CN107402291A - Method for judging whether dolomitic limestone aggregate has alkali dolomite activity - Google Patents

Abstract

The invention relates to a method for judging whether the dolomitic limestone aggregate has alkali-dolomite activity. The rock column specimen prepared by using the aggregate to be detected is maintained in a quaternary ammonium-tetramethylammonium hydroxide solution, and the For the expansion rate of the test piece, if the rock column expands, it has ADR activity, otherwise, it does not have ADR activity. The present invention utilizes the quaternary ammonium-tetramethylammonium hydroxide not to expand with the microcrystalline quartz in the dolomitic limestone aggregate, but to identify the ADR activity of the carbonate aggregate through the expansion mechanism of the dolomite in the dolomitic limestone. Excluding the expansion of the ASR response provides a good way to distinguish ASR from ADR.

Description

A method for judging whether dolomitic limestone aggregates have alkali dolomite activity

technical field

The invention belongs to the field of building materials, and relates to the use of carbonate rock dolomitic limestone as building aggregates, in particular to a detection method for judging whether the dolomitic limestone aggregate has alkali dolomite activity.

Background technique

The distribution area of carbonate rocks in China is 344×10 ⁴ km ² , accounting for about 1/3 of the country’s land area, and the exposed area of carbonate rocks is more than 90×10 ⁴ km ² , which is close to 1/10 of the country’s land area. The application of salt rock in concrete is inevitable. The application of carbonate rock in concrete engineering is very extensive, because of its complex mineral composition, structure and other factors, it can be divided into many types according to different classification methods. Some rocks in carbonate rocks can react with OH ^- and cause the concrete to expand and crack. This kind of carbonate rocks belongs to active carbonate rocks. Active carbonate rocks include many types of rocks: argillaceous dolomitic limestone, argillaceous limestone dolomite, argillaceous dolomite and dolomite may all be alkali active. The dolomite contained in the rock is a very important reason for its alkaline activity. Dolomite is a rhombohedral crystal, which exists in a dense matrix composed of fine calcite and clay and other impurities in the form of dispersed distribution. The difference in texture and the size of the alkali activity mainly depend on the dolomite, calcite, clay and other impurities and The relative amount of voids. Some carbonate rocks contain high active SiO ₂ components, which makes the use of this type of rock in concrete need to be very cautious, not only to prevent cracking caused by alkali dolomite reaction (ADR) activity but also to prevent cracking caused by alkali dolomite reaction (ADR) Expansion cracking due to silicic acid reaction (ASR) activity. Therefore, the detection of alkali activity of aggregates is very important, and the research on the detection method of alkali activity is also very meaningful and necessary. Because ADR is difficult to suppress, the international tendency is not to use rocks with ADR activity as concrete aggregates. Accurately identifying the ADR activity of carbonate aggregates is currently the only effective measure to prevent ADR damage.

The methods currently used for ADR identification mainly include petrographic method, rock column method, small concrete column method and concrete prism method. Among them, the petrographic method can only describe whether there are potential active components and their distribution, but cannot determine whether there is ADR activity; the rock column method, small concrete column method and concrete prism method cannot accurately determine whether the expansion is caused by ASR, ADR or Both ASR and ADR are caused. At the same time, the research on ADR mainly uses two inorganic bases, KOH and NaOH, which can react with microcrystalline quartz and dolomite in the aggregate, and cannot distinguish whether the alkali activity comes from ADR or ASR. To date there is no single method for identifying the ADR activity of aggregates. It is necessary to develop a new detection method specially used to identify ADR activity.

Contents of the invention

In order to develop a new detection method specially used for identifying ADR activity, the present invention utilizes organic base quaternary ammonium base-tetramethylammonium hydroxide (TMAH) as a curing solution.

In order to achieve the above object, the technical scheme adopted by the present invention is: a method for detecting the activity of alkali dolomite in concrete that distinguishes dolomitic limestone aggregates. Methyl ammonium hydroxide solution to detect the expansion rate of the test piece.

The test piece is a rock column test piece cut from the aggregate to be tested.

Preferably, the preparation method of the rock column test piece is as follows: a. Cut several groups of rock columns of a certain size from the rock; b. Bond measuring nail heads at the center of both ends of the rock column; Measure expansion.

Preferably, the rock column is a rock column of 8-12mm×8-12mm×28-32mm, the nail head is bonded on a surface of 8-12mm×8-12mm, and the nail head is bonded by non-alkali cement . The alkali-free cement is obtained by uniformly mixing the analytically pure CaCO ₃ , SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ and calcining at high temperature.

