Additive and cement adaptability problem is that all commercial concrete manufacturers feel fear, headache, also let a lot of admixture manufacturers feel aggrieved question. Can say at present in China, as long as the admixture and cement does not suit, resulting in commodity concrete slump loss of concrete is too large or too fast setting can not meet the construction requirements, and even bring engineering quality problems, eventually always blames admixture of the problem, it is not fair. Admixture and cement are not to adapt to the commodity concrete slump loss is too large, both admixture quality, chemical composition of reasons, but also belongs to the cement itself mineral composition, with the type of gypsum, the height and the alkali content of cement admixture types and other factors cause. Because I was learning silicate professional ( focusing on cement ) origin, since 1977 has also engaged in lignin sulfonate, naphthyl sulfonate, melamine and other types of admixture of the development, research, production, and in Japan and China joint venture company has long been engaged in commodity concrete admixture in concrete application to work, admixture in concrete industry, cement industry and ceramic industry in the application with deep experience, especially the commodity concrete is different from other industries, it has a time and distance constraints, the admixture is more demanding, than other industry more prone to problems, the admixture in concrete application problems and solutions about the experience!

One, the problem of additive and cement adaptability
On 1 mineral composition of cement admixture effect
Cement mineral composed of calcium aluminate ( C3A three ) three ( C3S ), calcium silicate, calcium silicate, two ( C2S ) and iron calcium aluminate ( C4AF four ), the hydration rate of cement with C3A as the most quickly, followed by C3S, C2S, C4AF again. According to the general rotary kiln cement clinker, cement mineral composition for general C3S : 45 ~ 65%, C2S: 15 ~ 32%, C3A: 4 ~ 11%, C4AF: 10 ~ 18%. But in practice it with admixture matched point of view, the fastest C3A hydration, adsorption of additives is the fastest, followed by C3S hydration, adsorption admixture also followed, the two is the effect of additive and cement adaptability of main factors. From many years of experience and lessons, the mineral composition of cement in the C3A, C3S as the following two conditions are met: a ) C3A = 8%, B < 65% ) C3A C3S that if C3A = 8%, C3S in 50 ~ 55%, and with two gypsum preparation of cement with various adaptability are good, with this cement general lignin water-reducer, naphthalene efficient composite superplasticizer, pumping agent and preparing a commodity concrete slump loss is smaller, generally can meet the requirements of construction. But when C3A > 8% or C3A C3S > 65% cases, appeared admixture and cement incompatibility, commodity concrete loss, unable to meet the requirements of construction.
This is only my years of experience data, I hope what research units have more interested, can further prove that in the future, the additive effect.
The following example illustrates the effects of mineral composition of cement admixture.
Hefei a research institute affiliated companies with a project using the admixture of a Shandong cement rotary kiln production of 42.5 ordinary portland cement and Hefei local production of 42.5 ordinary portland cement, the use of Shanghai Construction Engineering Masters high-tech building materials company imported raw materials imported formula production of polycarboxylic acid high efficiency of air-entraining water-reducing agent, the reducing agent in Shanghai on the used in the project has obtained good effect, can be said to be the best additive. But the company during concrete mixing, but found that the same admixture, the same volume, the production of Shandong cement concrete slump loss 30 minutes than local cement concrete slump loss in 50%, but could not be used, the use of naphthalene superplasticizer slump loss greater. The company v. calls to contact me, with many years of experience, I'll tell not admixture of the problem, but the problem of the mineral composition of cement. I immediately asked each other to investigate both the mineral composition of cement, the results it is as expected, the survey found that Shandong produces cementThe mineral composition is as follows: C3A10.96%, C3S64.36%, C2S10.23%, C4AF11.55%, and local cement C3A only 6%, finally the project abandoned Shandong produces cement.
