Addition Of Gypsum Research Articles

Physiological and yield response in maize in cohesive tropical soil is improved through the addition of gypsum and leguminous mulch

AbstractTropical soils tend to harden during drying due to the generally low content of free-iron and organic carbon, combined with high fine sand and silt proportions. It was hypothesized that the change in soil physical condition induced by the addition of a leguminous mulch in cohesive tropical soil enriched with calcium may mitigate soil hardening through wetting and drying cycles by rain or irrigation, thereby improving the soil rootability. A leguminous mulch was added in different concentrations to a structurally fragile tropical soil enriched with calcium, which then had different irrigation intervals. The treatments were with or without mulch (10 t/ha), with or without added nitrogen (100 kg/ha at 2 intervals) and two irrigation intervals. In 2015 the irrigation intervals were either 4 or 8 days, and in 2016 they were either 6 or 9 days. Two years were used in the attempt to achieve greater differences, as for tested variables, between treatments. Maize planted in these soil treatments was measured for physiological performance, water use efficiency and yield. Mulch used on structurally fragile tropical soil enriched with calcium was found to delay increased penetration resistance from hardening by wet/dry cycles. In this context, an improved soil rootability led to an enlargement of the leaf area index, greater nitrogen uptake and increased CO2 assimilation. This had important physiological consequences due to the positive effect on increased dry matter production and maize yield. In addition, these results suggested that mulch, used with urea, can delay the water supply for 3 or 4 days due to improvements in soil rootability caused by calcium and organic matter interactions. This may be crucial to a region where small intervals without rain are increasingly common due to global climate change. Therefore, due to a greater water use efficiency, this strategy may be a profitable way to increase crop productivity in tropical conditions rather than increasing water and nutrient application alone.

Investigation of the Incompatibilities of Cement and Superplasticizers and Their Influence on the Rheological Behavior.

The rheological behavior of cement paste and the improvement of its flowability takes center stage in many research projects. An improved flowability can be achieved by the addition of superplasticizers (SP), such as polycarboxylate ethers (PCE). In order to be able to use these PCEs effectively and in a variety of ways and to make them resistant to changes in the environment, it is crucial to understand the influence of SPs on cement hydration. For that reason, the topic of this paper was the incompatibility of a specific SP and an ordinary Portland cement (OPC). The incompatible behavior was analyzed using rheological tests, such as the spread flow test and penetration test, and the behavior was compared by means of an ultrasound technique and explained by the phase content measured by in-situ X-ray diffraction (XRD) the heat evolution measured by calorimetry, and scanning electron microscope (SEM) images. We showed that the addition of the SP in a high dosage led to a prevention of the passivation of the most reactive and aluminum-containing clinker phases, aluminate and brownmillerite. This induced the aluminate reaction to take place in the initial period and led to an immediate stiffening of the cement paste and, therefore, to the complete loss of workability. The results showed that in addition to the ettringite, which began to form directly after water addition, hemicarbonate precipitated. The fast stiffening of the paste could be prevented by delayed addition of the SP or by additional gypsum. This fast stiffening was not desirable for SPs, but in other fields, for example, 3D printing, this undesirable interaction could be used to improve the properties of printable mortar.

The stability of aggregates and organic carbon content after the application of gypsum, soil scarification and a succession of agricultural crops

Studies related to the monitoring of soil quality by physical attributes are important for the evaluation and maintenance of the sustainability of agricultural systems, besides indicating the appropriate management of the environment, aiming at its conservation and productivity. The objective of this study was to evaluate the stability of aggregates and organic carbon after the application of gypsum, soil scarification and a succession of crops. The treatments consisted of an absence and addition of gypsum, absence and presence of soil scarification, and three systems of crops in succession. The experimental design was made of randomized blocks, in a 2x2x4 factorial scheme, with eight replications. The aggregates were evaluated as stabled in water and soil organic carbon content. The treatment where gypsum was applied, as well as the soybean/maize/brachiaria/fallow (SMBF) succession system, presented better results in soil aggregation and higher levels of organic carbon.