Preferably, each group of rock pillars in step a is composed of rock pillars cut along three mutually perpendicular directions of the rock, and the expansion rate in step c is the maximum expansion rate in the same group of rock pillars.

The concentration of the curing solution is 1mol/L-2mol/L TMAH, preferably 1mol/L; the volume ratio Vs/Vl of the rock column to the curing solution is 1:5-15, preferably 1:10; the curing temperature of the rock column is 20-80 °C, preferably 80 °C; if the expansion rate of the specimen is greater than 0.1% when it is cured for 56 days, the aggregate used has ADR activity.

Preferably, the aggregate is mainly composed of calcite and dolomite.

Further, the test piece is a rock column test piece prepared by using the aggregate to be tested.

Beneficial effects produced by the present invention: the present invention utilizes quaternary ammonium alkali-tetramethylammonium hydroxide (TMAH) not to expand with microcrystalline quartz in dolomitic limestone aggregate, but to expand with dolomite in dolomitic limestone The mechanism identifies the ADR activity of carbonate aggregates, excluding the expansion caused by the ASR reaction; TMAH belongs to the quaternary ammonium base, which is a strong base, has the general properties of an inorganic strong base, is non-toxic and does not pollute the environment, and is easily soluble in water; The pH value of the 1mol/L solution is >13; storage conditions: 2°C-8°C; it has been verified by experiments that the drug does not interact with microcrystalline quartz in rocks, but has an effect with dolomite, which provides a good way to distinguish ASR from ADR. The present invention The rock column was selected as the experimental specimen, the influence of cement shrinkage was excluded, and the influence of other external factors such as cement was avoided in the process of analyzing the product.

Description of drawings

Fig. 1 XRD pattern of dolomitic rock;

Figure 2 The effect of the volume ratio V _s /V _l of the rock column to the curing solution on the expansion rate of the BFL-1 and BFL-10 rock columns maintained at 80°C in 1mol/L TMAH solution;

Fig. 3 Expansion ratios of BFL-1, BFL-10, GS-2 and HTS-8 rock columns when cured in 1mol/L TMAH solution at 20°C, 60°C and 80°C;

Fig. 4 Expansion rate of rock columns of BFL-1, BFL-10, BFL-2, BFL-6, BFL-3, BFL-12 maintained at 80°C in 1mol/L and 2mol/LTMAH solutions;

Fig. 5 Expansion rate of the rock column of CK;

Fig.6 Expansion rate of LHK rock column at 80°C;

Fig. 7 Expansion rate of LHK rock column at 60°C.

detailed description

In order to better implement the present invention, the present invention will be further described through the following examples, and some non-essential improvements and adjustments made to the present invention according to the contents of the present invention still belong to the protection scope of the present invention. The following is a detailed description with examples and test data.

A method for detecting damage of alkali dolomite reaction (ADR) and alkali silicate reaction (ASR) in concrete containing dolomitic limestone aggregates, comprising the following steps: a) selection of curing solution type; b) concentration of curing solution ; c) preparation of alkali-free cement; d) specimen type; e) curing solid-liquid volume ratio V _s /V _l ; f) selection of curing time; g) selection of curing temperature; h) evaluation of aggregate alkali dolomite Criterion for reactivity expansion ratio.

Wherein the curing solution described in step a) must not react with ASR active components such as microcrystalline quartz in dolomitic limestone or even if it reacts, it will not cause expansion phenomenon, but it can react with dolomite in dolomitic limestone and produce expansion . The curing solution is selected as quaternary ammonium base-tetramethylammonium hydroxide (TMAH), TMAH is a kind of alkaline and inorganic base: NaOH and KOH equivalent organic strong base, has the general properties of inorganic strong base, soluble in water, The boiling point is 120°C, and it is easily decomposed into trimethylamine and methanol when heated to 130°C.

Wherein in step b), the curing concentration is 1mol/L-2mol/L TMAH, preferably 1mol/L; in e), the volume ratio V _s /V _l of rock column and curing solution is 1:5, 1:10 and 1:15 , preferably 1:10; g) measuring the expansion rate of the rock column curing temperature at 20°C, 60°C and 80°C, preferably 80°C;

