Background
The construction industry in China generally keeps a rough on-site construction mode, and the mode has a plurality of defects: the potential safety hazard of a construction site is more, the preparation cost is high, the economic and environmental protection performance is poor, the engineering quality is not easy to be accurately controlled, and the like. Due to the defects of the field construction mode, the precast concrete member is produced at the same time. With the rapid development of infrastructure construction and the continuous improvement of the building industrialization level, a large number of precast concrete members are applied to actual engineering construction. The assembly type building vigorously advocated by the state at present brings wide prospects for the application of the prefabricated concrete member.
The wide application of the precast concrete member brings about the rapid increase of the number of precast concrete member enterprises in China. According to the incomplete statistics of the concrete and cement product association, the PC factories built nationwide exceed 2000 families by 2020, and the designed PC capacity reaches 5000-6000 ten thousand cubic meters. At present, the large-scale industrial production process of the prefabricated parts in China also has more problems: the quality management of production enterprises is weak, and the quality of the prefabricated part including appearance quality, manufacturing accuracy and internal quality is to be improved. The technical Standard for fabricated concrete construction (GB/T51231-2016) states that the strength of concrete when a prefabricated part is demolded and lifted is not less than 15 MPa. In order to accelerate the turnover of the die and improve the production efficiency, most prefabricated component production enterprises adopt a steam curing process. The steam curing process can enable the early strength of the concrete to be increased rapidly and achieve the demoulding and hoisting strength of the prefabricated part in a short time, but the following defects exist: firstly, the steam curing process needs to generate steam, consumes a large amount of energy, improves the production cost, and does not accord with the energy-saving and emission-reducing idea advocated by China; secondly, the steam curing brings heat damage to the concrete and is not beneficial to the durability of the concrete. Based on the defects of the steam-cured concrete, technicians and scholars at home and abroad research on the steam-cured-free concrete. Researchers prepare the non-autoclaved concrete by optimizing the mixing ratio of the raw materials and the concrete and adding various early strength agents and water reducing agents.
The present invention discloses, for example, a steam-curing-free precast concrete member and a forming method thereof, which is named as 201711331839.3. the early strength of the concrete is improved by adding an inorganic-organic composite early strength agent and a crystal nucleus type early strength agent into the concrete according to a certain proportion, but as can be seen from the disclosed test results, the curing time is at least 1 day.
For example, patent No. 202011436701.1, entitled C35 steam-free curing concrete for prefabricated buildings and a preparation method thereof, discloses that "after the concrete is cured for 24 hours, the mold is pushed out of a curing kiln, the mold is removed, the concrete member after the mold removal is hoisted into a curing pool for water curing for at least 7 days, the temperature T of the curing pool is 20 ± 3 ℃, and then the concrete member is hoisted out and stacked on a concrete product stacking site. "
In the above-mentioned patents, the maintenance time is required at least one day, and for the enterprises with larger production capacity, the mold occupation is still too large, and the production efficiency is still affected to a certain extent. For enterprises, the faster the mold turnover, the higher the production efficiency.
Disclosure of Invention
Based on the problems, the invention provides the steam curing-free concrete and the preparation method thereof, the early strength agent and the water reducing agent with a certain proportion are added simultaneously, the slump of the prepared concrete is 120 +/-30 mm, the compressive strength can reach 19Mpa through natural curing for 8 hours (the natural environment temperature is higher than 15 ℃), the requirement of the demolding strength of prefabricated parts can be met, the turnover of a mold can be obviously accelerated, and the production efficiency is improved.
Simultaneously, the raw materials are added by a fractional step method, cement, water, an early strength agent, a water reducing agent, first-level fly ash and S95 mineral powder are added into a stirrer in the first step, and are stirred at a high speed for 50-60 seconds, then sand and stones are added in the second step, and are stirred at a low speed for 55-65 seconds, so that concrete is prepared; the method reduces the permeation of water in the raw materials to the sand and the stones, namely reduces the water absorption of the sand and the stones, enhances the fluidity of the concrete, and is convenient to pour into the mold.
The invention is realized by adopting the following technical scheme:
the non-autoclaved concrete is prepared from the following raw materials in per cubic meter:
cement: 330-420 kg;
first-grade fly ash: 0-80 kg;
s95 mineral powder: 0-80 kg;
sand: 690-710 kg;
stone: 1080-1100 kg;
early strength agent: 5-12 kg;
water reducing agent: 10-18 kg;
water: 100-114 kg.
