What is the optimal pH of Portland cement

At room temperature (25 hours), pH>7 is alkaline < pH7 is acidic.

Composite Portland cement: a hydraulic cementitious material made of Portland cement clinker, 20% 50% two or more specified mixed materials and an appropriate amount of gypsum grinding, called composite Portland cement (referred to as composite cement), code.

Normally, the pH value tends to 0 means that the solution is more acidic, the more it tends to 14, the more alkaline the solution, when the pH < 7, the solution is acidic, when the pH > 7, the solution is alkaline, and when the pH = 7, the solution is neutral. The pH value is allowed to be less than 0, such as the pH of hydrochloric acid (10 mol l). Since the actual solution is not an ideal solution, it is not possible to accurately measure the H+ concentration alone, so the pH of the solution cannot be accurately calculated.

Therefore, H+ activity should be used, i.e., pH=-LG ah+=-LG·ch+. In this way, theoretically, as long as the activity of hydrogen ions is known, ah+, the exact pH of the solution can be obtained.

Only the solution has a pH.

Cement is solid and has no pH.

However, if the cement is stirred into mud and then tested, because the cement is silicate and the water solubility is very small, the pH of the mud will be slightly alkaline, about 7-8.

Standard consistency water consumption: The water consumption of cement standard consistency refers to the amount of water that needs to be burned when the cement slurry reaches the standard consistency. It is usually expressed as a percentage of the water used to the mass of cement. The standard consistency water consumption of Portland cement is generally between 21% and 28% in Cheongju.

The standard consistency water consumption of cement is mainly related to the fineness of cement and its mineral composition.

Only the solution has a pH. Cement is solid and has no allergenic pH.

The cement is churned into a slurry and then tested, with a pH value of about 7 to 8. Because cement is silicate, it is very water-soluble, and the pH of the mud will be slightly alkaline.

Cement is a powdered hydraulic inorganic cementitious material. After adding water and stirring into a slurry, it can be hardened in air or better hard pinned in water, and can firmly cement sand, stone and other materials together. As an important cementitious material, it is widely used in civil construction, water conservancy, national defense and other projects.

<>What is the specific content of the basic performance of Portland cement, the following Zhongda Consulting will answer for you.

The main mineral composition of Portland cement is: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium iron aluminate. Tricalcium silicate determines the strength of Portland cement in four weeks; Dicalcium silicate only exerts its strength effect after four weeks, and it reaches the strength of tricalcium silicate for about four weeks in about a year; The strength of tricalcium aluminate is fast, but the strength is low, which plays a certain role in the strength of Portland cement in 1 to 3 days or a little longer. The strength of tetracalcium ferroaluminate is also faster, but the strength is low, and the contribution to the strength of Portland cement is small.

A fast setting and hardening, high early strength and later strength, suitable for concrete with early strength requirements, winter construction concrete, high-strength concrete and prestressed concrete projects of important structures above ground and underground.

b. Good frost resistance, suitable for concrete projects subjected to repeated freeze-thaw cycles within the range of water level rise and fall in severe cold areas.

c. The heat of hydration is large, and it is not suitable for large-volume concrete projects, but it can be used for construction in low temperature season or winter.

d Poor corrosion resistance, not suitable for projects that are often in contact with corrosive media such as flowing fresh water or sulfate, nor should it be used in projects that are often in contact with corrosive media such as seawater and mineral water.

e Poor heat resistance, not suitable for concrete projects with heat resistance requirements.

f. Good carbonization resistance, suitable for environments with high CO2 concentration in the air, such as foundry workshops, etc.

g. Dry shrinkage, which can be used for concrete engineering in a dry environment.

h. Good wear resistance, can be used for pavement and ground engineering.

This kind of cement includes all kinds of Portland cement without or mixed materials, and China is divided into the following five categories according to the mixing of its mixed materials.

1.pure clinker Portland cement;

2.ordinary Portland cement;

3.slag Portland cement, pozzolana Portland cement, fly ash Portland cement;

4.Composite Portland cement.

According to the provisions of "Portland Cement, Ordinary Portland Cement" and "Cement Mortar Strength Test Method (ISO Method)", cement and standard sand are mixed according to 1:3, and the water-cement ratio is used to make specimens according to the specified method, and the compressive strength and flexural strength of 3D and 28D are measured in water at standard temperature (200C 1). According to the measurement results, Portland cement is divided into six strength grades.

The code R stands for early-strength cement. A certain strength grade cement must reach the specified compressive strength and flexural strength at the same time. If one of them is less than the specified value, the cement should be lowered to one level for use.

<> the performance of Portland cement is very important, and understanding the properties of the material itself plays a very important role in the subsequent construction and use, and the treatment of every detail is crucial. Zhongda Consulting will introduce the performance of Portland cement.

The relative density of Portland cement is: Cement in contact with water will release heat, and after a certain period of time will set (different types of cement have different setting times). In order to ensure that the cement has a suitable setting time, an appropriate amount of gypsum is often added, and phosphogypsum and fluorine gypsum, which are by-products of the fertilizer industry, can also be used as substitutes.

The amount of gypsum added is mainly determined by the content of aluminate in cement clinker, and the amount added cannot be exceeded in terms of sulfur trioxide. Cement should have good volume stability. The condensed cement hardens quickly in air and water and has mechanical strength (compressive and flexural strength).

Generally, the compressive and flexural strength of the mortar sample cured in water for 3 days, 7 days and 28 days in cement: sand = are in line with the national standard as the strength index of cement, calculated in kg cm, and the value of compressive strength for 28 days is called the label of cement. Portland cement is commonly marked with 625.

Some high-strength and ultra-high-strength cement can even reach more than 1000 grades. When the minerals in cement clinker are in contact with water, they undergo hydration reaction (i.e., calcium hydroxide), hydrated calcium silicate gel, calcium aluminate hydrate and calcium ferrite hydrate are generated at the same time. When gypsum is present, the latter two hydrates form hydrated calcium sulfoaluminate and hydrated calcium thioferrate, respectively.

Cement slurry shrinks in dry conditions and expands in wet conditions. Calcium hydroxide and calcium aluminate hydrate will be subject to the attack of sulfate in seawater, so the amount of calcium aluminate in cement used in seaports and other cement should be limited. If the alkali content in the cement is too high, and the aggregate made of concrete contains activated silica, the alkali-aggregate reaction will also occur, the volume will expand, and the cement stone and concrete will be destroyed.

Excessive free calcium oxide and galenite in the clinker also produce volume expansion during the hydration reaction, resulting in poor volume stability of cement, and this kind of cement is unqualified.

Hello Portland white cement generally has a cement content of one-half White Portland cement refers to the water and hard cementitious material made of white Portland cement clinker, an appropriate amount of gypsum and mixed materials (limestone and kiln ash) with less iron oxide content, referred to as white cement, code P·W. White Portland cement is mainly used for the decoration of buildings, such as floors, stairs, steps, exterior wall finishes, colored brushed stone and terrazzo manufacturing, facing mortar, cutting fake stone, cement brushing process, marble and tile inlay, concrete sculpture craft products, etc., as well as for the manufacture of colorful spike colored cement.