【文章內(nèi)容簡介】 PPC5 PPC6 PPC7 PPC8 PPC9 Fracture energyThe mixes with similar porosity (. around %), PPC3, PPC4 and SPC6, were chosen to test the fracture properties. 8% and 10% of SJ601 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 that both SPC and PPC show good elasticity under low stresses. When the load is up to some extent (. kN for SPC6), the straight line in Fig. 3 bees nonlinear at the point of % of the maximum load and the curve segment is quite short, illustrating that the damage mainly belongs to brittle fracture. In contrast, the starting points on the nonlinear section are at % for PPC3 and % 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 characteristics 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 pared to that of SPC6. So,pared 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 that neither the pore nor the ITZ is the weakest part within pervious concrete.Fig. 3 Load?deflection curves of pervious concrete with different dosages of SJ601Table 5 Fracture energy of pervious concreteMix IDw(SJ601)/%W/(Nm)SPC60PPC38PPC410Fig. 4 Different failure modes of pervious concrete: (a) Highstrength pervious concretePPC。 (b) Lowstrength pervious concreteSPC Flexural fatigue propertyTwoparameter Weibull probability function [17] could be written asln[ln(1/p)]=blnN－blnNa (4)To simplify the calculation, mathematical transformation is made:Y＝ln[ln(1/p)]－ln[ln1/(1﹣pˊ)] X＝ln N ，α=blnNa (5) where p means the survival probability and p′ is thus the failure probability。 therefore p=1?p′. N is the fatigue cycle, while b and Na are the Weibull parameters. Twice natural logarithm of both sides of Eq. (5) is rewritten as Eq. (6), which can be used to determine whether a group of test data obeys the distribution of twoparameter Weibull probability function: Y=bX?α (6) Results from the flexural fatigue test of pervious concrete are listed in Table 6, by linear regression of which there es Fig. 5. Linear relationships between ln[ln(1/p)] and lnN under different stress levels are observed. It is proved that twoparameter Weibull probability function is suitable to describe the flexural fatigue life of pervious concrete. So, Eq. (4) can be rewritten asN=Na| ln (1 －pˊ) |1/b (7)Table 6 Data of fatigue testMixStress level of SPCMixStress levels of PPCID ID SPC1 651 15 311 230 158PPC1 1054 — 604 121SPC3 478 10 178 101 134PPC3 815 14 331 371 580SPC5 379 70 145 57 894PPC4 707 12 067 248 741SPC8 295 3 422 31 490PPC6 426 9 015 112 055SPC10 204 930 20 158PPC7 315 3 088 30 851SPC12 107 395 8 345PPC9 187 801 12 334Fig. 5 Relationship between ln[ln(1/p)] and lnN for pervious concrete: (a) SPC。 (b) PPCFor specified failure probabilities p′, the corresponding fatigue lives are calculated and listed in Table 7. It is found that PPC has longer flexural fatigue life than SPC under different failure probabilities and at all stress levels, since the macromolecule polymer helps to limit cracking and delay cracking growth. Double logarithmic equation of the fatigue life of pervious concrete is established:lgS＝lga－clgN (8)Table 7 Fatigue life of previous concrete under different failureprobabilitiespˊStress level of SPCStress level of PPC 51 119 2 944 84 622 3 046 86 373 7 994140 1 712 10 771146 1 230 22 642234 4 922 24 623 203 2 588 43 401334 9 523 54 441 262 4 576 71 437431 15 786 99 963 324 7 427 106 113536 24 255 167 528where S refers to the stress level。 a and c are undetermined coefficients. Data in Table 7 are used for regression analysis in accordance with Eq. (8), and the results are presented in Table 8. For a given p′, the flexural fatigue equations of both SPC and PPC at porosities within the range of 15%?25% are thus obtained.Table 8 Fatigue equation parameters under different failureprobabilitiespˊSPCPPC lga c lga c 3 8 5 2 1 2 8 5 4 0 8 4 3 2 7 5 6