Drying Shrinkage Rate Research Articles

MECHANICAL PROPERTIES AND SHRINKAGE PROPERTIES OF THE CONCRETE WITH RECYCLED FINE AGGREGATE AND ADMIXTURE

In Japan, it is forecasted that massive amounts of concrete waste material will be generated in the future as a result of demolition of many buildings, and expansion of the use of recycled aggregate is expected. In this study, it was verified the effect when relatively large amount of admixture is mixed, a combination of recycled fine aggregate of different quality and various admixtures, combination of each admixture in order to realize high strength and high durability by using recycled aggregate. The increase in the drying shrinkage ratio due to the deterioration of the recycled fine aggregate quality was larger than the fluctuation due to the admixture mixing ratio and the drying shrinkage ratio was distributed by forming a group for each quality of recycled fine aggregate. In the relationship between the pore volume and the compressive strength, when evaluated with pore volume of 2 μm or less in both cases, a good linear relationship could be confirmed. The relationship between the pore volume and the drying shrinkage rate was similar. Therefore, it was suggested that compressive strength and drying shrinkage ratio of mortar contained composite recycled fine aggregate and admixture could be predicted by evaluating with the pore volume of 2 μm or less.

Drying Shrinkage and Suppression Technology of HPC in Extremely Arid Area

Supplementary materials Such As Slag (SG), Fly Ash (FA) and Silica Fume (SF) are necessary for reducing the drying shrinkage of High-performance Concrete (HPC) in arid environments and extremely arid area. This paper investigates the drying shrinkage of HPC with the composites of 10% Silica Fume (SF) and 20% Fly Ash (FA) additions and another HPC incorporated with 10% SF?20% FA and 20% slag (SG), which were exposed to the conditions of 30% Relative Humidity (RH) and 50% RH. The inhibitive mechanism of Aluminate Expansion Agent (AEA) on the drying shrinkage of HPC reveals that the dry shrinkage can be inhibited by the expansion agent as long as the high density of concrete structure and the internal “surplus water” can be ensured. Furthermore, the additions of the composites of SF, FA and SG, super-plasticizer, high modulus fiber (PF) and AEA, can reduce the drying shrinkage and improve the moisture sensitivity of shrinkage of the concrete. The drying shrinkage rate of HPC in extremely harsh environment decreased to about 300 × 10−6 and no shrinkage cracks appeared on the surface of the HPC incorporated with SF, FA and SG. The perfect combination of high volume stability and high durability of HPC was realized.

Evaluation of the preparation and fertilizer release performance of planting concrete made with recycled-concrete aggregates from demolition

This paper developed a new generation of planting concrete (PC) made from recycled aggregates of demolished concrete (RADC) to improve the fertilizer retention properties and reduce the cost. By optimizing the fabrication procedures and mix proportions of the planting concrete with RADC (PC-RADC), the interconnected porosity, water permeability coefficient and 28-day compressive strength can be enhanced to 40.9%, 2.88 cm/s and 6.5 MPa, respectively, which laid a fundamental basis for the improved release of fertilizer in the developed planting concrete. The experimental results revealed that with the addition of 4.4 kg/m3 urea fertilizer, not only the 28-day release rate of nitrogen, a key parameter representing the fertilizer release performance, of the PC-RADC was improved by 72.1%, but also a more stable pore fluid alkalinity at approximately 8.20 pH was developed, which provided a suitable environment for plant growth. Moreover, the frost resistance of the urea fertilized PC-RADC was enhanced by 12.4% with the reduction of 150-day drying shrinkage rate by 20.5%. In conclusion, utilization of RADC has a great potential for the sustainable PC development with improved fertilizer release performance.