The mineral composition of cement admixture in C3A on the impact of the most significant, in last few years, the cement plant in order to improve the early strength of cement, generally used to improve C3A content approach, this gives admixtures application brings a lot of trouble. I am in Nanjing joint concrete working period, there is a new year's day just passed, he found several concrete mixer car in the concrete can not discharge, several mixer driver in the car were abnormal phenomena of concrete tank. At that time China foreign immediately confirm the concrete mixture ratio did not change, using the same tank naphthalene admixture has not changed, the entire computer metering operation without exception, just from a local cement plant into a batch of cement ( the factory is the cement factory and old customers, the past never happened this phenomenon ), so we immediately suspect cement, immediately to the cement factory investigation, found that the cement factory is invited a German expert in cement rotary kiln technical reformation, new year's day around the C3A content from the previous 7 to 8% to 9.5%. We asked the factory to restore the original content of C3A, C3A control in less than 8%. At the same time will have storage cement to increase the amount of admixture and cement water ratio invariable situation, increase water and cement content, thereby increasing the slump of concrete factory, to ensure that the construction requirements, but such measures will increase the cost of commodity concrete, therefore, high C3A, either for general reduction agent or naphthalene superplasticizer and today's best polycarboxylate superplasticizer will bring cement and admixtures not suited to the situation, so the preparation of commodity concrete, cement, special attention should be paid to C3A C3S content.
Because I was studying cement, admixture and are engaged, and are now in use of admixtures cement and admixture, so it does not suit, I approach used is:
( 1) with the same kind of admixture with several different species, different brands ( different manufacturers) of cement mortar fluidity test, to determine the admixture of cement adaptability
( 2 ) the use of commonly used, known for its good adaptability to a cement with different types, different manufacturers admixture for mortar fluidity test, to determine the quality of various admixtures.
As a comparison, we can find that the problems are caused by admixture and cement by. As is the cement to cause, should be further analyzed the mineral composition of cement, gypsum type, content and mineral admixture on high admixture effect. As is the cause caused by admixture, should immediately and contact the manufacturer : a survey of additive formula is changed? Parent (mostly naphthyl sulfonate sodium and calcium lignosulphonate ) whether the quality of a wave? In recent years, lignin additive raw material change, coniferous raw material is in short supply, high quality wood calcium and export, resulting in many complex lignin additive manufacturers quality is not stable, the water reducing rate, gas content is too high, commodity concrete surface bubbles, concrete strength declined, and the reduction of naphthalene agent at home with the exception of a few manufacturers are using automatic control, stable quality, many production synthesis of naphthalene sulfonic acid sodium salt manufacturers or manual operation, so that the sulfonation, condensation and several other key production process is not stable, which leads to the matrix polymerization degree is not high, the water reducing rate is not stable, use this matrix composite of naphthalene water reducing agent, natural unstable product quality. In this case, we often encounter the ready-mixed concrete company. And admixture manufacturers negotiations, manufacturers believe that formula did not change, quality does not change, but ignore the quality change of product matrix. For the joint venture company, on the raw material of feed quality control strictly, once found to be additive, immediately return, two times return stop using, looking for more stable admixture. As an admixture of the user, need is a stable quality products, most of the current domestic manufacturers are engaged in admixture compound, more attention should be paid to the problem of population quality.
2 types of gypsum in cement clinker added to admixture effect
Mainly anhydrite effects, with hard gypsum as retarder in cement, not only with wood calcium, molasses type admixture not to suit, also produces a false set of phenomena, and anhydrite on naphthalene series water-reducing rate have a great impact. In the early 80's, when for the first time in Jiangsu and Nanjing found a medium-sized well-known local cement plants and wood calcium, molasses to produce false setting, construction units to bring a lot of trouble, I had the anhydrite and gypsum in two different proportions of cement of naphthalene water reducer compatibility test. The results showed that, 100% the anhydrite cement for configuration,Naphthalene series water reducing agent influence much the same, the fluidity of the paste is only 105 ~ 110, two and 100% of gypsum to prepare the cement, the same amount of naphthalene water reducer for cement paste fluidity is 240 ~ 245. But the anhydrite gypsum = 1: Two : 1, calcium lignosulphonate, molasses class still incommensurate, naphthalene superplasticizer underlying adaptation, paste flow dynamic degree is 200 ~ 210, anhydrite gypsum = 2: Two : 8, the FDN didn't have much effect, paste flow for 230, the wood calcium, molasses type water reducing agent has influence, but not false condensate phenomenon.
In the actual production of the commercial concrete, I also had encountered such situation. Nanjing a joint concrete company was soon put into production, with cement varieties, has ordered 2000 tons of a local cement production of cement, prudence, sampling test, the results both lignin and naphthalene series superplasticizer, are false and condensate quick-setting phenomenon. The foreign staff to contact me immediately, because at that time Nanjing anhydrite problems I know, immediately sent to investigate the cement plant with plaster, and the cement factory full use of anhydrite, after the concrete company, purchased the tickets will be 2000 tons of cement were returned.