Development of a cementitious material for thermal energy storage at low temperature

Energy storage systems are increasingly being used to improve energy performance in industry, transport and building. The storage of energy in the form of heat is widely used in the building sector in order to increase the use of solar energy, which is necessary to streamline energy management. The storage of excess summer solar energy appears to be a solution to compensate for the thermal energy deficit in winter and to reduce the environmental and socio-economic impacts of buildings. Currently, there are several adsorbent materials capable of storing thermal energy but they use high temperature storage (around 200 °C). Ettringite is a common hydrate found in cement-based materials and has the advantage of storing energy at high density but at low temperature, around 60 °C. Portland cements used in most construction materials produce small percentages of ettringite but calcium sulfoaluminate cements (CSA) can produce much larger amounts of this compound, with fairly rapid kinetics. In this paper, the hydration of CSA-based ettringitic systems is investigated with a view to synthesizing a new heat storage material. The hydration of CSA paste samples, with and without the addition of gypsum and portlandite, constituents allowing the exclusive production of ettringite, was followed by XRD and TGA. The ettringitic system (ES1) containing CSA, gypsum and portlandite produced only 48% of ettringite with an unstable structure (swelling), so ES1 was not selected. However, the ettringitic system (ES2) containing only hydrated CSA could reach between 65% and 70% of ettringite with a very stable solid structure. In order to use the ES2 as heat storage material, it was necessary to improve its permeability, thus enhancing its storage capacity. Improving the material by foaming provided an aerated ettringitic system (AES2) with high permeability, appropriate for heat storage. This allowed the development of an ettringite-based material with high heat storage density in low temperature conditions. The heat storage prototype allowed reaching a storage density of 117 kWh/m3 with a heat storage yield of 71%.

Comparison of advanced hydraulic properties between treated and untreated bauxite residue

Advanced hydraulic characteristics of treated and untreated Bauxite Residue (Red Mud) are studied and compared using a Steady-State Centrifugation (SSC) Unsaturated Flow Apparatus (UFA). Red Mud is the by-product waste from the Bayer process during aluminum production that has shown the potential of being reused as fill material in embankment construction, which can reduce the energy consumption of disposing the minging waste and producing fill materials. There is a limited number of documented studies on unsaturated hydraulic characteristics of RM. Furthermore, the high alkalinity (pH > 12) of the bauxite slurry is a challenge for reusing the material. Past studies have shown two effective and economic neutralization methods: (i) mixing with seawater and (ii) addition of gypsum. This study utilizes Cal State LA centrifuge facilities to characterize the unsaturated hydraulic properties of the treated and untreated Red Mud. The experimental results are used to develop the Soil Water Retention Curve (SWRC) for the three types of Bauxite Residue: untreated, treated with saline solution, and treated with gypsum. The results show that adding gypsum is more effective than mixing with saline solution in reducing the pH value of RM, and the samples treated with saline solution provide the lowest range of unsaturated hydraulic conductivity values compared with the other two types.

Mechanical Behaviour of Light Weight Concrete Panels

Light weight concrete (LWC) Playing a primary position in lowering the useless weight of the shape as properly as it meets the goals of load-bearing man or woman in some cases. LWC manufacture distinct in keeping with the use and availability of materials offers the freeness in concrete design blend. LWC advanced person including sound insulation, thermal resistivity and power lead for more use of the product. This paper deals LWC research at the partition panels with interlocking gadget to boom shear and flexural conduct compared to normal gypsum board partitions. The LWC gives more desirable energy at 0,050% in every of the aluminum and gypsum addition as compared to zero.0.5% in the cement substitute.

Influence of production parameters on calcium sulfoaluminate cements

The main appeal of calcium sulfoaluminate (CS¯A) cements is the possibility of reducing CO2 emissions. CS¯A clinkers can generally be produced at lower kiln temperatures and with lower limestone contents than required for portland cement clinker. However, it is important to assess the effects of various production parameters on the properties of CS¯A clinkers and cements. The influence of kiln maximum temperature, kiln retention time, and raw mixture proportioning on clinker properties, and those of water-to-cement ratio (W/C) and gypsum addition on cement hydration, were investigated. CS¯A clinkers were prepared in a laboratory furnace, with limestone, bauxite, and gypsum. Clinker and cement properties were explored with X-ray diffraction, isothermal calorimetry, thermogravimetric analysis, and scanning electron microscopy. Kiln temperatures as low as 1250 °C and retention times as low as 90 min. yielded satisfactory clinkers. Raw meal composition and calcination temperature have a greater effect on clinker phases than retention time. Hydration heat is affected mostly by raw meal composition. Hydration and strength gain were rapid until 3 d, after which they slowed down due to ettringite and AH3 coating the clinkers particles. Mortars with W/C = 0.6, achieved using citric acid as a retarder, gained ∼50 MPa strength at 28 d, 50–60% higher than mortars with W/C = 0.7.