Effect of Borax on Properties of Potassium Magnesium Phosphate Cement

The effects of borax on the setting time, compressive strength, bond strength, drying shrinkage and pH value were investigated for potassium magnesium phosphate cement (MKPC). The results show that with the increase of borax dosage, the setting time is gradually extended, both compressive strength and bond strength are greatly decreased, the drying shrinkage rate is increased. Especially high dosage of borax, the extension of setting time is more obvious. Compared with that without borax, when the dosage of borax is 12.5%, setting time can be prolonged by 214.8%.The influence of borax dosage on the time-dependent effect of compressive strength shows that when the dosage of borax is 2.5%~5.0%, compressive strength increases rapidly from 4h to 1d, and increases relatively slowly from 1d to 3d. When borax dosage is less than 2.5% or higher than 5%, the law of time-dependent effect of compressive strength is the opposite. Compared to borax prior to magnesia addition, the pH value of the system is larger and the time of inflection point is advanced when borax and magnesia are mixed together at the same time. The increase of borax dosage can reduce the pH value of the system, and decrease the rising rate of pH value, at the same time the required time when the final pH value is relatively stable is longer.

Effects of nano-particles on improvement in wear resistance and drying shrinkage of road fly ash concrete

Nano-materials have been widely applied in cement-based materials due to its excellent performance. Two types of nano-particles, namely nano-SiO2 (NS) and nano-SiC (NC), were employed to prepare nano-modified fly ash cement mortar and road fly ash concrete specimens respectively, and the effects of the nano-particles content on wear resistance and drying shrinkage were studied on the basis of strength test, the mechanisms were then analyzed theoretically. The results indicated that nano-particles could improve the wear resistance of road fly ash concrete, but increase thedrying shrinkage. The optimum added dosage of NS for single-doping NS concrete was 2%, and that for NC was 3%. The superior wear resistance of nano double-doped concrete could be found with 2% NS and 2% NC, and meanwhile, the wear loss was only 0.64kg/m2, with a decrease by 75%; the drying shrinkage rate of the concrete containing 2% NS and 2% NC at 28d was increased by 124.8% and 85.8%, respectively, compared to the reference concrete. Therefore, it is concluded that due to its surface effect, pozzolanic reaction and microscopic aggregate filling effect, nano-particles have larger surface energy, to change the orientation degree of calcium hydroxide crystals in the interface transition zone and fill pores among cementitious materials, thereby improving the wear resistance and drying shrinkage of fly ash concrete. These results would provide guidance on the design of the high wear resistance and low drying shrinkage fly ash concrete.

콘크리트 배합조건에 따른 수축저감제의 건조수축 특성

최근 소비패턴의 변화에 따라 대형마트, 아울렛 및 물류창고 등과 같은 구조물들이 증가하고 있다. 이와 같은 구조물들은 초평탄 바닥부재를 포함하고 있기 때문에 소성 및 건조수축에 의한 슬래브 부재의 균열 억제 관리를 철저하게 실시한다. 슬래브 부재의 균열을 억제하기 위한 방안으로 화학적 균열저감 방법을 사용하고 있으며, 특히 수축저감제에 대한 사용검토가 증가하고 있다. 그러나 이에 대한 국내 연구결과는 부족한 상황이다. 본 연구에서는 수축저감제를 사용한 콘크리트의 수축특성과 배합요인 변동에 따른 건조수축 특성을 검토하였다. 국내 수축저감제는 해외 고급형 수축저감제와 성능이 유사한 것으로 나타났으며, 수축저감제 사용량이 증가할수록 건조수축 억제 효과는 높아지는 것으로 나타났다. 수축저감제 1.5%를 사용한 시험체는 재령 100일에서 수축저감제를 사용하지 않은 시험체에 비해 건조수축량이 약 절반으로 나타났다. 또한, 혼화재료 사용에 대해 특별한 성능변화는 없는 것으로 확인되었다. Recently, structures such as large retailers, outlets and warehouses have been increasing in accordance with changes in consumption patterns. Since these structures include ultra-flat slab members, they are thoroughly managed to control slab cracking by the plastic and drying shrinkage. In order to control the cracking of the slab member, a chemical crack reduction method is used. In particular, the use of the shrinkage reducing agent has been examined. However, domestic research results are limited. In this study, the shrinkage properties of concrete using shrinkage reducing agent and the drying shrinkage properties according to the mixing factors were investigated. The performance of domestic shrinkage reducing agent was appeared similar to that of overseas high-grade shrinkage reducing agent. As the shrinkage reducing agent usage increased, the drying shrinkage reduction effect increased. At the age of 100 days, the dry shrinkage rate of specimen with the shrinkage reducing agent of 1.5%was shown about half that of the specimen without the shrinkage reducing agent. The shrinkage reducing agent was gound to have no specific performance change for the use of the admixture.