So the use of admixtures, also needs prior to the gypsum in cement type and content of doing a survey, in case there is not suited to the situation.
On 3 alkali content of cement admixture application effect
In admixture Society published some papers have been talked about cement alkali content is big, adaptability is worse, but in practical application, the general commodity concrete company does not pay much attention to this problem. In contrast, the mineral composition of cement and gypsum kinds of admixture effect than the alkali content of the more obvious effects, but the use of low alkali cement concrete can not only reduce because of adaptability and brought the slump loss problem, but also to avoid concrete alkali aggregate reaction. As a joint venture of concrete company, in order to ensure the quality of concrete, we choose high quality, high strength, low alkali cement.
4 cement and mineral admixture on adaptability effect
Generally speaking, the use of pure slag as mineral admixtures slag cement admixture, and good adaptability. Some commodity concrete company by slag of adaptability, advantageous, but also can improve the workability of concrete, pumping, reduce the hydration heat, increase the later strength, suitable for use in large volume concrete. Is currently on the market the slag is not low price, therefore the general commodity concrete company adopted the use of fly ash and admixture" Bi-adding" approach.
Whether in cement plant is in commodity concrete company, using fly ash as admixture, must strictly control the quality of fly ash, especially fly ash carbon content of carbon, due to admixture of adsorption. Carbon content is too large, too much influence adsorption admixture, additive effect. So the cement and admixture adaptability and fly ash carbon content related to quality. A fly ash carbon content had no effect on the lowest, adaptability, two of fly ash on adaptability is not affected, but two of fly ash in deep color, high carbon content, close to three of fly ash index, will bring adverse effect to the use of admixtures. Three of fly ash in concrete in general can not use. So in actual application, the ready-mixed concrete company from fly ash by color will be able to judge the admixture effect, color is light, the use of smaller effect, conversely, greater.
Other mixed with industrial waste slag, coal gangue, cement, because of complex composition, stability, adaptability is poor.
As a result of additive and cement can not adapt to the commercial concrete manufacturers brings is the greatest problem of slump loss is too large, sometimes to the scene, concrete mixing truck unloading from. In this case, our approach is the use of two adding method, i.e., laboratory personnel with high efficiency water reducing agent rushed to the construction site, again according to a certain proportion of high efficiency water reducing agent are uniformly added mixer mixing tank, and high speed stirring for a minute immediately after unloading, the pump pressure pouring. This situation must not be arbitrary if any water, water, water cement ratio increasing, not only affects the strength, also caused the drying shrinkage crack, to the project quality to bring future trouble.
In fact, about the problem of additive and cement adaptability, early in twentieth Century 60 ~ 70 age, also often occur in japan. Because Japanese cement production company has more than a dozen large companies, all belong to the Japan Cement Association member.

Additives company only ten, also belongs to the Japanese admixture Association member. Once the occurrence of additive and cement adaptability does not suit and affect the quality of concrete, two Association jointly invited University Professor, expert to root cause analysis and arbitration, who causes, who is responsible for the complete improvement, so since 80 time will no longer appear admixture and cement does not adapt to the situation. Similarly, the two times of commodity concrete additive in Japan for 70 years was also popular. Their practice is: the first use of lignin superplasticizer will commodity concrete prepared into slump 8 centimeters of the concrete, mixer truck to the site, the site added naphthalene superplasticizer ( field 150), mixer on high speed stirring after mixing tank discharge placement, but the scene again and add artificial needs, the Japanese labor cost is higher, and high speed stirring bring noise causes environmental pollution problem. So 80 time begin to study with polycarboxylate represented NJH highly effective, 85 years formally become commodities, begin to use, thereby solving the commodity concrete medium important one annulus, slump loss problem.
Due to different national conditions, China's cement factory optical rotary kiln is tens of thousands, or hundreds of admixture manufacturers large and small, may not like Japan, by association to solve the problem of additive and cement adaptability, which gives users - commercial concrete manufacturers brought most worried about is the most headache: additive and cement can not adapt, influence the quality of commodity concrete, or even accidents.