Properties of Blast-Furnace Slag Cement Concrete Subjected to Accelerated Curing

Accelerated curing is used for mass production in the precast concrete industry. Autogenous shrinkage and drying shrinkage occur in concrete, during and after accelerated curing. Thus, thermal cracks may occur in concrete due to both heating and cement hydration at early age, whereas drying shrinkage causes cracks after demolding. Ground granulated blast-furnace slag cement (GGBS), a byproduct in steel manufacture, has been used to improve concrete strength development during accelerated curing but poses a challenge of increased shrinkage. In this paper, two types of granulated blast-furnace slag cements were used to study mechanical and shrinkage properties of water cured and concrete subjected to accelerated curing. Limestone powder and gypsums, with two different types of fineness, were other additives used. An accelerated one day curing cycle was adopted that consisted of a 3 h delay period, heating to 65 °C, a peak temperature maintained for 3 h, and, finally, cooling. The results indicated that increment in gypsum fineness increased concrete expansion at one day for both sealed and accelerated cured concrete. In drying condition, similar shrinkage was observed. The addition of gypsum provided slightly lower shrinkage, and this may help to reduce cracking of concrete. Limestone powder improved concrete strength at early age. The difference in blast-furnace cement fineness did not have significant differences in compressive strengths, especially at 28 days.

Management of soil salinity associated with irrigation of protected crops

Long-term evaluation of soil chemical changes in the soil is required to optimize irrigation of protected crops and to control associated environmental issues. In this study, the multi-component solute transport module UNSATCHEM of HYDRUS-1D was used to assess the effects of long-term (2018–2050) irrigation on salt build-up in the soil under unheated greenhouse conditions. Blended water (recycled water, artificially recharged groundwater and harvested rainwater) was used to irrigate tomato, cucumber, capsicum, and eggplant. Irrigation management included four leaching fractions (LF), i.e., accounting for 0, 15, 20, and 30% of applied excess water. The effects of four amounts of annual gypsum application, i.e. 0, 1.7, 2.6, and 3.4 t/ha, were also simulated.Model-simulated annual root water uptake by cucumber, tomato, capsicum, and eggplant was 303, 476, 642, and 649 mm, respectively, for an irrigation schedule based on outdoor temperature thresholds. Annual drainage was 4.1–6.1% of irrigation for these crops. Average salinity in the soil solution (ECsw) at the end of the simulation (year 2050) reached 6.5 dS/m for cucumber, 7.6 dS/m for tomato, 8.7 dS/m for capsicum, and 9.3 dS/m for eggplant. Soil salinity was building up at a nearly constant rate over 33 years. Exchangeable sodium percentage (ESP) at the end of the simulation was 30.8% for tomato, 27.1% for capsicum, 33.2% for eggplant, and 31.4% for cucumber. These results indicate that both salinity and sodicity will exceed critical threshold values and thus must be managed to maintain sustainability of irrigated horticulture. Modeling showed that higher irrigation (up to 15–20%) coupled with an annual addition of gypsum of 1.7 t/ha kept both salinity and sodicity (SAR, ESP) below critical thresholds while pH was reduced from 8.7 to 7.8, thus creating a favorable soil environment for long-term sustainable vegetable production under greenhouse conditions. The new gypsum application module implemented in the UNSATCHEM model has broad applicability in evaluating soil amendment scenarios to address sodicity hazards linked to long-term irrigation.

Variation in the sulfate attack resistance of iron rich-phosphoaluminate cement with mineral admixtures subjected to a Na2SO4 solution

Phosphoaluminate cement (PAC) has excellent resistance to sulfate attack due to its unique hydration product and dense hardened matrix. Mineral admixtures (MAs) are also known to enhance the performance of conventional cementitious systems. Thus, in this study, the effects of three kinds of admixtures (limestone powder, fly ash and gypsum) on the performance of iron rich-phosphoaluminate cement (IR-PAC) against sulfate attack were analysed using XRD, MIP, DSC and MTS to examine any synergistic effects resulting from their combination. The results indicated that excessive limestone powder incorporation (more than 9%) was detrimental to the IR-PAC performance. The addition of fly ash resulted in fluctuation of the flexural strength of the mortar due to the reduction in cement content and the micro-aggregate action of fly ash particles. The resistance coefficient of the IR-PAC mortars (against sulfate attack) with fly ash replacement of 9% (by weight) at 90 d could reach 1.13–1.16, and at a 12% replacement, the value could even reach 1.12. The addition of gypsum could transform etched components in IR-PAC mortar into ettringite in the early stage of cement hydration. As a result, the IR-PAC could maintain the stability of its own components under external sulfate erosion. However, excessive gypsum at the expense of cement would cause a decrease in the strength of the mortar and result in a slight reduction in the sulfate attack resistance coefficient.