Comparative Study on the Effects of Recycled Glass–Fiber on Drying Shrinkage Rate and Mechanical Properties of the Self-Compacting Mortar and Fly Ash–Slag Geopolymer Mortar

AbstractIn this comprehensive experimental study, the effects of recycled glass fiber on the drying shrinkage and mechanical properties of the self-compacting mortar and fly ash–slag geopolymer mor...

Quality properties of self-consolidating concrete mixed with waste concrete powder

This study has been conducted as part of the research project of utilizing waste concrete powder (WCP) created in large quantity during the production of high quality recycled aggregates as a substitute for ordinary Portland cement. The Blaine fineness and the average particle size of WCP used in the study are 1360 cm2/g and 90μm, respectively. AS the main characteristic of WCP, it is particle were angular similar to cement, and hydrated products were attached on the surface of particles. Although the flowability, segregation resistance ability and filling ability of SCC tend to go beyond the target range with an increase of mixing ratio (0, 15, 30 and 45%) of WCP, improvements have been made with a proper use of GGBF. The compressive strength at 28days has achieved 30MPa or more at WCP’s mixing ratio of 15% and the splitting tensile strength and elastic moduli have shown similar results to those of previous studies. The drying shrinkage rate and carbonation depth of SCC with WCP in it have seen improvements on quality when used together with GGBF rather than WCP alone.

Vpliv kombinacije letečega pepela in dodatka za zmanjšanje krčenja na lastnosti malte iz z alkalijami aktivirane žlindre

This study is aimed at reducing the drying shrinkage of alkali-activated slag (AAS) through the use of low-calcium fly ash (FA) and commercially available shrinkage-reducing additives (SRAs) originally developed for OPC-based binders, since there are no such admixtures tailored for AAS systems. Generally, all the SRAs tested are based on modified alcohols. All the mortars were based on slag activated by waterglass, with the water-to-slag ratio equal to 0.40 and the sand-to-binder ratio 2:1. In the first step, the effect of the partial replacement of slag by FA (25, 50 and 75) % of mass fractions on the drying shrinkage and compressive strength was investigated. On the basis of the obtained results a mortar with 50 % FA in the binder was chosen for subsequent experiments, where the influence of three types of SRAs on the drying-shrinkage behaviour was examined. It was observed that while 25 % of the FA did not affect the drying shrinkage significantly, 50 % and 75 % of FA in the binder decreased the drying shrinkage by 57 % and 78 %, respectively. However, with an increasing content of FA, the compressive strength markedly decreased. All the tested SRAs had a similar effect on the drying shrinkage of the slag/fly ash (50/50) mortar: at a dose of 0.50 % (by mass of slag) the shrinkage was reduced only slightly, whereas 1.0–3.0 % of SRA resulted in a decrease by 49–66 %. Also, the drying shrinkage rate during the first days of drying was modified. However, all the SRAs reduced the compressive strength as compared to the neat slag-FA mortar, especially when the doses were higher than 0.50 %.

