粉煤灰微珠文献翻译已修改6the performance study on c80pacting concrete with different mineral admixtures

1、The performance study of C80 self-compacting concrete with different mineral additivesAbstract: The C80 self-compacting concrete made by adding the ultrafine slag and Ultra pozz respectively were compared through the tests. The results showed that: the working performance of concrete adding Ultra po

2、zz is significantly better than adding superfine slag powder, the compressive strength of concrete adding Ultra pozz with the prolonging of curing age showed a steady growth trend, and although the compressive strength of concrete adding Ultra pozz is lower than concrete adding superfine slag powder

3、 at early age, at late age, the compressive strength is higher. HCSA expansion agent can compensate shrinkage effect on concrete prepared by adding Ultra pozz. Keywords: Ultra pozz; ultrafine slag; compressive strength; autogenously shrinkage.IntroductionWith the rapid development of the constructio

4、n industry, concrete technology has been enhanced, high performance concrete are emerged. High performance concrete, compareing to ordinary concrete, has the following advantages: Firstly, high strength, the beam cross-section effectively reduced, structural weight reduced, the area for using increa

5、sed; Second, High levels elastic modulus, structural deformation smaller, more rigid, better stability; Third, good durability, the structural repair and reconstruction costs reduced; Fourth, good resistance to permeability, significantly extending the working life in the extremely chemical corrosio

6、n and other harsh conditions; Fifth, in order to solve the problem of construction in tunnel lining site, large reinforcement density but narrow section, Self-compacting high performance concrete are produced, which has more excellent performance and can rely on its own weight to fill wrap the model

7、 of reinforcement without vibration. Studies have shown that one of the key technologies to prepare self compacting concrete is Ultra-fine mineral additives. On one hand, ultrafine mineral admixture is able to fill in the cement holes between particles, significantly reduce concrete pore size and co

8、nnectivity, improve the cementitious gel composition as well as the concrete microstructure; On the other hand, ultra-fine mineral additives can increase the packing density of the system, replace pore water, resulting in improved performance of concrete workability; as the water-cement ratio (W/C r

9、atio) reduced and the incorporation of ultra-fine mineral additives. The volume stability of self-compacting concrete cant be ignored any more, especially the autogenously shrinkage, which has become one of the most important causation of cracks, reduce durability. Expanders has become a primary mea

10、sure to reduce cracks. Only a few researches studied about shrinkage-compensating concrete by adding different mineral additives in concrete, and the effect on physical and mechanical properties. A full of studies on C80 low shrinkage self-compacting concrete to meet engineering requirements, and fu

11、rther study on different properties of Ultra-fine mineral additives on concrete were investigated.1 Raw materials and test methods1.1 Raw Materials1.1.1 Cement and Mineral additivesP O 42.5cement, grade fly ash, S95 GGBS and super-fine GGBS, Ultra pozz. The chemical composition and physical properti

12、es are listed in Table 1 and Table 2.Table 1 The chemical composition of cement and mineral additivesRaw materialsSiO2Fe2O3Al2O3CaOMgOK2ONa2OSiO3LossCement23.473.767.4160.281.960.630.142.372.82Fly ash54.505.4428.784.681.231.650.450.582.24Ultra pozz64.487.7221.902.060.541.510.490.250.85GGBS33.060.771

13、6.3238.359.230.430.490.060.52Super-fine GGBS33.790.6013.5038.509.000.250.510.103.75Silica fume91.640.980.491.181.750.70Table 2 The Physical Properties of cement and mineral additivesRaw materialsDensity (g/cm3)Specific surface area (m2/kg)Water requirement ratio(%)Liquidity ratio(%)SiO2 Content(%)R2

14、8(MPa)28d Compressive strength ratio(%)P O 42.5ement3.00360100100-52.0100.0Fly ash2.2132691123-46.890.0Ultra pozz2.7375090105-52.0100.0S95 GGBS2.80455105100-51.098.1Super-fine GGBS2.8880011095-60.2115.8Silica fume2.1719000-9254.6105.01.1.2 Aggregate2.9 Fineness modulus , 0% mud content, 1.5% Clay co

15、ntent ,and 2630 kg/m3 apparent density, 1520kg/m3 bulk density; Basalt gravel particle coarse aggregates come from Hebei Zhangjiakou size 5 16mm, 2.0% flakiness particles Content, crushing index was 2.0%, 0.3%, 0.5% mud content, clay content , 2700kg/m3 apparent density, 1650kg/m3 bulk density.1.1.3

16、 AdmixturesPolycarboxylate superplasticizer , 33% solid content, water reduction of 35%, HCSA expanders is clinker from Tianjin factory. 1.2 Test Methods1.2.1 The performance of fresh concreteTest concrete cohesion by simple viscometer (the time of inverted concrete barrel for slump to become empty)

17、 according to the ordinary concrete mixture performance test methods (GB / T50080-2002); test self-compacting properties by U-box according to the self-compacting concrete application of technical regulations.1.2.2 The concrete compressive strength testConcrete strength are tested in accordance with

18、 the ordinary concrete mechanics performance test method standard (GB / T 50081-2002).1.2.3 Autogenously shrinkage testTest early age shrinkage of concrete using non-contact method in CABR-NES-type instrument, according to the Ordinary concrete long-term performance and durability test method standa

19、rds. (GB/T 50082-2009) Test the 7d C80 concrete shrinkage. Figure 1 and Figure 2 were the concrete autogenously shrinkage test equipment and test pieces. Figure1 Autogenously shrinkage test equipment Figure2 Autogenously shrinkage test pieces.2 C80 Concrete workability and mechanical propertiesThe m

