indicate that compared to conventional cemented soils, the improvement ratios after adding the optimal ratio of additives are 21 % (in freshwater environment) and 15 % (in seawater environment) for basalt fiber cemented soil, 196 % and 161 % for Nano-SiO2 cemented soil, and 257 % and 214 % for Nano-SiO2/basalt fiber composite cemented soil. Nano-SiO2 promotes the hydration reaction to generate more C-S-H, which wraps around the basalt fibers, enhances the bonding of basalt fibers in the cemented soil, effectively improves the mechanical properties and internal structure of the cemented soil, and the improvement effect is not weakened by seawater erosion.

Tensile properties of slag-based engineered cementitious composites with ground granulated blast-furnace slag

During the last decade, concrete technology has been undergoing rapid development, resulting in a new concept of engineered cementitious composite (ECC) to overcome the brittle behaviour of cement-based materials. ECC is one movement to fully incorporate waste material as an innovation in green material due to excellent toughness and energy absorption capacity, self-healing ability, fire performance, and remain durable under erosion environment. ECC exhibits a strain-hardening behaviour through the formation of micro cracking. This study is focusing on the tensile behaviour of the slag-based ECC. A total of five ECC mixes were designed with different cement to ground granulated blast-furnace slag (GGBS) ratio. Five samples of dog bone and three cylindrical for each mixture were prepared for direct tensile and compression tests. Compared to control samples, there are increments in compressive strength for samples contained 50-60% of GGBS and reductions in compressive strength for samples contained 70-80% of GGBS. The tensile strengths of ECC increase in the rate proportionally to the content of GGBS in ECC mixtures. The failure modes of the ECC cylinder samples including crushing under compressive load and few micro cracks are observed in ECC dog bones.