Study on the Drying Shrinkage Property of Magnesium Phosphate Cement

The influence of magnesium to phosphate weight ratios (M/P ratio), borax content, water to cement ratio (w/c ratio), fly ash, slag on magnesium phosphate cement of drying shrinkage is examined.The results show that the drying shrinkage of magnesium phosphate cementcan be affected at some extent by M/P ratio, w/c ratio,boraxcontent. Both the former two factors and the effects are significant.It was found that the drying shrinkage of magnesium phosphate cement decrease with the increase of M/P ratio,borax content, w/c ratio. If the 10%, 15% offly ashinstead of magnesium phosphate cement was added, drying shrinkage rate decreases with increases of dosage fly ash. When the 15% of magnesium phosphate cement is replaced by fly ash, the shrinkage rate of hydration 20d reachs11.2×10-5. When the 10% of magnesium phosphate cementis replaced by slag, the drying shrinkage rate reducedto 87.6%.comparing to the bench mark ,the drying shrinkage rate of 20d is only 2.78×10-5.

Effects of HEMC Powder and PP Fiber on the Drying Shrinkage of Cement Mortar

Influences of polypropylene (PP) fiber and hydroxyethyl methyl cellulose (M) on the shrinkage rate of cement mortar and its potential mechanism were investigated. Results show that both the addition of trilobal PP fiber and M would reduce the shrinkage rate of cement mortar if well applied. With the increasing of PP content, the shrinkage rate firstly decreases and then increases, and reaches the lowest shrinkage degree with fiber content of 0.20% (volume fraction). While for cement mortar with M, the greater the dosage, the less drying shrinkage rate. An addition of 0.6% M contributes to a decrease of 23.8% for the 180-days drying shrinkage than the control. Additionally, a combination of both PP fibers and M can significantly reduce the drying shrinkage of mortar, resulting in a decrease of 40% for the shrinkage rate.

An experimental research on self-consolidating concrete using tungsten Mine Tailings

This study examined the possibility of utilizing Tungsten Mine Tailings (TMT) as cement substitute for manufacturing Self-consolidating Concrete (SCC). Rheological properties of mortar mixed with TMT was evaluated using mortar viscometer and evaluation of SCC in the fresh state was examined by applying the standard presented by Japanese Society of Civil Engineering (JSCE). Its feature at hardening state was examined through compressive strength, splitting tensile strength, modulus of elasticity, carbonation depth and drying shrinkage test. As a result of examination, viscosity and yield stress decreased as the mixing ratio of TMT increased. Properties of SCC mixed with TMT while it is fresh state satisfied the standard within the mixing ratio of TMT at 20%. As for the mechanical properties of SCC, as the mixing ratio of TMT increased, the compressive strength decreased, carbonation depth and drying shrinkage rate increased. The relationship between the compression strength and the splitting tensile strength was found to be similar to the expression presented by CEB-FIP, and the relationship between the compression strength and the elastic moduli was found to be similar to the expression suggested by ACI 318-08 and CEB-FIP.

Effect of Mineral Additives on Internal Relative Humidity and Dry Shrinkage of Light Weight Aggregate Concrete

Effect of fly ash and slag on internal relative humidity (IRH) and dry shrinkage of light weight aggregate concrete (LWC) are studied in this paper. As indicated in this test, mixed with mineral additives can reduce dry shrinkage of concrete. The more volume of fly ash and slag ash, the lower decrease speed of IRH is, which contribute to the decreases of dry shrinkage rate too. At the same curing-age and dosage, the relative humidity inside the fly ash concrete is higher than the slag one. As consequence, the rate of dry shrinkage of fly ash concrete is lower than slag concrete. Also, there is a significant linear correlation between the lowered values of IRH and dry shrinkage rate.

Experimental Study on Drying Shrinkage Performance of Solid Concrete Bricks Made from Recycled Coarse Aggregate

Solid recycled coarse aggregate concrete bricks were produced by QTY4-40 brick machine with strength grades of MU15-MU30. Recycled aggregate replacement rate was up to 100%. Water absorption and moisture content were tested. Two methods were taken to test the drying shrinkage. The impact of recycled aggregate replacement rate and curing period on the drying shrinkage rate, water absorption, moisture content, density was analyzed, and the relationship between them was presented. The results indicate that recycled aggregate can increase the shrinkage of solid concrete brick. The shrinkage of recycled solid concrete bricks' (fully substitute) is larger than ordinary concrete bricks' by 1.6-2 times. Water reducer is helpful to improve the water retention and decrease the shrinkage of brick. One of the test results of shrinkage got by the methods recommended in relevant specification is smaller.