20、ixing proportion, workability performance and compressive strength of C80 Self-compacting concrete were showed in Table3, Table 4 and Table 5, respectively. HCSA expansive were used (respectively replace 3% S95 and 3% gradefly ash of Table1). Test 1 and test 2 showed that adding HCSA reduced workabi

21、lity and compressive strength of concrete.Table 3 The C80 self-compacting concrete mixing proportion (kg/m3)NO.Cement S95 GGBSSuper-fine GGBSFly ashUltra pozzSilica FumeHCSA expandersFine sandStonePCWater142882-82-38-69099018.9129242863-63-383869099018.91293428633330-383869099018.91294428465030-3838

22、69099018.9129542863-3033383869099018.9129642863-63383869099018.9129Table 4 The workability of C80 self-compacting concreteNO.Slump FluidityEmptying timeHigh differences for U-shaped box 3h Slump 3h Fluidity3h Emptying time3h High differences for U-shaped box 12506609.22022062014.04022406509.83021060

23、014.06032656906.702356359.52042556707.61021562011.83052657054.502456507.31062807203.002556706.50Test 2 resulted in ordinary workability, too long emptying time, too big height difference in U-shaped box, low early concrete compressive strength and slowly development. In test 3, 5% gradefly ash were

24、replaced by 5% super-fine GGBS comparing to test 2, the workability of self-compacting concrete C80 was moderately improved, however, the slump loss too much after 3h, long emptying time, the big height difference in U-shaped box. significantly increased early compressive strength, but slowly develo

25、ped later strength, even retrogressed. Comparing to test3, in test4, the dosage of super-fine GGBS is increased to 8%, 5% grade fly ash and 3% S95 GGBS are replaced respectively. The concrete workability was worse than Test3, but 28d compressive strength improved, the later stage strength not retrog

26、ressed. Super-fine GGBS has higher specific surface area and activity, but irregular particle morphology and much more water demand. When the dosage was under a appropriate content, effect by increasing water demand exceeded the effect by filling in the cement particles, it reduce the performance of

27、 concrete workability. Super-fine GGBS promote early cement hydration, accelerate the early strength development, but contribute little on the late strength.Comparing to test2, in test5, 5% gradefly ash was replaced by 5% Ultra pozz. The test resulted in excellent workability, little slumps loss, em

28、pty time 8s, and smooth pass through U-shaped box . Concrete compressive strength stablely increase, the 56d compressive strength is stronger than concrete with Super-fine GGBS.Table 5 The compress strength of C80 self-compacting concreteNO.R7 (MPa)R14 (MPa)R28 (MPa)R56 (MPa)172.385.096.2102.6268.78

29、0.492.598.2378.090.3103.5101.8480.293.6104.1100.3572.585.195.5104.4675.688.398.2105.3 Comparing to test5, in test6, all the fly ash was replaced by Ultra pozz, the workability, physical and mechanical properties were improved and enhanced. The particle size of Ultra pozz is mostly range 110m, but th

30、e gradefly ash is mostly range 2 37m, the size of Ultra pozz spherical particles are much smaller than fly-ash. On one hand, smaller average spherical particles have better “ball effect” to improve workability, spherical particles of Ultra pozz fill in pores and holes between cement and S95 GGBS par

31、ticles, better than fly-ash, which displace pore water, result in improved workability. On the other hand, the pozzolanic effect of Ultra pozz is between Super-fine GGBS and gradefly ash, which is conducive to late stage strength development.3 The autogenously shrinkage of C80 concreteThe autogenous

32、ly shrinkage of C80 self-compacting concrete was shown in Figure 3. In test1 the shrinkage rate of 7d concrete was 0.35. Test 2 showed that the 7d concrete is still slightly expanded. In test4, the autogenously shrinkage start from 3d, the shrinkage rate of 7d concrete was 0.10. In test6, small auto

33、genously shrinkage happened at 5d, shrinkage rate of 7d concrete was 0.05. Table 3 shows that test1 without any HCSA, test2, test4 and test6, 6% HCSA added in C80 concrete. The autogenously shrinkage of C80 self-compacting concrete is significantly compensated by hydration of HCSA. Since HCSA consum

34、ed part of water, the hydration of cement was inhibited, the hydration of HCSA produce expansive ettringite, which significantly improved the autogenously shrinkage of concrete.Figure3 The autogenously shrinkage contraction curves of concrete Comparing with the shrinkage curves of test 2 and test 6,

35、 the effection of HCSA expanders on shrinkage compensation of concrete with Gradefly ash is similar to Ultra pozz at 2d, but after 2d, grade fly is better. Why there are some differences? Test4 and test6 shows that the shrinkage compensation of concrete with Ultra pozz and HCSA agents were better th

36、an super-fine GGBS. Super-fine GGBS has potential hydration activity and participate in the hydration reaction with cement and water at early stage, lead to large amount of autogenously shrinkable C-S-H gel. The hydration reaction activity of Ultra pozz is lower than Super-fine GGBS, and less C-S-H

37、gels were generated, reduced the effect of filling, increased the coarse pores and reduced the fine pores, the content of free water within the big pores increases, the critical radius increases, the capillary negative pressure lowered, Ultra pozz partly reduce early drying rate and autogenously shr

38、inkage ratio at early stage.4 Conclusions(1) If the content of Ultra pozz and Super-fine GGBS are no more than 5.2% in C80 self-compacting concrete, the workability of concrete mixing with Ultra pozz is better than super-fine GGBS; If the content of Ultra pozz is increased to 10%, the performance of fresh concrete can be fur