The preparation method of the non-autoclaved concrete comprises the following steps:
s1, adding 420kg of cement 330 and 114kg of water 100, 5-12kg of early strength agent, 10-18kg of water reducing agent, 0-80kg of first-grade fly ash and 0-80kg of S95 mineral powder into a stirrer, and stirring at high speed for 50-60 seconds;
s2, adding sand 690-710kg and pebble 1080-1100kg into S1, and stirring at low speed for 55-65 seconds to obtain the concrete.
Further, the cement is P.I 52.5 cement.
Further, the early strength agent is a super early strength additive SBT-510 of Nanjing Subot; the water reducing agent is a CSP-12 early strength type polycarboxylic acid high-performance water reducing agent for Guangdong red wall.
Furthermore, the sand is medium sand, the fineness modulus is 2.3, and the mud content is 2.5%.
Furthermore, the stones are crushed stones with the particle sizes of 5-10mm and 10-25mm according to the proportion of 1: 2 mixing the components.
Furthermore, the sand rate is 38-40%.
The technical scheme of the invention has the following beneficial effects:
(1) the invention can meet the requirements of quick demoulding strength in the production process of precast concrete members and the cost control requirement of concrete. The non-autoclaved concrete can reduce the production cost of production enterprises. The steam curing process is omitted, the high-durability precast concrete member can be prepared, and the overall performance of the precast concrete member is improved.
(2) The slump of the prepared concrete is 120 +/-30 mm. After the mineral admixture is added, under the curing condition of 30 ℃, the highest compressive strength of concrete for 8h, 12h, 1d and 7d can reach 29.71MPa, 37.91MPa, 53.00Pa and 76.01MPa respectively; under the curing condition of 15 ℃, the highest compressive strength of the concrete for 8h, 12h, 1d and 7d can respectively reach 9.77MPa, 16.81MPa, 42.82Pa and 66.84 MPa. Under the condition of not doping mineral admixture and curing at 30 ℃, the highest compressive strength of the concrete in 8h and 12h can respectively reach 40.10MPa and 46.17 MPa; under the curing condition of 15 ℃, the highest compressive strength of the concrete for 8h and 12h can respectively reach 14.1MPa and 18.97 MPa.
Detailed Description
The following examples are provided to illustrate specific embodiments of the present invention.
Example 1
A non-autoclaved concrete is prepared from 417kg of P & I52.5 cement, 103kg of water, 700kg of sand, 1097kg of pebbles, 10kg of super early strength SBT-510 admixture of Nanjing Subot and 16.7kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall;
the preparation method comprises the following steps: adding cement, water, a Nanjing Subo SBT-510 super early strength external additive and a Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then, testing the slump of the concrete mixture, then loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 90mm, the compressive strength of the concrete in 12 hours is 22.7Mpa in standard curing, 18.1Mpa in natural environment curing at the temperature of 11-15 ℃, and 37.1Mpa in curing at the temperature of 30 ℃.
Example 2
A non-autoclaved concrete is prepared from 417kg of P & I52.5 cement, 106kg of water, 700kg of sand, 1097kg of pebbles, 10.5kg of super early strength SBT-510 admixture of Nanjing Subot and 16.7kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall;
the preparation method comprises the following steps: adding cement, water, a Nanjing Subo SBT-510 super early strength external additive and a Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then, testing the slump of the concrete mixture, then loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 90mm, the compressive strength of the concrete in 12 hours is 24.9Mpa through standard curing, 28.7Mpa through natural environment curing at 19-24 ℃, and 39.5Mpa through curing at 30 ℃.
Example 3
The non-autoclaved concrete is prepared from 396kg of P & I52.5 cement, 106kg of water, 700kg of sand, 1097kg of pebbles, 10.5kg of super early strength admixture SBT-510 of Nanjing Subot, 16.7kg of Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent and 21kg of fly ash;
the preparation method comprises the following steps: adding cement, water, fly ash, Nanjing Subot SBT-510 super early strength additive and Guangdong red wall CSP-12 early strength type polycarboxylic acid high performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then testing the slump of the concrete mixture, loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 156-180 mm, the compressive strength of the concrete in 12 hours is 23.2Mpa in standard curing, 35.6Mpa in natural environment curing at 21-32 ℃, 44.9Mpa in curing at 30 ℃ and 6.2Mpa in low-temperature curing at 9 ℃.
