Concrete admixture can improve the work performance of fresh concrete, construction environment improvement, and improve the mechanical properties and durability of hardened concrete, save the cement at the same time, reduce costs, speed up the construction speed, so the concrete admixture widely used. But, in the process of using some admixtures including common water reducing agent, high efficiency water reducing agent and retarder (organic retarder, and retarding water reducing agent, inorganic retarder) problems with cement adaptability etc, and lead to the effect of the difference is very big.
This paper studies the nai series high efficiency water reducing agent and the compatibility of three different cement, observe the different dosage of water reducing agent on flowability of neat cement initial fluidity and fluidity loss for 1 h, Observed on flowability of neat cement retarder initial fluidity impact (same water-cement ratio, and without cement retarder net paste fluidity of initial value contrast experiment); Observe the high efficiency water reducing agent and retarder mixed with different varieties and the compatibility of cement ternary system, analyses the experimental results, puts forward the existing problems. 1 raw materials, instruments and experimental method
1. 1 the experiment materials
1. 1. 1 the cement
Qinling 42. Level 5 ordinary Portland cement (hereinafter referred to as the QL); Zhengzhou longyuan 42. Level 5 ordinary Portland cement (hereinafter referred to as "LY"); Bridge 42. Level 5 ordinary Portland cement (hereinafter referred to as "TQ"); Shield stone 42. Level 5 ordinary Portland cement (hereinafter referred to as "DS").
1. 1. 2 high efficiency water reducing agent
Tianjin produce low concentrated type naphthalene sulfonate formaldehyde condensation compound (hereinafter referred to as the NX).
1. 1. 3 retarder
1. 2 experimental method and instrument
Net water cement ratio of 0. 29, change the mixing of high efficiency water reducing agent, through the determination of water after 5 min (i.e., just after the mixing) initial fluidity, and let stand for 1 h slurry fluidity ‰, comparing the difference between the different cement compatibility with high efficiency water reducing agent. Net water cement ratio of 0. 29, change the mixing of high efficiency water reducing agent, with a retarder (fixed content), and compare the water after 5 min (i.e., just after the mixing)'s initial fluidity and let stand for 1 h % slurry flow degree, joined to the same cement retarder and the improvement of high efficiency water reducer compatibility; Under the same conditions, appropriate increase dosage of retarder, and compare the effects of dosage of retarder. Change the varieties of cement, the above study, comparison of three different cement retarder compatibility with high efficiency water reducing agent
A third
Whether do the same thing.
By the same token, the change of retarder varieties, to do the research, compare different retarder for cement and the influence of high efficiency water reducer compatibility.
2 the experimental results and discussion
2. 1 naphthalene series high efficient water reducer compatibility with cement binary system
Generally speaking, the fluidity of net cement slurry water cement ratio must be increased with the increase of dosage of high efficiency water reducing agent, to a certain dose, fluidity no longer increases, or increase is small, the dosage of water reducing agent called the saturation point. When the content is more than that point too much, will increase the cost, at the same time causes a cement and aggregate segregation. Figure 1 is the three kinds of cement and water (W/C = O. 29) mixing in NX content change the fluidity of the experimental results. The NX has good compatibility with cement LY, show the saturation point, and when the content is more than one O. 8%, the 1 h fluidity loss is very small. NX and TQ cement and QL cement compatibility is bad, because of the high TQ cement despite initial fluidity, but 1 h fluidity loss is too big. Initial fluidity and QL cement is not high and 1 h fluidity loss is big, dosage by O. No 4%. Basic not to increase 9%, the F60.
Figure 1 NX content changes the fluidity
(a) LY cement; (b) TQ cement; (c) QL cement
2. 2 and cement retarder binary system compatibility
Main function is to delay the cement setting retarder hardening speed, make the concrete mixture in a long time to keep the plastic. According to the function which can be divided into only retarding effect of retarder and both retarded retarding water reducing agent and water reducing effect. The experiment of water cement ratio of 0. 29, the three kinds of cement mixed with 0.1% ~ O respectively. More than 3% of poly (sodium phosphate; with the increase of dosage, contrast blank experiment (cement and water), no change retarder, proof of sodium phosphate polymer water reducing effect. Also, the three kinds of cement mixed with O. 01% ~ 0. 1% of citric acid (cement and water) contrast blank experiment, proves that citric acid water reducing effect. The experiment also found that adding O. 01 ~ 0. 1% of D a sodium gluconate, and with the increase of dosage, contrast blank experiment (cement and water), a net increase pulp consistency, prove D sodium gluconate have weak water reducing effect.