Test and Study on Green High-Performance Marine Concrete Containing Ultra-Fine Limestone Powder

In order to solve the environment pollution of limestone powder during production of limestone manufactured sand and gravel and problem of lack of high quality fly ash or slag powder in ocean engineering, ultra-fine limestone powder was selected for preparation of green high-performance marine concrete containing fly ash and limestone powder and that containing slag powder and limestone powder for tests on workability, mechanical performance, thermal performance, shrinkage, and resistance to cracking and chloride ion permeability. And comparison was made between such green high-performance concrete and conventional marine concrete containing fly ash and slag powder. Moreover, the mechanism of green high-performance marine concrete was preliminary studied. Results showed that ultra-fine limestone powder with average particle size around 10μm had significant water reducing function and could improve early strength of concrete. C50 high-performance marine concrete prepared with 30% fly ash and 20% limestone powder or with 30% slag powder and 30% limestone powder required water less than 130kg/m3, and showed excellent workability with 28d compressive strength above 60MPa, 56d dry shrinkage rate below 300με, cracking resistance of grade V, 56d chloride ion diffusion coefficient not exceeding 2.5×10-12m2/s. Mechanical performance and resistance to chloride ion permeability of limestone powder marine concrete were quite equivalent to those of conventional marine concrete. But it had better workability, volume stability and cracking resistance. Moreover, it can serve as a solution to the lack of high quality fly ash and slag powder.

Strength and Drying Shrinkage of Pavement Concrete with Nano-Particles

With the development of national economy in Mainland China, the heavier vehicles and traffic flow have arisen in highway transportation. Concrete pavement has high strength and good durability, and thus is widely used in high-grade highway. Due to the small dimension, nano- materials have many unique physical and chemical properties, and become the focus of material science field. In this thesis, based on the unique characteristics of nano-materials, the ordinary concrete with nano-SiO2 or nano-TiO2 is prepared to research the drying shrinkage of pavement concrete. The test results indicate that the concrete with nano-SiO2 and nano-TiO2 in the amount of 2.0% and 1.0% by weight of binder have the respectively biggest drying shrinkage rate of the same concrete type, which are significantly increased than the ordinary concrete. After 28 days, the dying shrinkage rate of the concrete with nano-TiO2 is 1.6 times to the ordinary concrete.

Waste printed circuit boards nonmetallic powder as admixture in cement mortar

In this paper, the nonmetallic powder recycled from waste printed circuit boards (PCBs) is used in cement mortar as admixture. The mechanical properties, bulk density, air content, water-retention property, shrinkage rate and water capillary adsorption are tested. The results show that the waste PCBs nonmetallic powder causes an increase in air content and improves the water-retention property of fresh mortar, decreases the bulk density of hardened mortar. The compressive strength and flexural strength of mortar with PCBs nonmetallic powder change slightly with the mp/mc below 15%. The tensile bond strength goes down continuously with the increase of the mp/mc but the reducing trend in the mp/mc range from 0 to 10% is slow. The drying shrinkage rate of mortar has little change as the mp/mc varies from 0 to 15%. The water capillary adsorption of mortar with the mp/mc of 5, 10 and 15% are lower than that of control. Cement mortar made with recycled waste PCBs nonmetallic powder is a new type of green building materials, which is friendly to environment and has broad application prospects.

