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1、外文参考资料Mechanical properties of pervious cement concreteCHEN Yu1, WANG Ke-Jin2, LIANG Di11. School of Traffic and Transportation Engineering,Changsha University of Science and Technology, Changsha 410004, China;2.Department of Civil, Construction and Environmental Engineering, Iowa State University,
2、Ames, IA50010, USA Central South University Press and Springer-Verlag Berlin Heidelberg 2012 Abstract: Compressive and flexural strength, fracture energy, as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified, were anal
3、yzed. Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC), and porosity has little effect on their strength growth. PPC has higher flexural strength and remarkably higher flexural-to-compressive stre
4、ngth ratio than SPC at the same porosity level. Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer, reflecting the ductile damage features rather than brittleness. PPC displays far longer fati
5、gue life than SPC for any given failure probability and at any stress level. It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.Key words: pervious concrete; strength; fracture; fatigue life1 IntroductionPervious cement concrete was a con
6、crete with continuous voids that were intentionally incorporated into concrete by blending with no or very little amount of fine aggregates. Cementitious materials were not enough to fill the voids among coarse aggregates with special particle-size distribution to make interconnected macro pores 12.
7、 The range of porosity that was commonly reported for pervious concrete utilized in pavement, was about 15%25% 34. The significantly reduced strength of conventional pervious concrete due to high porosity, not only limited its application in heavy traffic roads but also influenced the stability and
8、durability of the structures, because of,for example, susceptibility to frost damage and low resistance to chemicals. However, by using appropriatelyselected aggregates, silica fume (SF) or organic intensifiers, and by adjusting concrete mixing proportion, the mechanical properties of pervious concr
9、ete could be improved greatly 56. YANG and JIANG 7 showed that the use of SF and superplasticizer (SP) in pervious concrete could obviously enhance its strength. The results also indicated that SF had a better effect for improving the properties of pervious concrete than polymer when using with SP;
10、and it could obtain compressive strength of 50 MPa and flexural strength of 6 MPa. KEVERN 8 presented that the addition of polymer (styrene butadiene rubber) in pervious concrete improved its workability, strength, permeability and freeze-thaw resistance, resulting in higher strength at relatively l
11、ower cement contents and higher porosity. Fundamental information, including the effects of porosity, water-to-cement ratio, cement paste characteristic, volume fraction of coarse aggregates, size of coarse aggregates on pervious concrete strength, had been studied 3, 912. However, for the reason th
12、at the porosity played a key role in the functional and structural performances of pervious concretes 1314, there was still a need to understand more about the mechanical responses of pervious concretes proportioned for desired levels of porosities.Although it was possible to have widely different p
13、ore structure features for a given porosity, or similar pore structure features for varied porosities in pervious concrete, it was imperative to focus on the mechanical responses of pervious concrete at different designed porosities. However, compared with the related research on conventional concre
14、te, very limited study had been conducted on the fracture and fatigue behaviors of pervious concrete, which were especially important for pavement concrete subjected to heavy traffic and to severe seasonal temperature change.The presented work outlined the raw materials and mixing proportions to pro
15、duce high-strength supplementary cementitious material (SCM) modified pervious concrete (SPC) and polymer-intensified pervious concrete (PPC) at different porosities within the range of 15%25%. Then, the mechanical properties of pervious concrete, including the compressive and flexural strengths, fr