Example 4
A non-autoclaved concrete is prepared from 334kg of P & I52.5 cement, 112kg of water, 700kg of sand, 1097kg of pebbles, 8.3kg of super early strength SBT-510 admixture of Nanjing Subot, 12.5kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall, 41.7kg of fly ash and 41.7kg of mineral powder;
the preparation method comprises the following steps: adding cement, water, fly ash, mineral powder, Nanjing Subot SBT-510 super early strength additive and Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then testing the slump of the concrete mixture, loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 170mm, the compressive strength of the concrete in 12 hours is 24.3Mpa through standard curing, 31.5Mpa through natural environment curing at 21-24 ℃, 38.8Mpa through curing at 30 ℃ and 8.4Mpa through low-temperature curing at 11 ℃.
Example 5
A non-autoclaved concrete is prepared from 333kg of P & I52.5 cement, 113kg of water, 700kg of sand, 1097kg of pebble, 6.3kg of super early strength SBT-510 admixture of Nanjing Subot, 12.5kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall, 41.7kg of fly ash and 41.7kg of mineral powder;
the preparation method comprises the following steps: adding cement, water, fly ash, mineral powder, Nanjing Subot SBT-510 super early strength additive and Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then testing the slump of the concrete mixture, loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 120-130 mm, the compressive strength of the concrete in 12 hours is 22.7Mpa in standard curing, the natural environment curing at 25-34 ℃ is 35.8Mpa, the natural environment curing at 30 ℃ is 40.0Mpa, and the low-temperature curing at 15 ℃ is 18.7 Mpa.
Example 6
A non-autoclaved concrete is prepared from 334kg of P & I52.5 cement, 113kg of water, 700kg of sand, 1097kg of pebbles, 6.3kg of super early strength SBT-510 admixture of Nanjing Subot, 12.5kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall, 41.7kg of fly ash and 41.7kg of mineral powder;
the preparation method comprises the following steps: adding cement, water, fly ash, mineral powder, Nanjing Subot SBT-510 super early strength additive and Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then testing the slump of the concrete mixture, loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 160mm, the compressive strength of the concrete for 8 hours is 13.1Mpa by standard curing, 19.1Mpa by natural environment curing at 25-34 ℃, 29.7Mpa by curing at 30 ℃ and 9.8Mpa by low-temperature curing at 11 ℃;
the concrete has the compression strength of 40.6Mpa after 1 day of standard curing, 48.2Mpa after 25-34 ℃ natural environment curing, 53.0Mpa after 30 ℃ curing and 42.8Mpa after 11 ℃ low-temperature curing;
the concrete has the compressive strength of 69.1MPa after 7 days of standard curing, 70.6MPa after 25-34 ℃ natural environment curing, 76.0MPa after 30 ℃ curing and 66.8MPa after 11 ℃ low-temperature curing.
Example 7
A non-autoclaved concrete is prepared from 417kg of P & I52.5 cement, 113kg of water, 700kg of sand, 1097kg of pebbles, 6.3kg of super early strength SBT-510 admixture of Nanjing Subot and 12.5kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall;
the preparation method comprises the following steps: adding cement, water, a Nanjing Subo SBT-510 super early strength external additive and a Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then, testing the slump of the concrete mixture, then loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 130mm, the compressive strength of the concrete in 12 hours is 33.1Mpa through standard curing, 42.5Mpa through natural environment curing at the temperature of 17-20 ℃, 46.2Mpa through curing at the temperature of 30 ℃ and 19.0Mpa through low-temperature curing at the temperature of 12 ℃.
Example 8
A non-autoclaved concrete is prepared from 417kg of P & I52.5 cement, 113kg of water, 700kg of sand, 1097kg of pebbles, 6.3kg of super early strength SBT-510 admixture of Nanjing Subot and 12.5kg of CSP-12 early strength type polycarboxylic acid high-performance water reducing agent of Guangdong red wall;
the preparation method comprises the following steps: adding cement, water, a Nanjing Subo SBT-510 super early strength external additive and a Guangdong red wall CSP-12 early strength type polycarboxylic acid high-performance water reducing agent into a stirrer according to the mass ratio, and stirring at high speed for 50-60 seconds; then adding sand and stones, and stirring at low speed for 55 seconds to obtain the concrete mixture. Then, testing the slump of the concrete mixture, then loading the mixture into a compression-resistant test mold, and manufacturing a compression-resistant test block for strength test;
the slump of the prepared concrete is 130mm, the compressive strength of the concrete for 8 hours is 16.4Mpa by standard curing, 29.9Mpa by natural environment curing at 20-24 ℃, 40.1Mpa by curing at 30 ℃ and 14.1Mpa by low-temperature curing at 15 ℃.
The above technical solutions are only preferred embodiments of the present invention, and it should be noted that: without departing from the principle of the invention, several modifications and refinements may be made by those skilled in the art, and these should also be considered as the protection scope of the present invention.