c) Preparation of cement: Alkali-free cement is prepared by uniformly mixing analytically pure CaCO ₃ , SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in a certain proportion and calcining at high temperature. The ratios of cement clinker are respectively SM= 1.80, IM=1.30 and KH=0.90. The raw material ratio of cement clinker is CaCO ₃ =78.18wt%, SiO ₂ =14.03wt%, Al ₂ O ₃ =4.40wt%, and Fe ₂ O ₃ =3.39wt%. The mineral compositions calculated by the Bogue method are C ₃ S=64.0wt%, C ₂ S=11.9wt%, C _4AF =10.9wt%, C ₃ A=13.2wt%, f-CaO=0.1wt%, f-MgO = 0.0 wt%. The specific preparation process of alkali-free cement is as follows: put each 500g of four kinds of raw materials into a 1000ml mixing cylinder, add 25 mixing balls, then put the mixing cylinder on the mixer and mix for 24 hours; use a press to apply 6MPa pressure to keep the pressure 5s; put the pressed raw material block vertically in the sagger, raise the temperature to 1450°C, and keep it warm for 1h; 10%.

d) Type of test piece; cutting of rock columns. Each type of rock takes 3 mutually perpendicular surfaces and cuts them into 10mm×10mm×30mm (±2mm) rock columns. Glue on the length measuring nail heads (the two nail heads are 5mm in length). The determination of the initial length of the rock column is to put the rock column into water at 20°C±2°C for 1 day, and measure its length with a micrometer after wiping off the surface moisture, which is recorded as the initial length L ₀ . When the rock column is cured to 7d, 14d, 21d, 28d, 42d and 56d, take out the rock column together with the curing container and cool it to 20°C±2°C, wash the rock column with water, wipe off the water on the surface, and measure its length Lt with a micrometer , the expansion rate of each rock column is taken as the maximum value as the experimental result. When measuring the length of the rock pillar at different ages, the relative position of the rock pillar and the micrometer should be kept unchanged as much as possible. If necessary, the length of the rock pillar should be measured every 14 days, and every 28 days after half a year. The expansion rate of the rock column is calculated according to formula (1):

In the formula: Pt—expansion rate of the rock column after curing for t days, %;

Lt—the length of the rock column after curing for t days, mm;

L0—the initial length of the rock column, mm.

Example 1 - Raw material

25% TMAH reagent, product of Zhenjiang Runjing High Purity Chemical Technology Co., Ltd.

The cement is P·II 52.5 Portland cement produced by Jiangnan Onoda Cement Co., Ltd.

The dolomitic rocks used in the test were taken from Baofuling, Hutoushan and Gushan in Weifang City, Shandong Province, numbered BFL-1, BFL-2, BFL-3, BFL-6, BFL-10, BFL-12, HTS- 8 and GS-2, their chemical compositions are shown in Table 1. Fig. 1 is the XRD pattern of each sample. It can be seen from Fig. 1 that each sample is mainly composed of calcite and dolomite, and contains a small amount of quartz.

Chemical composition/wt% of table 1 raw material

The 14d expansion rates of RILEM AAR-2 mortar specimens prepared by BFL-1, BFL-2, BFL-3, BFL-6, BFL-10, BFL-12, GS-2 and HTS-8 were 0.075%, 0.120 %, 0.062%, 0.162%, 0.158%, 0.180%, 0.036% and 0.077%, the expansion rates of mortar specimens prepared by BFL-2, BFL-6, BFL-10 and BFL-12 were 0.184%, 0.233%, 0.214%, and 0.255%. The 14d expansion rates of BFL-1, BFL-3, GS-2 and HTS-8 mortar specimens are all less than the threshold value 0.1% specified by RILEM AAR-2, and they do not have ASR activity. The expansion rate of BFL-2 mortar specimen 14d is greater than 0.1%, and the expansion rate of 28d is less than 0.2%, which is less than the threshold value specified by RILEM AAR-2, and has no ASR activity. The expansion rate of BFL-6, BFL-10 and BFL-12 mortar specimens is greater than 0.1% at 14d, and greater than 0.2% at 28d, which is greater than the threshold value specified by RILEM AAR-2, and has ASR activity. The 28d expansion rates of RILEMAAR-5 concrete specimens prepared by BFL-1, BFL-2, BFL-3, BFL-6, BFL-10, BFL-12, GS-2 and HTS-8 are 0.136% and 0.148% respectively , 0.085%, 0.179%, 0.229%, 0.245%, 0.141%, and 0.173%. According to RILEM AAR-5, BFL-3 does not have ADR activity, BFL-1, BFL-2, GS-2 and HTS-8 have ADR activity, BFL-6, BFL-10 and BFL-12 cannot Sure.

