| The vegetation-growing concrete ecology protection technology(CBS),a good ecological slope protection technology with high effects,combining organically slope surface protection with vegetation-growing restoration,can realize the ecological restoration and the organic combination of engineering,for which has been used widely in many engineering fields.Super absorbent polymer(SAP)is added into the vegetation-growing concrete to improve its water-holding ability during concrete ecological restoration of vegetation-growing in arid and semi-arid regions.However,vegetation-growing concrete is not pure soil for it adds organic matter,cement,green additives and so on and these substances will change the base material of physical and chemical properties,salt type and concentration,etc.which may affect the effect of super absorbent polymer.Therefore,it is necessary to further study whether the performance of super absorbent polymer in vegetation-growing concrete is changed compared with the soil without adding any material.This paper selected the vegetation-growing concrete and the soil as the research object,and then choose four kinds of SAP including Starch Grafted Acrylic Acid Sodium Super Absorbent Polymers(A),Acrylamide/Inorganic Mineral Compound Super Absorbent Polymers(B),Corn Starch Acrylic Graft Copolymer Super Absorbent Polymers(C)and Polyacrylic Acid Salt Polymer Super Absorbent Polymers(D).They are respectively put0%,0.1%,0.25%,0.5% and 0.75% dosages into the vegetation-growing concrete and the soil,researched the mechanism of super absorbent polymer on vegetation-growing concrete water-holding characteristics and the influence on its physical characteristics,analysis the effect of super absorbent polymer on the water-holding ability and physical properties of vegetation-growing concrete and the soil and comprehensively evaluated the effect of super absorbent polymer on vegetation-growing concrete.At the same time through outdoor pot experiment,adding 0%,0.1%,0.25%,0.5% and 0.75% concentration of 5 kinds of super absorbent polymers into vegetation-growing concrete to test the seed germination rate of Bermuda grass and Magnolia multiflora,and the growth of the plants to discuss the effect of the application of super absorbent polymers in the vegetation-growing concrete.The main results are as follows:The substrate moisture conditions improved dramatically after adding super absorbent polymers into vegetation-growing concrete and saturated water content enhanced significantly.But it did not change the general shape of vegetation-growing concrete water characteristic curves,only increased the amount of water that the vegetation-growing concrete holds under different suction.It illustrates that super absorbent polymers not only improved the water-holding capacity of vegetation-growing concrete in low suction segment but also in high suction capacity after using the super absorbent polymers the gravity water,field capacity,permanent wilting coefficient and total available water of the vegetation-growing concrete in each treatment all increased significantly.Compared with the soil adding super absorbent polymers,saturated water content,moisture characteristic curve,moisture constants and the effectiveness of the change rule and ecology base material is roughly same,but under different suction the water-holding capacity of soil is greater than that of vegetation-growing concrete,shows that due to the addition of cement,organic matter,green additives of the vegetation-growing concrete to a certain extent affect the effect of super absorbent polymers.In terms of the moisture availability of vegetation-growing concrete,applicability in vegetation-growing concrete is that: Starch Grafted Acrylic Acid Sodium Super Absorbent Polymers A > Polyacrylic Acid Salt Polymer Super Absorbent Polymers D > Acrylamide/Inorganic Mineral Compound Super Absorbent Polymers B > Corn Starch Acrylic Graft Copolymer Super Absorbent Polymers C.Super absorbent polymers obviously reduced the bulk density of the ecology base material.However,compared with soil,the change of vegetation-growing concrete’s bulk density is much weaker,which indicates that the addition of cement in the ecological substrate makes it better.The super absorbent polymers have no positive influence on the pore distribution of the vegetation-growing concrete,and the proportion of the pores in the capillary is decreasing,while the proportion of the inactive pores is increasing.However,the influence of super absorbent polymers on the pore distribution of vegetation-growing concrete is relatively weak,and the proportion of capillary pores is always more than 50%.In addition,the proportion of capillary pores in the soil was decreased,but the proportion of aerated pores was relatively increased.It can promote the formation of the structure of vegetation-growing concrete,especially the granule structure of 0.25-2mm in the vegetation-growing concrete.The effect of super absorbent polymers on the structure of soil aggregates in soil is more obvious,and the amount of soil of >0.25 mm in the same type of super absorbent polymers is significantly larger than that of vegetation-growing concrete.It is indicated that the super absorbent polymers can still improve its physical properties in the vegetation-growing concrete,but in soil the effect of the super absorbent polymers is relatively weaker.Experiment showed that super absorbent polymers has obvious promoting effect on the germination rate and growth index of the Bermuda grass and Magnolia multiflora in the vegetation-growing concrete,and it’s conducive to the accumulation of biomass,but it is a prerequisite for reasonable application of concentration.Under the concentration gradient of the test,0.5% concentration is the most appropriate for seed germination rate,leaf number,plant height and biomass.It’s a process of increasing at concentration of 0.1% to0.5%,but it decreased at concentration of 0.75%.It is indicated that the super absorbent polymers can be used to promote germination and plant growth in the vegetation-growing concrete ecological substrate only within a certain concentration range,and the promotion effect is affected when the concentration is too high.At the same time,we found that super absorbent polymers have a very significant influence on seed germination rate of both the Bermuda grass and Magnolia multiflora.But for the plant growth and biomass accumulation,super absorbent polymers have greater influences on Bermuda grass than Magnolia multiflora.It is shown that the super absorbent polymers has different effect on different plant application. |
