Preparation And Application Of Multi-functional Polycarboxylate Superplasticizer Based On Molecular Structure Design

Polycarboxylate superplasticizer plays a significant role in preparing high performance concrete. The study and application of polycarboxylate superplasticizer promoted the development of modern concrete technology. Meanwhile, the complication and various qualities of raw materials of concrete, as well as the diverse and high performance of concrete in application, make an urgent request to the preparation of multi-function and compounding technology of PCE. Currently endowing PCE with multi-function is the compounding of PCEs of different performances and admixtures, although it needs high technique of compounding and quality control. Additionally, there are compatibility problems among admixtures and limitation of the plants area, storage, stirring and measurement. It provides much more convenient and efficiency if all problems can be solved by only one product. Thus, preparation of multi-function PCE under chemical synthesis is the industry trend and has broad application prospects.The research of structural design,preparation and application of PCE possesses is carried out in water-reducing, slump retention and early-strength effect area.First of all, the relationship between molecular structure and properties is observed. The influences of the density of side chain, poly degree of back bone and the length of side chain on the properties of basic PCE system is discussed. The relationship between PCE possesses ideal dispersing and retention effectiveness and its parameter of molecular structure is obtained as well as the mathematic model for molecule design. The ideal poly degree of back bone and density of side chain can be obtained for the given macro monomer with a certain poly degree of side chain. The influence of ester and acrylamide group on PCE is also discussed on the basis of the principle mentioned above. The results indicated that PCE possesses long side chain requires low density of the side chain and short length of the back bone to reach the ideal dispersing and retention properties. Long side chain endows PCE product high slump retention and high early strength under the ideal molecular structure. PCEs with different slow-release potential can be synthesized by the variation density of ester groups. PCEs possess low initial dispersing effectiveness, short release period and high slow-release potential require high density of ester in the back bone. Conversely, PCEs possess high initial dispersing effectiveness, long release period and low slow-release potential require low density of ester in the back bone. The acrylamide group improved the strength of concrete and kept its fluidity as well. The amount of acrylamide in PCE should be no more than 5% by mole ratio to keep the balance of strength and fluidity properties of concrete.The molecule design principle of multi-function PCE is confirmed on the basis of the relationship between the structure and properties. The method for structural design of functional PCE molecules is observed. First, the complex system of various monomers is simplified into two basic PCE system. And then the structural parameters of basic PCE system containing acrylic acid and macro monomers were studied to optimize the excellent PCE product. Acrylic acid is substituted by the functional group at suitable ratio to synthesize the functional PCE with the optimized parameters.Water-reducing, slow-release and early-strength PCE is synthesized via the principle and method mentioned above. The performance of concrete evaluation and the molecular structure characterization were carried out. Water-reducing PCE is synthesized by HPEG macro monomer with a molecular weight of 4000g/mol with the density of side chain 15.60% and poly degree of back bone around 12.1. The water reduce rate is up to 34.0% at the dosage of 0.2% bwoc. The water reducing rate and the enhancement effect is better than the similar products in domestic market. When the high initial dispersing effectiveness, long release period and low slow-release potential PCE is optimized with a molecular weight of 4000g/mol, the density of ester, density of side chain and poly degree of back bone of are 30%, 15.6% and 12.1 separately. When the low initial dispersing effectiveness, short release period and long slow-release potential PCE is optimized with a molecular weight of 4000g/mol, the density of ester, density of side chain and poly degree of back bone are 50%, 15.6% and 12.1separately. Compared with the water-reducing PC-W, the slump performance of slow-release PCE is significantly improved, meanwhile the setting time and strength of concrete keeps constant. Early-strength PCE is synthesized by HPEG macro monomer with a molecular weight of 4000g/mol with the density of side chain 15.60% and poly degree of back bone 12.1 and density of acrylamide 5.0%. The setting time of concrete prepared by early-strength PCE is around 20 mins early than that of normal PCE, the compression strength ratio of one day can reach up to 240%.At last, the molecular structure and preparation of multi-function PCE combined water-reducing, slump retention and early-strength is studied. The density of ester, acrylamide and side chain are 20.0%, 5.0% and 15.2% separately. Meanwhile, its mole ratio of monomers is HPEG: AA: HA: AM = 1:5.0: 1.3: 0.3. The water reducing rate is 29.4% at the dosage of 0.2% bwoc. Given the initial slump of concrete containing multi-function PCE is(210±10)mm and the slump loss is 15 mm after 0.5 hour and 30 mm after 1 hour. The multi-function PCE, prepared on the basis of molecular structure principle, is manufactured in chemical admixture plant and completely met various requirements in bridge and railway construction work engineering.