scholarly journals Analisis Efektivitas Model Perkuatan dengan Injeksi Semen untuk Peningkatan Angka Keamanan Lereng

2017 ◽  
Vol 23 (1) ◽  
pp. 23
Author(s):  
Sumirin Sumirin ◽  
Rifqi Brilyanto Arief
Keyword(s):  
Slope Stability ◽  
Cement Paste ◽  
Safety Factor ◽  
Factor Of Safety ◽  
Coarse Aggregate ◽  
Field Testing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Drilling Technique ◽  
Mixed Samples

The problem of slope stability can be overcome by grouting of cement paste. But, the question often arises as to the extent of grouting of cement paste can increase the factor of safety. This study aims to determine the effectiveness of the effect of grouting on increasing safety factor on the slope of embankment. Experiments have been conducted in the laboratory using 6 types of mixed samples of sand and coarse aggregate. Field testing was conducted on 1 model to determine the effectiveness of grouting. The results of the experiments show that the injection of cement paste in this study proved to be effective in strengthening the embankment with the content of coarse aggregate 60%. The increase factor of safety (FS) using grouting is from FS= 1.9 (33.3%) to FS = 2.80 (90.0%). Factors determining the effectiveness of injection are: (a) injection method with drilling technique before injection to form cement column; (b) the optimum of water-cement ratio w/c = 1.5; (c) the ratio of spacing and injection diameter Lg / Dg = 8, the depth of injection 0.75 from the height of the embankment.

scholarly journals Carbonation Coefficients from Concrete Made with High-Absorption Limestone Aggregate

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Eric I. Moreno
Keyword(s):  
Cement Paste ◽  
Coarse Aggregate ◽  
Point Of View ◽  
Fine Aggregate ◽  
High Porosity ◽  
Accelerated Carbonation ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Limestone Aggregate ◽  
High Absorption

Normal aggregates employed in concrete have absorption levels in the range of 0.2% to 4% for coarse aggregate and 0.2 to 2% for fine aggregate. However, some aggregates have absorption levels above these values. As the porosity of concrete is related to the porosity of both the cement paste and the aggregate and the carbonation rate is a function, among other things, of the porosity of the material, there is concern about the effect of this high porosity material in achieving good quality concrete from the durability point of view. Thus, the objective of this investigation was to study the carbonation rates of concrete specimens made with high-absorption limestone aggregate. Four different water/cement ratios were used, and cylindrical concrete specimens were exposed to accelerated carbonation. High porosity values were obtained for concrete specimens beyond the expected limits for durable concrete. However, carbonation coefficients related to normal quality concrete were obtained for the lowest water/cement ratio employed suggesting that durable concrete may be obtained with this material despite the high porosity.

scholarly journals Effect of Water Cement Ratios on Compressive Strength of Palm Kernel Shell Concrete

2019 ◽  
Vol 2 (Issue 1) ◽  
Author(s):  
A.O Adeyemi ◽  
M.A Anifowose ◽  
I.O Amototo ◽  
S.A Adebara ◽  
M.Y Olawuyi
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Palm Kernel ◽  
Hardened Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Palm Kernel Shell ◽  
Compressive Strength Of Concrete ◽  
Palm Kernel Shells

This study examined the effect of varying water cement ratio on the compressive strength of concrete produced using palm kernel shell (PKS) as coarse aggregate at different replacement levels. The replacement levels of coarse aggregate with palm kernel shells (PKS) were 0%, 25%, 50%, and 100% respectively. PKS concrete cubes (144 specimens) of sizes 150mm x 150mm x 150mm were cast and cured in water for 7, 14, 21 and 28 days respectively. A mix ratio of 1:2:4 was adopted with water-cement ratio of 0.45, 0.5, and 0.6 respectively while the batching was done by weight. Slump test was conducted on fresh concrete while compressive strength test was carried out on the hardened concrete cubes using a compression testing machine of 2000kN capacity. The result of tests on fresh concrete shows that the slump height of 0.45 water cement ratio (w/c) increases with an increase in PKS%. This trend was similar to 0.50 and 0.60 w/c. However, the compressive strength of concrete cube decreases with an increase in w/c (from 0.45 to 0.60) but increases with respect to curing age and also decreases with increase in PKS%. Concrete with 0.45 water-cement ratio possess the highest compressive strength. It was observed that PKS is not a good substitute for coarse aggregate in mix ratio 1:2:4 for concrete productions. Hence, the study suggest the use of chemical admixture such as superplasticizer or calcium chloride in order to improve the strength of palm kernel shells-concrete.

scholarly journals Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

2021 ◽  
Vol 14 (4) ◽  
Author(s):  
Vanessa Fernandes Cesari ◽  
Fernando Pelisser ◽  
Philippe Jean Paul Gleize ◽  
Milton Domingos Michel
Keyword(s):  
Transition Zone ◽  
Cement Paste ◽  
Calcium Silicate ◽  
High Performance ◽  
Calcium Silicate Hydrate ◽  
Interfacial Transition Zone ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Nanomechanical Properties ◽  
Cementitious Matrix

abstract: Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

Revised Method for Rapid Determination of On-Site Water–Cement Ratio using Microwave Oven

2019 ◽  
Vol 2673 (8) ◽  
pp. 1-10
Author(s):  
Seyednavid Mardmomen ◽  
Hung-Liang (Roger) Chen ◽  
Guadalupe Leon
Keyword(s):  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Rapid Determination ◽  
Microwave Oven ◽  
Cementitious Material ◽  
Percentage Error ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Average Percentage ◽  
Site Water