16、acture energy, as well as fatigue property, were investigated in details.2 Experiment program2.1 Raw materials and mixing proportionsType I Ordinary Portland Cement (OPC, with the details in Table 1) and granite aggregates were used for all pervious concrete mixtures. The combined aggregates,4.75 mm
17、 and 9.5 mm particles were chosen to prepare the mixtures. To cast SPC, fly ash (type C, FA), SF and SP were used; while SJ-601, the mixture of vinyl acetate ethylene copolymer (VAE) and acrylic emulsion, was added to produce PPC. Table 2 lists the main properties of SJ-601.Two series of testing spe
18、cimens were cast in accordance with the designated mixing proportions presented in Table 3, in which indicates the mass ratio of aggregate in 1 m3 concrete to the loose density after being densely vibrated. The percentages of FA and SF were the replacements of the same mass of OPC; while those of SP
19、 and SJ-601 were the additional dosages. It should be clarified that too much polymer blocked the valid pores and badly influenced the permeability of pervious concrete. SJ-601 dosage more than 12% was not recommended 1, 6.2.2 Test methodsThe strength tests were carried out according to GT/B 50081 2
20、002 (Standard for Test Method of Mechanical Properties in Ordinary Concrete).Strain gauges were stick at the mid-point on the bottom surface of beam specimen (150 mm 150 mm 550 mm), which sustained two-thirds symmetrical loading F. The corresponding strain was measured by XY digital recorder. was th
21、en translated into , which meant the mid-span deflection of beam specimen in accordance with Eq. (1). So, the enveloped area by F curve and X-axis was defined as W, fracture energy of concrete, which could be calculated by Eq. (2) 1516: (1) (2) Whereis the dynamic deflection of the mid-span beam; L
22、and H are the span and height of beam specimen, respectively. is the strain value measured at the midpoint of beam bottom, while a refers to the horizontal distance from the loading point to the support abutments.MTS-810 TEST STAR, an electro-hydraulic servo-type material testing machine, was served
23、 to measure the flexural fatigue life of pervious concrete. Three stress levels of sine wave loading (0.90, 0.80 and 0.70) with 0.1 of cycling eigenvalue, 10 Hz of frequency and zero time gap, were adopted. The number of the cyclic load that the tested specimens were subjected until failure was reco
24、rded.Table 1 Properties of OPCChemical compositions /%Strength at 3 d/MPaStrength at 28 d/MPaSiO2 Al2O3 CaO MgO Fe2O3 SO3 K2O Compressive Flexural Compressive Flexural22.1 5.1 62.5 1.5 4.2 2.9 0.4 27.7 5.4 53.7 8.1Table 2 Properties of SJ-601Solid content/ Viscosity/ pH Density/Ratio of strength wit
25、h to without SJ-601 % （Pas） （gmL-1）Compression Bending Tension Cohesion 473 0.030.04 5 1.080.03 0.9 1.2 1.2 1.5Table 3 Mixing proportions of pervious concrete Porosity/SPCPPC %Water-to-binder ratio FA/% SF/% SP/%Water-to-cement ratio SJ-601/%0.900.98 1525 0.280.34 1218 610 0.30.8 0.300.34 8123 Resul
26、ts and discussion3.1 StrengthThe compressive strengths of all mixes are expressed as a percentage of their 28 d strength and shown in Fig. 1. No evident effect of porosity on the strength development for both SPC and PPC is observed, that is, pervious concretes at different porosities follow the sam
27、e strength growth process. The strength development of SPC is obviously rapid at early ages with more than 50% at 3 d and 80% at 7 d; while the further increments are only 5.6% at 56 d and 8.9% at 90 d on average, respectively (Fig. 1(a). Immediately after cement paste is hardened, which is accelera
28、ted by SF and SP, aggregates are wrapped and cemented together to form the skeleton- pore structure, obtaining quite strong ability to resist destructive load. However, due to much larger quantity of aggregates in pervious concrete compared to that in conventional concrete, it is reasonable that the
29、re is no remarkable strength increasing at later ages.Figure 1(b) shows that the compressive strength of PPC is short of 50% at 7 d and reaches only about 70% at 14 d, which quite lags behind the strength development of SPC. Cement hydration and polymer film-forming process take place at the same ti