Embodiment 2-solid-liquid ratio

Figure 2 shows the results of BFL-1 and BFL-10 rock pillars being cured in 1mol/L TMAH solution at 80°C with the volume ratio V _s /V _l of rock pillar and curing solution being 1:5, 1:10 and 1:15, respectively. Expansion rate. When V _s /V _l is 1:5, 1:10 and 1:15, the 28d expansion rates of BFL-1 rock column are 0.064%, 0.102% and 0.107%, respectively, and the 28d expansion rates of BFL-10 rock column are 0.177% respectively , 0.192%, and 0.197%. When V _s /V _l is 1:5, the rock column BFL-1 and BFL-10 28d expansion rate is smaller than V _s /V _l is 1:10 and 1:15, and when V _s /V _l is 1:10, the rock column The expansion rate of BFL-1 and BFL-10 at 28d is close to that of V _s /V _l when it is 1:15. After titration with 1.0867mol/L HCl, when V _s /V _l is 1:5, the concentrations of BFL-1 and BFL-10 curing solutions after soaking for 28 days decrease by 12.2% and 16.2%, respectively, and when V _s /V _l is 1:10 The concentration of curing solution decreased by 6.3% and 8.9%, respectively, and when V _s /V _l was 1:15, the concentration of curing solution decreased by 5.7% and 8.0%. When V _s /V _l is 1:5, the amount of curing solution is not enough, the concentration of TMAH solution decreases more, and the expansion of rock column is relatively slow, but when V _s /V _l is 1:10 and 1:15 , the concentration of TMAH solution did not decrease significantly, and the expansion of the rock column developed relatively quickly, indicating that the 1:10 and 1:15 curing solutions can provide enough alkali to ensure the reaction.

Embodiment 3-curing temperature

Figure 3 shows the expansion ratio of BFL-1, BFL-10, GS-2 and HTS-8 rock pillars cured in 1mol/L TMAH solution at 20°C, 60°C and 80°C respectively, the volume of rock pillars and curing solution during the test The ratio V _s /V _l is 1:10. At 56 days, the expansion ratios of BFL-1, BFL-10, GS-2 and HTS-8 rock columns cured in 1mol/LTMAH at 60°C are 0.070% and 0.055%, respectively , 0.064% and 0.065%, and the expansion rates of BFL-1, BFL-10, GS-2 and HTS-8 rock columns cured in 1mol/L TMAH at 80°C were 0.116%, 0.328%, 0.075% and 0.158%, respectively. At 84 days, the expansion rates of BFL-1, BFL-10, GS-2 and HTS-8 rock columns cured in 1mol/L TMAH at 60°C were 0.095%, 0.110%, 0.068% and 0.088%, respectively. The expansion rates of BFL-1, BFL-10, GS-2 and HTS-8 rock columns maintained in 1mol/L TMAH were 0.183%, 0.384%, 0.101% and 0.182%, respectively. At 160 days, the GS-2 and HTS-8 rock pillars did not expand significantly in 1mol/L TMAH solution at 20°C, and the expansion rates of BFL-1 and BFL-10 rock pillars were 0.174% and 0.216% respectively at 60°C %, the expansion ratios of BFL-1 and BFL-10 rock columns are 0.250% and 0.486% respectively under the curing condition of 80℃. Increasing the curing temperature helps to promote the development of rock column expansion. When the curing temperature increases from 60°C to 80°C, the expansion rates of BFL-1, BFL-10, GS-2 and HTS-8 rock pillars 56d increase by 66 %, 496%, 17% and 143%, the expansion rates of BFL-1, BFL-10, GS-2 and HTS-8 rock column 84d increased by 93%, 249%, 49% and 107%, respectively, BFL- 1 and BFL-10 rock columns 160d have increased expansion rates by 44% and 125%, respectively.

Embodiment 4-curing solution concentration

Figure 4 shows the expansion ratios of BFL-1, BFL-2, BFL-3, BFL-6, BFL-10 and BFL-12 rock columns when they were cured in 1mol/L and 2mol/L TMAH solutions at 80°C respectively. During the test The volume ratio V _s /V _l of rock column and curing solution is 1:10. The higher the concentration of TMAH curing solution, the greater the expansion rate of BFL-1 rock column. Before 80 days, the expansion rate of BFL-2, BFL-6 and BFL-10 rock pillars cured in 1mol/L TMAH solution was greater than that of rock pillars cured in 2mol/L TMAH solution, after that, the higher the concentration of TMAH curing solution, The expansion rate of BFL-2, BFL-6 and BFL-10 rock columns is larger. Before 80-100 days, the concentration of TMAH curing solution has no obvious effect on the expansion of BFL-3 and BFL-12 rock columns, and the higher the concentration of TMAH curing solution, the greater the expansion rate of BFL-3 and BFL-12 rock columns. Overall, the concentration of TMAH has little effect on the swelling development of rock pillars.