2. 3 cement, naphthalene series high efficient water reducing agent, gentle coagulant ternary system compatibility
Through the compound use of admixtures, improve the compatibility of high efficiency water reducing agent and cement, the composite with high efficiency water reducing agent and retarder use, can effectively control the concrete slump loss, show the same water-cement ratio and high efficiency water reducing agent dosage, add some kind of retarder, fluidity of cement slurry net value and fluidity of 1 h, cement, naphthalene series high efficient water reducing agent gentle good coagulant ternary system compatibility. At the same time, in the experiments, we found that some varieties of cement and naphthalene series high efficient water reducer compatibility is very poor, characterized by a high dosage of naphthalene series high efficient water reducing agent (up to 0. 8%), still no fluidity. But, composite retarder, the initial fluidity even in low dosage of naphthalene series high efficient water reducing agent case, also can get larger initial fluidity. But the fluidity of the ternary system of 1 h value compared with the binary system, no obvious change.
If use TQ cement with different dosage of NX compound 0. 1% to 0. More than 3% of poly (sodium phosphate, in high efficiency water reducing agent dosage is less than 0. Increase more than 6%, the composite poly sodium phosphate for net pulp initial fluidity and fluidity of 1 h value, lower the fluidity loss value for 1 h. Compared with the original binary system in the ternary system, efficient jianshuiji saturation point in advance. High efficiency water reducing agent dosage is greater than zero. Increase 6%, although the net pulp initial fluidity and fluidity of 1 h value effect is not obvious, but it is still effective inhibition of lh fluidity loss.
Two-thirds of the
Experiment of QL cement and LY cement, found similar to the above rules.
2. 4 cement, naphthalene series high efficient water reducing agent and D a sodium gluconate ternary system compatibility
Two cement test with DS and QL, D a sodium gluconate in dosage of 0. 01% ~ 0. 1%, within the scope of the all the original binary system of net cement slurry fluidity of initial value increase, but the two kinds of cement to the greatest extent promote the initial fluidity increasing on the D a different dosage of sodium gluconate requirements. DS cement at three over ten thousand, QL cement when D as per dosage of sodium gluconate in, had the greatest effect.
2. 5 cement, naphthalene series high efficient water reducing agent and citrate ternary system compatibility
With LY concrete with different dosage of NX compound 0. 01% to 0. 1% of citric acid test. After adding citric acid, net cement slurry fluidity and fluidity of 1 h value compared with the original binary system, no growth. And with the citric acid content increased, the net paste fluidity of initial value has a decreasing trend.
2. 6 compatibility factor analysis
2. 6. 1 the mineral composition of cement, fineness, and the morphology of calcium sulfate
Research suggests that cement clinker mineral composition, gypsum type and dosage, alkali content, the content of free lime, mixed material type and dosage, cement fineness, grain composition, etc., will affect the high efficiency water reducing agent and the compatibility of cement. CA, C4F content in cement is lower, naphthalene series high efficient water reducing agent has better compatibility with cement binary system, because the CA of water reducing agent adsorption capacity than other mineral composition. With the increase of cement fineness, C3A influence more and more obvious.
Due to the concentration of sulfuric acid root ion in the liquid phase controlled the rheological behavior of slurry, when it dissolve slowly, and the need to influence the C. A quantity is relatively large, because of A lack of sulfuric acid root ion, more C. A. in situ hydrated, high efficiency water reducing agent will adsorption in C. A and their hydration products and reduce the effective water reducing agent concentration in liquid phase, the dispersion effect is small. Therefore contain and half water gypsum dihydrate gypsum in cement is better than that of anhydrite, meanwhile, because the first two kinds of sulfuric acid root ion release speed is faster than the latter.
2. 6. 2 high efficiency water reducing agent
The molecular structure of water reducing agent, the polar group categories, types of nonpolar groups, average molecular weight and molecular weight distribution, degree of polymerization, and so on all affect its adaptability with cement content of impurities.
2. 6. 3 retarder
Theory is that of sodium phosphate polymer will extend the induction period of cement hydration, and C. A hydration speed slow down, the reason is that the phosphate ion phosphate ions react with cement hydration products, the generated on the surface of cement particles density of refractory phosphate thin layer, inhibit the infiltration of water molecules, hinder the normal cement hydration. Making C, A, hydration and ettringite formation process is slow and retarding action.
Three conclusions and problems
Through the cement, naphthalene series high efficient water reducing jing gentle coagulant ternary system compatibility research, get the following conclusion:
(1) the same high efficiency water reducing agent with different manufacturer production of ordinary Portland cement compatibility there is a difference.
(2) different with the same ordinary Portland cement retarder of naphthalene series high efficient water reducing agent and binary compatibility system there is a difference.
(3) some of the retarder in different manufacturer production of ordinary Portland cement and the same kind of naphthalene series high efficient water reducing agent of binary system compatibility effect are approximate.
Still needs further research problem is to change the sugar retarder and hydroxy hydroxy acids retarder types, find out the universal rule and from the Angle of the retarding mechanism is analyzed, and through the mortar experiment to validate the above experimental results.
∷