Use of Freeze‐Thaw Purified Saline Water to Leach and Reclaim Gypsum‐Amended Saline‐Alkali Soils

Core Ideas More salts were distributed in liquid water than saline ice during the saline water freeze‐thaw process. Leaching with saline ice melt‐water was better than leaching with saline water at reducing soil EC and SAR. Gypsum application could improve the soil Ks when leached by the saline ice melt‐water. The addition of gypsum could eliminate the soil alkalinity hazards post leaching. Saline‐alkali soils adversely affect both the construction of ecological landscapes and crop production in coastal areas. This study aimed to investigate the effects of freeze‐thaw process on purifying saline water, and evaluate the potential of combining saline ice melt‐water leaching and gypsum addition for remediating coastal saline‐alkali soil. Saline water with a salinity of 10 g L−1 was tested in this study, and the leaching experiment included four treatments: saline water direct leaching (S), saline water direct leaching combined with gypsum application (SG), saline ice melt‐water leaching (SI), and saline ice melt‐water leaching combined with gypsum application (SIG). The results showed that more salts were concentrated in the bottom ice layer than in the other ice layers after the saline water was completely frozen. The salinity of the melt‐water decreased during the melting process, and the mean salinity of melt‐water during the second half of the melting process was significantly lower than the salinity of source water samples. During the leaching phase, the cumulative leachate losses of Na+, Ca2+ and Mg2+ were significantly greater for the SI treatment than that for the S treatment. After leaching, the soil electrical conductivity (EC) significantly decreased, and the SI treatment exhibited better performance than the S treatment in terms of reducing the soil EC and sodium adsorption ratio (SAR). The application of gypsum improved the soil saturated hydraulic conductivity (Ks) and decreased both the soil pH and alkalinity when the coastal saline soil was leached by the saline ice melt‐water.

Corn and soybean grain yield responses to soil amendments and cover crop in upland soils

A field study was conducted on upland soils for six years to determine interactive effects of winter wheat (Triticum aestivum L.) cover crop, organic and inorganic soil amendments on grain yields and nutrient utilizations in a no-till corn (Zea mays)-soybean (Glycine max) rotation. Experimental design was a split-plot arrangement with four replicates. Cover crops were the main plots and fertilization treatments used as sub-plot. Fertilization treatments included an unfertilized control, poultry litter, poultry litter (PL) plus flue gas desulfurization (FGD) gypsum and inorganic N fertilizer applied every other year to corn. Corn grain yield and grain N and P uptake were greater with PL than inorganic fertilizer in 2014 and 2016. Addition of FGD gypsum to PL significantly increased corn grain yield by 15% in 2016. Cover crop increased corn and soybean grain yields in a year with less seasonal rainfall possibly by conserving soil moisture.

Hydration of clinkers doped with baryte with and without addition of gypsum

The use of alternative fuels and raw materials in cement industry leads to the incorporation of some undesirable compounds into the clinker phases. One of them is barium oxide which influences the formation of clinker phases and related properties of the produced cement. Barium in clinker was already studied; the phase composition is changed depending on the amount of barium. However, detailed research focused on hydration properties of these clinkers and cements has not been carried out, yet. A clinker with barium oxide addition to raw meal was prepared. As a source of barium oxide, barium sulphate (baryte) was used in amount of 4% calculated to BaO in the clinker. Barium incorporated in clinker inhibits formation of alite; therefore, lime saturation factor was slightly reduced. Compared to barium carbonate—another source of barium oxide—barium sulphate influences the ratio of clinker phases less significantly. This clinker and a reference sample without barium were milled with and without addition of gypsum. Hydration of barium clinker and cement was examined by XRD in situ hydration and isothermal calorimetry. Hydration products were evaluated by means of thermogravimetric and differential thermal analysis. An increase in total heat of hydration can be seen in samples with barium. The heat is influenced by different hydration of clinker phases with incorporated barium, sulphates and by higher content of free CaO and C3A. According to XRD in situ hydration, hydration of samples with barium is suppressed, the amount of portlandite during the whole measurement is much higher in samples without barium.