Based on the above, it is more appropriate to have a volume ratio V _s /V _l of rock column and curing solution of 1:10. Selecting a curing temperature of 80°C can shorten the test time. The concentration of TMAH curing solution at 80°C is 1mol/L TMAH solution as the curing solution, and the expansion rate of the 56d rock column is 0.1%, which can distinguish between rocks without ADR activity and rocks with ADR activity, and can also determine that ADR cannot be determined due to the influence of ASR expansion ADR activity of active rocks. This condition and criterion can be used as a method for the evaluation of ADR activity of dolomitic rocks.

Example 5

Aggregate dolomitic limestone CK with ADR activity in the international typical Kingston area of Canada is selected as the detection method for this method. The dolomite content is about 20%-30%, and the silica content is 11.01%. , there is no ADR activity in Lianghekou sandstone LHK in Ganzi Prefecture, Sichuan Province. The chemical analysis is shown in Table 2.

Chemical Composition (%) of Table 2 Aggregate

The rock column of CK was made, the size of the specimen was 10mm×10mm×30mm, the curing temperature was 80°C, soaked in 1mol/L NaOH, 1mol/L TMAH, 2mol/L TMAH solution; Expansion rate, the volume ratio Vs/Vl of the rock column and the curing solution during the test is 1:10. The higher the concentration of TMAH curing solution, the greater the expansion rate of CK rock column. The rock column 56d soaked in TMAH solution has an expansion rate of more than 0.1%, and has ADR activity, and the conclusion is consistent with reality. This condition and criterion can be used as a method for the evaluation of ADR activity of dolomitic rocks.

The rock column of LHK is made, the size of the specimen is 10mm×10mm×30mm, the temperature is 60°C and 80°C respectively, and it is maintained in 1mol/L NaOH, 1mol/L KOH, 1mol/L TMAH solution; The middle rock column does not expand, and does not have ADR activity, which is consistent with reality.

Claims (10)

1. a method for judging whether the dolomitic limestone aggregate has alkali dolomite activity, is characterized in that: the specimen maintenance that adopts aggregate to be detected to prepare is maintained in quaternary ammonium alkali-tetramethylammonium hydroxide solution, The expansion rate of the test piece is detected, if the test piece expands, the aggregate has ADR activity, otherwise, the aggregate does not have ADR activity. 2. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 1, characterized in that: the curing temperature of the test piece is 60-80°C, and the concentration of the solution is 1 ~2mol/L, if the expansion rate of the specimen is greater than 0.1% when it is cured for 56 days, the aggregate used has ADR activity. 3. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 1, characterized in that: the curing temperature of the test piece is 80°C, and the concentration of the solution is 1mol/L , if the expansion rate of the specimen is greater than 0.1% when it is cured for 56 days, the aggregate used has ADR activity. 4. the method for judging whether the dolomitic limestone aggregate according to claim 1 has alkali dolomite activity is characterized in that: the preparation method of the rock column test piece is as follows: a is cut on the aggregate rock to be detected Several groups of rock pillars of a certain size; b bonding measuring nail heads at the center of both ends of the rock pillar; c maintaining the rock pillar and measuring the expansion rate according to a certain age. 5. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 4, characterized in that: the rock column is a rock column of 8-12mm × 8-12mm × 28-32mm, The nail head is bonded on a surface of 8-12mm×8-12mm, and the nail head is bonded by non-alkali cement. 6. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 5, characterized in that: the alkali-free cement is analytically pure CaCO ₃ , SiO ₂ , Al ₂ O ₃ It is obtained by high-temperature calcination after uniform mixing with Fe ₂ O ₃ four substances. 7. the method for judging whether the dolomitic limestone aggregate has alkali dolomite activity according to claim 4 is characterized in that: in the described step a, each group of rock pillars is cut along 3 mutually perpendicular directions of the rock The obtained rock column composition, the expansion rate in the step c is the maximum expansion rate in the same group of rock columns. 8. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 1, characterized in that: the volume ratio V _s /V _l of the volume of the test piece to the curing solution is 1:10～15 . 9. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 1, characterized in that: said aggregates are mainly composed of calcite and dolomite. 10. The method for judging whether dolomitic limestone aggregates have alkali dolomite activity according to claim 1, characterized in that: the test piece is a rock column test piece prepared by using the aggregate to be tested.