The water–cement ratio (w/c) of delivered concrete is one of the most important parameters of the material’s quality. In this study, the AASHTO T318-15 guideline was adopted to estimate the water content of fresh concrete mixes and was revised for better precision. The additional step required sieving out the coarse aggregate after drying the sample in a microwave oven, and using it in the calculation of the absorbed water and cementitious material content. The cementitious content was assumed to be proportional to the mix design ratios. Several laboratory batches, as well as on-site water–cementitious material (w/cm) ratio tests, were performed on concrete mixes containing ordinary Portland cement, ground-granulated blast furnace slag, and Class F fly ash. The results of the experiments indicated the accuracy of the revised method was increased to have an average percentage error of about 2.16% from the actual w/cm ratio whereas the method based on AASHTO calculations was 6.2%. For cases with high chemical admixture dosages, washing vinegar was used to wash out the particles around the dried sieved coarse aggregate to calculate the w/cm ratio with a more precise mass for each sample. The correlation between the measured and calculated compressive strength using the measured amount of w/cm ratios provides evidence for the method’s accuracy. Therefore, the revised method can be used as an accurate and practical process of measuring the on-site w/cm ratios of fresh concrete mixes.

Microstructure of High Strength Cement Paste Systems

1984 ◽  
Vol 42 ◽  
Author(s):  
M. Regourd
Keyword(s):  
Cement Paste ◽  
Ultrafine Particles ◽  
High Strength ◽  
Interfacial Bond ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Composite Systems ◽  
Crystalline Hydrates ◽  
Low Porosity

AbstractHigh strength cement pastes include hot pressed, autoclaved, impregnated low water/cement ratio, macrodefect free, ultrafine particles arrangement systems. The densification of the microstrucure is mainly related to a low porosity and to the formation of poorly crystalline hydrates. In composite systems like mortars and concretes, the interfacial bond between the cement paste and aggregates is moreover less porous and more finely crystallized than the normal “auréole de transition”.

Finite Element Analysis of High Strength Recycled Concrete Beam Flexural Properties

2015 ◽  
Vol 730 ◽  
pp. 11-14 ◽  
Author(s):  
Hai Long Zhang ◽  
Chang Chun Pei
Keyword(s):  
Finite Element Analysis ◽  
Concrete Beam ◽  
Coarse Aggregate ◽  
High Strength ◽  
Recycled Concrete ◽  
Replacement Rate ◽  
Element Analysis ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Recycled Coarse Aggregate

By ANSYS finite element analysis we study the impact-span moment and deflection of high strength recycled concrete beam in state of initial cracking and yield with different water-cement ratio and recycled coarse aggregate replacement rate. The results showed that: 1With the increase of water-cement ratio and recycled coarse aggregate replacement rate, the deflection is on the rise. 2With the increase of recycled coarse aggregate replacement rate, the yield moment has a slight upward trend. And with the increase of water-cement ratio and recycled coarse aggregate replacement rate, the span deflection at the state of yield has a growing trend.

Evaluation of initial setting time due to superplasticizers

2017 ◽  
Vol 8 (2) ◽  
pp. 65
Author(s):  
Abhishek Singh ◽  
Shobha Ram ◽  
Alok Verma
Keyword(s):  
Water Content ◽  
Cement Paste ◽  
Setting Time ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Initial Setting Time ◽  
Initial Setting

This paper shows how polycarboxylate based superplasticizer affects the initial setting time of cement paste. Three superplasticizers are used in this study with different properties and aiming to determine the delay in initial setting time due to superplasticizer. Initial setting time is calculated as per IS: 4031-PART 5-1988 with different SP dosages (0.5%, 0.75%, 1.0% and 1.5% of weight of cement). Superplasticizer is an admixture which reduces the water-cement ratio or increase the workability at the same water content. This paper deals with the evaluation of initial setting time due to superplasticizers.

scholarly journals Strength and Deformability of Fiber Reinforced Cement Paste on the Basis of Basalt Fiber

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Yury Barabanshchikov ◽  
Ilya Gutskalov
Keyword(s):  
Crack Resistance ◽  
Cement Paste ◽  
Basalt Fiber ◽  
Fiber Content ◽  
Fiber Reinforced ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Particulate Reinforcement ◽  
Reinforced Cement ◽  
Basaltic Fiber

The research object of the paper is cement paste with the particulate reinforcement of basalt fiber. Regardless of fibers’ length at the same fiber cement mix workability and cement consumption equality compressive solidity of the specimens is reduced with increasing fiber content. This is due to the necessity to increase the water-cement ratio to obtain a given workability. The flexural stability of the specimens with increasing fiber content increments in the same conditions. There is an optimum value of the fibers’ dosage. That is why stability has a maximum when crooking. The basaltic fiber particulate reinforcement usage can abruptly increase the cement paste level limiting extensibility, which is extremely important in terms of crack resistance.

Prediction of Elastic Modulus of Cement-Based Materials Based on Power’s Volume Model

2012 ◽  
Vol 253-255 ◽  
pp. 474-477 ◽  
Author(s):  
Lang Wu ◽  
Bing Yan ◽  
Bin Lei
Keyword(s):  
Elastic Modulus ◽  
Elastic Properties ◽  
Cement Paste ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Micromechanics Model ◽  
Volume Model ◽  
Cement Based Materials ◽  
Hydrated Products ◽  
Multi Phase

The hydrated products, unhydrated cement and water (capillary pores) in the cement paste are seen as matrix, inclusion, Equivalent medium respectively, We used the micromechanics theories and Power’s Volume model to develop a multi-phase micromechanics model capable of simulating the elastic properties of cement-based materials, and the evolution of elastic properties in the hydration process was calculated at different water-cement ratio. The final experimental results show that this model can be used to predict the elastic properties of cement-based materials.

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