산소분리를 위한 Ba0.7Sr0.5CO0.8Fe0.2O3-δ관형 분리막 제조 및 투과 특성

<TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$</TEX> 조성의 관형 분리막을 압출 성형 방법으로 제조하였다. 압출성형 직후 분리막의 TGA 분석결과 3단계의 무게감소로 첨가제와 탄산염이 분해되었고, 건조 수축율은 68 h 경과 후 변화가 없었으며 외경이 큰 분리막에서 높게 나타났다. 소결 후 분리막의 XRD 및 SEM 분석결과, 분리막은 단일상의 페롭스카이트 구조를 갖는 치밀한 막을 보였고, EDS 분석을 통해 <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$</TEX>와 유사한 성분함량을 가짐을 확인하였다. 두께 0.95 mm <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$</TEX> 관형 분리막의 압환강도(radial crushing strength)는 5.7 kgf/<TEX>$mm^2$</TEX>이였으며, <TEX>$950^{\circ}C$</TEX>에서 산소투과량은 146.85 mL/min(<TEX>$Jo_2$</TEX>=2.33 mL/<TEX>$min{\cdot}cm^2$</TEX>)를 나타냈었다. 투과 측의 진공펌프 사용이 쓸개 가스를 활용한 것보다 산소 투과량 증진에 효과가 있음을 알 수 있었다. Tubular <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-<TEX>${\delta}$</TEX>}$</TEX> membranes were prepared by extrusion. TGA results of green body membrane after extrusion showed three successive weight losses due to decomposition of organic additives and carbonate. Drying shrinkage rate of tubular <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-<TEX>${\delta}$</TEX>}$</TEX> membranes was no change after 68 h and higher in the membrane with large outer diameter. XRD and SEM results showed the sintered membranes were the single phase structure and dense. The stoichiometric molar ratio agreed well with composition ratio calculated by EDS results for <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-<TEX>${\delta}$</TEX>}$</TEX> membrane. Radial crushing strength of tubular <TEX>$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-<TEX>${\delta}$</TEX>}$</TEX> membrane with 0.95 mm thickness was 5.7 kgf/<TEX>$mm^2$</TEX> and the oxygen permeation rate of same membrane was 146.85 mL/min (<TEX>$Jo_2$</TEX>=2.33 mL/<TEX>$min{\cdot}cm^2$</TEX>) at <TEX>$950^{\circ}C$</TEX>. Therefore, it was known that use of vacuum pump was more effective than that of sweep gas to obtain higher oxygen permeation flux.

Experimental Study on Drying Shrinkage and Water Absorption Rate of Recycled Concrete Hollow Block

On the premise of using the five dosage levels of recycled coarse aggregate, the paper primary study on the drying shrinkage and water absorption rate of recycled concrete hollow block in order to determine the maximum dosage of recycled coarse aggregate, then find out the relationship between the drying shrinkage and the water absorption rate of recycled concrete hollow block. The results showed that: the maximum dosage of recycled coarse aggregate can reach 100%; there is a quadratic relationship between the drying shrinkage and the water absorption rate of the block.

Property of High Volume Industrial Residue Concrete

To protect circumstance and improve of structure durability of Cao’e River floodgate, high volume industrial residue concrete (HVIRC) was prepared, and its mechanical property and durability were studied systematically. 10% of fly ash and 40% of ground granulated blast-furnace slag was used to replace 50% of cement in HVIRC. HVIRC had better anti-carking ability with larger tensile strength, larger ultimate tensile strain, larger tensile-compressive strength ratio and smaller elastic modulus-to-strength ratio. Dry shrinkage rate of HVIRC was similar with that of ordinary Portland concrete (OPC). HVIRC had higher compactness with smaller gas diffusion coefficient and relative permeability coefficient. Expansion caused by alkali-silica reaction reduced greatly by using high volume industrial residue and alkali-silica reaction was controlled markedly. HVIRC had better property of chloride ion penetration resistance with low effective diffusion coefficient. HVIRC could protect steel-bar from premature corrosions. Properties of sulfate resistance and frost resistance of HVIRC were also favorable. It’s proved that high volume industrial residue can enhance greatly mechanical property and durability of concrete and HVIRC can be used in Cao’e River floodgate.