As a joint venture of commodity concrete company, the quality and stability of raw materials, to scientific and reasonable mix, full automatic control system of production equipment and strict Cengcengbaguan, to the scene to provide quality of commodity concrete is our aim. Our approach is:
( 1) as far as possible the selected quality stability of large admixture manufacturers, large high quality cement manufacturers, high-quality gravel manufacturers as our fixed base of raw materials.
( 2) on various raw materials according to the national standard strictly into the factory inspection.
( 3) with mortar fluidity to judge the cement and admixture adaptability problems, such as unsuitable, judgment is a cement or admixture, and immediately associated with the occurrence of a contact, immediately asked to solve or return.
The reason why we use mortar fluidity to judge, without using the fluidity of the paste to judge the compatibility of cement and additive, because we have been met by the fluidity of the paste to judge, for some modification of the polymeric admixtures are not suitable for some, including poly carboxylic acid salt admixture. Large molecular weight, viscosity, using the fluidity of the paste method can not truly reflect its expansibility, the fluidity of the paste is not big, but the mortar fluidity is great, for use in concrete the effect of it. In this case, a single by the fluidity of the paste is easy to be mistaken as incommensurate. The use of mortar fluidity to judge, one is close to the concrete, two is the result of sand to join, give full play to its dispersion, overcomes the sticky side, this also with concrete test match. So it is suggested in the national standard, additive and cement adaptability judgment method for determination of modified mortar fluidity method.
( 4) such as the slump loss is too large ( especially in summer ) is difficult to discharge, using two times add methods to solve, absolute prohibition of water.
( 5) to preparation of high quality concrete, especially in high strength concrete, admixture, sand, gravel gradation, the stiffness ( crushing value ), shape, whether or not containing mud must strictly control. Especially in summer, sand and gravel in the outdoor exposure, high temperature, will cause the slump loss increases, so the summer must pay attention to the stone of continuous water spray, cooling, which is also very important, can avoid the slump loss increase.
( 6) different types of admixture must distinguish strictly, clearly identified. In the admixture adding tank, there must be a producer and concrete manufacturers mutual recognition to the tank, absolutely cannot be wrong, especially high-performance water-reducing agent and the common water reducing agent, if the mistake, the ordinary water-reducing agent used as superplasticizer, increase the use of 3 ~ 4 times, resulting in site concrete days condensate, serious engineering accident.
A few years ago, I work in Shanghai during the period, he heard a such accident. Various additives can have a variety of different applications, content range, beyond this range, there will be project quality accident, should be particularly cautious.
In commodity concrete admixture and cement, when not meet, high slump loss, can not meet the requirements of construction, how to do?

Generally speaking, the company purchased commodity concrete cement, one-time purchase of a large quantity, but are generally directly into the cement Chu Cangzhong, so generally admixture to cement, but obviously due to the mineral composition of cement or gypsum, produced very incommensurate, will consider replacing cement manufacturers, therefore generally not suited to, you can take the following measures:
( 1) appropriate to increase the amount of admixture.
( 2) the replacement of admixture, in general, additive and cement adaptability to poly carboxylic acid salt for the best, followed by amino sulfonate ( amino sulfonate used alone, bleeding severely, and naphthalene compound use ), again for naphthalene and its composite water reducing agent, lignin sulfonate, molasses etc.. But the domestic currently used admixture most is common, efficient, retarding and other composites, composite formula, the quality of monomers, are different, so when they do not adapt to the situation, desirable variety of local products mortar adaptability test, choose the suitable additive, that is to say, change the admixture to cement.
( 3) as the method still can not solve the problem, the slump loss or larger, can not meet the construction demand, can adopt two adding method, in situ unloading before joining the naphthalene series superplasticizer, mixing tank high-speed rotary 1 ~ 2 minutes is unloaded into the pump for pouring.
(4 ) is added to the slurry approach, increasing factory slump, increased to 20 ~ 22cm, whereby to maintain the water cement ratio unchanged, while increasing the cement content and water content. When a slump in the following 12cm, slump increase per unit of 1cm, an increase in the water content of 1.2%, when the slump than 15cm, slump increase per unit of 1cm, water consumption increases from 1.5 to 2.5%. Note: must also increase unit cement content and water content, in order to maintain a constant water-cement ratio, concrete strength unchanged, but to do so, will undoubtedly increase the cost of commodity concrete, general commercial concrete manufacturers cannot but, can use this method.