Composition of mixing gypsum additives as environmentally friendly material in tropical soil to reduce grounding resistance

Grounding resistance is directly proportional to the amount of soil type resistance. While soil type resistance is influenced by several things, namely soil structure, temperature, the effect of water content (moisture), and the effect of chemical content in the soil. The purpose of this study was to analyze the decrease in the value of earth resistance by adding additives in the form of gypsum without a mixture of soil and gypsum mixed with soil. The results showed that the value of grounding resistance with the addition of gypsum without soil mixtures had a higher resistance value than grounding resistance without the addition of additives. Grounding resistance with the addition of gypsum mixed with soil on average can reduce the value of grounding resistance by 153.56 ohms with 25% gypsum, 157.2 ohms with 75% gypsum and 169.91 ohms with 50% gypsum.

Investigation on Hydration Process and Biocompatibility of Calcium Silicate-Based Experimental Portland Cements

In this work, the hydration process and cytotoxicity of lab-synthesized experimental Portland cements (EPCs) were investigated for dental applications. For this purpose, EPCs were prepared using laboratory-synthesized clinker constituents, tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate (C3A). C-A was prepared by the Pechini method, whereas C3S and C2S were synthesized by solid-state reactions. The phase compositions were characterized by X-ray diffraction (XRD) analysis, and the hydration process of the individual constituents and their combinations, with and without the addition of gypsum, was investigated by electrochemical impedance spectroscopy (EIS). Furthermore, four EPC compositions were prepared using the lab-synthesized C-A, C3S, and C2S, and their hydration processes were examined by EIS, and their cytotoxicity to HPC and HIPC cells were tested by performing an XTT assay. None of the EPCs exhibited any significant cytotoxicity for 7 days, and no significant difference was observed in the cell viabilities of ProRoot MTA and EPCs. The results indicated that all the EPCs are sufficiently biocompatible with human dental pulp cells and can be potential substitutes for commercial dental cements. Key words: Experimental Portland cement, Hydration process, Electrochemical impedance spectroscopy, Cytotoxicity, Dental cement

Rammed Earth stabilised with waste materials: a sustainable and resistant solution

Earthen dwellings are part of the vernacular architecture and cultural heritage of many countries in the Mediterranean region, and a renovated interest towards these types of structures is now widespread in the same countries mainly due to sustainability reasons. However, poor resistance to weathering compromises their durability and their popular acceptance. A fascinating option to improve the resistance of earthen structures while preserving their environmental sustainability is to use locally available waste materials as stabilisers. In this paper, the evolution over time of the mechanical resistance of rammed earth stabilised with residues from widespread industrial processes (i.e. fly ash from coal combustion and calcium carbide residue from acetylene production) was investigated. Waste-stabilisation prompted optimal long-term mechanical resistance; on the other hand, laboratory samples exhibited low compressive strengths in the short-term when cured under standard conditions. The addition of a supplementary industrial residue (i.e. gypsum from flue gas desulfurization) was explored to enhance the early-age strength. Results confirmed the short-term strength benefits induced by gypsum addition.

ВЛИЯНИЕ ДОБАВКИ ГИПСА НА КАЧЕСТВО КОМПОЗИЦИОННОГО ВЯЖУЩЕГО ДЛЯ ИЗДЕЛИЙ ЯЧЕИСТОЙ СТРУКТУРЫ

The effect of gypsum additives on the process of lime slaking and the quality of the composite binder is discussed. It is established that a different water-solid ratio, the water temperature and the use of an additive of natural gypsum can regulate the rate of the lime slaking process. The effect of this additive on the kinetics of the process, the temperature factor, the dispersion of the product and the quality of the products obtained by slaking are considered. During the hydration of highly active lime, the slaking temperature reaches high values, at which the process of gypsum dehydration begins. The combination of the exothermic process of lime slaking and the formation of a medium of saturated water vapor with the addition of natural gypsum to lime forms the semi-aquatic gypsum СаSО4∙0,5Н2О. It does not dehydrate, does not become insoluble and retains its chemical properties. There is no exothermic effect of crystallization of anhydrite. Strength results of composite binder cellular structure demonstrate that lime-based binder samples with the addition of natural gypsum under autoclave conditions are more solid than binder-free samples.

The combined effects of nitrogen fertilizer, humic acid, and gypsum on yield-scaled greenhouse gas emissions from a coastal saline rice field.