30、me. It is time consuming for cement hydration products and organic films to intertwine, to interpenetrate and to build up the network structure of paste, firmly wrapping and binding aggregate particles together. Therefore, PPC obtains accelerated strength improving at later ages, i.e. up to 117% at
31、90 d on average. It is worth noting that because there is a contradiction between cement hydration and SJ-601 polymerization, it is beneficial for PPC to be wet cured at least 3 d to ensure continuous hydration of cement, and then to be stored at a dry environment with relative humidity less than 70
32、% for better forming of Polymer. Seen from Table 4, PPC has higher 28 d flexural strengths and remarkably higher flexural-to-compressive strength ratios than SPC at the same porosity level. SJ-601 intensifies pervious concrete by forming strongly cohesive film at the interfacial transition zone (ITZ
33、) between aggregates and hardened paste, and by filling the micro pores within concrete. It makes previous concrete less brittle and have stronger resistance to flexural damage. Figure 2 represents that the flexuralto-compressive strength ratios decrease with the increase of porosity, which may be a
34、ttributed to the fact that the flexural strength of pervious concrete is more sensitive to porosity than compressive strength.Fig. 1 Strength development of pervious concrete: (a) SPC; (b)PPCFig. 2 Flexural-to-compressive strength ratio of pervious concreteTable 4 Results of strength testMix IDPoros
35、ity/Compressive strength/MPaFlexural strengthRatio of flexural to% 3d 7d 14d 28d 56d 90dat 28 d/MPacompressive strength at 28 dSPC115.2 23.8 38.3 42.6 46.7 48.1 49.0 6.1 0.131SPC216.3 24.8 36.1 40.6 45.1 48.1 49.15.9 0.131SPC317.6 23.9 35.9 38.5 43.3 45.5 46.35.6 0.130SPC418.4 26.0 34.2 40.6 42.7 48
36、.7 51.15.4 0.127SPC5 18.9 22.7 34.4 37.8 42.0 44.5 45.8 5.4 0.129SPC6 19.5 24.8 35.6 38.2 41.4 43.5 46.0 5.30.128SPC720.1 21.0 32.8 36.5 40.5 41.7 43.3 5.1 0.127SPC821.1 19.7 32.7 35.9 39.4 42.2 43.0 5.0 0.127SPC922.8 22.2 31.5 36.2 38.9 40.4 42.0 4.80.124SPC1023.2 22.6 33.1 33.8 37.6 41.0 41.9 4.7
37、0.125SPC11 24.0 19.1 28.8 34.0 36.0 37.1 38.5 4.4 待添加的隐藏文字内容10.121SPC12 24.7 20.4 29.9 32.4 35.2 36.3 36.7 4.20.119PPC115.8 11.8 22.4 30.7 43.9 50.9 51.87.3 0.166PPC217.0 13.1 19.1 32.2 43.5 48.7 50.57.4 0.157PPC319.3 13.2 17.8 29.4 42.7 48.6 48.77.0 0.163PPC4 19.7 11.5 18.9 28.8 41.2 47.2 48.9 7.20
38、.170PPC521.2 14.7 20.3 31.2 40.5 44.1 46.76.3 0.156PPC622.5 11.5 15.7 28.3 38.2 43.9 44.3 6.20.162PPC7 23.4 9.2 16.1 26.0 36.6 39.9 41.0 5.5 0.151PPC824.3 9.8 13.5 24.3 33.7 39.6 40.15.00.149PPC925.0 9.6 15.1 21.8 32.1 38.2 39.2 4.8 0.1483.2 Fracture energyThe mixes with similar porosity (i.e. aroun
39、d 19.5%), PPC3, PPC4 and SPC6, were chosen to test the fracture properties. 8% and 10% of SJ-601 were added into PPC3 and PPC4, respectively, while SPC6 had no polymer addition. The results are shown in Fig. 3.At the beginning of loading, the curve is approximately a straight line, which explains th
40、at both SPC and PPC show good elasticity under low stresses. When the load is up to some extent (i.e. 17.3 kN for SPC6), the straight line in Fig. 3 becomes nonlinear at the point of 94.2% of the maximum load and the curve segment is quite short, illustrating that the damage mainly belongs to brittl
41、e fracture. In contrast, the starting points on the nonlinear section are at 87.9% for PPC3 and 82.5% for PPC4 of the corresponding maximum load with more and more apparent deflection. Therefore, the conclusion can be drawn that with the increase of polymer dosage, pervious concrete reflects some ch
42、aracteristics of plastic flow and good toughness.Results of fracture test are also given in Table 5. It is demonstrated that the fracture energy significantly increases with the increase of polymer dosage. The fracture energies of PPC3 and PPC4 are improved by 44% and 73% individually compared to th
43、at of SPC6. So,compared to SPC, PPC has much more excellent resistance to cracking and crack propagation, and needs more fracture energy to be totally destroyed. It is proved that polymer materials in pervious concrete intensify cement paste and modify ITZ, leading to the change of failure mode, as shown in Fig. 4. For PPC, the fracture passes though the core of aggregate particles, proving