In coastal saline rice fields, rice production shows high greenhouse gas (GHG) emissions but low nitrogen use efficiency (NUE). However, few studies have focused on the combined effects of nitrogen (N) fertilizer and soil ameliorants on GHG emissions. Thus, a field experiment was conducted to study the combined effects of N fertilizer, humic acid, and gypsum on the global warming potential (GWP), yield-scaled greenhouse gas intensity (GHGI), rice grain yield, and NUE in coastal saline rice fields in southeastern China. The experiment was conducted with eight treatments: N0, N1, N0H1, N1H1, N0G1, N1G1, N0H1G1, and N1H1G1. The codes N0, N1, H1, and G1 represented treatments without N (0 kg N ha-1), with N (300 kg N ha-1), with humic acid (0.6 t ha-1), and with gypsum (0.6 t ha-1), respectively. Compared with the treatments without N addition, the application of N fertilizer significantly increased N2O emissions and grain yield by 41.9~130.6% and 32.8~57.5%, respectively, while significantly decreased the yield-scaled GHGI by 9.4~31.9%. Humic acid amendment significantly increased N2O emissions and grain yield as compared with the treatments without humic acid. Gypsum addition had no significant effects on CH4 and N2O emissions, GWP, yield-scaled GHGI, and grain yield in relation to the treatments without gypsum. In addition, compared with the N1 treatment, the N1H1, N1G1, and N1H1G1 treatments increased the grain yield by 18.3% (p < 0.05), 2.3%, and 10.4%, and decreased yield-scaled GHGI by 9.6%, 20.5%, and 31.2% (p < 0.05), despite similar GWPs, respectively. Overall, the N1H1 and N1H1G1 treatments are the appropriate fertilizer management to realize high yield together with low environmental impacts in coastal saline rice fields in China.

Long-term leaching and mechanical behaviour at recycled aggregate with different gypsum contents.

Construction and demolition recycling is regarded as an essential subject in the EU, as the target established by its policies to 2020 ratio is far from being achieved. The use of materials recycled from such waste has been widely deemed a contribution to the sustainability of the construction sector. Gypsum is one the limiting components of recycled aggregates used as a base layer in road construction. The aim of this research was to analyse the effect on mechanical properties, leaching behaviour and dimensional changes at long term in recycled aggregates with different gypsum contents. Load bearing capacity was conducted by California bearing ratio on prepared samples. Moreover, the compressive strength was conducted on samples prepared with a 3% cement addition. Both tests were studied long term. Dimensional changes were studied through swelling in California bearing ratio test mould under the modified Proctor conditions for 1 year and using an oedometer device for 5 months. Furthermore, environmental risk assessment was performed, classifying the material with gypsum addition as non-hazardous, given that sulphate anion was above the inert limit. Good mechanical behaviour in the long term and no significant dimensional changes were found regardless of gypsum content.

PEAT SOIL STABILIZATION IN RAWA PENING SALATIGA CENTRAL JAVA USING SYNTHETIC GYPSUM AND SALT

Peat is known as a problematic soil due to its low bearing capacity as well as its high and long settlement process. Necessary treatment is needed to improve peat soil capability. One of the methods to improve peat soil characteristics is by adding mixed materials. In this study the added materials are synthetic gypsum (CaSO4.2H20) and salt (NaCl). The research was conducted in a Soil Mechanics Laboratory using a consolidation test and direct shear tests. This research aims to find out the effect of CaSO4.2H20 and NaCl on consolidation and shear strength parameters. The soil samples taken for consolidation and direct shear tests were original and treated peat soil. The gypsum synthesis doses varied between 10%, 15%, and 20%, whereas the salt varied between 2%, 4%, and 6%, calculated from the dry weight of peat soil. The mixing of soil and the added materials was carried out under optimum water conditions of Standard Proctor compaction results. After the consolidation and direct shear tests were completed, the Scanning Electron Microscope (SEM) test was performed on the soil samples to determine the components of the peat soil on micron size. The addition of synthetic gypsum and salt resulted in the smallest Cc value of 0.0302 at 4% salt + 20% gypsum and the highest Cv value of 0.130 cm2/s at 6% salt + 20% gypsum. The addition of synthetic gypsum and salt mixture resulted in the highest cohesion, c value of 61,55 kPa at 6% salt + 15% gypsum and the greatest friction angle, ϕ value of 52.24° at 4% salt + 20% gypsum. NaCl gave better results than Gypsum in improving shear strength. A composition of 4%-6% of NaCl and 15%-20% of Gypsum is recommended, if NaCl and gypsum were to be applied simultaneously to improve shear strength.